Aluminum-silicon plated hot-formed steel sheet, aluminum-silicon plated hot-formed steel part having sacrificial anode protection and excellent painting properties, and method for manufacturing the same

Abstract

The application relates to the technical field of automobile steel parts, and discloses an aluminum-silicon plated hot forming steel plate, an aluminum-silicon plated hot forming steel part with excellent sacrificial anode protection and coating performance and a preparation method of the aluminum-silicon plated hot forming steel part, the aluminum-silicon plated hot forming steel plate comprises a steel base plate, an aluminum alloy plating layer is plated on at least one surface of the steel base plate, and a surface treatment layer is further coated on the surface of the aluminum alloy plating layer; the aluminum alloy plating layer contains the following chemical elements in percentage by weight: 8%<=Si<=12%, Fe<=3%, and the rest is aluminum and inevitable impurities; the surface treatment layer contains copper elements; the copper elements in the surface treatment layer come from one or more than two of copper, copper oxide, copper hydroxide, copper acetate and copper citrate. The aluminum-silicon plated hot forming steel part has excellent sacrificial anode protection effect, excellent paint adhesion after painting and good corrosion resistance, and solves the problem of paint peeling after painting caused by insufficient alloying.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of automobile steel parts, in particular to an aluminum-silicon plated hot-formed steel plate, an aluminum-silicon plated hot-formed steel part with sacrificial anode protection and excellent coating performance, and a preparation method thereof. BACKGROUND

[0002] Due to the requirements of lightweighting and corrosion resistance, high-strength coated hot-formed steels are widely used in automobile parts. Among the coated hot-formed steels, aluminum-silicon plated hot-formed steel plates are widely used.

[0003] However, there are outstanding technical problems: (1) the aluminum-silicon plating layer has a mirror reflection effect when heated, reducing the heating efficiency; (2) since the aluminum-silicon plating layer after hot forming cannot undergo pretreatment reaction, the blank must be heated sufficiently to diffuse Fe into the aluminum-silicon plating layer to form a microscopically rough aluminum-iron alloy on the surface to ensure the adhesion of the subsequent paint; (3) a large amount of Fe diffusion into the plating layer results in no sacrificial anode protection of the plating layer to the substrate, and a large proportion of Fe in the plating layer also increases the risk of red rust at the part cutting edge and punching position. All of the above are unacceptable to some automobile manufacturers.

[0004] The ideal technical solution is that the plating layer after hot forming has a sacrificial anode protection effect, changes the pretreatability of the plating layer, and can manufacture hot-formed parts with high heating efficiency.

[0005] Attempts to improve the sacrificial anode effect or pretreatment effect by adding active metal elements such as zinc to the aluminum-silicon plating layer have been studied (such as 201280073231.4), but such technologies have technical problems such as liquid metal intrusion (LME) and a large change in plating solution composition, which are difficult to be applied in industrialization on existing production lines, and have not been commercialized.

[0006] Known technical solutions aimed at improving the pretreatment performance of aluminum-silicon plating layers include patent application 201480068599.0, which discloses a steel plate for press hardening including an aluminum-based coating and a ZnO coating. For example, Chinese patent application 201680011130.2 discloses a steel plate coated with an aluminum-based coating and further including a second zinc coating, which has the effect of improving phosphate surface treatment. However, these technologies cannot solve the technical problem of no sacrificial anode protection after hot forming of the plating layer, nor can they improve the heating efficiency.

[0007] It is also known that there are technologies for improving the heating efficiency of aluminum-based plated hot-formed steel (201280012158.X, 201580017679.8, 202210869048.0) by applying a substance with higher heat absorption efficiency than aluminum alloy on the surface of the steel sheet to improve the heating efficiency. However, these methods for improving the heating efficiency cannot solve the technical problems of low paint adhesion after hot forming, lack of sacrificial anode protection of the plating layer, and easy occurrence of red rust.

[0008] In summary, there is currently a lack of technical solutions for aluminum-silicon plated hot-formed parts with sacrificial anode protection and excellent coating performance that can be manufactured with high heating efficiency. SUMMARY

[0009] The purpose of the present application is to overcome the current lack of aluminum-silicon plated hot-formed parts with sacrificial anode protection and excellent coating performance that can be manufactured with high heating efficiency. The present application provides an aluminum-silicon plated hot-formed steel sheet, an aluminum-silicon plated hot-formed steel part with sacrificial anode protection and excellent coating performance, and a method for manufacturing the same. The present application achieves the manufacture of hot-formed steel parts with sacrificial anode protection and good adhesion after coating with high heating efficiency, and solves the technical defects of low heating efficiency, lack of sacrificial anode protection, easy occurrence of red rust, inability to react during pretreatment, and poor adhesion and corrosion resistance after coating of existing aluminum-silicon hot-formed steel parts.

[0010] To achieve the above-mentioned purpose, the present application provides an aluminum-silicon plated hot-formed steel sheet, which comprises a steel substrate, and an aluminum alloy plating layer plated on at least one surface of the steel substrate, wherein the surface of the aluminum alloy plating layer is further coated with a surface treatment layer (i.e., the aluminum alloy plating layer is located between the steel substrate and the surface treatment layer).

[0011] The chemical element weight percentage of the aluminum alloy plating layer comprises 8%≤Si≤12%, Fe≤3%, and the balance being aluminum and unavoidable impurities.

[0012] The surface treatment layer contains copper elements.

[0013] The copper elements in the surface treatment layer come from one or more of copper, copper oxide, copper hydroxide, copper acetate, and copper citrate.

[0014] The present application is not subject to the composition of the base steel substrate, as a conventional example of implementation steel substrate type 22MnB5, the chemical elements weight percentage contains: 0.20%≤C≤0.25%; 0.15%≤Si≤0.35%; 1.10%≤Mn≤1.40%; 0%≤Cr≤0.30%; 0%≤Mo≤0.35%; 0%≤P≤0.025%; 0%≤S≤0.005%; 0.020%≤Ti≤0.060%; 0.020%≤Al≤0.060%; 0.002%≤B≤0.004%, the balance is iron and unavoidable impurities from steel manufacturing.

