Preparation method of thermoformed part

Abstract

The invention relates to a hot stamping method, in particular to a preparation method of a hot forming part, which comprises the following steps: providing a blank of a bare plate, and preheating the blank of the bare plate; a high-temperature-resistant lubricating coating is arranged on the surface of the bare plate blank, and the high-temperature-resistant lubricating coating comprises hexagonal boron nitride and graphite; and hot stamping forming is conducted on the bare plate blank with the high-temperature-resistant lubricating coating, a hot stamping part is formed, after the hot stamping part is formed, the high-temperature-resistant lubricating coating on the surface of the hot stamping part is removed, and electroplating and electrophoresis treatment is sequentially conducted on the hot stamping part with the high-temperature-resistant lubricating coating removed. By means of the structure, the high-temperature-resistant lubricating coating containing the special mixture of hexagonal boron nitride and graphite is arranged on the surface of the blank before hot stamping forming is conducted on the blank of the bare plate, the heating rate is high, and hot stamping parts are not prone to deformation.

Description

Technical Field

[0001] The invention relates to a hot stamping method, in particular to a method for preparing a hot formed part. Background Art

[0002] The description in this section merely provides background information related to the present disclosure and does not constitute prior art.

[0003] Bare sheet hot stamping is a common method for preparing hot-formed parts in the field of hot stamping. However, bare sheet blanks are prone to oxide scale, and during the hot stamping process, due to the tensile deformation of the bare sheet blank, it is easy to scratch the steel substrate mold and form nodules. The nodules and oxide scale will cause serious damage to the bare sheet blank, especially the side wall and R corner of the bare sheet blank. At the same time, the raised burrs generated at the damaged position will affect the coating thickness of the hot stamping parts, resulting in no electrophoresis or a thin electrophoresis layer, which will then affect the anti-corrosion performance of the hot stamping parts.

[0004] Patent CN114790561A provides a method for preparing hot stamping parts, which sprays hexagonal boron nitride on bare plate blanks and then performs hot stamping, which can effectively solve the problem of roughening of hot stamping parts. However, hexagonal boron nitride is white in color and has a thermal conductivity of 56.94W / (m·K). Its reflectivity is relatively high when heated at high temperatures, and its heating rate is slow. During the heating and forming process, the heat conduction with the mold is relatively slow, which can easily cause dimensional deformation of hot stamping parts. Some other prior arts also use graphite as an auxiliary coating, but the thermal conductivity of graphite is generally 150-300W / (m·K), which is more than three times that of hexagonal boron nitride, and its color is black, which is easy to absorb high-temperature radiation and burn easily, and it is still not an ideal coating material.

[0005] It should be noted that the above introduction to the technical background is only for the convenience of providing a clear and complete description of the technical solutions of the present invention and for the convenience of understanding by those skilled in the art. It cannot be considered that the above technical solutions are well known to those skilled in the art simply because these solutions are described in the background technology section of the present invention. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preparing hot-formed parts. Before hot stamping a bare plate blank, a high-temperature resistant lubricating coating including hexagonal boron nitride and graphite is arranged on the surface, which has a high heating rate and makes the hot stamped parts less likely to deform.

[0007] In order to achieve the above object, the present invention discloses the following method for preparing a thermoformed part, the method for preparing the thermoformed part comprising:

[0008] Providing a bare plate blank, and performing a preheating treatment on the bare plate blank;

[0009] Disposing a high temperature resistant lubricating coating on the surface of the bare plate blank, wherein the high temperature resistant lubricating coating comprises hexagonal boron nitride and graphite;

[0010] Hot stamping the bare plate blank with the high temperature resistant lubricating coating to form a hot stamping part;

[0011] After the hot stamping part is formed, removing the high temperature resistant lubricating coating on the surface of the hot stamping part;

[0012] The hot stamping parts after the high temperature resistant lubricating coating is removed are subjected to electroplating and electrophoresis treatments in sequence.

