A device for precision forming of metal bipolar plates

Abstract

The present invention provides a device for precision forming of metal bipolar plates, belonging to the technical field of manufacturing metal bipolar plates for fuel cells. In the stamping process, the present invention can introduce pulsed current in multiple directions of the flow channels of the metal bipolar plates, reducing the flow stress of the metal sheet and improving its plasticity, and solving problems such as insufficient depth of the flow channels of the bipolar plates, rupture of the flow channels, serious springback, and low dimensional accuracy. The present invention can realize that the direction of the applied current is set according to the shape of the bipolar plate, and by regulating the pulsed current to flow in different directions in the sheet metal according to the time sequence, it is beneficial to overcome the non-uniformity caused by the loading of a single current direction. At the same time, the present invention combines the functions of blank holding and electrode. It can not only play a role in blank holding to avoid wrinkles for the sheet metal, but also introduce pulsed current into the sheet metal, facilitating the blank holding and electroplastic stamping processes. The present invention has high production efficiency, simple production equipment, and high flexibility, and can adopt various forms to meet metal bipolar plates with different requirements.

Description

Technical Field

[0001] The present invention belongs to the technical field of manufacturing metal bipolar plates for fuel cells, and relates to a device for precision forming of metal bipolar plates. Background Art

[0002] The bipolar plate, also known as the current collector plate, is one of the most critical components of a proton exchange membrane fuel cell (PEMFC). The main functions of the bipolar plate are to provide gas flow channels, prevent the hydrogen and oxygen in the fuel cell from mixing, and form a current path after being connected in series between the anode and the cathode. Metal bipolar plates have the advantages of good electrical conductivity, high mechanical strength, low cost, and easy mass production. Common materials for metal bipolar plates include stainless steel, titanium, aluminum, nickel alloy, etc. Currently, the research on metal bipolar plates mainly focuses on 304 or 316 stainless steel materials, which are also commonly used materials for bipolar plates in vehicle fuel cells. Secondly, titanium and its alloys also have extremely high application value and development prospects as the base materials of metal bipolar plates. The specific strength of titanium is about 3.5 times that of stainless steel. Using titanium alloy can reduce the weight of the fuel cell while ensuring the strength of the bipolar plate. Although titanium alloy has many advantages as the base material of the metal bipolar plate, its yield strength is high, the elongation rate is low, and it is difficult to form; in addition, the elastic modulus of titanium alloy is low, resulting in more serious springback than stainless steel, leading to poor forming consistency of the bipolar plate flow channels; finally, the anisotropy of titanium alloy is serious, which will cause the flow channel depths in different directions of the bipolar plate to be inconsistent. The above problems make it still lack suitable forming technologies and devices when using ultra-thin titanium alloy as the bipolar plate material, and it is difficult to prepare bipolar plate microchannels with a high aspect ratio.

[0003] Currently, there are mainly three types of forming technologies for manufacturing metal bipolar plates: one is hot forming and superplastic forming technologies; the second is pulsed forming technology using electromagnetic induction; the third is stamping forming, hydroforming, and soft die forming technologies. However, when the thickness of the metal bipolar plate is 0.1 mm or thinner, the above-mentioned forming technologies are all difficult to simultaneously consider forming efficiency, production cost, and dimensional accuracy. Among them, stamping forming has become the most promising manufacturing method in industrial production due to its advantages such as low process cost, high production efficiency, and long die life.

[0004] An externally applied pulsed current can change the mechanical properties of metal materials in a short time and has currently been applied in various forming processes such as rolling, drawing, bending, and roll forging. Applying the pulsed current in a specific form to the stamping process of a metal bipolar plate can reduce its flow stress, improve the forming ability, and suppress springback, which is beneficial to promoting the development and application of bipolar plates in proton exchange membrane fuel cells. Patent document CN114420963A discloses a method for forming a metal bipolar plate for a hydrogen fuel cell. In this method, two sheets are stacked, welded, and edge-sealed, and the encapsulated parts are placed in an internal high-pressure mold for hydroforming. After hydroforming, the excess material is removed to obtain two finished bipolar plates. However, this method requires a very large hydroforming force, and it is difficult to ensure the forming efficiency and quality.

