A method for manufacturing a high-strength steel plate composite body floor integrated battery upper cover

Abstract

The application provides a preparation method of a high-strength steel plate composite vehicle body floor integrated battery upper cover, which comprises the following steps: preparing a PCM prepreg; pasting a PET film on the outer side of a steel plate; splicing and laminating the PCM prepreg on the inner side of the steel plate; plugging the hole positions on the steel plate by using rubber particles; placing the product on the lower die of a hot-pressing mold, and then preparing a formed product by heating and pressurizing the steel plate and the prepreg through the cooperation of the upper and lower dies of the hot-pressing mold to obtain a battery upper cover prefabricated part; demolding the battery upper cover prefabricated part, and then polishing to obtain a finished product of the vehicle body floor integrated battery upper cover. The high-strength steel plate and the PCM prepreg are first applied to realize the composite die pressing process, the product has high strength, smooth and flat surface quality, good sealing property, and realizes assembly without cracking; the production cycle is short, the operation is simple, the product qualified rate is improved, and the production cost is saved; and the vehicle body floor integration realizes the lightweight of the whole vehicle.

Description

Technical Field

[0001] This invention belongs to the field of composite material molding technology, specifically relating to a method for preparing a high-strength steel plate composite material vehicle floor integrated battery cover. Background Technology

[0002] PCM prepreg (Preimpregnated Materials) is a prepreg sheet product made by impregnating a matrix with reinforcing continuous fibers. It is an intermediate material in composite materials and an important type of semi-finished composite product, experiencing rapid development in recent years. Composite materials prepared from prepregs are corrosion-resistant, heat-resistant, lightweight, and high-strength. They simplify parts manufacturing processes, reduce machining and assembly steps, decrease production costs, improve product safety and reliability, reduce maintenance costs, and lower life cycle costs (LCC). Furthermore, they allow for lightweighting while meeting material performance requirements. Therefore, they are widely used in industries such as automotive engineering, rail transportation, building materials, and aerospace.

[0003] New energy vehicles are an industry that is being vigorously promoted in China. Currently, most new energy vehicle battery covers use sheet metal parts and SMC materials. However, with the increasing demand for lightweighting, PCM prepreg composite materials have become the preferred material for battery covers.

[0004] PCM composite material compression molding process involves cutting pre-tightened material into pre-designed sheets using a cutting device, accurately laying the sheets onto a pre-laying blank, and continuously laying multiple layers before feeding the product into a molding device, where it is cured and molded under temperature and pressure. However, the following problems still exist in the current preparation of battery covers using PCM composite materials: (1) When preparing relatively complex battery cover products, it is necessary to prepare a preform and a large number of qualified sheet materials in advance according to the shape of the product. During the cutting process, a lot of waste material will inevitably be generated. Each sheet material needs to be accurately positioned and laid on the preform. The operation is cumbersome, the cycle is long, and the overall cost is high. (2) PCM prepreg is prone to sand holes and pits during the molding process, which will cause the product to fail to seal. Moreover, since the sheet material is generally laid in a butt-to-button manner and the thickened area is overlapped during the laying process, multiple sheet materials are very easy to misalign. The fault tolerance rate is low and overpressure is easy to cause cracking during the assembly process. (3) After the battery cover is assembled with the battery cell and the lower tray, it also needs to be connected to the vehicle floor. The vehicle is heavy and does not meet the requirements for lightweighting. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a battery cover integrated into a high-strength steel plate composite material vehicle floor, which solves the following problems in the prior art: the material laying method is complicated and cumbersome, the operation is complicated and the cycle is long and the cost is high, the local surface quality is prone to sand holes and pits during the production process, which leads to sealing failure, there is a risk of assembly cracking during installation, the battery pack needs to be connected to the vehicle floor when assembling the whole vehicle, which increases the weight of the whole vehicle.

