Partition temperature hot pressing and anti-rebound leveling method for flexible graphite polar plate
By using a flexible graphite electrode plate with zoned temperature hot pressing and a four-stage continuous leveling method, the problems of warping and springback deformation were solved, achieving a highly efficient leveling effect and reducing edge cracking rate and production costs.
Patent Information
- Application Number
- CN202511427137.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-30
- Publication Date
- 2026-02-17
AI Technical Summary
Traditional hot-pressing leveling methods are difficult to effectively solve the warping and springback problems of flexible graphite plates, resulting in edge cracking and excessively long leveling time, which affects product yield and production costs.
A flexible graphite electrode plate partition temperature hot pressing and four-stage continuous leveling method is adopted, including pre-pressing, main pressing, shape preservation and cooling shaping stages. The electrode plate is heated in partitions and different temperatures and pressures are applied through tooling fixtures, combined with tensile strain to improve warping and springback.
It reduced the cracking rate at the edge of the electrode plate, improved flatness, shortened the leveling time, increased product yield, and saved production costs.
Smart Images
Figure CN121536029A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of electrode hot pressing technology, and in particular to a method for partitioned temperature hot pressing and anti-rebound leveling of flexible graphite electrode plates. Background Technology
[0002] A fuel cell is a chemical device that directly converts the chemical energy of fuel into electrical energy. It produces no noise and no harmful gases, making it a clean, efficient, and environmentally friendly power source. The bipolar plate, a key component of the fuel cell, primarily provides channels for hydrogen, oxygen, and coolant flow, separates hydrogen and oxygen, collects electrons, and conducts heat. Flexible graphite plates are made from expanded graphite as the base material. They are prefabricated into low-density flexible pre-formed graphite plates through rolling, then pressed into high-density plates, followed by polymer impregnation, curing, and leveling processes to finally obtain the flexible graphite plate.
[0003] After the flexible graphite electrode completes the impregnation, cleaning, curing, and drying processes, uneven curing shrinkage leads to stress concentration and warping deformation. Traditional hot-pressing leveling fixtures typically use constant temperature pressing for leveling, which takes a long time. After the pressure is released, the graphite electrode is prone to springback deformation, and electrodes with large warping deformation may even develop cracks at the edges. In summary, traditional leveling methods are difficult to achieve ideal leveling results and may even cause irreversible damage to the electrode. Summary of the Invention
[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method for partitioned temperature hot pressing and anti-rebound leveling of flexible graphite electrodes. This method combines partitioned hot pressing of the electrode at different temperatures with continuous leveling in four stages. This approach improves upon the problems of electrode edge cracking and rebound deformation after pressure unloading caused by traditional hot pressing. It reduces the electrode edge cracking rate, improves electrode flatness, shortens electrode leveling time, increases product yield, and saves production costs.
[0005] To achieve the above objectives, the present invention is implemented through the following technical solution: A method for partitioned temperature hot pressing and anti-rebound leveling of flexible graphite electrode plates includes: S1: Pre-compression stage: Place the electrode plate in the tooling fixture, apply a temperature of 25-30℃ to the electrode plate, and apply linearly increasing pressure to the entire electrode plate through the tooling fixture. When the set pressure is reached, maintain the pressure for a set time. S2: Main pressure stage: The electrode plates are hot-pressed in different zones using tooling fixtures. The central reaction zone of the electrode plate is heated to a first temperature, which is greater than the resin Tg value to increase resin fluidity. The edge zone of the electrode plate, excluding the central reaction zone, is heated to a second temperature to maintain the interlayer bonding force of graphite. At the same time, the pressure on the central reaction zone of the electrode plate is greater than the pressure on the edge zone of the electrode plate. S3: Shape-preserving stage: Apply the same pressure to the entire plane of the electrode plate, heat the central reaction zone of the electrode plate at the third temperature, continue to heat the edge zone of the electrode plate at the second temperature, the third temperature is lower than the first temperature, and at the same time apply tensile strain to the edge zone of the electrode plate for a set shape-preserving time. S4: Cooling and Shaping Stage: Based on the shaping stage, the electrode plate is cooled down. During the process, the entire plane of the electrode plate is kept under the same pressure as in the shaping stage, and the edge area of the electrode plate is kept under tensile strain. When the temperature of the electrode plate is below 50°C, the tensile force is released. When the temperature drops to room temperature, the pressure on the entire plane of the electrode plate is released, and the electrode plate is removed.