[0005] Patent document CN112974642 discloses an electro-assisted forming device and process for a fuel cell metal plate. The device includes a power supply, a forming die, a metal thin plate to be formed, and a sensor, etc. This method is to connect the two ends of the sheet to the power supply or connect the power supply to the upper and lower ends of the forming die for stamping forming, and realize the precision forming of the sheet by controlling the Joule heat generated by the current and the electroplastic effect. However, this method uses a single-direction current acting on the bipolar plate, without considering the effect differences brought by the flow channels with different directions. And because the metal sheet itself also has anisotropy, this exacerbates the control of the forming profile size uniformity and precision of the single-direction current on the flow channels, and it is impossible to achieve high-quality forming of metal plates with complex-shaped flow channels in actual production.

[0006] Patent document CN111842611B discloses a forming device and method for a titanium alloy bipolar plate based on multi-temporal pulsed current. The device includes multiple sets of pulsed power supplies, which can discharge the titanium alloy sheet and the Helmholtz coil according to the time sequence. By using the thermal effect and electroplastic effect of the pulsed current on the titanium alloy sheet, and the pulsed magnetic field generated in the Helmholtz coil acting together, the titanium alloy sheet is driven to impact the die to realize the forming of the titanium alloy bipolar plate. However, this method has a relatively complex forming device, and it needs to be evacuated before forming, with low efficiency; and the forming process is also difficult to control, which is not conducive to large-scale production. Summary of the Invention

[0007] In order to solve the above-mentioned technical problems existing in the prior art, the present invention provides a device for precision forming of metal bipolar plates, which can solve the problem that it is difficult to form metal bipolar plates with high aspect ratio microchannels in the prior art. The electroplastic precision forming of metal bipolar plates is realized by passing a pulsed current through the metal sheet during the stamping process of the present invention.

[0008] In order to achieve the above purpose, the technical solution adopted by the present invention is:

[0009] A device for precision forming of metal bipolar plates, the device comprising a die assembly, a blank-holder electrode assembly, a wire 13, a cyclic timing control switch 14, and a pulse power supply 15.

[0010] The die assembly includes an upper die base 1, a punch 2, a die 6, a lower die base 7, guide pillars 8, guide sleeves 9, and insulating gaskets 12. The lower die base 7 is of a plate-like structure, with a die 6 fixedly connected to the middle thereof, and a plurality of guide pillars 8 are provided on the lower die base 7 on both sides of the die 6; the die 6 is of a plate-like groove surface structure; the upper die base 1 is of a plate-like structure, which is installed under a press, and a punch 2 is fixedly connected to the middle of its lower surface. The upper die base 1 and the punch 2 are located above the lower die base 7. Holes are provided at positions on the upper die base 1 corresponding to the guide pillars 8, and guide sleeves 9 are provided in the holes. The guide sleeves 9 are slidably engaged with the guide pillars 8 for positioning the upper die base 1; the punch 2 is of a plate-like convex surface structure, which cooperates with the die 6. During use, the metal sheet to be formed is placed between the die 6 and the punch 2, and the convex part of the punch 2 corresponds to the groove position of the die 6. When the die is closed, the metal sheet to be formed is extruded into the groove shape of the die 6; the insulating gaskets 12 are respectively provided between the punch 2 and the upper die base 1 and between the die 6 and the lower die base 7 to prevent the formation of other current loops during the energization process.

[0011] The blank-holder electrode assembly includes a blank-holder ring 3, blank-holder springs 4, blank-holder ring guide pillars 5, guide sleeves 9, blank-holder electrodes 11, and insulating gaskets 12. The blank-holder ring 3 is of a frame-like structure, which is located below the punch 2, and the punch 2 can pass through its inner circle. The blank-holder ring 3 is used to press the edge of the metal sheet. The contour shapes of the inner and outer circles of the blank-holder ring 3 depend on the shape of the formed plate (for example, it can be rectangular or oval, etc.). A plurality of blank-holder ring guide pillars 5 are provided on its upper surface. Holes are provided at positions on the upper die base 1 corresponding to the blank-holder ring guide pillars 5, and guide sleeves 9 are provided in the holes. The guide sleeves 9 are slidably engaged with the blank-holder ring guide pillars 5 for positioning the blank-holder ring 3; a blank-holder spring 4 is sleeved on each blank-holder ring guide pillar 5, and both ends of the blank-holder spring 4 are fixedly connected to the upper die base 1 and the blank-holder ring 3 respectively, for pressing and resetting the blank-holder ring 3; a plurality of blank-holder electrodes 11 with the same shape are provided, which are respectively fixed to the bottom of the blank-holder ring 3. An insulating gasket 12 is provided between the blank-holder electrode 11 and the blank-holder ring 3 to prevent short circuit caused by current passing through the blank-holder ring 3; when the press moves downward, the blank-holder ring 3 together with the blank-holder electrodes 11 fixed below presses on the edge of the metal sheet to be formed, playing a blank-holding role and also used for introducing pulsed current. The process of introducing current can occur before the die is closed, during the die closing process, and after the die is closed.

