Method for preparing hot-formed part

Abstract

A method for preparing a hot-formed part, comprising: providing a bare sheet blank, and preheating the bare sheet blank; providing a high-temperature-resistant lubricating coating on the surface of the bare sheet blank, wherein the high-temperature-resistant lubricating coating comprises hexagonal boron nitride and graphite; and hot stamping the bare sheet blank having the high-temperature-resistant lubricating coating to form a hot stamped part, removing the high-temperature-resistant lubricating coating on the surface of the hot stamped part after the hot stamped part is formed, and sequentially performing electroplating and electrophoresis treatment on the hot stamped part from which the high-temperature-resistant lubricating coating has been removed. By providing the high-temperature-resistant lubricating coating comprising hexagonal boron nitride and graphite on the surface before hot stamping the bare sheet blank, the heating rate is high, and the hot stamped part is not prone to deformation.

Description

A method for preparing a thermoformed part

[0001] Cross-reference related citations

[0002] This application claims priority to Chinese Patent Application No. 202411807246X, filed on December 10, 2024, entitled “A Method for Preparing a Thermoformed Part”, which is incorporated herein by reference. Technical Field

[0003] This invention relates to a hot stamping method, and more particularly to a method for preparing thermoformed parts. Background Technology

[0004] The description in this section provides only background information related to the disclosure of this invention and does not constitute prior art.

[0005] Hot stamping of bare sheet metal is a common method for preparing thermoformed parts in the hot stamping field. However, bare sheet metal blanks are prone to oxide scale formation. Furthermore, during the hot stamping process, the stretching deformation of the bare sheet metal blank makes it susceptible to scratching against the die on the steel substrate, forming burrs. These burrs and oxide scale can cause severe tearing of the bare sheet metal blank, especially on the sidewalls and radius corners. Simultaneously, the raised burrs generated at the tearing sites can affect the thickness of the electrophoretic coating on the hot-stamped parts, leading to incomplete electrophoresis or a thinner electrophoretic layer, thereby affecting the corrosion resistance of the hot-stamped parts.

[0006] Patent CN114790561A discloses a method for preparing hot-stamped parts, which involves spraying hexagonal boron nitride onto a bare blank and then hot-stamping it, effectively solving the problem of roughening in hot-stamped parts. However, hexagonal boron nitride is white in color and has a thermal conductivity of 56.94 W / (m·K). It has high reflectivity at high temperatures and a slow heating rate, resulting in slow heat transfer with the mold during the hot-stamping process, which can easily lead to dimensional deformation of the hot-stamped parts. Other existing technologies use graphite as an auxiliary coating, but graphite's thermal conductivity is generally 150-300 W / (m·K), more than three times that of hexagonal boron nitride, and its black color makes it prone to absorbing high-temperature radiation and flammability, making it still not an ideal coating material.

[0007] It should be noted that the above description of the technical background is only for the purpose of providing a clear and complete explanation of the technical solutions of the present invention and facilitating understanding by those skilled in the art. It should not be assumed that the above technical solutions are known to those skilled in the art simply because they have been described in the background section of this invention. Summary of the Invention

[0008] The purpose of this invention is to provide a method for preparing thermoformed parts, which can be achieved by applying a high-temperature resistant lubricating coating consisting of hexagonal boron nitride and graphite to the surface of the bare blank before hot stamping, resulting in a high heating rate and making the hot-stamped parts less prone to deformation.

[0009] To achieve the above objectives, the present invention discloses a method for preparing a thermoformed part, the method comprising:

[0010] Provide bare slab blanks and preheat the bare slab blanks;

[0011] A high-temperature resistant lubricating coating is provided on the surface of the bare plate blank, the high-temperature resistant lubricating coating comprising hexagonal boron nitride and graphite;

[0012] The bare plate blank having the high-temperature lubricating coating is hot-stamped to form a hot-stamped part;

[0013] After the hot-stamped part is formed, the high-temperature lubricating coating on the surface of the hot-stamped part is removed;

[0014] The hot-stamped parts, after the high-temperature lubricating coating is removed, are subjected to electroplating and electrophoresis treatments in sequence.

