Aluminum coating hot-formed steel plate with high heating efficiency and paint adhesive force and manufacturing method and application of aluminum coating hot-formed steel plate

Abstract

The invention provides an aluminum coating hot-formed steel plate with high heating efficiency and paint adhesion and a manufacturing method and application thereof, and belongs to the field of aluminum coating hot-formed steel plate production. Compared with the prior art, a lithium manganate surface treatment layer is applied to the surface of an aluminum coating, so that the heat absorption efficiency of aluminized hot-formed steel is improved, and the service life of the aluminized hot-formed steel plate is prolonged. And meanwhile, the coating performance after hot forming is remarkably improved, and the coating has excellent after-painting adhesive force and corrosion resistance.

Description

Technical Field

[0001] The present invention belongs to the field of production of aluminum-coated hot-formed steel plates, and in particular relates to an aluminum-coated hot-formed steel plate with high heating efficiency and paint adhesion, a manufacturing method and an application thereof. Background Art

[0002] Due to the demand for lightweight and corrosion-resistant properties, automotive parts utilize a large number of high-strength coated hot-formed steels. Among these coated hot-formed steels, aluminum-silicon-coated hot-formed steel sheets are the most widely used. In the production of hot-formed steel sheets, minimizing the heating time in the furnace is desirable for both production efficiency and energy conservation and emission reduction. However, the aluminum-silicon coating exhibits high reflectivity during heating, which reduces heating efficiency.

[0003] Furthermore, auto body parts require phosphating to form a phosphate film to ensure adhesion between the paint and the substrate. However, aluminum-silicon-coated hot-formed steel is difficult to form a film on after hot forming. Current practices require sufficient heating during the heating process to create a rough, alloyed phase structure in the coating, thereby ensuring paint adhesion and corrosion resistance. Therefore, sufficient heating, increasing the heating temperature and duration, is necessary to ensure product adhesion and corrosion resistance, but this inevitably leads to low heating efficiency.

[0004] Among the existing technologies for improving the coating performance of aluminum-silicon coatings, the patent with publication number CN107250414 A published on October 13, 2017, discloses a method for producing phosphate-capable parts from plates coated with an aluminum-based coating and a zinc coating. The technical solution disclosed therein is: a steel plate coated with an aluminum-based coating and also including a second zinc coating has the effect of improving phosphate surface treatment. However, the heating time at 900°C disclosed in the embodiment thereof exceeds 5 minutes, which does not solve the problem of low heating efficiency.

[0005] In summary, due to the contradiction between sufficient heating to ensure phosphating performance, improving adhesion, and improving heating efficiency, there is currently a lack of technical solutions to simultaneously improve the heating efficiency and paint adhesion of aluminum-silicon coated hot-formed steel. Summary of the Invention

[0006] The object of the present invention is to provide an aluminum-coated hot-formed steel plate with high heating efficiency and paint adhesion and a manufacturing method. By applying a surface treatment layer on the surface of the aluminum coating, spinel-type lithium manganese oxide is formed during hot forming, thereby improving the heating efficiency and reducing the hot forming heating time; at the same time, the present invention significantly improves the painting performance after hot forming, and has excellent post-paint adhesion and corrosion resistance.

[0007] Another object of the present invention is to provide an application of an aluminum-coated hot-formed steel sheet with high heating efficiency and paint adhesion for use in the manufacture of automobile parts.

[0008] The specific technical solutions of the present invention are as follows: An aluminum-coated hot-formed steel plate with high heating efficiency and paint adhesion, comprising a steel substrate, an aluminum alloy coating and a surface treatment layer; The surface treatment layer contains Li, Mn, and O, with a molar ratio of Li to Mn of 0.45-0.55:1. This ratio allows for the formation of spinel lithium manganese oxide during hot forming, improving heating efficiency. When Li:Mn is less than 0.45, a large amount of Mn will appear as yellow, rust-like Mn3O4 after hot pressing, which is unacceptable to the automotive industry. When Li:Mn is greater than 0.55, a large amount of ineffective Li will be present, increasing costs.