[0006] As a further implementation method, during the pre-pressurization stage, the pressure applied to the electrode plate is increased at a rate of 0.1 MPa / s to ensure uniform pressure distribution and a pressure difference of ≤0.08 MPa at each location; when the pressure reaches 0.5 MPa, the pressure is kept constant and maintained for at least 10 seconds.
[0007] As a further implementation, the tooling fixture includes two sets of clamping plates arranged above and below the electrode plate, and the clamping plates are spliced together by a middle clamping plate and an edge clamping plate.
[0008] As a further implementation, pressure is applied by a press, the output end of which is equipped with a pressure plate. The pressure plate includes an intermediate pressure plate and an edge pressure plate that are spliced together and can be independently pressurized. The positions of the intermediate pressure plate and the intermediate clamping plate correspond to the positions of the central reaction zone of the electrode plate, and the positions of the edge pressure plate and the edge clamping plate correspond to the positions of the edge zone of the electrode plate. The intermediate pressure plate presses down on the central reaction zone of the electrode plate through the intermediate clamping plate, and the edge pressure plate presses down on the edge zone of the electrode plate through the edge clamping plate.
[0009] As a further implementation, the central reaction zone of the electrode is heated by the intermediate clamping plate to a first temperature between 120-130°C, and the edge zone of the electrode is heated by the edge clamping plate to a second temperature between 80-90°C.
[0010] As a further implementation method, the pressure in the central reaction zone of the electrode plate during the main pressure stage is 4.5-5.5 MPa, and the pressure in the edge zone of the electrode plate is 2.5-3.5 MPa; the hot pressing during the main pressure stage lasts for 3-5 minutes.
[0011] As a further implementation method, during the shape-keeping stage, the pressure applied to the electrode plate is 0.8-1.0 MPa; the central reaction zone of the electrode plate is heated through the intermediate clamp, and the third temperature is between 100-110℃; the edge zone of the electrode plate is heated through the edge clamp; a tensile strain of 0.2%±0.02% is applied to the edge zone of the electrode plate, and the shape-keeping time is not less than 1 min.
[0012] As a further implementation, the cooling rate of the electrode edge region is less than the cooling rate of the electrode central reaction region.
[0013] As a further implementation, the cooling rate of the heating temperature in the central reaction zone of the electrode is 2℃ / min.
[0014] As a further implementation, the cooling rate of the heating temperature in the edge region of the electrode is 1.5℃ / min.
[0015] The beneficial effects of the present invention are as follows: This invention employs a method combining zoned hot pressing of electrode plates at different temperatures with continuous leveling in four stages. This method improves upon the problems of edge cracking and springback deformation of electrode plates caused by traditional hot pressing. It reduces the edge cracking rate, improves electrode plate flatness, shortens electrode plate leveling time, increases product yield, and saves production costs.
[0016] In the pre-pressing stage, the present invention applies linearly increasing pressure to the entire electrode plate through tooling fixtures on the press plate of the press, which can avoid impact displacement and cause slippage and damage between graphite layers. The local stress of the electrode plate can be released by holding the pressure.
[0017] In the main pressing stage, this invention uses tooling fixtures to perform zoned temperature hot pressing on the electrode plates. The central reaction zone of the electrode plate is heated at a first temperature, which is greater than the resin Tg value, to increase resin fluidity. The edge zone of the electrode plate, excluding the central reaction zone, is heated at a second temperature to maintain the interlayer bonding force of graphite. By using a high-temperature, high-pressure treatment on the central reaction zone of the electrode plate, the porosity of the central reaction zone can be reduced, eliminating tiny voids inside the electrode plate. On the other hand, the lower-temperature, low-pressure hot pressing on the edge zone of the electrode plate can effectively reduce edge crack damage and prevent cracks from forming in the interlayer of the graphite electrode plate.
[0018] The first temperature of the main compression stage of the present invention is between 120-130°C. The high temperature significantly reduces the resin viscosity, which is beneficial for filling the internal micro-gaps. The third temperature of the shape-preserving stage is between 100-110°C, which allows the resin to be in a highly elastic state, which is beneficial for the plasticity of the resin. Attached Figure Description
[0019] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.
[0020] Figure 1 This is a schematic diagram of the structure of a single clamping plate in the tooling fixture of this invention embodiment; Figure 2 This is a schematic diagram of the structure of the pressure plate at the output end of the press in an embodiment of the present invention; Figure 3 This is a schematic diagram of the partitioned layout of the electrode plates in an embodiment of the present invention.