[0015] As a further description of the above technical solution, in the step of "providing bare slab blanks and preheating the bare slab blanks", the preheating temperature for preheating the bare slab blanks is between 100-300℃.

[0016] As a further description of the above technical solution, the high-temperature resistant lubricating coating also includes an anti-flash rust agent and a metal alkali salt.

[0017] As a further description of the above technical solution, in the high-temperature resistant lubricating coating, the content of hexagonal boron nitride and graphite is 10-50 wt%, the content of the anti-flash rust agent is 0.1-5 wt%, the content of the metal alkali salt is 0.1-10 wt%, and the balance of the high-temperature resistant lubricating coating is a solution with a pH value greater than 7.

[0018] As a further description of the above technical solution, the graphite content accounts for 1-80 wt% of the total content of hexagonal boron nitride and graphite.

[0019] As a further description of the above technical solution, in the step of "setting a high-temperature resistant lubricating coating on the surface of the bare plate blank", the thickness of the high-temperature resistant lubricating coating is 1-20 μm, preferably 2-10 μm.

[0020] As a further description of the above technical solution, in the step of "setting a high-temperature resistant lubricating coating on the surface of the bare plate blank", the high-temperature resistant lubricating coating is set by spraying, roller coating or dip coating, preferably by spraying.

[0021] As a further description of the above technical solution, in the step of "setting a high-temperature resistant lubricating coating on the surface of the bare plate blank", the area where the high-temperature resistant lubricating coating is set on the surface of the bare plate blank can be the entire surface of the bare plate blank, or only a local scratch on the surface of the bare plate blank.

[0022] As a further description of the above technical solution, in the process of "removing the high-temperature resistant lubricating coating from the surface of the hot-stamped part", the high-temperature resistant lubricating coating on the surface of the hot-stamped part is removed by a five-step process of ultrasonic degreasing, pickling, electrolysis, ultrasonic water washing, and water washing.

[0023] As a further description of the above technical solution, in the process of "removing the high-temperature resistant lubricating coating from the surface of the hot-stamped part", high-pressure water with a pH value greater than 7 is used to remove the high-temperature resistant lubricating coating from the surface of the hot-stamped part.

[0024] As a further description of the above technical solution, in the process of "removing the high-temperature resistant lubricating coating from the surface of the hot-stamped part", the high-temperature resistant lubricating coating on the surface of the hot-stamped part is removed by shot blasting or sandblasting.

[0025] By employing the above technical solutions, the beneficial effects of the present invention are as follows:

[0026] The method for preparing thermoformed parts of the present invention involves applying a high-temperature resistant lubricating coating comprising hexagonal boron nitride and graphite to the surface of a bare blank before hot stamping. The hexagonal boron nitride material reduces surface oxide scale and increases the strength of the blank during stamping, effectively solving the problem of roughening in hot-stamped parts. Furthermore, the combination of graphite and hexagonal boron nitride improves the problems of slow heat absorption at high temperatures and slow heat conduction during hot stamping associated with pure hexagonal boron nitride. The addition of hexagonal boron nitride also addresses the issue of graphite's poor high-temperature resistance and susceptibility to oxidation and combustion; the two components complement each other.

[0027] The method for preparing thermoformed parts of the present invention adds metal alkali salts to the high-temperature lubricating coating, which can prevent the bare blank from rusting after the high-temperature lubricating coating is applied. In addition, gas can be generated in the subsequent acid washing and electrolysis steps when removing the high-temperature lubricating coating, making the high-temperature lubricating coating easier to peel off.