[0009] Preferably, the composition of the surface treatment layer includes lithium manganate; The surface treatment layer may be doped with one or more cationic doping elements to enhance the high temperature stability of lithium manganate, including metal elements such as Al, Mg, Fe, Co, Cr, etc., but preferably these elements are not particularly doped.

[0010] The surface treatment layer has a Li content of 0.01-0.50 g / m 2 Weight, less than 0.01g / m 2 The ability to improve heating efficiency is insufficient, higher than 0.50g / m 2 The heating efficiency cannot be further improved, and the cost is preferably lower than 0.50g / m 2 .

[0011] The steel substrate of the aluminum-coated hot-formed steel plate with high heating efficiency and paint adhesion has an aluminum alloy coating and a surface treatment layer on at least one surface; The composition of the aluminum alloy coating includes: 8-12% Si, up to 2% Fe, and the rest is aluminum and inevitable impurities; The weight of each single side of the aluminum alloy coating is 20-80 g / m 2 ; The steel substrate can be selected from a substrate that can be used to prepare an aluminum-coated hot-formed steel plate. For example, the steel substrate can be a 22MnB5 steel plate, and the 22MnB5 steel plate includes the following components in mass percentage: 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%, and the balance is iron and unavoidable impurities from steel manufacturing.

[0012] Furthermore, the surface treatment layer is provided with an anti-rust oil layer; The aluminum-coated hot-formed steel plate with high heating efficiency and paint adhesion has an aluminum alloy coating and a surface treatment layer on the steel substrate in sequence.

[0013] Alternatively, the aluminum-coated hot-formed steel plate with high heating efficiency and paint adhesion comprises an aluminum alloy coating, a surface treatment layer and an anti-rust oil layer on a steel substrate in sequence.

[0014] The present invention provides a method for manufacturing an aluminum-coated hot-formed steel plate with high heating efficiency and paint adhesion, which specifically comprises: applying a coating containing a manganese source and a lithium source to the aluminum alloy-coated steel plate, and heating and drying.

[0015] Furthermore, a degreasing step is performed before coating to remove surface contaminants.

[0016] Furthermore, a water washing step is provided after degreasing to prevent the degreasing solution from remaining on the surface.

[0017] Furthermore, after washing, drying is performed and then coating is performed.

[0018] The coating containing the manganese source and the lithium source is prepared by dispersing the manganese source and the lithium source in a solvent to obtain the coating; The solvent of the coating containing manganese source and lithium source is water, ethanol, acetone, butyl ether or N-methyl-2-pyrrolidone; In the coating containing a manganese source and a lithium source, the molar ratio of the lithium source to the manganese source is 0.45-0.55:1; The total mass concentration of the manganese source and the lithium source in the coating is 40-50 g / L; The manganese source and the lithium source may be derived from the same raw material or different raw materials; if derived from the same raw material, the manganese source and the lithium source are both lithium manganate; if derived from different raw materials, the manganese source is manganese acetate, and the lithium source is selected from lithium carbonate or lithium acetate; Furthermore, the coating containing the manganese source and the lithium source also contains a binder to enhance the adhesion of the coating to the coating and prevent the coating from falling off before hot pressing. The type of the binder is not particularly limited. Examples of conventional implementations include polyvinyl pyrrolidone, polyacrylic resin, polyurethane, hydroxypropyl methylcellulose, silane or polyvinylidene fluoride.

[0019] If a binder is present, the concentration of the binder in the coating is 5-20 g / L; The aluminum alloy coated steel plate is obtained by hot dip plating. The specific method is as follows: the steel substrate is hot dipped in a hot rolled or annealed state to obtain the aluminum alloy coated steel plate. For example, a hot-based aluminum alloy coated steel plate is obtained by hot rolling → pickling → hot dip plating → leveling; or, for example, an aluminum alloy coated steel plate is obtained by hot rolling → pickling → cold rolling → cleaning → annealing → hot dip plating → leveling. The aluminum alloy coating in the obtained aluminum alloy coated steel plate includes the following components in mass percentage: 8-12% Si, up to 2% Fe, and the rest is aluminum and unavoidable impurities. The aluminum alloy coated steel plate can be prepared according to conventional methods.