[0006] To address the aforementioned technical problems, this invention provides a method for preparing a high-strength steel plate composite material vehicle floor integrated battery cover, comprising the following steps:

[0007] Step 1: Prepare PCM prepreg sheets;

[0008] Step 2: Apply the PET film to the outer side of the steel plate;

[0009] Step 3: After splicing the PCM prepreg sheets together, stack them and lay them on the inner side of the steel plate;

[0010] Step 4: Use rubber granules to plug the holes in the high-strength steel plate;

[0011] Step 5: Place the product on the lower mold of the hot press mold, and then heat and press the steel plate and prepreg through the upper and lower molds of the hot press mold to form the battery cover preform.

[0012] Step 6: Demold the battery cover preform and then grind it to obtain the finished battery cover integrated into the vehicle floor.

[0013] Preferably, in step 2, the PET film is overlapped with an interference fit to cover the entire steel plate, and the width and length of the interference fit of multiple PET films do not need to be accurately positioned, and then a roller is used for pressing.

[0014] Preferably, in step 3, the PCM prepreg sheets are spliced ​​into the required shape and size of the product, and multiple layers are laminated according to the required thickness. Then, the laminated PCM prepreg sheets are laminated to the inner side of the steel plate in a hole-to-hole positioning manner.

[0015] Preferably, in step 4, the plugging includes plugging all the mounting holes on the steel plate with rubber particles, wherein the diameter of the rubber particles is at least 0.15 mm larger than the diameter of the hole.

[0016] Preferably, in step 5, the temperature of the upper hot-pressing mold is 140°C to 150°C, and the temperature of the lower hot-pressing mold is 130°C to 140°C.

[0017] Preferably, in step 5, the molding pressure of the upper and lower hot pressing molds includes a first stage molding and a second stage molding, wherein the first stage molding pressure is 80 to 120T and the second stage molding pressure is 400 to 600T.

[0018] Preferably, in step 5, the molding time of the upper and lower hot press molds includes a first molding time and a second molding time, wherein the first molding time is 10 to 20 seconds and the second molding time is 280 to 340 seconds.

[0019] Preferably, in step 5, the hot pressing mold is a metal steel mold, and the upper and lower molds of the hot pressing mold adopt a hard-press double-sided mold structure.

[0020] Preferably, in step 6, the peel strength between the PCM composite layer and the steel plate layer of the battery integrated cover on the vehicle floor is ≥180N / m, and the dyne value of the PCM composite layer surface is ≥48.

[0021] Preferably, in step 6, the sander is an SFR-RD1450 wide-band sander.

[0022] Preferably, the yield strength of the steel plate is at least 180 MPa. The steel plate includes, but is not limited to, steel plates of grades such as HC340, 590DP, HC380, 590TR, and DP780.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) This invention is the first to use high-strength steel plate and PCM prepreg to achieve composite molding process. The product has high strength, smooth and flat surface quality, good sealing performance, and achieves zero cracking during customer assembly.

[0025] (2) The production cycle is short and the operation is simple. It can increase the product qualification rate from 96% to 99%, which greatly saves production costs.

[0026] (3) The vehicle body floor is integrated to achieve the lightweight requirements of the whole vehicle and realize the mass production application of high-strength steel plate composite materials in the production of battery covers for new energy vehicles. Attached Figure Description

[0027] Figure 1 This is a process flow diagram of the manufacturing process of the high-strength steel plate composite material vehicle body floor integrated battery cover of the present invention.

[0028] Figure 2 This is a schematic diagram of the mold structure used in the preparation method of the high-strength steel plate composite material vehicle floor integrated battery cover of the present invention.

[0029] Figure 3This is a schematic diagram of the structure of the high-strength steel plate composite material vehicle body floor integrated battery cover of the present invention. Detailed Implementation

[0030] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the present invention will be further described below in conjunction with specific embodiments and accompanying drawings. It should be understood that the embodiments and accompanying drawings described below are merely exemplary and not intended to limit the scope of protection of this application.

[0031] like Figure 1 The diagram shows the manufacturing process flow of the high-strength steel plate composite material vehicle body floor integrated battery cover of the present invention. The steps of the manufacturing process are as follows:

[0032] (1) Prepare a PCM prepreg sheet, which can be any PCM prepreg sheet commonly used in the art for preparing battery top covers, typically with a width of 1270 mm.