[0028] To further understand the features and technical content of the present invention, please refer to the following detailed description and drawings of the present invention. However, the drawings provided are for reference and illustration only and are not intended to limit the present invention. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments or prior art of this specification, the drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this specification. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 is a flowchart of a method for preparing a thermoformed part provided in an embodiment of this specification;

[0031] Figure 2 shows the processing results of Example 1;

[0032] Figure 3 shows the processing results of Comparative Example 2;

[0033] Figure 4 shows the processing results of Example 3;

[0034] Figure 5 is a diagram showing the processing results of Example 1;

[0035] Figure 6 is a diagram showing the processing results of Example 2;

[0036] Figure 7 is a diagram showing the processing results of Example 3;

[0037] Figure 8 is a metallographic cross-sectional view of Example 1;

[0038] Figure 9 is a metallographic cross-sectional inspection diagram of Example 2;

[0039] Figure 10 is a metallographic cross-sectional view of Example 3;

[0040] Figure 11 is a partial view of the appearance after electroplating;

[0041] Figure 12 shows the appearance after the electrophoretic corrosion test. Detailed Implementation

[0042] To enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this specification, and not all embodiments. Based on the embodiments in this specification, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this specification.

[0043] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can understand the advantages and effects of the present invention from the content disclosed in this specification. The present invention can be implemented or applied through other different specific embodiments, and various details in this specification can also be modified and changed based on different viewpoints and applications without departing from the concept of the present invention. Furthermore, the accompanying drawings of the present invention are for simple illustrative purposes only and are not depictions of actual dimensions; this is stated in advance. The following embodiments will further describe the relevant technical content of the present invention in detail, but the disclosed content is not intended to limit the scope of protection of the present invention.

[0044] It should be understood that while terms such as "first," "second," and "third" may be used in this document to describe various components or signals, these components or signals should not be limited by these terms. These terms are primarily used to distinguish one component from another, or one signal from another. Furthermore, the term "or" as used herein should, as appropriate, include any combination of one or more of the related listed items.

[0045] Please refer to Figure 1 for the flowchart, which illustrates a method for preparing a thermoformed part according to this embodiment. The method for preparing a thermoformed part includes:

[0046] Provide bare slab blanks and preheat them;

[0047] A high-temperature resistant lubricating coating is applied to the surface of the bare plate blank. The high-temperature resistant lubricating coating includes hexagonal boron nitride and graphite.

[0048] The bare sheet metal blank is hot-stamped to form hot-stamped parts, and the high-temperature lubricating coating on the surface of the hot-stamped parts is removed. Then, the hot-stamped parts are electroplated and electrophoretically treated in sequence.

[0049] Using the above method, before hot stamping the bare sheet blank into hot-stamped parts, a high-temperature resistant lubricating coating is first applied to the surface of the bare sheet blank. The coefficient of friction of the hexagonal boron nitride material in the high-temperature resistant lubricating coating can be as low as 0.16 and does not increase at high temperatures, thus having a higher high-temperature resistance than commonly used lubricating coatings such as molybdenum disulfide and graphite. Therefore, it can effectively act as a lubricating medium. This coating is applied to the surface of the bare sheet blank, at least at locations with local scratches, to minimize the formation of oxide scale. At the same time, the graphite in the high-temperature lubricating coating allows a certain mass of graphite to exhibit high thermal conductivity, preventing the thermal conductivity of the high-temperature lubricating coating from being excessively affected by the low thermal conductivity of the hexagonal boron nitride, ultimately solving the problem of slow heat conduction. In other words, in this embodiment, the hexagonal boron nitride and graphite in the high-temperature lubricating coating complement each other, mutually inhibit each other, and produce a better gain effect on the entire hot forming process. This not only compensates for the poor thermal conductivity of hexagonal boron nitride but also avoids the problem of the low ignition point of graphite.

[0050] Specifically, in this embodiment, hexagonal boron nitride and graphite can be mixed in a certain proportion as powder and placed in the raw material of the high-temperature lubricating coating. The raw materials are readily available and easy to process.

[0051] Furthermore, in this embodiment, during the step of "providing bare plate blanks and preheating the bare plate blanks", the preheating temperature for preheating the bare plate blanks is between 100-300°C. By preheating the bare plate blanks, the rust-preventive oil and aqueous solution on the surface of the bare plate blanks can be effectively evaporated, leaving only fixed powder on the surface of the bare plate blanks, which is beneficial for the subsequent application of high-temperature resistant lubricating coatings.