[0020] In the aluminum alloy coating, Si forms a Fe-Al-Si inhibition layer on the steel sheet surface, effectively hindering the formation of the brittle Fe2Al5 phase and improving coating adhesion. When the Si content is less than 8%, the Fe-Al alloy layer becomes thicker, reducing coating adhesion. When the Si content exceeds 12.0%, the coating surface quality is affected. Based on the above considerations, the Si content in the coating of the present invention is controlled to be between 8.0 and 12.0%.

[0021] The heating and drying process described in the manufacturing method of the aluminum-coated hot-formed steel plate with high heating efficiency and paint adhesion is performed at a temperature of 80-300°C and a drying time of 5-120s. After drying, lithium manganese oxide or its precursor is formed, and the precursor can be further heated to form lithium manganese oxide during the hot stamping process.

[0022] The invention provides an application of an aluminum-coated hot-formed steel plate with high heating efficiency and paint adhesion, which is used in the manufacture of automobile parts.

[0023] The specific application method is: after the aluminum-coated hot-formed steel plate with high heating efficiency and paint adhesion is made into a blank, it is heated, kept warm, and then hot stamped.

[0024] The use of the coated steel plate containing the surface treatment layer of the present invention can significantly improve the heating efficiency. As a common hot stamping process, the steel plate is cut to obtain a blank, the blank is heated to 840°C-1100°C, kept warm, and then the blank is transferred to a hot stamping tool for hot stamping.

[0025] The heating rate is ≥5°C / s; When the blank thickness is ≥1.4mm, the total heating and holding time is 3-5 minutes; when the blank thickness is <1.4mm, the total heating and holding time is 1-3 minutes, preferably ≤2.5 minutes. Due to the presence of the surface treatment layer, the sheet metal's heat absorption efficiency is improved, and the time required to heat up to the austenitizing temperature is shortened. This heating process shortens the heating time by more than 1 minute compared to conventional hot forming processes.

[0026] Furthermore, the heated and heat-insulated blank is transferred to a hot stamping tool, and hot stamping is performed on the blank at a temperature of 500° C. to 700° C.

[0027] Furthermore, after hot stamping, the obtained component is cooled in the tool itself or after being transferred to a special cooling tool.

[0028] The aluminum-coated hot-formed steel sheet produced by the present invention exhibits excellent coating properties, eliminating the need for specialized hot-forming process control. The lithium manganate in the present invention is a dark gray material with excellent heat absorption, which improves heating efficiency. Furthermore, the surface lithium manganate dissolves during the coating process. In a phosphate environment, the manganate ions react with phosphoric acid to form a phosphate film, enhancing the bond with paint. This results in excellent paint adhesion and corrosion resistance after painting. Compared to existing technologies, the present invention improves the heat absorption efficiency of the aluminum-coated hot-formed steel by applying a surface treatment layer to the aluminum coating, reducing hot-forming heating time. Furthermore, the present invention significantly improves the coating properties after hot-forming, resulting in excellent post-paint corrosion resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the structural changes of aluminum-coated hot-formed steel plates with high heating efficiency and paint adhesion. DETAILED DESCRIPTION

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0031] The steel substrates used in Examples 1 to 5 below are the same as those in Comparative Examples 1 to 5, and include the following compositions by mass: 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%, and Mo 0.0017%, with the remainder being iron and unavoidable impurities obtained during steel production.

