Preparation method of fuel cell metal plate and metal plate multi-step forming production line

Abstract

Disclosed are a preparation method for a fuel cell metal plate and a metal plate multi-step forming production line, wherein a preparation method for a fuel cell metal plate comprises: a loading step, loading a metal substrate onto a first-order stamping device having a first-order forming mold; the thickness of the metal substrate is less than 0.2 mm; a first-order forming step, performing a first-order stamping pre-forming on the metal substrate by using the first-order stamping device to form a pre-formed metal plate; a transport and electrical treatment step, controlling the transport electrical treatment device to move the pre-formed metal plate to an electrical treatment station on the transport electrical treatment device for electrical treatment, and taking out the electrically treated metal plate after the electrical treatment is completed; the electrical treatment clamping area is greater than 500 mm 2 ; A second forming step, using a second stamping device to perform a second stamping forming on the metal plate after the electrical treatment to obtain a fully formed metal plate; a blanking step, removing the fully formed metal plate from the second stamping device.

Description

Technical Field

[0001] The present application relates to the field of fuel cells, and in particular to a multi-step forming production line for metal plates based on an electrical treatment modification effect and a process thereof, and in particular to a preparation method for fuel cell metal plates and a multi-step forming production line for metal plates. Background Art

[0002] Hydrogen energy is an important strategic means to promote the green transformation of the world's energy industry. Proton exchange membrane fuel cells are the key technology for the utilization of hydrogen energy, and high power, long life and high performance are the development trends of fuel cells. As one of the core components of fuel cells, bipolar plates have sub-millimeter microchannel characteristics, and the fineness of their channels has an important impact on the power generation efficiency, reliability and service life of fuel cells. Compared with traditional graphite bipolar plates, metal bipolar plates have multiple advantages such as small thickness, low cost, excellent mechanical properties, and excellent electrical and thermal conductivity. They have become one of the mainstream trends in fuel cell manufacturing technology research.

[0003] However, as fuel cells continue to increase their requirements for the transport efficiency of reactant gases and product water, bipolar plates need to have more sophisticated flow channel structures and higher flow channel depth-to-width ratios. The forming performance bottleneck of ultra-thin metal substrates will cause them to crack prematurely during the stamping process, restricting the high-performance development of fuel cells. In recent years, extensive innovations have been made in the forming methods of metal bipolar plates at home and abroad. Although new laboratory-level processes such as electromagnetic high-speed forming and high-temperature forming can effectively improve the forming limit of metal plates, they all exhibit low production efficiency and poor compatibility with existing bipolar plate production lines, limiting their application in actual production. Therefore, it is urgent to develop a method for manufacturing high-performance metal bipolar plates for fuel cells that is both efficient and simply compatible with existing metal plate production lines.

[0004] Patent document CN112974642A (An electric-assisted forming device and process for fuel cell metal plates) discloses an electric-assisted forming process for fuel cell metal plates, which passes current through the metal plates still in the mold during the metal plate stamping process, uses Joule heat and electroplasticity to reduce the forming force of the plates, and improves their forming accuracy and consistency. However, the electric-assisted forming process of the invention focuses on improving the manufacturing accuracy of the single-step stamping of the metal plates, and has no significant effect on improving the forming limit of the metal plates.

[0005] Patent document CN111842611A (A titanium alloy bipolar plate forming device and method based on multi-sequence pulse current) proposes an electromagnetic-thermal composite forming method for titanium alloy bipolar plates. Through multi-stage sequential pulse current discharge, the forming limit of titanium alloy plates is improved by utilizing thermal effect, electroplastic effect and high strain rate effect of pulse electromagnetic force. However, the electromagnetic forming device included in this technology is complex, the cost is high, and the production efficiency is low, which is not suitable for actual production applications.