[0052] Furthermore, the high-temperature lubricating coating also includes anti-flash rust agents and metal alkali salts. The inclusion of anti-flash rust agents and metal alkali salts prevents rust formation on the surface of the bare sheet blank during the initial spraying process and before hot stamping. The metal alkali salts also allow for neutralization reactions during electrolysis and pickling, making the high-temperature lubricating coating easier to peel off, thus improving powder removal efficiency and electroplating quality. Specifically, in this embodiment, the metal alkali salt can be one or more of NaOH, KOH, Na2CO3, NaHCO3, K2CO3, and KHCO3, preferably Na2CO3. Na2CO3 releases a large amount of CO2 during pickling, which can loosen the high-temperature lubricating coating and facilitate its removal.

[0053] Furthermore, in the high-temperature resistant lubricating coating, the content of hexagonal boron nitride and graphite is 10-50 wt%, the content of flash rust inhibitor is 0.1-5 wt%, the content of metal alkali salt is 0.1-10 wt%, and the balance of the high-temperature resistant lubricating coating is a solution with a pH value greater than 7. That is to say, in this embodiment, apart from the alkaline solution, hexagonal boron nitride and graphite powder are the main components. Specifically, the graphite content accounts for 1-80 wt% of the total content of hexagonal boron nitride and graphite, which can be set as needed.

[0054] Furthermore, in the step of "setting a high-temperature resistant lubricating coating on the surface of the bare blank", the thickness of the high-temperature resistant lubricating coating is 1-20 μm, preferably 2-10 μm. That is to say, the overall thickness of the high-temperature lubricating coating is relatively thin, so as to avoid affecting the heat conduction effect of the heating and forming process of the bare blank.

[0055] Furthermore, in the step of "setting a high-temperature resistant lubricating coating on the surface of the bare blank", the high-temperature resistant lubricating coating is set by spraying, roller coating or dip coating. In this embodiment, spraying is preferred. The coating has high uniformity and can form a uniform coating on complex geometric surfaces (such as grooves and curved areas). It is suitable for uniformly dispersing hexagonal boron nitride and graphite in powder form on the surface of the bare blank.

[0056] Furthermore, in the step of "applying a high-temperature resistant lubricating coating to the surface of the bare blank," the area where the high-temperature resistant lubricating coating is applied to the surface of the bare blank can be the entire surface of the bare blank, or only a localized area of ​​the scratches on the surface of the bare blank. Spraying the entire surface area of ​​the bare blank can achieve a better coverage effect, avoiding omissions and helping to further reduce the formation of oxide scale, but the cost is higher, and it affects the subsequent step of removing the high-temperature resistant lubricating coating from the surface of the hot-stamped parts, making the removal more difficult.

[0057] Furthermore, in the step of "removing the high-temperature lubricating coating from the surface of the hot-stamped parts," a five-step process is employed to remove the high-temperature lubricating coating from the surface of the hot-stamped parts: ultrasonic degreasing, pickling, electrolysis, ultrasonic water washing, and water washing. Specifically, ultrasonic water washing first removes dirt or part of the coating from the surface of the hot-stamped parts using high-frequency sound waves. Then, pickling uses a chemical reaction to neutralize the Na2CO3 and other metal alkali salts in the high-temperature lubricating coating, generating gas and causing the high-temperature lubricating coating to further detach. Next, electrolytic cleaning removes the residual coating through a chemical reaction generated by the electrolyte. Finally, ultrasonic water washing and the final water washing completely clean the remaining parts, preparing the clean surface for electroplating and electrophoresis to form a protective layer with uniform thickness and stable quality. The above five-step method achieves a good cleaning effect for the residual coating. The duration, intensity, and sequence of each step can be adjusted according to the thickness and adhesion of the high-temperature lubricating coating after hot stamping.

[0058] In another embodiment, the method for applying a high-temperature resistant lubricating coating to the surface of hot-stamped parts can also be configured to use high-pressure rinsing with a pH value greater than 7. Alkaline substances, anti-flash rust agents, etc. can be added to the water washing tank to prevent the hot-stamped iron parts from rusting after cleaning.