[0013] As a further description of the above technical solution, in the step of "providing a bare plate blank and preheating the bare plate blank", the preheating temperature of the bare plate blank is between 100-300°C.

[0014] 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.

[0015] 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 10-50wt%, the content of the anti-flash rust agent is 0.1-5wt%, the content of the metal alkali salt is 0.1-10wt%, and the balance of the high-temperature resistant lubricating coating is a solution, and the pH value of the solution is greater than 7.

[0016] As a further description of the above technical solution, the graphite content accounts for 1-80wt% of the total content of the hexagonal boron nitride and graphite.

[0017] As a further description of the above technical solution, in the step of "arranging 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 um, preferably 2-10 um.

[0018] As a further description of the above technical solution, in the step of "arranging a high temperature resistant lubricating coating on the surface of the bare plate blank", the high temperature resistant lubricating coating is arranged by spraying, roller coating or dipping, preferably by spraying.

[0019] As a further description of the above technical solution, in the step of "arranging a high-temperature resistant lubricating coating on the surface of the bare plate blank", the area where the high-temperature resistant lubricating coating is arranged on the surface of the bare plate blank can be the entire surface of the bare plate blank, or only the local tensile marks on the surface of the bare plate blank.

[0020] As a further description of the above technical solution, in the step of "removing the high-temperature resistant lubricating coating on the surface of the hot stamping part", the high-temperature resistant lubricating coating on the surface of the hot stamping part is removed in five steps of ultrasonic degreasing, pickling, electrolysis, ultrasonic water washing and water washing.

[0021] As a further description of the above technical solution, in the step of "removing the high-temperature resistant lubricating coating on the surface of the hot stamping part", high-pressure water washing with a pH value greater than 7 is used to remove the high-temperature resistant lubricating coating on the surface of the hot stamping part.

[0022] As a further description of the above technical solution, in the step of "removing the high temperature resistant lubricating coating on the surface of the hot stamping part", the high temperature resistant lubricating coating on the surface of the hot stamping part is removed by shot blasting or sand blasting.

[0023] By means of the above technical solution, the beneficial effects of the present invention are as follows:

[0024] The preparation method of the hot-formed parts of the present invention can be provided with a high-temperature resistant lubricating coating including hexagonal boron nitride and graphite on the surface before hot stamping the bare plate blank, and the hexagonal boron nitride material can be used to reduce the surface oxide scale and increase the strength of the blank during stamping, effectively solving the problem of roughening of hot stamped parts, and the mixture of graphite and hexagonal boron nitride can improve the problems of slow heat absorption under high temperature conditions of pure hexagonal boron nitride and slow heat conduction during hot stamping. Among them, due to the assistance of hexagonal boron nitride, the problem of graphite not being resistant to high temperature and being easily oxidized and burned is solved, and the two complement each other.

[0025] The preparation method of the hot-formed parts of the present invention adds metal alkali salts to the high-temperature resistant lubricating coating, which can prevent the bare plate blank from rusting after the high-temperature resistant lubricating coating is set. When the high-temperature resistant lubricating coating is subsequently removed, gas can be generated during the pickling and electrolysis steps, making the high-temperature resistant lubricating coating easier to peel off.

[0026] To further understand the features and technical contents of the present invention, please refer to the following detailed description and drawings of the present invention. However, the drawings provided are only for reference and description and are not intended to limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of this specification or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this specification. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0028] Figure 1 is a flow chart of a method for preparing a thermoformed part provided in an embodiment of this specification;

[0029] Figure 2 This is a processing result diagram of Example 1;

[0030] Figure 3 This is a processing result diagram of Example 2;

[0031] Figure 4 This is a processing result diagram of Example 3;

[0032] Figure 5 is a processing result diagram of Example 1;

[0033] Figure 6 is a processing result diagram of Example 2;

[0034] Figure 7 is a processing result diagram of Example 3;

[0035] Figure 8 is a metallographic cross-section inspection diagram of Example 1;

[0036] Fig. 9 is a metallographic cross-section inspection diagram of Example 2;

[0037] Fig.10 is a metallographic cross-section inspection diagram of Example 3;

[0038] Fig.11 This is the local appearance after electroplating;

[0039] Fig.12 This is the appearance picture after electrophoresis corrosion test. DETAILED DESCRIPTION

[0040] In order 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 in conjunction with the drawings in the embodiments of this specification. Obviously, the described embodiments are only part of the embodiments of this specification, not all of the embodiments. Based on the embodiments in this specification, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of this specification.