[0006] Patent document CN116154208B (High-precision and high-corrosion-resistant titanium bipolar plates for fuel cells, preparation methods, and mold assemblies thereof) proposes a heat-assisted forming process for ultra-thin titanium plates for fuel cells. By adding an annealing heat treatment process between the two-step stamping forming process, the internal stress of the titanium plate after the first-order forming is released and the work hardening is eliminated, thereby improving its re-deformation performance and increasing the forming limit. However, the heat treatment process in this invention is time-consuming (2-30 minutes), which affects the production efficiency of the titanium plate. In addition, the static recovery process of the heat treatment is often accompanied by grain growth, which limits its effect on improving the forming limit of the plate. Summary of the invention

[0007] In view of the deficiencies of the above-mentioned prior art, the present invention aims to propose a multi-step forming production line and process for metal plates based on electrical treatment modification, which can significantly improve the forming limit and forming accuracy of metal plates, so as to solve the problems of insufficient microchannel depth, channel cracking, poor dimensional accuracy, etc. existing in the existing metal plate forming process, without affecting production efficiency.

[0008] To achieve the above-mentioned objectives, the present invention provides a method for preparing fuel cell metal plates based on electrical treatment modification and a multi-step forming production line for metal plates. The multi-step forming production line for metal plates comprises, in sequence: a loading robot (loading equipment), a first-sequence stamping equipment, a transfer electrical treatment equipment, an electrical treatment equipment, a second-sequence stamping equipment and a unloading robot (unloading equipment).

[0009] At the same time, the present invention proposes a multi-step forming production process of metal plates based on electrical treatment modification around the aforementioned production line as follows:

[0010] S1, a material acquisition step, obtaining a titanium substrate or a ferritic stainless steel substrate having a thickness of not less than 0.05 mm and not more than 0.2 mm;

[0011] S2. Electrical treatment parameter acquisition process. Electrical treatment refers to the material modification process of passing direct current into the metal plate to repair its internal defects and stimulate its plasticity. Compared with the traditional furnace annealing heat treatment, ultra-short electrical treatment can release internal stress, eliminate deformation twins and dislocation accumulation generated by ultra-thin metal plates during the pre-deformation process, and significantly promote static recrystallization, thereby improving the re-deformation performance of the pre-deformed metal plate and increasing the forming limit. The electrical treatment equipment can provide constant voltage direct current or pulsed direct current of arbitrary waveform, with an output voltage amplitude of 0-300V, a duty cycle of 0-100%, and a frequency of 100-4000Hz.

[0012] For plates of different sizes, the amount of electrical energy required to process defects is also different. The temperature rise of the plates caused by the Joule heating effect of electrical treatment is easy to measure, and can be used as a simple means to determine the level of electrical energy input and to determine the threshold of electrical treatment parameters. The target temperature range of electrical treatment is 500-1200°C, and the power-on time needs to be controlled within the range of 0.5-10 seconds. In actual production, the electrical treatment time should be selected based on the production rhythm requirements, and then the electrical treatment process parameters such as output voltage, duty cycle and frequency should be determined based on the target heating temperature;

[0013] S3, loading process, the loading robot automatically transfers the blank to the first-order stamping equipment through the vacuum suction cup, and positions the blank in the first-order forming die;

[0014] S4, a first forming step, the punching machine moves downward, and the metal sheet is preformed by a first forming die to obtain a metal plate;

[0015] S5, transfer and electrical treatment process, the transfer electrical treatment equipment sucks up the preformed metal plate through the vacuum suction cup, and moves it out of the first-order stamping equipment first. Then, it moves to the position of the electrical treatment fixture integrated in the transfer electrical treatment equipment, and the upper clamp of the electrical treatment fixture moves down to clamp the two ends of the preformed metal plate, and the vacuum suction cup stops working and moves up. The pre-deformed metal plate is clamped by the electrical treatment fixture to complete its transfer between the two-order stamping equipment, and the pre-deformed metal plate is electrically treated and modified at the same time, and it is ensured that the metal plate has completed the electrical treatment modification and cooled to room temperature before reaching the second-order stamping equipment. Finally, the vacuum suction cup moves down to suck up the metal plate, the electrical treatment fixture is released and returned, and the metal plate is transferred to the second-order stamping equipment and positioned;

[0016] S6, second forming process, the punching machine moves downward, and the preformed metal plate after the electrical treatment is completely stamped and formed by the second forming die;

[0017] S7, unloading process, the unloading robot transfers the fully formed metal plates out of the second-order stamping equipment.