[0015] In the above-mentioned chemical element composition of the aluminum alloy coating, Si can form an Fe-Al-Si inhibition layer on the surface of the steel substrate, which can effectively hinder the formation of brittle phase Fe2Al5 and improve the adhesion of the coating. When the content of Si is less than 8%, the Fe-Al alloy layer becomes thicker and the adhesion of the coating decreases. When the content of Si is greater than 12.0%, the surface quality of the coating is affected. According to the above situation, the content of Si in the aluminum alloy coating is controlled to be 8.0-12.0%.

[0016] In the present application, the steel substrate can be hot-dip plated in a hot-rolled state or an annealed state to coat an aluminum alloy coating on at least one surface of the steel substrate. For example, the aluminum alloy coating can be coated on at least one surface of the steel substrate by the method of hot rolling→acid pickling→hot-dip plating→smoothing. Alternatively, the aluminum alloy coating can be coated on at least one surface of the steel substrate by the method of hot rolling→acid pickling→cold rolling→cleaning→annealing→hot-dip plating→smoothing.

[0017] In the preferred embodiment, after the aluminum alloy coating is coated on at least one surface of the steel substrate, the steel substrate coated with the aluminum alloy coating needs to be degreased to wash away the contaminants on the surface of the steel plate, and finally a surface treatment layer is formed on the aluminum alloy coating.

[0018] Optionally, a water washing step is further provided after the degreasing operation to avoid the residue of the degreasing solution used for degreasing on the surface.

[0019] Optionally, a drying step is further provided after the water washing step.

[0020] Further, a rust-proof oil layer can be optionally coated on the surface of the surface treatment layer, that is, the aluminum alloy coating is coated on at least one surface of the steel substrate of the aluminum-silicon plated hot-formed steel plate, and the surface of the aluminum alloy coating is further coated with a surface treatment layer; or the aluminum alloy coating is coated on at least one surface of the steel substrate of the aluminum-silicon plated hot-formed steel plate, and the surface of the aluminum alloy coating is further coated with a surface treatment layer, and the surface of the surface treatment layer is further coated with a rust-proof oil layer.

[0021] The rustproof oil layer is formed by coating with rustproof oil.

[0022] In the present application, the copper element in the surface treatment layer is derived from one or more than two of copper, copper oxide, copper hydroxide, copper acetate and copper citrate. This is because the inventors have found that these copper and copper-containing substances can form black copper oxide during the thermoforming process, thereby significantly improving the heating efficiency. The inventors have also found that the copper oxide can exist in ionic form in the zirconium solution and accelerate the zirconium reaction, making it possible to zirconize the aluminum-silicon coating layer that is difficult to zirconize, and significantly improving the adhesion and corrosion resistance after coating.

[0023] More specifically, the surface treatment layer of the present application is prepared using one or more than two of copper, copper oxide, copper hydroxide, copper acetate and copper citrate. These copper-containing substances do not release toxic gases during heating and drying, and are environmentally friendly and do not corrode equipment.

[0024] In a preferred embodiment, the surface treatment layer of the present application can be obtained by physical vapor deposition (PVD) of copper metal on the surface of the aluminum alloy coating; or a solution or coating of one or more than two of copper, copper oxide, copper hydroxide, copper acetate and copper citrate can be applied to the aluminum alloy coating, and then dried to form. In this embodiment, the type of substance after drying depends on the drying temperature and the atmosphere, and generally, the temperature is 50-300°C in an air atmosphere.

[0025] In a specific embodiment, when the surface treatment layer of the present application is formed by applying a solution or coating of one or more than two of copper, copper oxide, copper hydroxide, copper acetate and copper citrate to the aluminum alloy coating, and then drying:

[0026] When one or more than two of copper metal powder, copper oxide and copper hydroxide are used to form the surface treatment layer, since these substances are difficult to dissolve in water, it is preferred to first disperse these substances with a dispersant to form a dispersion coating before coating; preferably, the dispersant is one or more than two of water, ethanol, acetone, butyl ether and N-methyl-2-pyrrolidone, and a small amount of adhesive can also be used to enhance the adhesion of the coating to the coating, and the adhesive is selected from one or more than two of polyvinylpyrrolidone, polyacrylic acid resin, polyurethane, silane and polyvinylidene fluoride.

[0027] When copper acetate and / or copper citrate are used to form the surface treatment layer, it is preferable to first prepare a solution of the respective copper salt and then apply the coating. These two copper salts do not release toxic gases when dried, and do not react violently with the Al-Si plating layer during the drying process after coating, which does not cause uneven color and black spots caused by severe corrosion of the plating layer after pre-treatment (these uneven color and black spots caused by severe corrosion of the plating layer occur when using copper sulfate, copper nitrate, and copper chloride as the copper source). The material formed after drying not only includes copper acetate and / or copper citrate, but also contains elemental copper on the surface due to the partial or complete displacement reaction of aluminum with the solution containing copper ions, and part of the elemental copper can be partially oxidized to copper oxide during the drying and heating process.

[0028] The Al-Si plating layer hot-formed steel sheet according to the present application has high heating efficiency in hot forming, and has excellent sacrificial anode protection performance and good coating performance after hot forming.

[0029] The Al-Si plating layer hot-formed steel sheet according to the present application has high heating efficiency in hot forming, and has excellent sacrificial anode protection performance and good coating performance after hot forming.

[0030] The Al-Si plating layer hot-formed steel sheet according to the present application has high heating efficiency in hot forming, and has excellent sacrificial anode protection performance and good coating performance after hot forming.

[0031] The Al-Si plating layer hot-formed steel sheet according to the present application has high heating efficiency in hot forming, and has excellent sacrificial anode protection performance and good coating performance after hot forming.

[0032] The Al-Si plating layer hot-formed steel sheet according to the present application has high heating efficiency in hot forming, and has excellent sacrificial anode protection performance and good coating performance after hot forming.

[0033] The Al-Si plating layer hot-formed steel sheet according to the present application has high heating efficiency in hot forming, and has excellent sacrificial anode protection performance and good coating performance after hot forming.