[0012] The pulse power supply 15 includes one or more pulse power supply devices, which can output DC or AC pulse current of any waveform. It is connected to the cyclic timing control switch 14 through a wire 13 and is used to apply pulse current to the metal sheet to be formed. The cyclic timing control switch 14 is connected to multiple sets of blank-holding electrodes 11 through the wire 13, and applies pulse current to the metal sheet to be formed in a fixed loading mode in a cycle, so as to control the pulse power supply current to be applied to the metal sheet to be formed in a specific mode, and realize the forming of the metal electrode plate through stamping.

[0013] An insulating gasket 12 is arranged at the connection between the mold and the mold base, effectively avoiding the current flowing to the machine tool during the contact between the mold and the energized sheet; an insulating gasket 12 is arranged at the connection between the blank-holding ring 3 and the blank-holding electrode 11, effectively avoiding the short circuit formed by the current passing through the metal blank-holding ring 3 when electrified.

[0014] Furthermore, the number, shape and position of the blank-holding electrodes 11 are set according to the shape requirements of the metal sheet to be formed and the required number of electrode groups.

[0015] Furthermore, the blank-holding electrode 11 can be replaced with a flexible electrode form to deal with metal bipolar plates with more complex forming shapes; the flexible electrode includes a cover plate, an insulating spring and an electrode piece. Among them, the cover plate is fixedly connected to the lower surface of the blank-holding ring 3, the upper ends of several insulating springs are fixedly connected to the bottom surface of the cover plate, and the lower ends are fixedly connected to the electrode piece, and each insulating spring is connected to an electrode piece, and the electrode pieces are connected in parallel with each other.

[0016] Furthermore, the pulse power supply 15 can output DC or AC pulse current of any required waveform, the duty cycle is adjustable arbitrarily, the output current is adjustable within 1000A, and the frequency is 1Hz - 20KHz.

[0017] Furthermore, the device is applicable to metal materials that meet the application of fuel cell bipolar plates.

[0018] Furthermore, the metal materials applicable to the metal bipolar plate to be formed by the device include stainless steel, titanium alloy, aluminum alloy and nickel-based alloy.

[0019] The device utilizes the electroplastic effect, and applies multi-directional pulse current to the metal sheet through timing control to complete the process of stamping and forming the metal bipolar plate.

[0020] The beneficial effects of the present invention:

[0021] 1. The present invention can introduce pulse current in multiple directions to the flow channels of the metal bipolar plate during the stamping process, reduce the flow stress of the metal thin plate, improve the plasticity, and to a certain extent improve its tissue performance, thereby solving problems such as insufficient depth of the bipolar plate flow channel, flow channel rupture, serious springback, and low dimensional accuracy.

[0022] 2. The present invention is applicable to stamping forming methods, featuring high production efficiency, simple production equipment, and high flexibility. It can adopt various forms to meet the requirements of metal bipolar plates with different specifications.

[0023] 3. The present invention combines the functions of blank holding and electrode. During the forming process, the blank holder can not only hold the sheet metal to prevent wrinkles from appearing on the formed sheet metal, but also act as a support for introducing pulsed current electrodes to the sheet metal, making it more convenient for the blank holding and electroplastic stamping processes of the sheet metal.