[0059] In another embodiment, during the step of "removing the high-temperature lubricating coating from the surface of the hot-stamped parts," the high-temperature lubricating coating is removed by shot blasting or sandblasting. Specifically, shot blasting can be performed using steel grit with a diameter of 4 mm, with blasting parameters of 50 Hz and a force of 35 Hz, or sandblasting can be performed using 120-mesh alumina sand to remove the high-temperature lubricating coating from the surface. Shot blasting and sandblasting are both mature mechanical and physical processing methods, which are more adaptable to sensitive parts and can be optimized according to different coating thicknesses and part requirements, especially suitable for the removal of coatings with hexagonal boron nitride and graphite in this embodiment.

[0060] The present invention will be described in detail below through specific embodiments:

[0061] Example 1

[0062] The bare slab blank is set with a threshold thickness of 1.4mm. A high-temperature resistant lubricating coating is locally sprayed onto the upper surface of the bare slab blank. The content of hexagonal boron nitride and graphite is 20wt%, flash rust inhibitor is 0.5wt%, Na2CO3 is 1wt%, and the balance is water. The graphite content in the hexagonal boron nitride and graphite is 10wt%. First, the flash rust inhibitor and sodium carbonate powder are poured into water and stirred evenly. Then, the hexagonal boron nitride and graphite powder are added to the aqueous solution and stirred evenly. First, the bare plate blank is heated to 130℃ using induction heating. Then, it is coated with a high-temperature lubricating coating of 2-10µm thickness using a spraying production line. The bare plate blank of the threshold is then placed in a heating furnace for hot stamping, with a heating time of 210s and a holding time of 8s. The surface of the hot-formed threshold contains the high-temperature lubricating coating. The threshold with the high-temperature lubricating coating is then removed using a five-step process: ultrasonic degreasing, pickling, electrolysis, ultrasonic water washing, and water washing. In the final water washing step, a large amount of air is introduced for agitation to remove the high-temperature lubricating coating from the surface of the hot-stamped part. Finally, the clean surface is subjected to electroplating and electrophoretic treatment.

[0063] Example 2

[0064] The bare plate blank is set with 1.8mm longitudinal beams. The surface of the bare plate blank is sprayed with a high-temperature lubricating coating, with hexagonal boron nitride and graphite content of 15wt%, anti-flash rust agent of 2wt%, NaOH of 2wt%, and the balance being alcohol. The graphite content in hexagonal boron nitride and graphite is 20wt%. First, the anti-flash rust agent and sodium hydroxide powder are poured into alcohol and stirred evenly. Then, hexagonal boron nitride and graphite powder are added to the aqueous solution and stirred evenly to obtain a high-temperature resistant lubricating coating with a thickness of 4-8 μm. The bare blank of the longitudinal beam is placed in a heating furnace for hot stamping and forming. The heating time is 260s and the holding time is 10s. The surface of the hot-formed longitudinal beam contains the high-temperature resistant lubricating coating. Then, the high-temperature resistant lubricating coating on the longitudinal beam is removed by a five-step process of ultrasonic degreasing, pickling, electrolysis, ultrasonic water washing, and water washing. In the final water washing step, a large amount of air is introduced for stirring to remove the high-temperature resistant lubricating coating from the surface of the hot-stamped parts. Finally, electroplating and electrophoresis are performed on the clean surface.

[0065] Example 3

[0066] The bare slab blank is set as a 1.6mm B-pillar. The blank is heated to 150℃ in a furnace. A high-temperature lubricating coating is then sprayed onto the entire surface of the blank. The coating contains 25wt% hexagonal boron nitride and graphite, 3wt% anti-flash rust agent, 2wt% NaHCO3, and the balance is water. The graphite content in the hexagonal boron nitride and graphite is 50wt%. First, the anti-flash rust agent and sodium bicarbonate powder are added to the water and stirred until homogeneous. Then, the hexagonal boron nitride and graphite powder are added to the aqueous solution and stirred until homogeneous, resulting in the coating. A high-temperature resistant lubricating coating with a thickness of 4-8 μm is applied. The bare blank of the B-pillar is placed in a heating furnace for hot stamping and forming. The heating time is 240 seconds, and the holding time is 10 seconds. The surface of the hot-formed B-pillar contains a high-temperature resistant lubricating coating. Then, the B-pillar with the high-temperature resistant lubricating coating is placed in a ring-shaped high-pressure water spray cleaning line, and the pH value of the water is kept greater than 7. Alkaline substances and anti-flash rust agents are added to the water to remove the high-temperature resistant lubricating coating from the surface of the hot-stamped parts. Finally, electroplating and electrophoresis are performed on the clean surface.