[0034] Further, the Al-Si plating layer hot-formed steel sheet according to the present application has high heating efficiency in hot forming, and has excellent sacrificial anode protection performance and good coating performance after hot forming.

[0035] Further, the Al-Si plating layer hot-formed steel sheet according to the present application has high heating efficiency in hot forming, and has excellent sacrificial anode protection performance and good coating performance after hot forming. Further, the Al-Si plating layer hot-formed steel sheet according to the present application has high heating efficiency in hot forming, and has excellent sacrificial anode protection performance and good coating performance after hot forming.

[0036] In a preferred case, the content of Fe in the interdiffusion layer is greater than 60wt%; the content of Fe in the first iron-aluminum alloy phase is greater than 40wt% and less than 75wt%; the content of Fe in the first iron-aluminum-silicon ternary alloy phase is greater than 25wt% and less than 68wt%; the content of Fe in the second iron-aluminum alloy phase is greater than 40wt% and less than 75wt%; the content of Fe in the second iron-aluminum-silicon ternary alloy phase is greater than 25wt% and less than 70wt%.

[0037] In the aluminum-silicon plated hot-formed steel part, the material of the surface heat treatment layer is copper metal and / or copper oxide, and does not contain zinc oxide, and is formed by the hot forming process of the surface treatment layer.

[0038] The aluminum-silicon plated hot-formed steel part of the present application has excellent sacrificial anode protection effect, and the outermost layer of the aluminum alloy phase plated layer is an Al-Si alloy phase with Fe content less than 5% by weight, so that the aluminum alloy phase plated layer obtained after hot forming has a sacrificial anode effect. In particular, it is found that by controlling the area ratio of the surface aluminum-silicon alloy phase to be greater than or equal to 20% through the hot forming process, the sacrificial anode protection effect of the aluminum alloy phase plated layer can be ensured, and no obvious red rust is formed in the corrosion test. The present application solves the problems of paint peeling and large corrosion width after coating caused by insufficient alloying of the aluminum alloy phase plated layer by using a surface heat treatment layer. The inventors found that copper and / or copper oxide on the surface of aluminum-silicon after hot pressing can exist in ionic form again in the slightly acidic environment of the zirconium solution and act as a catalyst to accelerate the deposition of zirconium oxide, promote the zirconium treatment reaction, and form a film in the phosphating reaction. Therefore, the paint adhesion after painting is excellent and the corrosion resistance is good.

[0039] The third aspect of the present application provides a preparation method of the above-mentioned aluminum-silicon plated hot-formed steel part, comprising: heating and hot stamping the above-mentioned aluminum-silicon plated hot-formed steel sheet to obtain the aluminum-silicon plated hot-formed steel part.

[0040] The heating and hot stamping is a hot forming process, and the above-mentioned aluminum-silicon plated hot-formed steel sheet can be used to manufacture the aluminum-silicon plated hot-formed steel part with high heating efficiency.

[0041] The use of the aluminum-silicon plated hot-formed steel sheet of the present application can significantly improve the heating efficiency. The aluminum-silicon plated hot-formed steel sheet can be cut into appropriate size blanks according to actual needs before hot forming, or directly hot formed without cutting.

[0042] Preferably, the temperature of heating is 840-1100℃.

[0043] In the preferred case, when the thickness of the aluminum-silicon plated hot-formed steel sheet is > 1.4 mm, the heating time is 3-5 min; when the thickness of the aluminum-silicon plated hot-formed steel sheet is ≤ 1.4 mm, the heating time is 1-3 min.

[0044] In the preferred case, when the thickness of the aluminum-silicon plated hot-formed steel sheet is > 1.4 mm, the heating time is 3-5 min; when the thickness of the aluminum-silicon plated hot-formed steel sheet is ≤ 1.4 mm, the heating time is 1-3 min.

[0045] Specifically, the heating atmosphere does not affect the coating performance, and for the purpose of coating improvement, the heating can be performed in any atmosphere, preferably in an atmosphere containing 15-25% oxygen by volume (in air for cost considerations), in this preferred embodiment, the heating efficiency is the highest, and during the heating process, the copper element or its compound is oxidized to copper oxide, and the black surface of the copper oxide can realize heating at the maximum heating rate. During the subsequent transfer to the hot stamping tool, the surface treatment layer can be partially or completely oxidized to copper oxide, thereby improving the coating performance.

[0046] Further, during the heating process, due to the formation of a black surface by the thermal oxidation of the surface treatment layer, the heat absorption efficiency of the sheet is improved, and the time required for heating to the austenitizing temperature is shorter, and the heating time of this heating process is shortened by more than 1 min compared with the conventional hot forming process.

[0047] In the preferred case of the present application, the hot stamping conditions include a temperature of 500-700°C and a holding time of 5-40 s.

[0048] In a specific embodiment, hot stamping is performed using a hot stamping tool, and after hot stamping, the obtained part is cooled in the tool itself or after being transferred to a specific cooling tool to obtain an aluminum-silicon plated hot-formed steel part.

[0049] The aluminum-silicon plated hot-formed steel part of the present application has excellent sacrificial anode protection effect, and under the high heating rate of the present application, the diffusion time of Fe in the steel matrix in the aluminum alloy plating layer is short, and the alloying is insufficient, so that the aluminum alloy phase plating layer after hot forming has a sacrificial anode effect, in particular, by controlling the area ratio of the surface aluminum-silicon alloy phase to be ≥ 20% through the hot forming process, the sacrificial anode protection effect of the plating layer is ensured, and no obvious red rust is formed in the corrosion test. In addition, the hot-formed part of the present application has excellent coating performance, because copper or copper oxide can exist in ionic form again in the slightly acidic environment of the zirconium solution and act as a catalyst to accelerate the deposition of zirconium oxide, promote the zirconium treatment reaction, and form a film in the phosphating reaction, so that the paint adhesion after painting is excellent, the corrosion resistance is good, and the problem of paint peeling after painting caused by insufficient alloying is solved.