[0021] The diagram exaggerates the spacing or dimensions between parts to show their positions; the diagram is for illustrative purposes only.
[0022] 1. Edge clamping plate, 2. Middle clamping plate, 11. Edge heating circulation pipe, 21. Middle heating circulation pipe; 3. Edge region of the electrode plate, 4. Central reaction region of the electrode plate, 5. Edge pressure plate, 6. Middle pressure plate. Detailed Implementation
[0023] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.
[0024] In a typical embodiment of the present invention, reference is made to Figures 1-3 As shown, a method for partitioned temperature hot pressing and anti-springback leveling of flexible graphite plates includes four stages: pre-pressing stage, main pressing stage, shape-preserving stage, and cooling and shaping stage. Different heating temperatures and pressures are applied to the center and edges of the plate to achieve pressure leveling. The specific steps are as follows: S1: Pre-compression stage: The electrode plate is placed in the tooling fixture and heated by the tooling fixture. The applied temperature is close to room temperature, preferably 25-30℃, and the maximum temperature does not exceed 32℃. The press plate of the press applies linearly increasing pressure to the entire electrode plate through the tooling fixture, which can avoid impact displacement and cause slippage and damage between graphite layers. When the set pressure is reached, the pressure is held for a set time.
[0025] During the pre-compression stage, the pressure applied to the electrode plate is increased at a rate of 0.1 MPa / s to ensure uniform pressure distribution, with a pressure difference of ≤0.08 MPa at each location. When the pressure reaches 0.5 MPa, the pressure is kept constant for at least 10 seconds. By holding the pressure, local stress can be released.
[0026] During the pre-compression stage, the applied temperature is a heating temperature close to room temperature. The purpose is to control the temperature below 32°C to prevent the resin from softening prematurely. Operating at room temperature can eliminate assembly gaps and stabilize material positioning.
[0027] like Figures 1-3As shown, the tooling fixture includes two sets of clamping plates, arranged above and below the electrode plate. The upper and lower clamping plates have the same structure, both consisting of a middle clamping plate 2 and an edge clamping plate 1 spliced together. Each edge clamping plate 1 is formed by connecting four sets of edge plates, which together enclose one edge clamping plate 1. The edge plates 1 are hollow, forming a central opening. The middle clamping plate is positioned at the central opening. The purpose of the edge clamping plate 1 being formed by connecting four sets of edge plates is to facilitate subsequent stretching operations. Correspondingly, pressure is applied through a press. The press output end is equipped with a pressure plate, which includes a middle pressure plate 6 and an edge pressure plate 5, both spliced together and capable of independent pressure application. The electrode plate is divided into a central reaction zone 4 and an edge zone 3.
[0028] The intermediate pressure plate 6 and intermediate clamping plate 2 are positioned to correspond to the position of the central reaction zone 4 of the electrode plate, and the edge pressure plate 5 and edge clamping plate 1 are positioned to correspond to the position of the edge zone 3 of the electrode plate; the intermediate pressure plate 6 presses down on the central reaction zone 4 of the electrode plate through the intermediate clamping plate 2; the edge pressure plate 5 presses down on the edge zone 3 of the electrode plate through the edge clamping plate 1.
[0029] The intermediate clamping plate 2 and the edge clamping plate 1 are spliced together, that is, the intermediate clamping plate 2 is arranged at the center opening of the edge clamping plate 1, the shape of the opening is the same as the shape of the intermediate clamping plate, the shape of the intermediate clamping plate 2 is the same as the shape of the central reaction zone 4 of the electrode plate, and the shape of the edge clamping plate 1 is the same as the shape of the edge zone of the electrode plate. The intermediate clamping plate 2 and the edge clamping plate 1 can be independently temperature controlled, and under the action of the intermediate pressure plate and the edge pressure plate, the intermediate clamping plate and the edge clamping plate can be independently pressure controlled.