[0067] Comparative Example 1

[0068] The steps and procedures of Comparative Example 1 are the same as those of Example 1, except that the high-temperature lubricating coating in Comparative Example 1 has a graphite content of 20 wt%, an anti-flash rust agent of 0.5 wt%, and the balance is alcohol. It does not contain hexagonal boron nitride, and the heating time is 260 s, while the holding time is 15 s. The surface of the sill after thermoforming has a large amount of oxide scale and a small amount of residual graphite powder, indicating that the graphite powder has essentially reached its ignition point.

[0069] Comparative Example 2

[0070] The steps and procedures of Comparative Example 2 are the same as those of Example 1, but the high-temperature lubricating coating in Comparative Example 2 is configured with a hexagonal boron nitride content of 20wt%, an anti-flash rust agent of 0.5wt%, and the balance being alcohol. It does not contain graphite, and the heating time is 260s, with a holding time of 15s. The sill surface after thermoforming contains a high-temperature resistant lubricating coating.

[0071] Comparative Example 3

[0072] The steps and procedures of Comparative Example 3 are the same as those of Example 1, except that Comparative Example 3 does not contain a high-temperature resistant lubricating coating, and the heating time is 260s and the holding time is 15s. The sill surface after thermoforming is an oxide layer and does not contain a high-temperature resistant lubricating coating.

[0073] The temperature performance of the results from the six cases described above is summarized in the table below, where A represents hexagonal boron nitride and B represents graphite. For specific actual processing results, please refer to Figures 2 through 7.

[0074] The schemes in Comparative Examples 1, 2, and 3 do not all contain hexagonal boron nitride and graphite. In Comparative Examples 1 and 3, the graphite burned, and the entire threshold surface was covered with oxide scale, resulting in severe sidewall damage to the product. Comparative Example 2, at a temperature, was clearly less thermally conductive than the other examples that contained hexagonal boron nitride and graphite, demonstrating the beneficial effects of the characteristic mixture.

[0075] By applying hexagonal boron nitride and graphite to the bare blank and then electroplating it, the surface roughness of the electroplated surface is reduced, the surface is smooth, and the roughness is decreased.

[0076] Specifically, the table below shows the surface roughness data of the parts in the above embodiments and comparative examples, wherein three locations were sampled for testing in each embodiment and comparative example:

[0077] The dimensions of the hot-stamped parts were inspected. The parts produced under normal conditions (Comparative Example 3) had dimensions within the normal range. Adding only hexagonal boron nitride resulted in outward expansion of the part dimensions, while adding only graphite resulted in inward reduction. This is because hexagonal boron nitride has a lower heat transfer coefficient, while graphite has a higher heat transfer coefficient, leading to significant dimensional changes during hot stamping. By adding a mixture of hexagonal boron nitride and graphite, the dimensions of the parts returned to the normal range, as shown in Examples 1-3. The specific dimensional results are shown in the table below:

[0078] Furthermore, during the cleaning process of the high-temperature resistant lubricating coating, the cleaning efficiency in Examples 1-3 was higher than that in Comparative Example 2, which only contained hexagonal boron nitride, due to the addition of graphite and metal alkali salts. Also, referring to Figures 8-10, metallographic cross-sectional inspections of the electroplated parts from Examples 1-3 revealed no powder residue within the zinc layer, indicating that the cleaning effect met the standards. The detailed cleaning process is shown in the table below:

[0079] After electroplating, the parts in the embodiments showed no scratches, normal electrophoretic adhesion, and excellent corrosion resistance. The specific local appearance after electroplating and the appearance after electrophoretic corrosion test are shown in Figures 11 and 12.