[0024] 4. In the present invention, the cyclic timing control switch controls the flow direction of the pulsed current in the sheet metal. Multiple groups of electrodes are connected to the sheet metal to control the pulsed current to flow horizontally, vertically, and obliquely along the sheet metal. After being energized in a certain direction for a period of time, it can automatically switch to the next flow direction. The current direction can be flexibly set according to the forming requirements, which is beneficial to overcoming the anisotropy of the sheet metal and the non-uniformity caused by the single current direction loading of the flow channels in different forming directions, facilitating the electroplastic stamping forming of the sheet metal. That is to say, the present invention can realize the setting of the externally applied current direction according to the shape of the bipolar plate and adjust it according to the timing, with flexible changes. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the overall structure of the device of the present invention.

[0026] Figure 2 It is the front view of the device of the present invention.

[0027] Figure 3 It is the bottom view of the connection between the blank holding electrode assembly and the pulsed power supply.

[0028] Figure 4 It is a schematic diagram of the cyclic timing switch loading mode.

[0029] Figure 5 It is an example of the form of the blank holding electrode assembly.

[0030] Figure 6 It is a schematic diagram of the typical flow channel shape of the metal bipolar plate.

[0031] Figure 7 It is a schematic diagram of the flexible blank holding electrode structure.

[0032] In the figure: 1 upper die holder; 2 punch; 3 blank holder; 4 blank holding spring; 5 blank holder guide pillar; 6 die; 7 lower die holder; 8 guide pillar; 9 guide sleeve; 10 titanium alloy sheet to be formed; 11 blank holding electrode; 12 insulating gasket; 13 wire; 14 cyclic timing control switch; 15 pulsed power supply. DETAILED DESCRIPTION OF THE INVENTION

[0033] The following further describes the present invention in conjunction with specific embodiments.

[0034] Embodiment 1

[0035] Reference Figure 1 , which shows the structure of the device for precision forming of metal bipolar plates provided in the embodiment of the present invention.

[0036] The device for precision forming of metal bipolar plates provided in the embodiment of the present invention is used for electroplastic stamping forming of fuel cell metal bipolar plates, and includes a die assembly, a blank holding electrode assembly, a wire 13, a cyclic timing control switch 14, and a pulse power supply 15. Among them:

[0037] The die assembly includes an upper die base 1, a punch 2, a die 6, a lower die base 7, guide pillars 8, guide sleeves 9, and an insulating gasket 12. The upper die base 1 is of a plate-like structure and is installed under a press. The punch 2 is fixedly connected to the middle position of the lower surface of the upper die base 1, and the insulating gasket 12 is sandwiched between the upper die base 1 and the punch 2. Among them, the punch 2 is of a plate-like groove surface structure; the lower die base 7 is of a plate-like structure and is placed below the upper die base 1. The die 6 is fixedly connected to the middle position of the upper surface of the lower die base 7, and the insulating gasket 12 is sandwiched between the die 6 and the lower die base 7. Among them, the die 6 is of a plate-like convex surface structure; the lower parts of 4 guide pillars 8 are fixedly connected to the lower die base 7 on both sides of the die 6, and guide sleeves 9 are provided at the corresponding positions of the guide pillars 8 on the upper die base 1. The upper parts of the guide pillars 8 are inserted into the guide sleeves 9, and the two are in sliding fit for positioning the upper die base 1.

[0038] The blank holding electrode assembly includes a blank holder 3, a blank holding spring 4, blank holder guide pillars 5, guide sleeves 9, blank holding electrodes 11, and an insulating gasket 12. The blank holder 3 is of a frame-like structure and is located below the punch 2, and the punch 2 can pass through its inner circle. The blank holder 3 is used to press the edge of the metal sheet to be formed. Both the inner and outer circles of the blank holder 3 are rectangular, and 4 blank holder guide pillars 5 are provided on its upper surface. Guide sleeves 9 are provided at the corresponding positions of the blank holder guide pillars 5 on the upper die base 1. The upper ends of the blank holder guide pillars 5 are inserted into the guide sleeves 9 and are in sliding fit with them for positioning the blank holder 3; a blank holding spring 4 is sleeved on each blank holder guide pillar 5, and both ends of the blank holding spring 4 are fixedly connected to the upper die base 1 and the blank holder 3 respectively for pressing and resetting the blank holder 3; a total of 6 blank holding electrodes 11 are provided, all of which are trapezoidal, with the trapezoidal bottom edges facing inwards. The 6 blank holding electrodes 11 are uniformly arranged and fixedly connected to the lower surface of the blank holder 3, and the insulating gasket 12 is placed between the blank holding electrodes 11 and the blank holder 3.