[0030] like Figure 1 As shown, the clamping plates have channels to facilitate the connection of heating circulation pipes. Each layer of clamping plates has channels in its four sets of edge plates and one set of middle clamping plates. The channel openings of the edge plates connect to the external edge heating circulation pipes. The middle heating circulation pipe 21 extends from the joint gap between the two sets of edge plates to the channel opening of the middle clamping plate and connects to the outlet. Channels to facilitate pipe passage are required at the joint gaps. Figure 1 Only one set of internal channels on the edge plates is shown. The other end of the heating circulation pipeline is connected to the corresponding heating component, which is existing technology; any component that can achieve the circulation and heating of the medium within the channels and pipeline is acceptable. With this structural arrangement, the intermediate clamping plate 2 and the edge clamping plate 1 can be independently temperature-controlled. It is understood that the extension path of the channels within the clamping plates can be specifically configured.
[0031] S2: Main pressure stage: The electrode plates are hot-pressed in different zones using tooling fixtures. Specifically, the central reaction zone of the electrode plate is heated to a first temperature, which is greater than the resin Tg value, to increase the resin fluidity. The edge zone of the electrode plate, excluding the central reaction zone, is heated to a second temperature to maintain the interlayer bonding force of the graphite. At the same time, the pressure on the central reaction zone of the electrode plate is greater than the pressure on the edge zone of the electrode plate.
[0032] The central reaction zone of the electrode is heated via an intermediate clamp, with a first temperature between 120-130℃. The edge zone of the electrode is heated via an edge clamp, with a second temperature between 80-90℃. During the main pressing stage, the pressure on the central reaction zone is 4.5-5.5 MPa, and the pressure on the edge zone is 2.5-3.5 MPa. The main pressing stage lasts for 3-5 minutes. On the one hand, the high temperature and high pressure treatment on the central reaction zone reduces the porosity of the central reaction zone and eliminates micro-voids inside the electrode. On the other hand, the lower temperature and lower pressure hot pressing on the edge zone effectively reduces edge crack damage and avoids interlayer damage and cracking of the graphite electrode.
[0033] S3: Shape-preserving stage: Apply the same pressure to the entire plane of the electrode plate, heat the central reaction zone of the electrode plate at a third temperature, continue to heat the edge zone of the electrode plate at a second temperature, the third temperature is lower than the first temperature, and at the same time apply tensile strain to the edge zone of the electrode plate for a set shape-preserving time.
[0034] Specifically, during the conformation stage, the pressure applied to the electrode plate is 0.8-1.0 MPa; the central reaction zone of the electrode plate is heated through the intermediate clamp, with a third temperature between 100-110℃; the edge zone of the electrode plate is heated through the edge clamp at a second temperature between 80-90℃. It can be understood that the first temperature during the main pressure stage is between 120-130℃, and this high temperature significantly reduces the resin viscosity, which is beneficial for filling internal micro-voids; the third temperature during the conformation stage, between 100-110℃, keeps the resin in a highly elastic state, which is beneficial for resin plasticity.
[0035] A tensile strain of 0.2% ± 0.02% is applied to the edge region of the electrode, and the shape retention time is not less than 1 minute. This shape retention method can suppress resin shrinkage and springback, while the tensile force at the edge can compensate for the amount of curing shrinkage.
[0036] Specifically, four sets of tension members can be installed on the four sides of the clamping plate. The output end of each tension member is fixedly connected to the side of the edge plate of the upper and lower clamping plates. By pulling the edge plate outward through the tension members, tensile strain can be applied to the edge area of the electrode plate while the clamping plate is clamping the electrode plate. The upper edge plate can cooperate with the pressure plate through a slide rail to facilitate tensile strain.
[0037] Alternatively, on the workbench supporting the lower clamping plate, there are grooves at the corresponding stretching positions and stretching directions. There are also grooves at the corresponding positions on the pressure plate. The output end of the stretching component is clamped to the upper and lower edge plates by a clamp. The clamp can move in the groove, which can also achieve the stretching of the electrode plate by the clamp.
[0038] Alternatively, the output end of the stretching component can be connected to a plate via a rotating bolt. The bolt is rotatably connected to the plate, and the outer side of the edge plate has screw holes into which the bolt can be screwed for fixation. The stretching component can then stretch the edge plate outward through the plate and bolt. A slide rail can also be considered between the clamping plate and the worktable.
[0039] The tensioning component can be a hydraulic cylinder or other tensioning structure. The specific tensioning method can be selected as needed, as long as it can pull the two edge plates sandwiching the electrode plate between the worktable and the pressure plate outward to apply tensile strain to the electrode plate. The tensioning method is not within the protection scope of this invention.