[0041] The following is an explanation of the embodiments of the present invention through specific embodiments. Those skilled in the art can understand the advantages and effects of the present invention from the contents disclosed in this specification. The present invention can be implemented or applied through other different specific embodiments, and the details in this specification can also be modified and changed in various ways based on different viewpoints and applications without departing from the concept of the present invention. In addition, the drawings of the present invention are only simple schematic illustrations and are not depicted according to actual sizes. It is stated in advance. The following embodiments will further explain the relevant technical contents of the present invention in detail, but the disclosed contents are not intended to limit the scope of protection of the present invention.

[0042] It should be understood that, although the terms "first", "second", "third", etc. may be used herein to describe various components or signals, these components or signals should not be limited by these terms. These terms are mainly used to distinguish one component from another component, or one signal from another signal. In addition, the term "or" used herein may include any one or more combinations of the associated listed items depending on the actual situation.

[0043] See also Figure 1 The process is a method for preparing a thermoformed part in this embodiment, wherein the method for preparing a thermoformed part comprises:

[0044] Providing bare plate blanks and preheating the bare plate blanks;

[0045] A high temperature resistant lubricating coating is provided on the surface of the bare plate blank, wherein the high temperature resistant lubricating coating comprises hexagonal boron nitride and graphite;

[0046] The bare sheet blank is hot stamped to form a hot stamped part, and the high temperature resistant lubricating coating on the surface of the hot stamped part is removed, and then the hot stamped part is electroplated and electrophoretically treated in sequence.

[0047] Through the above method, during the operation, before the bare plate blank is hot stamped into a hot stamping part, a high-temperature resistant lubricating coating is first set on the surface of the bare plate blank. The friction coefficient of the hexagonal boron nitride material in the high-temperature resistant lubricating coating can be as low as 0.16, and it does not increase at high temperature, so it has a higher high-temperature resistance effect than commonly used lubricating coatings such as molybdenum disulfide and graphite. Therefore, it can effectively act as a lubricating medium, and the surface position of the bare plate blank surface at least containing local scratches is set to minimize the generation of oxide scale. At the same time, with the help of graphite in the high-temperature lubricating coating, a certain mass of graphite can play the characteristics of high thermal conductivity, so that the thermal conductivity of the high-temperature lubricating coating is avoided from being too greatly affected by the low thermal conductivity hexagonal boron nitride, and finally solves the problem of slow thermal conductivity. That is to say, the hexagonal boron nitride and graphite in the high-temperature lubricating coating in this embodiment complement each other, inhibit each other and produce a better gain effect on the entire hot forming process, which not only makes up for the problem of poor thermal conductivity of hexagonal boron nitride, but also avoids the problem of low ignition point of graphite.

[0048] Specifically, the hexagonal boron nitride and graphite in this embodiment can be provided in the raw material of the high-temperature lubricating coating in the form of mixed powder in a certain proportion, and the raw materials are easily available and easy to process.

[0049] Furthermore, in the present embodiment, in the step of "providing a bare plate blank and preheating the bare plate blank", the preheating temperature of the bare plate blank is between 100-300°C. By preheating the bare plate blank, the anti-rust oil and aqueous solution on the surface of the bare plate blank can be effectively evaporated, so that only fixed powder is left on the surface of the bare plate blank, which is beneficial to the subsequent setting of the high-temperature resistant lubricating coating.