[0050] The present application realizes the manufacture of hot-formed steel parts with good adhesion after coating and sacrificial anode protection with high heating efficiency, and solves the technical defects of low heating efficiency, no sacrificial anode protection, easy red rust, no pre-treatment reaction, poor adhesion and corrosion resistance of the existing aluminum-silicon hot-formed steel parts. BRIEF DESCRIPTION OF DRAWINGS

[0051] Figure 1 is the aluminum alloy metallographic coating structure diagram of the aluminum-silicon coated hot-formed steel plate part of Example 1;

[0052] Figure 2 is the aluminum alloy metallographic coating structure diagram of the aluminum-silicon coated hot-formed steel plate part of Example 2. DETAILED DESCRIPTION

[0053] The specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present application, and are not used to limit the present application.

[0054] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The endpoints of the ranges and the values are approximate values and should be understood as including values approximately near to the stated values. For ranges of values, the endpoints of the ranges are combined with the individual points to form new ranges that are not specifically disclosed.

[0055] It should be noted that if the present application involves directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative positional relationship between the components, the movement condition, etc. in a certain posture (as shown in the drawings), and if the specific posture changes, the directional indications will also change accordingly.

[0056] In addition, if the present application involves descriptions of "first", "second", etc., the descriptions of "first", "second", etc. are only for description purposes, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second" can explicitly or implicitly include at least one of the features. In addition, the technical solutions of each embodiment provided by the present application can be combined with each other, but it must be based on the realization of a person skilled in the art, and when the combination of technical solutions contradicts each other or cannot be realized, it should be considered that the combination of technical solutions does not exist, and is not within the protection scope required by the present application.

[0057] The present application will be described in detail below by way of examples. The experimental methods in the following examples are all conventional methods in the art unless otherwise specified. The experimental materials used in the following examples are all commercially available unless otherwise specified.

[0058] The steel substrate used in the following examples and comparative examples has the following chemical element weight percentage: C: 0.2252%, Mn: 1.1735%, P: 0.0126%, S: 0.0009%, Si: 0.2534%, Cr: 0.180%, Al: 0.0371%, Ti: 0.0382%, B: 0.0028%, Mo: 0.0017%, and the balance of iron and inevitable impurities.

[0059] The rust-proof oil used in the following examples and comparative examples is Ferroc at N 6130, and the coating amount is 1.5 g / m 2 .

[0060] Example 1

[0061] (1) A steel blank was subjected to hot rolling, pickling, cold rolling, cleaning, annealing, hot dip plating and flattening in sequence to obtain a steel substrate plated with an aluminum alloy plating layer on the surface, and then subjected to degreasing, water washing and drying operations for standby use; the aluminum alloy plating layer has the following chemical element weight percentage: Si: 8.0%, Fe: 2.0%, and the balance of aluminum and inevitable impurities; the thickness of the steel substrate is 1.0 mm, and the aluminum alloy plating layer is plated on both sides with equal thickness, and the weight of each single-side plating layer is 75 g / m 2 ;

[0062] (2) Copper metal powder, N-methyl-2-pyrrolidone and polyvinylidene fluoride were mixed uniformly to obtain a dispersion coating (based on 100 parts by weight of the total weight of copper metal powder, N-methyl-2-pyrrolidone and polyvinylidene fluoride, the amount of copper metal powder is 40 parts by weight, the amount of N-methyl-2-pyrrolidone is 50 parts by weight, and the amount of polyvinylidene fluoride is 10 parts by weight), which was coated on the surface of the aluminum alloy plating layer of the steel substrate plated with the aluminum alloy plating layer obtained in step (1), and then dried at a temperature of 200°C in an air atmosphere to form a surface treatment layer on the surface of the aluminum alloy plating layer, followed by coating a rust-proof oil on the surface of the surface treatment layer to form a rust-proof oil layer, thereby obtaining an aluminum-silicon plating layer hot-formed steel plate; the aluminum-silicon plating layer hot-formed steel plate comprises a steel substrate, and the surface of the steel substrate is plated with an aluminum alloy plating layer, the surface of the aluminum alloy plating layer is further coated with a surface treatment layer, and the surface of the surface treatment layer is further coated with a rust-proof oil layer.

[0063] Example 2

[0064] (1) The steel billet is sequentially subjected to hot rolling, pickling, hot dipping and skin passing to obtain a steel substrate plated with an aluminum alloy plating layer, and then subjected to degreasing, water washing and drying operations, ready for use; the aluminum alloy plating layer has the following weight percentage contents: Si: 9.0%, Fe: 1.0%, and the rest is aluminum and unavoidable impurities; the steel substrate has a thickness of 1.2 mm, and the aluminum alloy plating layer is coated on both sides with an equal thickness, and the weight of each single-side plating layer is 75 g / m 2 ;

[0065] (2) The copper acetate is mixed with water to prepare a copper acetate solution with a Cu ion content of 0.10 mol / L, the copper acetate solution is coated on the surface of the aluminum alloy plating layer of the steel substrate obtained in step (1), and then dried at a temperature of 300°C in an air atmosphere to form a surface treatment layer on the surface of the aluminum alloy plating layer, and then a rust-proof oil layer is formed by coating a rust-proof oil on the surface of the surface treatment layer, to obtain an aluminum-silicon plating layer hot-formed steel plate; the aluminum-silicon plating layer hot-formed steel plate comprises a steel substrate, the surface of the steel substrate is plated with an aluminum alloy plating layer, the surface of the aluminum alloy plating layer is further coated with a surface treatment layer, and the surface of the surface treatment layer is further coated with a rust-proof oil layer.

[0066] Example 3

[0067] (1) The steel billet is sequentially subjected to hot rolling, pickling, cold rolling, cleaning, annealing, hot dipping and skin passing to obtain a steel substrate plated with an aluminum alloy plating layer, and then subjected to degreasing, water washing and drying operations, ready for use; the aluminum alloy plating layer has the following weight percentage contents: Si: 10.0%, Fe: 1.5%, and the rest is aluminum and unavoidable impurities; the steel substrate has a thickness of 1.4 mm, and the aluminum alloy plating layer is coated on both sides with an equal thickness, and the weight of each single-side plating layer is 75 g / m 2 ;

[0068] (2) The copper acetate is mixed with water to prepare a copper acetate solution with a Cu ion content of 0.10 mol / L, the copper acetate solution is coated on the surface of the aluminum alloy plating layer of the steel substrate obtained in step (1), and then dried at a temperature of 100°C in an air atmosphere to form a surface treatment layer on the surface of the aluminum alloy plating layer, and then a rust-proof oil layer is formed by coating a rust-proof oil on the surface of the surface treatment layer, to obtain an aluminum-silicon plating layer hot-formed steel plate; the aluminum-silicon plating layer hot-formed steel plate comprises a steel substrate, the surface of the steel substrate is plated with an aluminum alloy plating layer, the surface of the aluminum alloy plating layer is further coated with a surface treatment layer, and the surface of the surface treatment layer is further coated with a rust-proof oil layer.