[0032] The steel sheets of the above embodiments and comparative examples were hot-dip plated in a hot-rolled or annealed state to obtain aluminum alloy-coated steel sheets. For example, a hot-dip aluminum alloy-coated steel sheet was obtained by hot rolling, pickling, hot-dip plating, and smoothing. Another example was a hot-dip aluminum alloy-coated steel sheet obtained by hot rolling, pickling, cold rolling, cleaning, annealing, hot-dip plating, and smoothing. Conventional methods can be used for preparation. The aluminum alloy-coated steel prepared contains 8.0-12.0% by mass of Si, up to 2% by mass of Fe, with the remainder being aluminum and unavoidable impurities.

[0033] The following is a detailed description of the methods for obtaining the coatings in each embodiment and comparative example.

[0034] Example 1

[0035] A method for manufacturing an aluminum-coated hot-formed steel plate with high heating efficiency and paint adhesion comprises the following steps: 1) First, aluminum alloy-coated steel sheets were prepared using the steel substrates described above. The process involved hot rolling, pickling, cold rolling, cleaning, annealing, hot-dip plating, and smoothing. After completing these steps, the aluminum alloy coating contained 8.0% by mass of Si, 2.0% by mass of Fe, and the remainder was aluminum and unavoidable impurities. The sheet was 1.2 mm thick, with the coating applied to both sides with equal thickness, and the coating weight per side was 75 g / m². 2 ; 2) A surface coating containing a manganese source and a lithium source is then prepared. The coating comprises the following raw materials in parts by weight: Lithium manganate: 40 parts Solvent N-methyl-2-pyrrolidone: 50 parts Polyvinyl pyrrolidone (K90): 10 parts.

[0036] The above raw materials were mixed to obtain a coating containing a manganese source and a lithium source. The coating was applied to the surface of the aluminum alloy coated steel plate and heated and dried at 150°C for 80 seconds. The specific coating thickness was controlled according to the Li content of the surface treatment layer in Table 1.

[0037] 3) Apply anti-rust oil on the surface treatment layer, use Quaker Ferrocoat N 6130 anti-rust oil 1.5g / m 2 The purpose of applying anti-rust oil is to temporarily prevent rust and prevent the coating from being scratched during blanking. Since it decomposes during hot forming, the amount of anti-rust oil applied does not affect the effect of the present invention.

[0038] Example 2

[0039] A method for manufacturing an aluminum-coated hot-formed steel plate with high heating efficiency and paint adhesion comprises the following steps: 1) First, aluminum alloy-coated steel sheets were prepared using the steel substrates described above. The aluminum alloy-coated steel sheets were obtained by hot rolling, pickling, hot-dip plating, and smoothing. After completing these steps, the aluminum alloy coating contained 9.0% Si by mass, 1.0% Fe by mass, and the remainder was aluminum and unavoidable impurities. The sheet thickness was 1.2 mm, and the coating was applied to both sides with equal thickness. The coating weight per side was 60 g / m². 2 .

[0040] Step 2) and step 3) are the same as in Example 1.

[0041] Example 3

[0042] A method for manufacturing an aluminum-coated hot-formed steel plate with high heating efficiency and paint adhesion comprises the following steps: First, aluminum alloy-coated steel sheets are prepared using the steel substrates with the above composition. The process is as follows: hot rolling → pickling → cold rolling → cleaning → annealing → hot dip plating → flattening to obtain aluminum alloy-coated steel sheets. After completing the above steps, the aluminum alloy coating contains 10.0% by mass of Si, 1.5% by mass of Fe, and the remainder is aluminum and unavoidable impurities. The plate thickness is 1.4mm, and the coating is applied to both sides with equal thickness. The coating weight on each side is 60g / m 2 .

[0043] 2) Then, a surface coating containing a manganese source and a lithium source is prepared. The coating comprises the following components: Lithium carbonate: 1 mol / L Manganese acetate: 2 mol / L Hydroxypropyl methylcellulose (viscosity 200,000): 20g / L The solvent is water.

[0044] The above raw materials were mixed to obtain a coating containing a manganese source and a lithium source. The coating was applied to the surface of the aluminum alloy coated steel plate and heated and dried at 150°C for 80 seconds. The specific coating thickness was controlled according to the Li content of the surface treatment layer in Table 1.