[0033] (2) Apply PET (polyethylene terephthalate) film to the outer side of the steel plate (i.e., the side opposite to the battery cover, also known as "side A"); specifically, the PET film should be applied to the steel plate with an interference overlap, and the width and length of the interference overlap of multiple PET films do not need to be accurately positioned, and then the roller is used to press them together.

[0034] (3) After splicing the PCM prepreg sheets together, stack them together and lay them on the inner side of the steel plate (i.e., the side facing the battery cover, also known as the "B side"). The specific laying method is as follows: splice the PCM prepreg sheets into the required shape and size of the product, and lay multiple layers (e.g., two or more layers) according to the required thickness. Then, take the laid PCM prepreg sheets and lay them on the inner side of the steel plate in a hole-to-hole positioning manner.

[0035] (4) Use rubber granules to plug the holes in the steel plate. This prevents prepreg from entering the holes and causing blockage during molding. The plugging operation specifically includes: plugging all assembly holes in the steel plate with rubber granules. The diameter of the rubber granules should be at least 0.15 mm larger than the diameter of the hole to ensure that the holes are plugged and achieve good sealing. If the diameter of the rubber granules is the same as or differs from the diameter of the hole by less than 0.15 mm, it will be difficult to achieve a sealing effect.

[0036] (5) The product is placed on the lower mold of the hot press mold. Then, the steel plate and prepreg are heated and pressed through the upper and lower molds of the hot press mold to form the battery cover preform. The mold closing speed parameter of the press is 3-7 mm / s; the temperature of the upper mold is 140℃ to 150℃, and the temperature of the lower mold is 130℃ to 140℃. The forming time of the upper and lower molds includes the first molding time and the second molding time. The first molding time is 10 to 20 seconds, and the second molding time is 280 to 340 seconds. The forming pressure of the upper and lower molds includes the first molding pressure and the second molding pressure. The first molding pressure is 80 to 120T, and the second molding pressure is 400 to 600T. That is, compression molding is segmented compression molding: the first stage of compression molding is performed at a pressure of 80 to 120T for 10 to 20 seconds, and the second stage of compression molding is performed at a pressure of 400 to 600T for 280 to 340 seconds. The hot press mold is preferably a metal steel mold, and the upper and lower molds of the hot press mold adopt a hard-press double-sided mold structure.

[0037] (6) Demold the battery cover preform and then grind it (the grinding machine is an SFR-RD1450 wide belt sander) to obtain the finished battery cover integrated into the vehicle floor.

[0038] Comparative Examples

[0039] One of the key points of the manufacturing process of the high-strength steel plate composite material vehicle floor integrated battery cover of the present invention is to reasonably control various parameters in the molding process, such as mold temperature, molding time and molding pressure. Any change in parameters may affect the performance of the final vehicle floor integrated battery cover.

[0040] Using the above steps and referring to the table below, the integrated battery cover for the vehicle floor was prepared under different conditions. The PCM prepreg sheet used was model BAC-449C-41450-50, manufactured by Zhejiang Baihe Aerospace Composite Materials Co., Ltd., and the high-strength steel plate was model HC340, manufactured by Shanghai Baosteel Steel Trading Co., Ltd.

[0041]

[0042]

[0043] Figure 3A schematic diagram of the structure of the high-strength steel plate composite material battery cover integrated into the vehicle floor, prepared by the method of the present invention, is shown. As shown in the figure, the battery cover includes a PCM prepreg and a high-strength steel plate, which are molded and bonded together. The prepreg contains rubber particles. Through molding and bonding, the molten and fused PCM prepreg and high-strength steel plate can be further combined and formed, effectively enhancing the strength of the battery cover integrated into the vehicle floor. This results in a high-strength battery cover with a tensile strength ≥480MPa, a peel strength between the PCM composite layer and the steel plate layer ≥180N / m, and a dyne value ≥48 on the surface of the PCM composite layer. This allows for good adhesion to the battery, solving assembly cracking and weight reduction issues, thereby obtaining a product with high strength, good sealing, and good adhesion.