[0069] Example 4

[0070] (1) Steel billets are sequentially subjected to hot rolling, pickling, cold rolling, cleaning, annealing, hot-dip plating and skin passing to obtain a steel substrate plated with an aluminum alloy plating layer on the surface, and then subjected to degreasing, water washing and drying operations, ready for use; the aluminum alloy plating layer has the following chemical element weight percentage contents: Si: 12%, Fe: 2.0%, and the rest is aluminum and unavoidable impurities; the steel substrate has a thickness of 1.6 mm, and the plating layer is coated on both sides with equal thickness, and the weight of each single-side plating layer is 75 g / m 2 ;

[0071] (2) Copper citrate is mixed with water to prepare a copper citrate solution with a Cu ion content of 0.10 mol / L, the copper citrate solution is coated on the surface of the aluminum alloy plating layer of the steel substrate plated with the aluminum alloy plating layer obtained in step (1), and then dried at a temperature of 50°C in an air atmosphere to form a surface treatment layer on the surface of the aluminum alloy plating layer, and then a rust-proof oil layer is formed by coating rust-proof oil on the surface of the surface treatment layer, to obtain an aluminum-silicon plating layer hot-formed steel plate; the aluminum-silicon plating layer hot-formed steel plate comprises a steel substrate, the surface of the steel substrate is plated with an aluminum alloy plating layer, the surface of the aluminum alloy plating layer is further coated with a surface treatment layer, and the surface of the surface treatment layer is further coated with a rust-proof oil layer.

[0072] Example 5

[0073] (1) Steel billets are sequentially subjected to hot rolling, pickling, cold rolling, cleaning, annealing, hot-dip plating and skin passing to obtain a steel substrate plated with an aluminum alloy plating layer on the surface, and then subjected to degreasing, water washing and drying operations, ready for use; the aluminum alloy plating layer has the following chemical element weight percentage contents: Si: 10%, Fe: 3.0%, and the rest is aluminum and unavoidable impurities; the steel substrate has a thickness of 2.0 mm, and the plating layer is coated on both sides with equal thickness, and the weight of each single-side plating layer is 75 g / m 2 ;

[0074] (2) Copper citrate is mixed with water to prepare a copper citrate solution with a Cu ion content of 0.10 mol / L, the copper citrate solution is coated on the surface of the aluminum alloy plating layer of the steel substrate plated with the aluminum alloy plating layer obtained in step (1), and then dried at a temperature of 50°C in an air atmosphere to form a surface treatment layer on the surface of the aluminum alloy plating layer, and then a rust-proof oil layer is formed by coating rust-proof oil on the surface of the surface treatment layer, to obtain an aluminum-silicon plating layer hot-formed steel plate; the aluminum-silicon plating layer hot-formed steel plate comprises a steel substrate, the surface of the steel substrate is plated with an aluminum alloy plating layer, the surface of the aluminum alloy plating layer is further coated with a surface treatment layer, and the surface of the surface treatment layer is further coated with a rust-proof oil layer.

[0075] Comparative Example 1

[0076] The method according to Example 1 was carried out, except that a surface treatment layer was not formed, and a rust preventive oil layer was formed by applying a rust preventive oil directly on the surface of the aluminum alloy plating layer, to obtain a plated steel sheet; the plated steel sheet included a steel substrate, and an aluminum alloy plating layer was plated on the surface of the steel substrate, and a rust preventive oil layer was further provided on the surface of the aluminum alloy plating layer.

[0077] Comparative Example 2

[0078] The method according to Example 2 was carried out, except that a surface treatment layer was not formed, and a rust preventive oil layer was formed by applying a rust preventive oil directly on the surface of the aluminum alloy plating layer, to obtain a plated steel sheet; the plated steel sheet included a steel substrate, and an aluminum alloy plating layer was plated on the surface of the steel substrate, and a rust preventive oil layer was further provided on the surface of the aluminum alloy plating layer.

[0079] Comparative Example 3

[0080] The method according to Example 3 was carried out, except that a surface treatment layer was not formed, and a rust preventive oil layer was formed by applying a rust preventive oil directly on the surface of the aluminum alloy plating layer, to obtain a plated steel sheet; the plated steel sheet included a steel substrate, and an aluminum alloy plating layer was plated on the surface of the steel substrate, and a rust preventive oil layer was further provided on the surface of the aluminum alloy plating layer.

[0081] Comparative Example 4

[0082] The method according to Example 4 was carried out, except that a surface treatment layer was not formed, and a rust preventive oil layer was formed by applying a rust preventive oil directly on the surface of the aluminum alloy plating layer, to obtain a plated steel sheet; the plated steel sheet included a steel substrate, and an aluminum alloy plating layer was plated on the surface of the steel substrate, and a rust preventive oil layer was further provided on the surface of the aluminum alloy plating layer.

[0083] Comparative Example 5

[0084] The method according to Example 5 was carried out, except that a surface treatment layer was not formed, and a rust preventive oil layer was formed by applying a rust preventive oil directly on the surface of the aluminum alloy plating layer, to obtain a plated steel sheet; the plated steel sheet included a steel substrate, and an aluminum alloy plating layer was plated on the surface of the steel substrate, and a rust preventive oil layer was further provided on the surface of the aluminum alloy plating layer.

[0085] Comparative Example 6

[0086] The method according to Example 5 was carried out, except that a surface treatment layer was not formed, and a rust preventive oil layer was formed by applying a rust preventive oil directly on the surface of the aluminum alloy plating layer, to obtain a plated steel sheet; the plated steel sheet included a steel substrate, and an aluminum alloy plating layer was plated on the surface of the steel substrate, and a rust preventive oil layer was further provided on the surface of the aluminum alloy plating layer.