[0045] 3) Apply anti-rust oil on the surface treatment layer, use Quaker Ferrocoat N 6130 anti-rust oil 1.5g / m 2 .

[0046] Example 4

[0047] A method for manufacturing an aluminum-coated hot-formed steel plate with high heating efficiency and paint adhesion comprises the following steps: 1) First, aluminum alloy-coated steel sheets were prepared using the steel substrates described above. The process involved hot rolling, pickling, cold rolling, cleaning, annealing, hot-dip plating, and smoothing. After these steps, the aluminum alloy coating contained 12% Si by mass, 2.0% Fe by mass, and the remainder was aluminum and unavoidable impurities. The sheet was 1.6 mm thick, with the coating applied to both sides with equal thickness, and the coating weight per side was 75 g / m². 2 .

[0048] Step 2) and step 3) are the same as in Example 3.

[0049] Example 5

[0050] A method for manufacturing an aluminum-coated hot-formed steel plate with high heating efficiency and paint adhesion comprises the following steps: 1) First, aluminum alloy-coated steel sheets were prepared using the steel substrates described above. The process was as follows: hot rolling → pickling → cold rolling → cleaning → annealing → hot-dip plating → flattening. After completing these steps, the aluminum alloy coating contained 10% by mass of Si, 1.5% by mass of Fe, and the remainder was aluminum and unavoidable impurities. The sheet was 2.0 mm thick, with the coating applied to both sides with equal thickness, and the coating weight per side was 75 g / m². 2 .

[0051] 2) Then, a surface coating containing a manganese source and a lithium source is prepared. The coating comprises the following components: Lithium carbonate: 1 mol / L Manganese acetate: 2.22 mol / L Hydroxypropyl methylcellulose (viscosity 200,000): 20g / L The solvent is water.

[0052] The above raw materials were mixed to obtain a coating containing a manganese source and a lithium source. The coating was applied to the surface of the aluminum alloy coated steel plate and heated and dried at 150°C for 90 seconds. The specific coating thickness was controlled according to the Li content of the surface treatment layer in Table 1.

[0053] 3) Step 3) is the same as in Example 3.

[0054] Comparative Example 1

[0055] A method for manufacturing an aluminum-coated hot-formed steel plate comprises the following steps: 1) Prepared according to the same method as step 1) of Example 1; 2) No surface coating is prepared and no surface coating is performed; 3) Proceed as in step 3) of Example 1, except that the rust-proof oil is applied on the aluminum alloy coating.

[0056] Comparative Example 2

[0057] A method for manufacturing an aluminum-coated hot-formed steel plate comprises the following steps: 1) Prepared according to the same method as step 1) of Example 2; 2) Then prepare the coating, which includes the following components: Lithium carbonate: 1 mol / L Manganese acetate: 2.5 mol / L Hydroxypropyl methylcellulose (viscosity 200,000): 20g / L The solvent is water.

[0058] The above raw materials are mixed to obtain a coating containing a manganese source and a lithium source, and the coating is applied to the surface of the aluminum alloy coated steel plate, and heated and dried at 150°C; 3) Proceed according to step 3) of Example 2.

[0059] Comparative Example 3

[0060] A method for manufacturing an aluminum-coated hot-formed steel plate comprises the following steps: 1) Prepared according to the same method as step 1) of Example 3; 2) Then prepare the coating, which includes the following components: Manganese acetate: 2.0 mol / L Hydroxypropyl methylcellulose (viscosity 200,000): 20g / L The solvent is water.

[0061] The above raw materials are mixed to obtain a coating containing a manganese source and a lithium source, and the coating is applied to the surface of the aluminum alloy coated steel plate, and heated and dried at 150°C; 3) Proceed according to step 3) of Example 3.

[0062] Comparative Example 4

[0063] A method for manufacturing an aluminum-coated hot-formed steel plate comprises the following steps: 1) Prepared according to the same method as step 1) of Example 4; 2) Then prepare the coating, which includes the following components: Lithium carbonate: 1 mol / L Hydroxypropyl methylcellulose (viscosity 200,000): 20g / L The solvent is water.