[0044] Preferably, the high-strength steel plate used in this invention has a yield strength of at least 180 MPa. Steel plates suitable for this invention include, but are not limited to, steel plates of grades such as HC340, 590DP, HC380, 590TR, and DP780, which have sufficient strength to be used as vehicle body floors.

[0045] Figure 2 A schematic diagram of the mold structure for the preparation method of the integrated battery cover for a high-strength steel plate composite vehicle body floor according to the present invention is shown. The press mold used in the method of the present invention includes an upper mold 1 and a lower mold 2. The upper mold 1 is electrically connected to the press control panel 7. Relevant molding parameters (including molding pressure, molding time, holding time, molding temperature, etc.) can be input through the press control panel 7, and the downward pressing action of the upper mold 1 can be controlled. Rubber granules 3, PCM prepreg 4, high-strength steel plate 5, and PET protective film 6 are integrally bonded onto the lower mold 2, thereby realizing the molding process. This press can be any mold press commonly used in the art. For the sake of simplicity and clarity, Figure 2 Other components of the press are not shown, however, those skilled in the art will understand that, in addition to Figure 2 In addition to the upper mold 1, lower mold 2 and press control panel 7 shown, the press also includes other components, including but not limited to brackets, actuation mechanisms, etc.

[0046] In summary, this invention is the first to apply high-strength steel plates and PCM to achieve a composite molding process, resulting in high-strength products that can achieve zero cracking during customer assembly. Furthermore, the material laying process is simple, with short operation time, high material utilization, and a short production cycle, increasing the product qualification rate from 96% to 99% and significantly reducing production costs. The integrated vehicle floor achieves the lightweight requirements of the entire vehicle and enables the mass production application of high-strength steel plate composite materials in the production of battery covers for new energy vehicles.

Claims

1. A method for preparing a battery cover integrated into a high-strength steel plate composite material vehicle floor, characterized in that... Includes the following steps: Step 1: Prepare PCM prepreg sheets; Step 2: Apply the PET film to the outer side of the steel plate; Step 3: After splicing the PCM prepreg sheets together, stack them and lay them on the inner side of the high-strength steel plate; Step 4: Use rubber granules to plug the holes in the steel plate; Step 5: Place the product on the lower mold of the hot press mold, and then heat and press the steel plate and prepreg through the upper and lower molds of the hot press mold to form the battery cover preform. Step 6: Demold the battery cover preform and then grind it to obtain the finished battery cover integrated into the vehicle floor; In step 2, the PET film is overlapped with an interference fit to cover the entire steel plate, and the width and length of the interference fit of multiple PET films do not need to be accurately positioned. Then, a roller is used to press them together. In step 3, the PCM prepreg sheets are spliced ​​into the required shape and size of the product, and multiple layers are laminated according to the required thickness. Then, the laminated PCM prepreg sheets are laminated to the inner side of the steel plate in a hole-to-hole positioning manner. In step 4, the plugging includes plugging all the mounting holes on the steel plate with rubber particles, wherein the diameter of the rubber particles is at least 0.15 mm larger than the diameter of the hole. In step 5, the temperature of the upper hot press mold is 140°C to 150°C, and the temperature of the lower hot press mold is 130°C to 140°C. In step 5, the molding pressure of the upper and lower hot press molds includes a first stage molding and a second stage molding, wherein the first stage molding pressure is 80 to 120T and the second stage molding pressure is 400 to 600T. In step 5, the molding time of the upper and lower hot press molds includes a first molding time and a second molding time. The first molding time is 10 to 20 seconds, and the second molding time is 280 to 340 seconds. In step 6, the peel strength between the PCM composite layer and the steel plate layer of the battery integrated cover on the vehicle floor is ≥180N / m, and the dyne value of the PCM composite layer surface is ≥48.

2. The preparation method according to claim 1, characterized in that, In step 5, the hot pressing mold is a metal steel mold, and the upper and lower molds of the hot pressing mold adopt a hard-press double-sided mold structure.

3. The preparation method according to claim 1, characterized in that, The yield strength of the steel plate is at least 180 MPa.

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