[0018] A method for preparing a fuel cell metal plate, comprising:

[0019] A loading step, loading a metal substrate onto a first-order stamping device having a first-order forming die; the thickness of the metal substrate is less than 0.2 mm;

[0020] A first forming step, using a first stamping device to perform a first stamping pre-forming on the metal substrate to form a pre-formed metal plate;

[0021] The transfer and electrical treatment process controls the transfer electrical treatment equipment to move the preformed metal electrode plate to the electrical treatment station on the transfer electrical treatment equipment for electrical treatment, and takes out the electrically treated metal electrode plate after the electrical treatment; the electrical treatment clamping area is >500mm 2 ; Further, the electrical treatment clamping area> 1500mm 2 ; Furthermore, the electrical treatment clamping area> 2000mm 2 .

[0022] A second forming step, using a second stamping device to perform a second stamping forming on the metal plate after the electrical treatment to obtain a fully formed metal plate;

[0023] The blanking step is to remove the fully formed metal plate from the second-order stamping equipment.

[0024] As a preferred aspect, the first forming step and the second forming step further include at least one intermediate forming step to perform stamping on the metal plate, and the electrical treatment step is provided between the two forming steps.

[0025] As a preferred aspect, the transport electric treatment equipment comprises an electric treatment carrying platform and a transport platform located above the electric treatment carrying platform; the electric treatment carrying platform comprises electrode units arranged relatively; the electrode units comprise electrode clamps which can be operated to be pressed and opened; the transport platform is installed above the electric treatment carrying platform through a vertical movable bracket; the transport platform can be operated to be moved up and down on the vertical movable bracket; the transport platform comprises a rectangular frame and a suction cup assembly which can be operated to be moved in a horizontal direction on the bracket; the suction cup assembly is used to absorb a metal substrate or a metal electrode plate;

[0026] The suction cup assembly has a first horizontal position (initial position) and a second horizontal position in a horizontal direction relative to the rectangular frame; the transfer platform has a first height position and a second height position above the first height position on the vertical movable bracket 5.

[0027] As a preferred aspect, during the transfer and electrical treatment process, the suction cup assembly is controlled to suck the preformed metal electrode plate at the second horizontal position and the second height position, then, the electrode clamp is opened, the suction cup assembly is controlled to descend to the first height position and then move from the second horizontal position to the first horizontal position, the preformed metal electrode plate is delivered between the electrode clamps, the suction cup assembly is controlled to release the preformed metal electrode plate and the electrode clamp is controlled to press the preformed metal electrode plate for electrical treatment, finally, the electrode clamp is opened and the suction cup assembly is controlled to re-absorb the electrically treated metal electrode plate and move it from the first horizontal position to the second horizontal position, and then the electrically treated metal is moved upward to the second height position.

[0028] As a preferred aspect, during the loading process, the manipulator is controlled to load the metal substrate to the first-order stamping equipment, and after the first-order forming process is completed, the preformed metal plate is removed from the first-order stamping equipment;

[0029] After the transfer and electrical treatment process is completed, the electrically treated metal plate is transferred to the second-order stamping equipment by a robot;

[0030] During the unloading process, the robot is controlled to remove the fully formed metal plate from the second-order stamping equipment.

[0031] As a preferred aspect, it also includes an electrical treatment parameter acquisition step, obtaining the electrical treatment parameters when the maximum temperature of the preformed metal electrode reaches 500-1200°C when the power is turned off at the end of the electrical treatment time; the electrical treatment time is 0.5-10 seconds.

[0032] As a preferred aspect, the temperature of the preformed metal plate under the electrical treatment condition is monitored by an infrared thermal imager.

[0033] As a preferred aspect, the electrical treatment uses constant voltage direct current or pulsed direct current; wherein the output voltage amplitude is 0-300V, the duty cycle is 0-100%, and the frequency is 100Hz-4000Hz.

[0034] As a preferred aspect, the channel thickness range of the fully formed metal plate is less than 24 μm.

[0035] As a preferred aspect, a first electric drive rail is provided on the electrical processing carrier platform, and the electrode fixture comprises a lower electrode whose two ends are fixedly connected to the first electric drive rail and an upper electrode whose two ends are movably connected to the electric drive rail, and the first electric drive rail can drive the upper electrode to move up and down to open and close the electrode fixture;

[0036] The transfer platform includes an electrically driven telescopic rail disposed on the lower side of the rectangular frame; the suction cup assembly is connected between the two electrically driven telescopic rails and is driven to switch between a first horizontal position (initial position) and a second horizontal position;

[0037] The vertical movable bracket 5 includes two second electric drive rails vertically arranged on the electrical processing bearing platform, and the rectangular frame vertically connects the two second electric drive rails and is driven to switch between the first height position and the second height position.