[0087] Comparative Example 7

[0088] The method according to Example 5 was conducted, except that copper sulfate was used instead of copper acetate; an aluminum-silicon plated hot-formed steel sheet including a steel substrate, an aluminum alloy plated layer plated on the surface of the steel substrate, a surface treatment layer further coated on the surface of the aluminum alloy plated layer, and a rust-preventive oil layer further coated on the surface of the surface treatment layer was obtained.

[0089] Comparative Example 8

[0090] The method according to Example 5 was conducted, except that copper sulfate was used instead of copper acetate; an aluminum-silicon plated hot-formed steel sheet including a steel substrate, an aluminum alloy plated layer plated on the surface of the steel substrate, a surface treatment layer further coated on the surface of the aluminum alloy plated layer, and a rust-preventive oil layer further coated on the surface of the surface treatment layer was obtained.

[0091] Comparative Example 9

[0092] The method according to Example 5 was conducted, except that copper sulfate was used instead of copper acetate; an aluminum-silicon plated hot-formed steel sheet including a steel substrate, an aluminum alloy plated layer plated on the surface of the steel substrate, a surface treatment layer further coated on the surface of the aluminum alloy plated layer, and a rust-preventive oil layer further coated on the surface of the surface treatment layer was obtained.

[0093] Test Example 1

[0094] The aluminum-silicon plated hot-formed steel sheets obtained in Examples 1 to 5 and the plated steel sheets obtained in Comparative Examples 1 to 6 were subjected to performance evaluation according to the following method.

[0095] Total austenitizing time: each steel sheet was cut, the cut sheet was placed in a 930°C box furnace, and heating was started at 1 min and then was extended by 30 s at a time, and then the steel was cooled in a flat die, a 10 mm x 10 mm x thickness sample was cut from the quenched test steel, and was ground, mechanically polished, and picral etched, and the original austenite grain size was observed and measured under an optical microscope, and the martensite structure was observed, and the heating time for complete formation of martensite was taken as the total austenitizing time; the total austenitizing time of each steel sheet is shown in Table 1.

[0096] The aluminum-silicon coated hot-formed steel sheets obtained in Examples 1-5 and the coated steel sheets obtained in Comparative Examples 1-6 were heated in air at 930°C for the time shown in Table 1 (the heating times for Comparative Examples 5 and 6 were different). Then, they were hot-stamped in a hot stamping tool at 650°C for 30 seconds. After that, they were removed and cooled to room temperature in air to obtain aluminum-silicon coated hot-formed steel sheet parts. (The aluminum-silicon coated hot-formed steel parts obtained in Examples 1-5 include a steel substrate with an aluminum alloy metallographic coating on its surface, and the surface of the aluminum alloy metallographic coating is also covered with a surface heat treatment layer; the aluminum-silicon coated hot-formed steel parts obtained in Comparative Examples 1-6 include a steel substrate with an aluminum alloy metallographic coating on its surface.)

[0097] Coating structure: A 10mm×10mm×plate thickness sample cut from the hot-formed steel plate parts with aluminum-silicon coating obtained by the above mold quenching was ground and mechanically polished. The structure of the coating was observed in a scanning electron microscope, and the area ratio of the aluminum-silicon alloy phase on the surface of the aluminum-silicon coating was recorded.

[0098] The aluminum alloy metallographic coating structures of the aluminum-silicon coated hot-formed steel plate parts in Examples 1 and 2 are respectively as follows: Figure 1 and Figure 2 As shown, the Fe content in each metallographic structure was further detected using the EDS measurement method; Figure 1 The aluminum alloy metallographic coating comprises, sequentially stacked along the direction away from the steel substrate, an interdiffusion layer (α-Fe containing Al and Si elements), a first iron-aluminum-silicon ternary alloy phase, and a surface layer; the surface layer is an aluminum-silicon alloy phase, wherein the Fe content in the aluminum-silicon alloy phase is 1.2 wt%, the Fe content in the interdiffusion layer is 70 wt%, and the Fe content in the first iron-aluminum-silicon ternary alloy phase is 34 wt%. Figure 2 The aluminum alloy metallographic coating comprises, sequentially stacked along the direction away from the steel substrate, an interdiffusion layer, a first iron-aluminum alloy phase, a first iron-aluminum-silicon ternary alloy phase, a second iron-aluminum alloy phase, and a surface layer; the surface layer is an aluminum-silicon alloy phase and a second iron-aluminum-silicon ternary alloy phase, wherein the aluminum-silicon alloy phase contains 2.0 wt% Fe, the interdiffusion layer contains 75 wt% Fe, the first iron-aluminum alloy phase contains 44.8 wt% Fe, the first iron-aluminum-silicon ternary alloy phase contains 49.5 wt% Fe, the second iron-aluminum alloy phase contains 45 wt% Fe, and the second iron-aluminum-silicon ternary alloy phase contains 28.9 wt% Fe.

[0099] The aluminum alloy metallurgical coating of the aluminum-silicon plated hot-formed steel part obtained in Example 3-5 comprises, in sequence from the direction away from the steel substrate, a mutual diffusion layer, a first iron-aluminum alloy phase, a first iron-aluminum-silicon ternary alloy phase, a second iron-aluminum alloy phase, and a surface layer; the surface layer is an aluminum-silicon alloy phase and a second iron-aluminum-silicon ternary alloy phase; the content of Fe in the mutual diffusion layer is greater than 60 wt%; the content of Fe in the first iron-aluminum alloy phase is greater than 40 wt% and less than 75 wt%; the content of Fe in the first iron-aluminum-silicon ternary alloy phase is greater than 25 wt% and less than 68 wt%; the content of Fe in the second iron-aluminum alloy phase is greater than 40 wt% and less than 75 wt%; the content of Fe in the second iron-aluminum-silicon ternary alloy phase is greater than 25 wt% and less than 70 wt%; and the content of Fe in the aluminum-silicon alloy phase is less than 5 wt%.