[0064] The above raw materials are mixed to obtain a coating containing a manganese source and a lithium source, and the coating is applied to the surface of the aluminum alloy coated steel plate, and heated and dried at 150°C; 3) Proceed according to step 3) of Example 4.

[0065] Comparative Example 5

[0066] A method for manufacturing an aluminum-coated hot-formed steel plate comprises the following steps: 1) Prepared according to the same method as step 1) of Example 5; 2) Carry out coating according to step 2) of Example 5, and control the Li content to 5 mg / m 2 ; 3) Proceed as in step 3) of Example 5, except that the rust-proof oil is applied on the aluminum alloy coating.

[0067] The performance of the steel plates of each embodiment and comparative example was evaluated according to the following methods: Determination of the time / s required to heat from 20°C to 900°C and the heating rate: Place the cut sheet in a 900°C box furnace, use a thermocouple to measure the time required to heat to 900°C, and calculate the heating rate.

[0068] Total heating time: The cut sheet was placed in a 900 °C box furnace, starting from 1 min and extending for 30 s in sequence, and then cooled in a flat die. A 10 mm × 10 mm × plate thickness sample cut from the experimental steel after die quenching was ground, mechanically polished and picric acid etched. The original austenite grain size was observed and measured under an optical microscope to observe the martensite structure. The heating time for complete formation of martensite was taken as the total heating time.

[0069] The test panels used to evaluate the following properties were heated at 930°C for 1.5-8.0 min and then cooled in a flat mold. The specific heating times are listed in Table 1.

[0070] Phosphate pretreatment performance evaluation: A two-component automotive degreaser (FC-L5000A (40 g / L) / FC-E2021SB (16 g / L)) from Shanghai Parker Seikyo Co., Ltd. was used. The degreasing solution was heated to 50°C. The steel plates were immersed in the degreasing solution for 2 minutes, then removed and rinsed with deionized water. Following degreasing, the steel plates were then immersed in 2 g / L PL-X surface conditioner for 30 seconds. Phosphate treatment was then performed in PB-L3035SM phosphating agent (Shanghai Parker Seikyo Co., Ltd.) at 35°C, with a free acidity (FA) of 0.9 parts per billion, a total acidity (TA) of 20.0 parts per billion, and an accelerator concentration (AC) of 3.0 parts per billion for 2 minutes. After pretreatment, the steel plates were rinsed and air-dried. Phosphate film coverage was observed using a scanning electron microscope.

[0071] Corrosion resistance evaluation after coating: After pretreatment, electrophoresis coating was performed using an optimized process to achieve a dry film thickness of 20±2μm. The electrophoretic paint used was Hunan Xiangjiang Guanxi Paint HT8000C. After electrophoresis, a scratch corrosion test was performed. The paint was scratched with a scratch knife and then placed in a corrosive environment for 26 days. After testing, the paint was removed, loose rust removed, and the scratched area was peeled off with tape. The width of the paint peeled off was used as the evaluation indicator. The cyclic corrosion test method consisted of 8 hours of room temperature (25±3°C, during which time four 3-minute sprays of a salt solution were applied. The salt solution composition was: 0.9wt% NaCl, 0.1wt% CaCl2, 0.0750.9wt% NaHCO3), 8 hours of damp heat (49±2°C, 100% RH), and 8 hours of drying (60±2°C, <30% RH), for a total of 26 cycles.

[0072] The surface treatment methods and evaluation results of each embodiment and comparative example are listed in Table 1.

[0073]

[0074] like Figure 1 , which is a schematic diagram of the structural changes of aluminum-coated hot-formed steel plates with high heating efficiency and paint adhesion. In the present invention, the steel substrate is coated with an aluminum alloy coating, and a lithium manganese oxide coating is coated on the aluminum alloy coating. It can also be a precursor coating that can form lithium manganese oxide (i.e., a coating containing a manganese source and a lithium source). After hot pressing, a lithium manganese oxide surface treatment layer is formed.