[0038] A multi-step forming production line for metal plates for fuel cells implementing the above-mentioned preparation method comprises: a loading device, a first-order stamping device, a transfer and processing device, a second-order stamping device, and a unloading device; wherein:

[0039] The feeding device is used to feed the metal substrate to a first-order stamping device having a first-order forming die;

[0040] The first-order stamping equipment is used to perform first-order stamping pre-forming on the metal substrate to form a pre-formed metal plate;

[0041] The transport electro-processing equipment is used to move the preformed metal electrode plate to the electro-processing station on the transport electro-processing equipment for electro-processing, and to take out the electro-processed metal electrode plate after the electro-processing is completed;

[0042] The second-order stamping equipment is used to perform second-order stamping on the metal plate after the electrical treatment to obtain a fully formed metal plate;

[0043] The unloading equipment removes the fully formed metal plate from the second-order stamping equipment.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] 1. The preparation method of the fuel cell metal plate and the metal plate multi-step forming production line of the present invention add an electrical treatment process between the two-step stamping process, which can release the internal stress of the preformed metal plate in a very short processing time and eliminate deformation twins and dislocation accumulation, ultimately significantly improving the forming limit and forming accuracy of the metal plate;

[0046] 2. The preparation method of the fuel cell metal plate and the metal plate multi-step forming production line of the present invention integrate the electrical processing equipment on the transfer electrical processing equipment, and can perform electrical processing on the preformed metal plate while it is being transferred to the next stamping process to eliminate deformation twins and dislocation accumulation, without affecting production efficiency;

[0047] 3. The preparation method of the fuel cell metal plate and the metal plate multi-step forming production line of the present invention propose that the metal plate multi-step forming production line based on the electrical treatment modification effect can be obtained by simply modifying the existing series stamping automatic production line, with low investment cost and wide application range.

[0048] With reference to the following description and the accompanying drawings, the specific embodiments of the present invention are disclosed in detail, indicating the manner in which the principles of the present invention can be adopted. It should be understood that the embodiments of the present invention are not limited in scope thereby.

[0049] Features described and / or illustrated with respect to one embodiment may be used in the same or similar manner in one or more other embodiments, combined with features in other embodiments, or substituted for features in other embodiments.

[0050] It should be emphasized that the term “include / comprises” when used herein refers to the presence of features, integers, steps or components, but does not exclude the presence or addition of one or more other features, integers, steps or components. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without paying creative labor.

[0052] Figure 1 The temperature distribution and local temperature history of the target plate microchannel during the electrical treatment in Example 1;

[0053] Figure 2 are the design parameters of the flow channel cross-section of (a) the first forming die and (b) the second forming die in Example 1;

[0054] Figure 3 The titanium plate is (a) a titanium plate formed by conventional multi-step stamping at room temperature in Example 1 and (b) a titanium plate formed by the new method of the present invention;

[0055] Figure 4 The thickness distribution of the flow channel of the titanium plate formed by (a) conventional multi-step stamping at room temperature and (b) the new method of the present invention in Example 1;

[0056] Figure 5 It is a bar graph of total elongation of the sample after long-term electrical treatment at 550℃;

[0057] Figure 6 , Figure 7It is a bar graph of total elongation when the samples are electrically treated at 500℃ (E10.5%) / 600℃ (E13.5%) / 700℃ (E16.8%) for 2sec, 3sec, 5sec or 10sec respectively;

[0058] Figure 8 It is a bar graph of total elongation when the sample is rapidly heated to different target temperatures for 2 seconds;

[0059] Fig. 9 It is a bar graph of the total elongation of the specimens subjected to different pre-deformations and heated to different target temperatures.

[0060] Fig.10 This is a comparison chart of the results of two intermediate electrical treatments of the sample formed by a single die;

[0061] Fig.11 It is a schematic diagram of the three-dimensional structure of a transport electrical treatment device provided by one embodiment of the present invention;

[0062] Fig.12 yes Fig.11 Another view of;

[0063] Fig.13 yes Fig.11 A side view of

[0064] Fig.14 Is adopted Fig.11 The process view of the transfer electro-processing equipment shown is for transfer electro-processing. DETAILED DESCRIPTION

[0065] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0066] It should be noted that when an element is referred to as being "disposed on" another element, it may be directly on the other element or there may be another element centered thereon. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be another element centered thereon at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only and do not represent the only implementation method.