[0040] S4: Cooling and Shaping Stage: Based on the shaping stage, the electrode plate is cooled down. During the process, the entire plane of the electrode plate is kept under the same pressure as in the shaping stage, that is, the pressure applied to the electrode plate is 0.8-1.0MPa. The edge area of the electrode plate maintains a tensile strain of 0.2%. When the electrode plate temperature is below 50℃, which is lower than the resin TG temperature, the molecular chains are fully shaped, the edge tensile force is released, and when the temperature drops to room temperature, the pressure on the entire plane of the electrode plate is released, and the electrode plate is removed.
[0041] The cooling rate of the electrode edge region is less than that of the central reaction region of the electrode. The cooling rate of the heating temperature in the central reaction region of the electrode is 2℃ / min, while the cooling rate of the heating temperature in the electrode edge region is 1.5℃ / min.
[0042] The method allows for zoned control of temperature and pressure across four stages, effectively improving issues such as electrode warping, edge cracking, and hidden cracks.
[0043] This plate partitioning temperature hot pressing and anti-rebound leveling method improves the problems of plate edge cracking and plate springback deformation caused by traditional hot pressing. It reduces the plate edge cracking rate, improves plate flatness, increases product yield, and saves production costs.
[0044] Example 1 Pre-compression stage: ① Place the electrode plate in the tooling fixture and apply the same temperature of 25℃ (room temperature) to the entire electrode plate using the tooling fixture; ② Use the pressure plate on the press to apply linearly increasing pressure to the entire plane of the electrode plate through the tooling fixture, with a pressure rate of 0.1MPa / s, to ensure uniform pressure distribution and a pressure difference of ≤0.08MPa at each location; ③ When the pressure reaches 0.5MPa, keep the pressure constant for 10s.
[0045] Main pressing stage: ① The electrode plates are hot-pressed in zones using a tooling fixture. The central reaction zone of the electrode plate is heated to 120℃ via the middle clamp, which is higher than the resin's Tg value, increasing resin fluidity. The edge zone of the electrode plate is heated to 85℃ via the edge clamp, which improves resin fluidity while maintaining the interlayer bonding force of graphite. ② Simultaneously, the pressure in the central reaction zone of the electrode plate is set to 5.5MPa using a specially designed tooling fixture, and the pressure in the surrounding edge zone is set to 3.5MPa. ③ The hot-pressing time is 3 minutes. On the one hand, the high temperature and high pressure can reduce the porosity of the central zone of the electrode plate; on the other hand, the lower temperature hot-pressing in the edge zone can effectively reduce edge crack damage.
[0046] Conformation retention stage: ① The temperature of the central reaction zone of the electrode is set to 105℃, and the temperature of the edge area of the electrode is set to 85℃; ② The entire plane of the electrode is subjected to the same pressure of 0.8MPa, while the tooling applies a tensile strain of 0.2%±0.02% to the edge area of the electrode; ③ The conformation retention time is 1 minute. This conformation retention method can suppress resin shrinkage and rebound, while the tensile force at the edge can compensate for the amount of curing shrinkage.
[0047] Cooling and shaping stage: ① The temperature of the central reaction zone of the electrode is slowly reduced by the intermediate clamp at a rate of 2℃ / min, and the temperature of the edge area of the electrode is slowly reduced by the edge clamp at a rate of 1.5℃ / min; ② The clamp is pressed down by the pressure plate to keep the entire plane of the electrode under the same pressure of 0.8MPa, and the edge area under 0.2% tensile strain; ③ When the temperature of the electrode drops to 50℃, the edge tensile force is released, and when the temperature drops to room temperature, the pressure on the entire plane of the electrode is released, and the electrode is removed.
[0048] Example 2 Pre-compression stage: ① Place the electrode plate in the tooling fixture and apply the same temperature of 32℃ (room temperature) to the entire electrode plate using the tooling fixture; ② Use the pressure plate on the press to apply linearly increasing pressure to the entire plane of the electrode plate through the tooling fixture, with a pressure rate of 0.1MPa / s, to ensure uniform pressure distribution and a pressure difference of ≤0.08MPa at each location; ③ When the pressure reaches 0.5MPa, keep the pressure constant for 15s.