[0100] The aluminum alloy metallurgical coating of the aluminum-silicon plated hot-formed steel part obtained in Comparative Example 1-5 comprises, in sequence from the direction away from the steel substrate, a mutual diffusion layer, an iron-aluminum layer, an iron-aluminum-silicon ternary alloy phase, and an iron-aluminum layer, without an aluminum-silicon alloy phase; the aluminum alloy metallurgical coating of the aluminum-silicon plated hot-formed steel part obtained in Comparative Example 6 comprises, in sequence from the direction away from the steel substrate, a mutual diffusion layer, a first iron-aluminum alloy phase, a first iron-aluminum-silicon ternary alloy phase, a second iron-aluminum alloy phase, and a surface layer; the surface layer is an aluminum-silicon alloy phase and a second iron-aluminum-silicon ternary alloy phase; the content of Fe in the mutual diffusion layer is greater than 60 wt%; the content of Fe in the first iron-aluminum alloy phase is greater than 40 wt% and less than 75 wt%; the content of Fe in the first iron-aluminum-silicon ternary alloy phase is greater than 25 wt% and less than 68 wt%; the content of Fe in the second iron-aluminum alloy phase is greater than 40 wt% and less than 75 wt%; the content of Fe in the second iron-aluminum-silicon ternary alloy phase is greater than 25 wt% and less than 70 wt%; and the content of Fe in the aluminum-silicon alloy phase is less than 5 wt%.

[0101] Sacrificial anode protection test: each aluminum-silicon plated hot-formed steel part was cut into a 20 mm x 20 mm x plate thickness sample, a CHI 660D electrochemical workstation and attached software were used to analyze the material polarization curve, a three-electrode system was used, the reference electrode was a saturated calomel electrode (SCE), the auxiliary electrode was a Pt electrode, the steel plate was the working electrode, and the electrolyte was a 5% by weight NaCl solution, and the test temperature was room temperature. If the coating potential is lower than -0.74 V (the self-corrosion potential of the steel substrate 22MnB5 is -0.591 V), it is determined that the aluminum alloy metallurgical coating has sacrificial anode protection for the steel substrate, otherwise not.

[0102] Zirconium pretreatment performance evaluation: use Shanghai Parka Sejing Co., Ltd. FC-L5000A (40 g / L) / FC-E2021SB (16 g / L) two-component automotive degreaser, the degreasing liquid temperature is 50°C, immerse each aluminum-silicon plated hot forming steel plate parts into the degreasing liquid for 2 minutes, then take out and rinse with deionized water. After the above degreasing is completed, zirconium treatment is carried out, and Parka CT8000 type zirconium-based phosphorus-free pretreatment agent (Shanghai Parka Sejing Co., Ltd.) is used. Temperature 35°C, PH 3.8, time 2 min. After pretreatment, rinse and dry. Use XRF fluorescence spectroscopy to test the film weight with Zr as the characteristic element.

[0103] Phosphating pretreatment performance evaluation: use Shanghai Parka Sejing Co., Ltd. FC-L5000A (40 g / L) / FC-E2021SB (16 g / L) two-component automotive degreaser, the degreasing liquid temperature is 50°C, immerse each aluminum-silicon plated hot forming steel plate parts into the degreasing liquid for 2 minutes, then take out and rinse with deionized water. After the above degreasing is completed, zirconium treatment is carried out, and Parka CT8000 type zirconium-based phosphorus-free pretreatment agent (Shanghai Parka Sejing Co., Ltd.) is used. Temperature 35°C, PH 3.8, time 2 min. After pretreatment, rinse and dry. Use XRF fluorescence spectroscopy to test the film weight with Zr as the characteristic element.

[0104] Coating corrosion resistance evaluation method: after the zirconium pretreatment is completed, the sample is electrophoresed, and the optimized process is used to make the electrophoresis dry film thickness reach 20±2 μm. The electrophoresis paint type is Hunan Xiangjiang Guanxi Coatings HT8000C. After electrophoresis, scratch corrosion test is carried out, the paint is scratched with a scratch knife, then placed in a corrosion environment for 26 days, then taken out, and observed whether red rust is generated in the scratch area. Remove the rust, use adhesive tape to peel off the scratch area, and use the width of the paint peeling in the scratch area as the evaluation index. The cyclic corrosion environment test method includes 8h constant temperature maintenance (25±3°C, 4 times of spraying salt solution each for 3 min during the period, the salt solution composition is: 0.9wt% NaCl, 0.1wt% CaCl2, 0.0750.9wt% NaHCO3), 8h humid heat (49±2°C, 100%RH), 8h drying (60±2°C, <30%RH), a total of 26 cycles.

[0105] The evaluation results are listed in Table 1.

[0106] Table 1

[0107] No. Source of copper element in surface treatment layer of aluminum-silicon plated hot-formed steel sheet Total time required for complete austenitization / min Heating time / min Area fraction of aluminum-silicon alloy phase on surface of aluminum alloy metallographic plating layer / % Whether there is protection of sacrificial anode Zirconium film adhesion amount (mg / m 2 )]> Paint peeling width (mm) Whether there is red rust in scratch area Phosphating film coverage / % Example 1 Copper metal 1.5 1.5 100 Yes 20 2.5 No 100 Example 2 Copper acetate 2.0 2.0 80 Yes 30 2.5 No 100 Example 3 Copper acetate 2.5 2.5 60 Yes 18 2.0 No 100 Example 4 Copper citrate 3.0 3.0 40 Yes 35 2.5 No 100 Example 5 Copper acetate 5.0 5.0 20 Yes 19 2.5 No 95 Comparative Example 1 / 2.5 2.5 0 No 5 3.5 Yes 0 Comparative Example 2 / 3.5 3.5 0 No 2 4.5 Yes 0 Comparative Example 3 / 4.5 4.5 0 No 5 4.5 Yes 1 Comparative Example 4 / 5.0 5.0 0 No 3 4.0 Yes 0 Comparative Example 5 / 8.0 8.0 0 No 1 5.0 Yes 0 Comparative Example 6 / 8.0 6.0 10 No 4 9.0 Yes 5

[0108] As can be seen from the results in Table 1, the total austenitizing time of the examples is significantly shortened compared with the comparative examples, and the total heating time is shortened by 1-3 min. The pretreatment performance of the examples is significantly improved compared with the comparative examples, and the pretreatment film weight is higher, and the corrosion resistance after electrophoretic coating is excellent.