[0075] Evaluation results: Compared to Comparative Example 1, which does not undergo surface treatment, Example 1 significantly shortens the 20-900°C heating time, increasing the heating rate by over 40%. The total heating time is shortened by 1 minute. Furthermore, compared to Comparative Example 1, Example 1 exhibits significantly improved pre-coating performance, significantly increased phosphate film coverage, and superior corrosion resistance after electrophoretic coating.

[0076] The Li / Mn ratio of Comparative Example 2 is lower than 0.45. Although it also improves the heating efficiency and the phosphate film, the effect is not as good as that of Example 2, and the yellow appearance is similar to rust and is unacceptable.

[0077] Comparative Example 3 uses a single Mn salt for coating. Compared with Example 3, the heating rate is significantly reduced, the coverage of the phosphate film is slightly reduced, and yellow Mn3O4 is formed, which is similar to the appearance of rust and is unacceptable.

[0078] Comparative Example 4 uses a single Li salt for coating. Compared with Example 4, the heating rate, phosphate film coverage, and corrosion resistance after coating are significantly reduced.

[0079] The Li deposition amount of Comparative Example 5 is 5 mg / m 2Compared with Example 5, the heating rate, phosphate film coverage and corrosion resistance after coating are significantly reduced.

[0080] The above embodiments are described to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. An aluminum-coated hot-formed steel plate with high heating efficiency and paint adhesion, characterized in that: The aluminum-coated hot-formed steel plate with high heating efficiency and paint adhesion comprises a steel substrate, an aluminum alloy coating and a surface treatment layer; The surface treatment layer contains Li, Mn and O elements, and the molar ratio of Li to Mn is 0.45-0.55:1; the surface treatment layer has a Li content of 0.01-0.50 g / m 2 weight.

2. The aluminum-coated hot-formed steel sheet with high heating efficiency and paint adhesion according to claim 1, characterized in that: The surface treatment layer comprises lithium manganate.

3. The aluminum-coated hot-formed steel sheet with high heating efficiency and paint adhesion according to claim 1 or 2, characterized in that: The composition of the aluminum alloy coating includes: 8-12% Si, up to 2% Fe, and the rest being aluminum and inevitable impurities.

4. The aluminum-coated hot-formed steel sheet with high heating efficiency and paint adhesion according to claim 1 or 2, characterized in that: The steel substrate of the aluminum-coated hot-formed steel plate with high heating efficiency and paint adhesion has an aluminum alloy coating and a surface treatment layer on at least one surface.

5. A method for manufacturing the aluminum-coated hot-formed steel sheet with high heating efficiency and paint adhesion according to any one of claims 1 to 4, characterized in that: The manufacturing method comprises the following steps: coating a coating containing a manganese source and a lithium source on an aluminum alloy coated steel plate, heating and drying the coating, wherein the drying temperature is 80-300° C. and the drying time is 5-120 seconds.

6. A method for manufacturing the aluminum-coated hot-formed steel sheet with high heating efficiency and paint adhesion as claimed in claim 5, characterized in that: The coating containing the manganese source and the lithium source also contains a binder, and the concentration of the binder in the coating is 5-20 g / L.

7. An application of the aluminum-coated hot-formed steel sheet with high heating efficiency and paint adhesion according to any one of claims 1 to 6, characterized in that: Used in automobile parts manufacturing.

8. The use according to claim 7, characterized in that The application method is as follows: after the aluminum-coated hot-formed steel plate with high heating efficiency and paint adhesion is made into a blank, it is heated, kept warm, and then hot stamped.

9. The use according to claim 8, characterized in that The heating has a heating rate of ≥5°C / s.

10. The use according to claim 8 or 9, characterized in that: When the thickness of the blank is ≥1.4mm, the total heating and holding time is 3-5min; when the thickness of the blank is <1.4mm, the total heating and holding time is 1-3min.

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