[0050] Furthermore, the high-temperature resistant lubricating coating also includes an anti-flash rust agent and a metal alkali salt. The provision of the anti-flash rust agent and the metal alkali salt can prevent the surface of the bare plate blank from rusting during the early spraying process and before hot stamping. The provision of the metal alkali salt can cause a neutralization reaction of the metal alkali salt during the electrolysis and pickling process, making the high-temperature lubricating coating easier to peel off, which helps to improve the efficiency of powder removal and improve the quality of electroplating. Specifically, in this embodiment, the metal alkali salt can be set to one or more of NaOH, KOH, Na2CO3, NaHCO3, K2CO3, and KHCO3, preferably Na2CO3. Na2CO3 can release a large amount of CO2 during the pickling process, which can loosen the high-temperature lubricating coating and is more conducive to the removal of the coating.

[0051] Further, in the high temperature resistant lubricating coating, the content of hexagonal boron nitride and graphite is 10-50wt%, the content of flash rust inhibitor is 0.1-5wt%, the content of metal alkali salt is 0.1-10wt%, and the balance of the high temperature resistant lubricating coating is solution, and the pH value of the solution is greater than 7, that is, in this embodiment, in addition to the alkaline solution, the powder of hexagonal boron nitride and graphite is the main component. Specifically, the content of graphite accounts for 1-80wt% of the total content of hexagonal boron nitride and graphite, which can be set as needed.

[0052] Furthermore, in the step of "providing a high-temperature resistant lubricating coating on the surface of the bare plate blank", the thickness of the high-temperature resistant lubricating coating is 1-20um, preferably 2-10um, that is, the overall thickness of the high-temperature lubricating coating is relatively thin to avoid affecting the heat conduction effect of the heating and forming process of the bare plate blank.

[0053] Furthermore, 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 dipping. In the present embodiment, spraying is preferred, and the coating has high uniformity and can form a uniform coating on complex geometric surfaces (such as grooves and curved areas), which is suitable for evenly dispersing hexagonal boron nitride and graphite in powder state on the surface of the bare plate blank.

[0054] Furthermore, in the step of "arranging a high temperature resistant lubricating coating on the surface of the bare sheet blank", the area where the high temperature resistant lubricating coating is arranged on the surface of the bare sheet blank may be the entire surface of the bare sheet blank, or only the local scratches on the surface of the bare sheet blank. Spraying the entire surface area of ​​the bare sheet blank can achieve a better coverage effect, avoid omissions, and help to further reduce the generation of oxide scale, but the cost is high, and it affects the subsequent step of removing the high temperature resistant lubricating coating on the surface of the hot stamping part, making it more difficult to remove.

[0055] Furthermore, in the process of the step of "removing the high-temperature resistant lubricating coating on the surface of the hot stamping parts", the high-temperature resistant lubricating coating on the surface of the hot stamping parts is removed in five steps of ultrasonic degreasing, pickling, electrolysis, ultrasonic water washing, and water washing. Specifically, firstly, ultrasonic water washing is used to remove dirt or part of the coating on the surface of the hot stamping parts with the help of high-frequency sound waves, and then pickling is used to react with metal alkali salts such as Na2CO3 in the high-temperature lubricating coating through chemical reaction to generate gas and further fall off the high-temperature lubricating coating, and then electrolytic cleaning is performed to remove the residual coating on the surface through the chemical reaction generated by the electrolyte, and finally the residual part is completely cleaned by ultrasonic water washing and the last step of water washing, and electroplating and electrophoresis operations are prepared on the clean surface to form a protective layer with uniform thickness and stable quality. For the treatment of the residual coating, a better cleaning effect can be achieved through the above-mentioned five-step method, in which the duration, intensity, and sequence of each step can be adjusted accordingly according to the thickness and adhesion of the high-temperature lubricating coating after hot stamping.

[0056] In another embodiment, the method for applying a high temperature resistant lubricating coating on the surface of hot stamping parts can also be set to use high pressure washing with a pH value greater than 7, and alkaline substances, anti-rust agents, etc. can be added to the washing tank to prevent the iron hot stamping parts from rusting after washing.