[0049] Main pressing stage: ① The electrode plates are hot-pressed in zones using tooling fixtures. The central reaction zone of the electrode plate is heated to 130℃ via the middle clamp, which is higher than the resin's Tg value, increasing resin fluidity. The edge zone of the electrode plate is heated to 80℃ via the edge clamps, which improves resin fluidity while maintaining the interlayer bonding force of graphite. ② Simultaneously, the pressure in the central reaction zone of the electrode plate is set to 5MPa using specially designed tooling fixtures, and the pressure in the surrounding edge zone is set to 2.5MPa. ③ The hot-pressing time is 5 minutes. On the one hand, the high temperature and high pressure can reduce the porosity of the central zone of the electrode plate; on the other hand, the lower temperature hot-pressing in the edge zone can effectively reduce edge crack damage.
[0050] Conformation retention stage: ① The temperature of the central reaction zone of the electrode is set to 100℃, and the temperature of the edge area of the electrode is set to 80℃; ② The entire plane of the electrode is subjected to the same pressure of 0.9MPa, while the tooling applies a tensile strain of 0.2%±0.02% to the edge area of the electrode; ③ The conformation retention time is 2 minutes. This conformation retention method can suppress resin shrinkage and rebound, while the tensile force at the edge can compensate for the amount of curing shrinkage.
[0051] Cooling and shaping stage: ① The temperature of the central reaction zone of the electrode is slowly reduced by the intermediate clamp at a rate of 2℃ / min, and the temperature of the edge area of the electrode is slowly reduced by the edge clamp at a rate of 1.5℃ / min; ② The clamp is pressed down by the pressure plate to keep the entire plane of the electrode under the same pressure of 0.9MPa, and the edge area under 0.2% tensile strain; ③ When the temperature of the electrode drops to 50℃, the edge tensile force is released, and when the temperature drops to room temperature, the pressure on the entire plane of the electrode is released, and the electrode is removed.
[0052] Example 3 Pre-compression stage: ① Place the electrode plate in the tooling fixture and apply the same temperature of 30℃ (room temperature) to the entire electrode plate using the tooling fixture; ② Use the pressure plate on the press to apply linearly increasing pressure to the entire plane of the electrode plate through the tooling fixture, with a pressure rate of 0.1MPa / s, to ensure uniform pressure distribution and a pressure difference of ≤0.08MPa at each location; ③ When the pressure reaches 0.5MPa, keep the pressure constant for 15s.
[0053] Main pressing stage: ① The electrode plates are hot-pressed in zones using a tooling fixture. The central reaction zone of the electrode plate is heated to 125℃ via the middle clamp, which is higher than the resin's Tg value, increasing resin fluidity. The edge zone of the electrode plate is heated to 90℃ via the edge clamp, which improves resin fluidity while maintaining the interlayer bonding force of graphite. ② Simultaneously, the pressure in the central reaction zone of the electrode plate is set to 4.5MPa using a specially designed tooling fixture, and the pressure in the surrounding edge zone is set to 3MPa. ③ The hot-pressing time is 4 minutes. On the one hand, the high temperature and high pressure can reduce the porosity of the central zone of the electrode plate; on the other hand, the lower temperature hot-pressing in the edge zone can effectively reduce edge crack damage.
[0054] Conformation retention stage: ① The temperature of the central reaction zone of the electrode is set to 110℃, and the temperature of the edge area of the electrode is set to 90℃; ② The entire plane of the electrode is subjected to the same pressure of 1MPa, while the tooling applies a tensile strain of 0.2%±0.02% to the edge area of the electrode; ③ The conformation retention time is 2 minutes. This conformation retention method can suppress resin shrinkage and rebound, while the tensile force at the edge can compensate for the amount of curing shrinkage.
[0055] Cooling and shaping stage: ① The temperature of the central reaction zone of the electrode is slowly reduced by the intermediate clamp at a rate of 2℃ / min, and the temperature of the edge area of the electrode is slowly reduced by the edge clamp at a rate of 1.5℃ / min; ② The clamp is pressed down by the pressure plate to keep the entire plane of the electrode under the same pressure of 1MPa, while the edge area maintains a tensile strain of 0.2%; ③ When the temperature of the electrode drops to 50℃, the edge tensile force is released, and when the temperature drops to room temperature, the pressure on the entire plane of the electrode is released, and the electrode is removed.
[0056] Existing hot pressing methods typically involve hot pressing the electrode plates without partitioning them, maintaining constant temperature and pressure, and using constant temperature pressing for leveling. This results in a long hot pressing and leveling time, and after the pressure is unloaded, the graphite electrode plates are prone to springback deformation. Electrode plates with large warping deformation may also develop cracks at their edges.