[0067] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0068] See also Figures 1 to 14 In one embodiment of the present invention, a method for preparing a fuel cell metal plate is provided. Accordingly, in order to implement the preparation method, a metal plate multi-step forming production line is also provided in the embodiment. The metal plate multi-step forming production line includes: a loading device, a first-order stamping device, a transfer electricity processing device, a second-order stamping device, and a unloading device.

[0069] The loading equipment is used to load the metal substrate to the first-order stamping equipment with a first-order forming mold. The loading equipment adopts a loading robot, specifically a manipulator. The first-order stamping equipment is used to perform a first-order stamping pre-forming on the metal substrate to form a preformed metal plate. The transfer electrical treatment equipment is used to move the preformed metal plate to the electrical treatment station on the transfer electrical treatment equipment for electrical treatment, and take out the electrically treated metal plate after the electrical treatment. The second-order stamping equipment is used to perform a second-order stamping forming on the electrically treated metal plate to obtain a fully formed metal plate. The unloading equipment removes the fully formed metal plate from the second-order stamping equipment. The unloading equipment adopts a unloading robot, specifically a manipulator. The loading manipulator and the unloading manipulator are different manipulators, which are arranged along the process steps of the production line. Of course, as feasible, the loading equipment and the unloading equipment can adopt the same manipulator,

[0070] The stamping equipment includes a stamping machine and a mold. Among them, the mold structure can adopt the mold disclosed in the patent publication number CN116154208A entitled "High-precision and high-corrosion-resistant titanium bipolar plates for fuel cells and their preparation methods and mold assemblies", and the repeated parts will not be repeated. The stamping machine adopts a precision press, such as a YKP-630 precision press. The electrical processing equipment includes a DC power supply, a copper electrode and an insulating bakelite clamp. Among them, the electrodes and the insulating clamps are integrated into the transport electrical processing equipment for grabbing and transporting preformed metal plates.

[0071] like Figures 11 to 14As shown, this embodiment also provides a transfer electrical treatment device. The transfer electrical treatment device includes an electrical treatment carrying platform 1, and a transfer platform 3 located above the electrical treatment carrying platform 1; the electrical treatment carrying platform 1 includes electrode units 4 arranged opposite to each other; the electrode unit 4 includes an electrode clamp that can be operated to be pressed and opened. The transfer platform 3 is installed above the electrical treatment carrying platform 1 through a vertical movable bracket 5; the transfer platform 3 can be operated to be moved up and down on the vertical movable bracket 5. The transfer platform 3 includes a rectangular frame, and a suction cup assembly 2 that can be operated to be moved in a horizontal direction on the bracket; the suction cup assembly 2 is used to absorb the metal substrate or the metal electrode plate 100.

[0072] The suction cup assembly 2 has a first horizontal position and a second horizontal position relative to the rectangular frame in a horizontal direction; the transfer platform 3 has a first height position and a second height position located above the first height position on the vertical movable bracket 5. The first horizontal position at the second height position is the initial position of the suction cup assembly 2.

[0073] Specifically, a first electric drive rail 40 is provided on the electrical treatment carrying platform 1. The electrode fixture includes a lower electrode 42 whose two ends are fixedly connected to the first electric drive rail 40 and an upper electrode 41 whose two ends are movably connected to the first electric drive rail 40, and the first electric drive rail 40 can drive the upper electrode 41 to move up and down to open and close the electrode fixture. The lower electrode 42 and the upper electrode 41 are copper electrodes.

[0074] The transfer platform 3 includes an electrically driven telescopic rail 31 disposed on the lower side of the rectangular frame. The suction cup assembly 2 is connected between two parallel electrically driven telescopic rails 31 and is driven to switch between a first horizontal position and a second horizontal position. The vertical movable bracket 5 includes two second electrically driven rails 51 vertically disposed on the electrical processing bearing platform 1, and the rectangular frame vertically connects the two second electrically driven rails 51 and is driven to switch between a first height position and a second height position.