[0080] The content disclosed above is only a preferred and feasible embodiment of the present invention, and is not intended to limit the scope of the patent application of the present invention. Therefore, all equivalent technical changes made using the contents of the present invention specification and drawings are included in the scope of the patent application of the present invention.

[0081] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0082] Although this application has been described by way of examples, those skilled in the art will know that this application has many modifications and variations without departing from the spirit of this application, and it is intended that the appended embodiments include these modifications and variations without departing from this application.

Claims

1. A method for preparing a thermoformed part, characterized in that, The method for preparing the thermoformed part includes: Provide bare slab blanks and preheat the bare slab blanks; A high-temperature resistant lubricating coating is provided on the surface of the bare plate blank, the high-temperature resistant lubricating coating comprising hexagonal boron nitride and graphite; The bare plate blank having the high-temperature lubricating coating is hot-stamped to form a hot-stamped part; After the hot-stamped part is formed, the high-temperature lubricating coating on the surface of the hot-stamped part is removed; The hot-stamped parts, after the high-temperature lubricating coating is removed, are subjected to electroplating and electrophoresis treatments in sequence.

2. The method for preparing a thermoformed part according to claim 1, characterized in that: In the step of "providing bare slab blanks and preheating the bare slab blanks", the preheating temperature for preheating the bare slab blanks is between 100-300℃.

3. The method for preparing a thermoformed part according to claim 1, characterized in that: The high-temperature resistant lubricating coating also includes anti-flash rust agents and metal alkali salts.

4. The method for preparing a thermoformed part according to claim 3, characterized in that: In the high-temperature resistant lubricating coating, the content of hexagonal boron nitride and graphite is 10-50 wt%, the content of anti-flash rust agent is 0.1-5 wt%, the content of metal alkali salt is 0.1-10 wt%, and the balance of the high-temperature resistant lubricating coating is a solution with a pH value greater than 7.

5. The method for preparing a thermoformed part according to claim 4, characterized in that: The graphite content accounts for 1-80 wt% of the total content of hexagonal boron nitride and graphite.

6. The method for preparing a thermoformed part according to claim 1, characterized in that: In the step of "applying a high-temperature resistant lubricating coating to the surface of the bare plate blank", the thickness of the high-temperature resistant lubricating coating is 1-20 μm, preferably 2-10 μm.

7. The method for preparing a thermoformed part according to claim 1, characterized in that: In the step of "applying a high-temperature resistant lubricating coating to the surface of the bare sheet blank", the high-temperature resistant lubricating coating is applied by spraying, roller coating or dip coating, preferably by spraying.

8. The method for preparing a thermoformed part according to claim 1, characterized in that: In the step of "applying a high-temperature resistant lubricating coating to the surface of the bare slab blank", the area where the high-temperature resistant lubricating coating is applied to the surface of the bare slab blank can be the entire surface of the bare slab blank, or only a localized area of ​​the scratches on the surface of the bare slab blank.

9. The method for preparing a thermoformed part according to claim 1, characterized in that: In the step of "removing the high-temperature resistant lubricating coating from the surface of the hot-stamped parts", the high-temperature resistant lubricating coating on the surface of the hot-stamped parts is removed by a five-step process in sequence: ultrasonic degreasing, pickling, electrolysis, ultrasonic water washing, and water washing.

10. The method for preparing a thermoformed part according to claim 1, characterized in that: In the step of "removing the high-temperature lubricating coating from the surface of the hot-stamped part", the high-temperature lubricating coating on the surface of the hot-stamped part is removed by high-pressure water washing with a pH value greater than 7.

11. The method for preparing a thermoformed part according to claim 1, characterized in that: In the step of "removing the high-temperature lubricating coating from the surface of the hot-stamped part", the high-temperature lubricating coating on the surface of the hot-stamped part is removed by shot blasting or sandblasting.

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