[0057] This embodiment combines zoned hot pressing of the electrode plates at different temperatures with a four-stage continuous leveling process. This method improves upon the problems of edge cracking and springback deformation of the electrode plates after pressure unloading caused by traditional hot pressing. It reduces the edge cracking rate, improves electrode plate flatness, shortens leveling time, increases product yield, and saves production costs. The four stages of this method allow for zoned control of temperature and pressure, effectively improving electrode plate warping, edge cracking, and hidden cracking issues.
[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for temperature hot pressing and anti-rebound flattening of flexible graphite plates, characterized in that, Comprise: S1: pre-pressing stage: the polar plate is placed in the fixture, the temperature of the polar plate is 25-30℃, the linearly increasing pressure is applied to the whole polar plate by the fixture, and the pressure is kept for a set time when the set pressure is reached; S2: main pressing stage: the polar plate is heated and pressed by the fixture, the central reaction area of the polar plate is heated by the fixture at a first temperature, the first temperature is greater than the Tg value of the resin to increase the resin flowability, the edge area of the polar plate is heated at a second temperature to maintain the interlayer bonding force of the graphite layer; at the same time, the pressure on the central reaction area of the polar plate is greater than that on the edge area of the polar plate; S3: shape preserving stage: the same pressure is applied to the whole polar plate, the central reaction area of the polar plate is heated at a third temperature, and the edge area of the polar plate is continuously heated at a second temperature, the third temperature is less than the first temperature, and a tensile strain is applied to the edge area of the polar plate, and the shape is kept for a set time; S4: cooling and shaping stage: based on the shape preserving stage, the polar plate is cooled, the whole polar plate keeps the same pressure as in the shape preserving stage, the edge area of the polar plate keeps the tensile strain, the tensile force is removed when the temperature of the polar plate is lower than 50℃, the pressure on the whole polar plate is unloaded when the temperature drops to room temperature, and the polar plate is taken out.
2. The method of claim 1, wherein the method further comprises: In the pre-pressing stage, the pressure application rate of the polar plate is 0.1 MPa / s to ensure uniform pressure distribution, and the pressure difference between different positions is less than or equal to 0.08 MPa; when the pressure reaches 0.5 MPa, the pressure remains unchanged, and the pressure keeping time is at least 10 s.
3. The method of claim 1, wherein the method further comprises: The fixture comprises two sets of clamping plates arranged above and below the polar plate, and the clamping plates are spliced by middle clamping plates and edge clamping plates.
4. The method of claim 3, wherein the method further comprises: The pressure is applied by a press, and the output end of the press is provided with a pressure plate, which comprises middle pressure plates and edge pressure plates spliced and independently pressurized; the positions of the middle pressure plates and the middle clamping plates correspond to the position of the central reaction area of the polar plate, and the positions of the edge pressure plates and the edge clamping plates correspond to the position of the edge area of the polar plate; the middle pressure plates press down the central reaction area of the polar plate through the middle clamping plates; and the edge pressure plates press down the edge area of the polar plate through the edge clamping plates.
5. The method of claim 4, wherein the method further comprises: The central reaction area of the polar plate is heated by the middle clamping plates, and the first temperature is between 120-130℃; and the edge area of the polar plate is heated by the edge clamping plates, and the second temperature is between 80-90℃.
6. The method of claim 5, wherein the method further comprises: In the main pressing stage, the pressure on the central reaction area of the polar plate is 4.5-5.5 MPa, and the pressure on the edge area of the polar plate is 2.5-3.5 MPa; and the hot pressing time in the main pressing stage is 3-5 min.
7. The method for partitioned temperature hot pressing and anti-rebound leveling of flexible graphite electrode plates according to claim 4, characterized in that, In the shape preserving stage, the pressure applied to the polar plate is 0.8-1.0 MPa; the central reaction area of the polar plate is heated by the middle clamping plates, and the third temperature is between 100-110℃; the edge area of the polar plate is heated by the edge clamping plates; a tensile strain of 0.2%±0.02% is applied to the edge area of the polar plate, and the shape preserving time is not less than 1 min.
8. The method of claim 7, wherein the method further comprises: The cooling rate of the edge area of the polar plate is less than that of the central reaction area of the polar plate.
9. The method of claim 8, wherein the method further comprises: The cooling rate of the heating temperature of the central reaction area of the polar plate is 2℃ / min.
10. The method of claim 9, wherein the method further comprises: The cooling rate of the heating temperature of the edge area of the polar plate is 1.5℃ / min.