[0039] The number, shape, and distribution of the blank holding electrodes 11 in the above blank holding electrode assembly can also be arbitrarily designed according to the use requirements, and some examples are shown as Figure 5 shown.

[0040] The input end of the cyclic timing control switch 14 is the positive and negative wires led out from the electroplastic power supply device, and the output end is connected to the blank holding electrodes 11 fixed at the bottom of the blank holder 3 by several groups of wires 13. The power connection is as Figure 3As shown, the cyclic timing control switch 14 forms a circuit with the positive and negative poles of the pulse power supply 15 and switches the path mode at regular intervals. The path modes can be arranged arbitrarily, and the current direction can be set accordingly.

[0041] The duration of the above path mode is at least one pulse cycle and at most 4 - 10 s.

[0042] Embodiment 2: The device described in Embodiment 1 is used in this embodiment to form a typical metal bipolar plate, and its flow channel shape is as Figure 6 shown, and the specific steps are as follows:

[0043] Step 1: Place the titanium alloy sheet 10 to be formed at the corresponding position above the female die 6.

[0044] Step 2: The press drives the upper die holder 1, the punch 2, and the blank-holding electrode assembly to move downward together.

[0045] Step 3: The blank-holding electrode 11 of the blank-holding electrode assembly first contacts the titanium alloy sheet 10 to be formed, and continues to move downward so that the compression force of the blank-holding spring 4 acts on the blank-holding ring 3 and the blank-holding electrode 11, applying a certain blank-holding force to the periphery of the titanium alloy sheet 10 to be formed. At this time, the punch 2 does not contact the titanium alloy sheet 10 to be formed.

[0046] Step 4: Turn on the pulse power supply 15 with the preset frequency, duty cycle, and current density; turn on the cyclic timing control switch 14 with the set cyclic action duration and timing sequence, and generate a current that flows through the wire 13 and the blank-holding electrode 11 and acts on the titanium alloy sheet 10 to be formed in the corresponding loading mode. Among them, the loading mode controlled by the cyclic timing control switch 14 is combined with Figure 4 description;

[0047] such as Figure 4As shown in the figure, the pulse power supply 15 in the figure is a DC pulse power supply, with an adjustable output current of 1 - 1000 A and an adjustable frequency of 1 Hz - 20 KHz. It is connected to the cyclic timing control switch 14, and six wires 13 are led out from six interfaces of the switch and connected to six edge pressing electrodes 11. The interfaces numbered ① to ⑥ are respectively connected to the electrodes ① to ⑥. Electrode ① is opposite to electrode ⑤, electrode ② is opposite to electrode ④, electrode ③ is opposite to electrode ⑥. Electrode ① and electrode ② are on the same side and adjacent, electrode ④ and electrode ⑤ are on the same side and adjacent, and electrode ⑥; When operating in mode one, the interfaces numbered ② and ⑤ are respectively used as the positive and negative poles to be connected, forming a loop in the left - right horizontal direction of the sheet metal; When operating in mode two, the interfaces numbered ① and ③ are connected, and the current flows vertically in the left half of the sheet metal; When operating in mode four, the interfaces numbered ③ and ⑥ are connected, and the current flows obliquely in the sheet metal. And so on, multiple modes can process the titanium alloy sheet 10 to be formed horizontally, vertically, and obliquely through current, and can be automatically switched after the required duration of different mode operations. The mode sequence can be adjusted arbitrarily, and the positive and negative pole directions can be mutually converted, realizing multi - polar and multi - direction conforming applications.

[0048] In this embodiment, the specific process of current application during the forming process is as follows:

[0049] 1) Electrodes ① and ② are used as the positive poles, and electrodes ⑤ and ⑥ are used as the negative poles. Turn on the pulse power supply 15 to apply a pulse current in the direction of the flow channel. After passing through the set time, the power supply of the loop stops.

[0050] 2) Electrode ③ is used as the positive pole, and electrode ⑥ is used as the negative pole. Turn on the pulse power supply 15 to apply a pulse current in the direction across the flow channel. After passing through the set time, the power supply of the loop stops.

[0051] 3) Electrode ① is used as the positive pole, and electrode ④ is used as the negative pole. Turn on the power supply, and the current flows from the upper - left electrode ① to the lower - right electrode ④. After passing through the set time, the power supply of the loop stops.