[0057] In another embodiment, during the step of "removing the high temperature resistant lubricating coating on the surface of the hot stamping parts", the high temperature resistant lubricating coating on the surface of the hot stamping parts is removed by shot blasting or sand blasting. Specifically, 4mm diameter steel sand can be used for shot blasting, wherein the shot blasting parameters are 50HZ and the force value is 35HZ, or 120 mesh alumina sand can be used for sand blasting to remove the high temperature resistant lubricating coating on the surface. Shot blasting or sand blasting are both mature mechanical and physical processing methods, which have better adaptability to surface sensitive parts, and can be optimized according to different coating thicknesses and part requirements, and are particularly suitable for the removal of the coating with hexagonal boron nitride and graphite in this embodiment.

[0058] The present invention can be described in detail below through specific embodiments:

[0059] Example 1

[0060] The bare plate blank is set to a threshold of 1.4mm thickness, and the upper surface of the bare plate blank is partially sprayed with a high temperature resistant lubricating coating, with hexagonal boron nitride and graphite content of 20wt%, anti-flash rust agent of 0.5wt%, Na2CO3 of 1wt%, and the balance of water, and the graphite content of hexagonal boron nitride and graphite of 10wt%. First, pour the anti-flash rust agent and sodium carbonate powder into water, and then stir evenly, then add the hexagonal boron nitride and graphite powder into the aqueous solution and stir evenly. First, the bare plate blank is heated to 130°C by induction heating, and then the bare plate blank is sprayed with a high-temperature resistant lubricating coating thickness of 2-10um through a spraying production line. The bare plate blank of the threshold is placed in a heating furnace for hot stamping. The heating time is 210s and the holding time is 8s. The surface of the threshold after hot stamping contains a high-temperature resistant lubricating coating; then the threshold containing the high-temperature resistant lubricating coating is removed by ultrasonic degreasing, pickling, electrolysis, ultrasonic water washing, and water washing. In the last water washing step, a large amount of air is introduced for stirring to remove the high-temperature resistant lubricating coating on the surface of the clean hot stamping parts. Finally, electrogalvanizing and electrophoresis are performed on the clean surface.

[0061] Example 2

[0062] The bare plate blank is set to a 1.8mm longitudinal beam, and the entire surface of the bare plate blank is sprayed with a high-temperature lubricating coating, the hexagonal boron nitride and graphite content is 15wt%, the anti-flash rust agent is 2wt%, NaOH is 2wt%, and the balance is alcohol. The graphite content in the hexagonal boron nitride and graphite is 20wt%. First, pour the anti-flash rust agent and sodium hydroxide powder into alcohol and then stir evenly. Then, add hexagonal boron nitride and graphite powder into the aqueous solution and stir evenly to obtain a high-temperature resistant lubricating coating with a coating thickness of 4-8um. Put the bare plate blank of the longitudinal beam into a heating furnace for hot stamping. The heating time is 260s and the holding time is 10s. The surface of the longitudinal beam after hot forming contains a high-temperature resistant lubricating coating; then, the longitudinal beam containing the high-temperature resistant lubricating coating is removed by ultrasonic degreasing, pickling, electrolysis, ultrasonic water washing, and water washing. In the last water washing step, a large amount of air is introduced for stirring to remove the high-temperature resistant lubricating coating on the surface of the clean hot stamping parts. Finally, electrogalvanizing and electrophoresis are performed on the clean surface.