[0109] Coating structure and sacrificial anode protection: Since the area ratio of the aluminum-silicon alloy phase on the surface of the aluminum alloy phase coating of the examples is greater than 20%, the examples all have the effect of sacrificial anode protection, while the aluminum alloy phase coating surface of the comparative examples is Fe2Al5 (comparative examples 1-5) or a small amount of AlSi alloy phase (comparative example 6), without the effect of sacrificial anode protection.

[0110] Coating performance: Compared with comparative examples 1-6, the examples can significantly improve the zirconium film weight and improve the paint peeling width, and no red rust is generated at the scratch position. Since the total heating time of comparative example 6 is short, the total austenitizing time is not reached, and thus the substrate is not fully austenitized, and the surface of the aluminum-silicon coating hot-formed steel plate part obtained has an aluminum-silicon alloy phase with a reserved area ratio of 10%, but the paint corrosion resistance after coating is significantly reduced, and red rust is generated in the scratch area.

[0111] Test Example 2

[0112] Comparative examples 7-9 were heated and hot-stamped according to the method of test example 1 to obtain aluminum-silicon coating hot-formed steel plate parts. The appearance quality of the aluminum-silicon coating hot-formed steel plate parts of comparative examples 1, 2 and 4 and comparative examples 7-9 is shown in Table 2.

[0113] Table 2

[0114] No. Source of copper element in surface heat treatment layer Appearance quality of parts after treatment Example 1 Copper metal Uniform appearance, yellow-red Example 2 Copper acetate Uniform appearance, dark green Example 4 Copper citrate Uniform appearance, dark green Comparative Example 7 Copper sulfate Non-uniform, large area of black spots Comparative Example 8 Copper nitrate Non-uniform, large area of black spots Comparative Example 9 Copper chloride Non-uniform, large area of black spots

[0115] As can be seen from Table 2, the surface appearance quality of the aluminum-silicon coating hot-formed steel plate parts obtained by the present application is good, while the steel plate surface coating is severely corroded after using copper sulfate, copper nitrate and copper chloride in the comparative examples, resulting in poor surface quality and a large number of unevenly distributed black spots.

[0116] It should be understood that parts not described in detail in the specification are all prior art.

[0117] The above describes the preferred embodiments of the present application, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including combining various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. An aluminum-silicon plated hot-formed steel part having sacrificial anode protection and excellent paintability, characterized in that, The aluminum-silicon plated hot-formed steel part is obtained by hot forming an aluminum-silicon plated hot-formed steel plate. The aluminum-silicon plated hot-formed steel plate comprises a steel substrate, and an aluminum alloy plated layer plated on at least one surface of the steel substrate, and a surface treatment layer coated on the surface of the aluminum alloy plated layer. The aluminum alloy plated layer contains 8%≤Si≤12%, Fe≤3%, and the rest is aluminum and inevitable impurities. The surface treatment layer contains copper element. The copper element in the surface treatment layer is derived from one or more than two of copper, copper oxide, copper hydroxide, copper acetate and copper citrate. The aluminum-silicon plated hot-formed steel part comprises a steel substrate, and an aluminum alloy metallurgical plated layer plated on at least one surface of the steel substrate, and a surface heat treatment layer coated on the surface of the aluminum alloy metallurgical plated layer. The aluminum alloy metallurgical plated layer comprises an aluminum-silicon alloy phase located on the side close to the surface heat treatment layer, and the area fraction of the aluminum-silicon alloy phase on the surface of the aluminum alloy metallurgical plated layer is ≥20%. The content of Fe in the aluminum-silicon alloy phase is less than 5wt%.

2. The aluminum-silicon clad hot-formed steel part according to claim 1, characterized in that, The aluminum alloy metallurgical plated layer comprises, in sequence from the direction away from the steel substrate, a mutual diffusion layer, a first iron-aluminum-silicon ternary alloy phase and a surface layer; and the surface layer contains an aluminum-silicon alloy phase.

3. The aluminum-silicon clad hot-formed steel sheet part according to claim 1, characterized in that, The aluminum alloy metallurgical plated layer comprises, in sequence from the direction away from the steel substrate, a mutual diffusion layer, a first iron-aluminum alloy phase, a first iron-aluminum-silicon ternary alloy phase, a second iron-aluminum alloy phase and a surface layer; and the surface layer contains an aluminum-silicon alloy phase and a second iron-aluminum-silicon ternary alloy phase.

4. The aluminum-silicon clad hot-formed steel sheet part according to claim 3, characterized in that, The content of Fe in the mutual diffusion layer is greater than 60wt%. The content of Fe in the first iron-aluminum alloy phase is greater than 40wt% and less than 75wt%. The content of Fe in the first iron-aluminum-silicon ternary alloy phase is greater than 25wt% and less than 68wt%.

5. The aluminum-silicon clad hot-formed steel sheet part according to claim 4, characterized in that, The content of Fe in the second iron-aluminum alloy phase is greater than 40wt% and less than 75wt%. The content of Fe in the second iron-aluminum-silicon ternary alloy phase is greater than 25wt% and less than 70wt%.

6. Method for the production of an aluminium-silicon-coated hot-formed steel part according to any one of claims 1 to 5, characterized in that The method comprises: heating and hot stamping the aluminum-silicon plated hot-formed steel plate to obtain the aluminum-silicon plated hot-formed steel part.

7. The preparation method according to claim 6, characterized in that, The heating temperature is 840-1100℃.

8. The production method according to claim 6 or 7, characterized by, When the thickness of the aluminum-silicon plated hot-formed steel plate is >1.4mm, the heating time is 3-5min; When the thickness of the aluminum-silicon plated hot-formed steel plate is ≤1.4mm, the heating time is 1-3min.

9. The preparation method according to claim 6, characterized in that, The hot stamping conditions comprise: temperature 500-700℃, and pressure holding time 5-40s.

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