[0075] like Fig.14 As shown in Figure a, when the suction cup assembly 2 is located at the second horizontal position and at the second height position, it is used to suck or unload the metal substrate or metal plate. When the suction cup assembly 2 is located at the second horizontal position, it is used to switch between the first height position and the second height position. Fig.14 The horizontal position shown in Figure b. Fig.14 As shown in Figure b, when the suction cup assembly 2 is located at the second horizontal position and the first height position, it can be moved to the first horizontal position to deliver the metal substrate or the metal electrode plate between the opened electrode clamps.

[0076] In this embodiment, the method for preparing the fuel cell metal plate includes the following steps:

[0077] A feeding step of feeding a metal substrate having a thickness of not less than 0.05 mm and not more than 0.2 mm to a first-order stamping device having a first-order forming die;

[0078] A first forming step, using a first stamping device to perform a first stamping pre-forming on the metal substrate to form a pre-formed metal plate;

[0079] The transfer and electrical treatment process controls the transfer electrical treatment equipment to move the preformed metal electrode plate to the electrical treatment station on the transfer electrical treatment equipment for electrical treatment, and takes out the electrically treated metal electrode plate after the electrical treatment; the electrical treatment clamping area is >500mm 2 ;

[0080] A second forming step, using a second stamping device to perform a second stamping forming on the metal plate after the electrical treatment to obtain a fully formed metal plate;

[0081] The blanking step is to remove the fully formed metal plate from the second-order stamping equipment. The flow channel thickness range of the fully formed metal plate is less than 24 μm, and the flow channel depth-to-width ratio is greater than 0.79.

[0082] In other embodiments, the preparation method of the fuel cell metal plate is not limited to two stamping processes and one intermediate electrical treatment, and it can be a multi-step stamping process and multiple electrical treatment processes. In this way, the first forming process and the second forming process also include at least one intermediate forming process, the metal plate is stamped, and the electrical treatment process is provided between the two forming processes. Through multiple electrical treatments, the metal plate can ultimately achieve a higher forming limit.

[0083] like Fig.14 As shown, during the transfer and electrical treatment process, first, Fig.14 As shown in Figure a, the suction cup assembly 2 is controlled to suck the preformed metal plate at the second horizontal position and the second height position, and then, as shown in Fig.14 As shown in Figures b to c, the electrode clamp is opened, the suction cup assembly 2 is controlled to descend to the first height position and then move from the second horizontal position to the first horizontal position, the preformed metal plate is sent between the electrode clamps, and the suction cup assembly 2 is controlled to release the preformed metal plate. Fig.14As shown in Figure d, the electrode fixture is controlled to press the preformed metal plate for electrical treatment, and the suction cup assembly 2 is lifted to the initial position (the second horizontal position of the second height position). Finally, the electrode fixture is opened and the suction cup assembly 2 is controlled to return to the position shown in Figure d to absorb the metal plate after electrical treatment from the first horizontal position to the second horizontal position, and then the metal after electrical treatment is moved upward to the second height position.

[0084] In the loading process, the robot is controlled to load the metal substrate to the first-order stamping equipment, and the preformed metal plate is removed from the first-order stamping equipment after the first-order forming process. After the transfer and electrical treatment process, the metal plate after electrical treatment is transferred to the second-order stamping equipment by the robot. In the unloading process, the robot is controlled to remove the fully formed metal plate from the second-order stamping equipment.

[0085] The preparation method of the fuel cell metal plate also includes an electrical treatment parameter acquisition step, which acquires the electrical treatment parameters when the maximum temperature of the preformed metal plate reaches 500-1200°C when the power is turned off after the electrical treatment time ends; the electrical treatment time is 0.5-10 seconds. In the electrical treatment parameter acquisition step, the temperature of the preformed metal plate under the electrical treatment condition is monitored by an infrared thermal imager.

[0086] The electrical treatment adopts constant voltage direct current or pulse direct current; wherein the output voltage amplitude is 0-300V, the duty cycle is 0-100%, and the frequency is 100Hz-4000Hz.