[0063] Example 3

[0064] The bare plate blank is set to a 1.6mm B-pillar, and the bare plate blank is heated to 150°C in a heating furnace, and a high-temperature lubricating coating is sprayed on the entire surface of the bare plate blank. The content of hexagonal boron nitride and graphite is 25wt%, the anti-flash rust agent is 3wt%, NaHCO3 is 2wt%, and the balance is water. The graphite content in the hexagonal boron nitride and graphite is 50wt%. The anti-flash rust agent and sodium bicarbonate powder are first poured into water and then stirred evenly. Then, the hexagonal boron nitride and graphite powder are added to the aqueous solution and stirred evenly to obtain a coating. The thickness of the high-temperature resistant lubricating coating is 4-8um. The bare sheet blank of the B-pillar is placed in a heating furnace for hot stamping. The heating time is 240s and the holding time is 10s. The surface of the B-pillar after hot stamping contains a high-temperature resistant lubricating coating; then the B-pillar containing the high-temperature resistant lubricating coating is placed in a circular high-pressure water spray cleaning line, and the pH value of the water is maintained greater than 7. Alkaline substances, anti-flash rust agents, etc. are added to the water to remove the high-temperature resistant lubricating coating on the surface of the clean hot stamping parts, and finally electrogalvanizing and electrophoresis treatment are performed on the clean surface.

[0065] Comparative Example 1

[0066] The links and steps of Comparative Example 1 are the same as those of Example 1, but the high-temperature lubricating coating of Comparative Example 1 is set to have a graphite content of 20wt%, an anti-flash rust agent of 0.5wt%, and the balance of alcohol, and does not contain hexagonal boron nitride, and the heating time is 260s, and the holding time is 15s. Among them, a large amount of oxide scale is formed on the surface of the threshold after hot forming, and a small amount of graphite powder remains, which indicates that the graphite powder has basically reached the ignition point.

[0067] Comparative Example 2

[0068] The links and steps of Comparative Example 2 are the same as those of Example 1, but the high-temperature lubricating coating of Comparative Example 2 is set to have a hexagonal boron nitride content of 20wt%, an anti-flash rust agent of 0.5wt%, and a balance of alcohol, without graphite, and the heating time is 260s and the holding time is 15s. The surface of the threshold after hot forming contains a high-temperature resistant lubricating coating.

[0069] Comparative Example 3

[0070] The links and steps of Comparative Example 3 are the same as those of Example 1, wherein Comparative Example 3 does not contain a high temperature resistant lubricating coating, and the heating time is 260 seconds, and the holding time is 15 seconds. Among them, the surface of the threshold after hot forming is an oxide scale, and does not contain a high temperature resistant lubricating coating.

[0071] Through the above six cases, the temperature performance of the results is summarized in the following table, where A represents hexagonal boron nitride and B represents graphite. The specific actual treatment results can also be found in Figures 2 to 7 :

[0072]

[0073] Among them, 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 burns, the surface of the threshold is completely oxide scale, and the side wall of the product is seriously scratched. Comparative Example 2 is obviously not as efficient in thermal conductivity as the other embodiments having hexagonal boron nitride and graphite at temperature, which illustrates the beneficial effect of the characteristic mixture.

[0074] By applying hexagonal boron nitride and graphite on the bare plate blank and then electroplating, the roughness of the electroplated surface is reduced, the surface is smooth, and the roughness is reduced.

[0075] Specifically, the following table shows the surface roughness data of the parts in the above-mentioned embodiments and comparative examples, wherein three locations of each embodiment and comparative example are sampled for detection:

[0076]

[0077]

[0078] The dimensions of the parts after hot stamping were tested. The normally produced parts are comparative example 3, and the dimensions are within the normal range. After adding only hexagonal boron nitride, the dimensions of the parts are outward, and after adding only graphite, the dimensions of the parts are inward. This is because the heat transfer coefficient of hexagonal boron nitride is low, while the heat transfer coefficient of graphite is large, which causes the dimensions of the parts to change greatly during the hot stamping process. After adding a mixture of hexagonal boron nitride and graphite, the dimensions of the parts become within the normal range, as shown in Examples 1-3. The specific dimensional results are shown in the following table:

[0079] size Position 1 Position 2 Location 3 Example 1 0.4mm 0.3mm 0.2mm Example 2 0.2mm 0.1mm 0.2mm Example 3 -0.2mm -0.1mm -0.1mm Comparative Example 1 -0.5mm -0.6mm -0.4mm Comparative Example 2 0.4mm 0.5mm 0.4mm Comparative Example 3 0.1mm 0.3mm 0.2mm