[0052] 4) Electrode ② is used as the positive pole, and electrode ⑤ is used as the negative pole. Turn on the power supply, and the current flows from the upper - right electrode ② to the lower - right electrode ⑤. After passing through the set time, the power supply of the loop stops.

[0053] The above power - on process is controlled by the cyclic timing control switch 14 to cycle.

[0054] Step five: The press continues to descend at a speed of 0.1 mm / s, and the upper and lower molds are closed; After complete closing of the molds, the current continues to be maintained for a period of time and then automatically turns off. The total pressure - holding time is about 15 s; The upper and lower molds are separated and the formed metal electrode plate is taken out, completing the precision forming process.

[0055] Embodiment 3: This embodiment uses the device described in Embodiment 1 to form a fuel - cell metal bipolar plate, which specifically includes the following steps:

[0056] Step 1: Place the titanium alloy sheet 10 to be formed at the corresponding position of the female die 6;

[0057] Step 2: The press drives the upper die base 1, the punch 2 and the blank-holding electrode assembly to move downward together;

[0058] Step 3: After the blank-holding electrode 11 presses the titanium alloy sheet 10 to be formed, it stops moving downward;

[0059] Step 4: Turn on the pulse power supply 15 with pre-set parameters. In this embodiment, the pulse power supply 15 is an AC pulse power supply, the output current is adjustable from 1 to 1000 A, and the frequency is adjustable from 1 Hz to 20 KHz. Perform pre-forming pretreatment on the titanium alloy sheet 10 to be formed in a specific loading mode, and the treatment duration is 60 s;

[0060] Step 5: Turn off the pulse power supply 15, and the press continues to move downward, and the upper and lower dies are gradually closed;

[0061] Step 6: Separate the upper and lower dies and take out the formed metal electrode plate to complete the precision forming process.

[0062] Example 4: In this example, the device described in Example 1 is used to form the fuel cell metal bipolar plate, which specifically includes the following steps. Steps 1 to 5 are the same as those in Example 3:

[0063] Step 6: Turn on the pulse power supply 15 with specific parameters again. After the current acts for 30 s, turn off the power supply;

[0064] Step 7: Open the die and take out the formed metal electrode plate to complete the precision forming process.

[0065] Example 5: The blank-holding electrode 11 can be replaced with a flexible electrode form to deal with the metal bipolar plate with a more complex forming shape, as shown in Figure 7 shown.

[0066] The flexible electrode includes a cover plate, an insulating spring and an electrode plate; the cover plate is fixedly connected to the lower surface of the blank-holding ring 3, and a plurality of insulating springs are fixedly connected to the bottom surface of the cover plate. The upper end of the insulating spring is fixedly connected to the cover plate, and the lower end is fixedly connected to the electrode plate, and each insulating spring is connected to an electrode plate. The electrode plates are connected in parallel with each other. During use, the electrode plates are attached to the metal sheet to be formed, and are used for forming the metal bipolar plate with a more complex shape.