[0080] Furthermore, in the process of cleaning the high temperature resistant lubricating coating, due to the addition of graphite and metal alkali salt, the cleaning efficiency in Examples 1-3 is higher than that in Comparative Example 2, which only has hexagonal boron nitride. Figure 8-10 , respectively, the parts after electroplating of Example 1 to Example 3 were subjected to metallographic cross-section inspection, and it was found that there was no powder residue in the zinc layer, and the cleaning effect met the standard. The specific cleaning process can be seen in the following table:

[0081] time Ultrasonic degreasing Pickling electrolysis Ultrasonic cleaning Example 1 5min 5min 6min 30s Example 2 5min 5min 6min 30s Example 3 5min 5min 6min 30s Comparative Example 2 5min 10min 10min 30s

[0082] After the parts in the embodiment are electroplated, the electroplated appearance has no scratches, the electrophoretic bonding strength is normal, and the anti-corrosion performance is excellent. The specific local appearance after electroplating and the appearance after the electrophoretic corrosion test are as follows: Fig.11 and Fig.12 shown.

[0083] The contents disclosed above are only preferred feasible embodiments of the present invention, and are not intended to limit the scope of the present invention. Therefore, all equivalent technical changes made using the contents of the present invention's specification and drawings are included in the scope of the present invention.

[0084] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other. Each embodiment focuses on the differences from other embodiments.

[0085] Although the present application has been described through embodiments, those skilled in the art will appreciate that there are many modifications and changes to the present application without departing from the spirit of the present application. It is intended that the attached embodiments include these modifications and changes without departing from the present application.

Claims

1. A method for preparing a thermoformed part, characterized in that: The method for preparing the thermoformed part comprises: Providing a bare plate blank, and performing a preheating treatment on the bare plate blank; Disposing a high temperature resistant lubricating coating on the surface of the bare plate blank, wherein the high temperature resistant lubricating coating comprises hexagonal boron nitride and graphite; Hot stamping the bare plate blank with the high temperature resistant lubricating coating to form a hot stamping part; After the hot stamping part is formed, removing the high temperature resistant lubricating coating on the surface of the hot stamping part; The hot stamping parts after the high temperature resistant 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 a bare plate blank and preheating the bare plate blank", the preheating temperature of the bare plate blank is between 100-300°C.

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

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 10-50wt%, the content of the anti-flash rust agent is 0.1-5wt%, the content of the metal alkali salt is 0.1-10wt%, and the balance of the high temperature resistant lubricating coating is solution, and the pH value of the solution is greater than 7.

5. The method for preparing a thermoformed part according to claim 4, characterized in that: The content of graphite 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 "arranging 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 um, preferably 2-10 um.

7. The method for preparing a thermoformed part according to claim 1, characterized in that: In the step of "arranging a high temperature resistant lubricating coating on the surface of the bare plate blank", the high temperature resistant lubricating coating is arranged by spraying, roller coating or dipping, preferably by spraying.

8. The method for preparing a thermoformed part according to claim 1, characterized in that: In the step of "arranging a high temperature resistant lubricating coating on the surface of the bare plate blank", the area where the high temperature resistant lubricating coating is arranged on the surface of the bare plate blank may be the entire surface of the bare plate blank, or only the local scratches on the surface of the bare plate blank.

9. The method for preparing a thermoformed part according to claim 1, characterized in that: In the process of "removing the high temperature resistant lubricating coating on the surface of the hot stamping part", the high temperature resistant lubricating coating on the surface of the hot stamping part is removed by five steps of 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 resistant lubricating coating on the surface of the hot stamping part", high pressure water washing with a pH value greater than 7 is used to remove the high temperature resistant lubricating coating on the surface of the hot stamping part.

11. 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 on the surface of the hot stamping part", the high temperature resistant lubricating coating on the surface of the hot stamping part is removed by shot blasting or sand blasting.

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