[0067] The above embodiments only represent the implementation modes of the present invention, but should not be construed as limiting the scope of the patent of the present invention. It should be noted that for those skilled in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A device for precision forming of metal bipolar plates, characterized in that, The device includes a die assembly, a blank-holding electrode assembly, a wire (13), a cyclic timing control switch (14), and a pulse power supply (15); The die assembly includes an upper die base (1), a punch (2), a die (6), a lower die base (7), guide pillars (8), guide bushes (9), and insulating gaskets (12); the lower die base (7) is of a plate-like structure, with a die (6) of a plate-like groove surface structure fixedly connected to the middle thereof, and several guide pillars (8) are provided on the lower die base (7); the upper die base (1) is of a plate-like structure, which is installed under a press, and a punch (2) is fixedly connected to the middle of its lower surface. The upper die base (1) and the punch (2) are located above the lower die base (7). Holes are provided at positions corresponding to the guide pillars (8) on the upper die base (1), and guide bushes (9) are arranged in the holes. The guide bushes (9) are slidably engaged with the guide pillars (8) for positioning the upper die base (1); the punch (2) is of a plate-like convex surface structure, which cooperates with the die (6). During use, the metal sheet to be formed is placed between the die (6) and the punch (2), and the convex part of the punch (2) corresponds to the groove position of the die (6). When the die is closed, the metal sheet to be formed is extruded into the groove shape of the die (6); the insulating gaskets (12) are respectively arranged between the punch (2) and the upper die base (1) and between the die (6) and the lower die base (7) to prevent other current loops from being formed during the energization process; The blank-holding electrode assembly includes a blank-holding ring (3), blank-holding springs (4), blank-holding ring guide pillars (5), blank-holding ring guide bushes, blank-holding electrodes (11), and insulating gaskets (12); the blank-holding ring (3) is of a frame structure, which is located below the punch (2), and the punch (2) can pass through its inner circle. The blank-holding ring (3) is used to press the edge of the metal sheet. The contour shapes of the inner and outer circles of the blank-holding ring (3) depend on the shape of the formed electrode plate. Several blank-holding ring guide pillars (5) are provided on its upper surface. Holes are provided at positions corresponding to the blank-holding ring guide pillars (5) on the upper die base (1), and blank-holding ring guide bushes are arranged in the holes. The blank-holding ring guide bushes are slidably engaged with the blank-holding ring guide pillars (5) for positioning the blank-holding ring (3); a blank-holding spring (4) is sleeved on each blank-holding ring guide pillar (5), and both ends of the blank-holding spring (4) are respectively connected to the upper die base (1) and the blank-holding ring (3) for pressing and resetting the blank-holding ring (3); several blank-holding electrodes (11) of the same shape are provided, which are respectively fixed to the bottom of the blank-holding ring (3). An insulating gasket (12) is arranged between the blank-holding electrode (11) and the blank-holding ring (3) to prevent short circuit caused by current passing through the blank-holding ring (3); The pulse power supply (15) includes one or more pulse power supply devices, which can output DC or AC pulse currents of any waveform. It is connected to the cyclic timing control switch (14) through a wire (13) and is used to apply pulse currents to the metal sheet to be formed. The cyclic timing control switch (14) is connected to multiple groups of blank-holding electrodes (11) through a wire (13). It applies pulse currents to the metal sheet to be formed in a fixed loading mode in a cycle and realizes the forming of metal electrode plates through stamping; The cyclic timing control switch (14) controls the flow direction of the pulsed current in the sheet metal. Multiple groups of electrodes are connected to the sheet metal to control the pulsed current to flow horizontally, vertically, and obliquely along the sheet metal, and after being energized in a certain direction for a period of time, it can automatically switch to the next flow direction.

2. The device for precision forming of metal bipolar plates according to claim 1, characterized in that, The number, shape, and position of the blank-holding electrodes (11) are set according to the shape requirements of the metal sheet to be formed and the number of electrode groups required.

3. A device for precision forming of metal bipolar plates according to claim 1 or 2, characterized in that, The blank-holding electrodes (11) are replaced with a flexible electrode form to deal with the metal bipolar plates with complex forming shapes; the flexible electrode includes a cover plate, a plurality of insulating springs, and a plurality of electrode plates. Among them, the number of insulating springs is the same as that of the electrode plates. The cover plate fits on the lower surface of the blank-holding ring (3). The upper end of the insulating spring is fixedly connected to the bottom surface of the cover plate, and the lower end is fixedly connected to the electrode plate. The electrode plates are connected in parallel with each other.

4. A device for precision forming of metal bipolar plates according to claim 1, characterized in that, The pulse power supply (15) can output any required DC or AC pulsed current, the duty cycle is adjustable arbitrarily, the output current is adjustable within 1000 A, and the frequency is 1 Hz - 20 KHz.

5. A device for precision forming of metal bipolar plates according to any one of claims 1, 2 or 4, characterized in that, The device is applicable to metal materials that meet the application requirements of fuel cell bipolar plates.

6. The device for precision forming of metal bipolar plates according to claim 3, characterized in that, The device is applicable to metal materials that meet the application requirements of fuel cell bipolar plates.

7. A device for precision forming of metal bipolar plates according to claim 5, characterized in that, The metal materials include stainless steel, titanium alloy, aluminum alloy, or nickel-based alloy.

8. The device for precision forming of metal bipolar plates according to claim 6, characterized in that, The metal materials include stainless steel, titanium alloy, aluminum alloy, or nickel-based alloy.

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