[0087] In this embodiment, considering that the bipolar plate thickness is small (<0.2 mm), but the electrical treatment clamping area is large (>500 mm 2 , generally >2000mm 2 ), so the contact quality between the copper electrode and the metal plate is high, but because it is a rigid surface contact, the surface flatness error during the processing of the upper and lower electrodes, the assembly error between the upper and lower electrodes and the electrode fixture, and the movement error during the downward movement of the upper electrode may lead to uneven stress distribution on the clamped surface of the bipolar plate when the electrodes are closed. This may cause problems in the electrical processing of the preformed plate: uneven current density due to local contact resistance differences, and even electrolytic corrosion damage on the contact surface; local bending and deformation of the clamping section; the clamping force cannot be evenly and effectively applied, resulting in sliding and other problems.

[0088] In order to solve the occurrence of such problems, a rubber pad is added to the surface of the upper electrode facing the lower electrode, thereby improving stress transfer and increasing the actual contact area, making the conduction more uniform and the clamping more reliable. The rubber pad is a rectangular rubber pad, and the thickness of the rubber pad is less than the thickness of the lower electrode. In the upper and lower electrodes, the rubber pad covers the lower surface of the upper electrode, and the upper surface area of ​​the lower electrode is larger than the lower surface area of ​​the rubber pad. The end of the metal plate is clamped between the rubber pad and the upper surface of the lower electrode.

[0089] The preparation method of the fuel cell metal plate and the metal plate multi-step forming production line provided in the embodiments of the present invention add an electrical treatment process between the two-step stamping processes, which can release the internal stress of the pre-formed metal plate in an extremely short processing time and eliminate deformation twins and dislocation accumulation, ultimately significantly improving the forming limit and forming accuracy of the metal plate.

[0090] The embodiment of the present invention performs electrical treatment on the preformed metal plate, especially the titanium plate, which is a means of adding a step of material modification in the process of forming the material into the part, and its purpose is to improve the machinability of the material (manufacturability of the part), and then Figures 5 to 11 The verified ductility (elongation), the present invention hopes to completely eliminate defects such as dislocations and twins for the electrical treatment of metal plates (titanium plates) under the most ideal conditions, and complete recrystallization, replacing deformed grains with new equiaxed grains, thereby maximizing the ductility of the material and achieving a higher forming limit of the metal plate.

[0091] Figures 5 to 10 This is a diagram of the verification results obtained by the inventor to verify the effect of electrical treatment on the metal plate forming process.

[0092] in, Figure 5 The results are as follows: a titanium substrate with a thickness of 0.1 mm produced by a steel plant was stretched in multiple steps and the total elongation was measured (i.e., the scenario described in Example 3 below). Specifically, the titanium substrate was first stretched to 15% along the rolling direction, and then Figure 5 The electro-treatment was performed under different electro-treatment conditions shown in the figure (5s@550℃, i.e., electro-treatment for 5 seconds, the highest temperature of the sheet material when the power is off reaches 550℃. The highest temperature of this group of experiments is 550℃, but the electro-treatment time varies), and finally the sheet material is loaded and stretched again until it breaks. The total elongation of the titanium substrate after two stretches is calculated and compared with the sample after the same two stretches but without electro-treatment in between (i.e., Figure 5 The elongation of the sample is about 35.8% at the position marked by the green dotted line in the middle. The elongation of the samples under each electrical treatment condition has increased to varying degrees. The elongation is an important indicator for evaluating the ductility of the sample. The higher the elongation, the greater the tensile deformation that the material can withstand before breaking, thus proving the ability of electrical treatment to improve the forming limit of the titanium substrate.

[0093] Figure 6 , Figure 7 , Figure 8 The tensile test results of similar titanium plates are shown in Figure 1, where only the parameters of the electrical treatment are changed. It can also be seen that the elongation of the samples under different electrical treatment conditions is improved to varying degrees. Fig. 9 The pre-deformation was changed to different amounts (originally only 15%, now 10%, 15%, 20% are compared together), and then the total elongation after 2sec@500℃, 600℃ and 700℃ electrical treatment was compared. It can also be seen that the electrical treatment is equally effective for samples with different pre-deformation amounts, and the overall trend of the effect is the same.

[0094] Fig.10 Not used Figure 2 The comparison results of the two forming processes are performed by controlling the stamping depth in the second forming die instead of the first forming die in the first forming die. Fig.10 The improved process is ( Fig.10 (Picture below) During the first forming, the punching depth is controlled to about 0.25mm. At this time, the plate still does not crack. After that, the plate is electrically treated and then put back into the mold to be fully punched to the final depth of 0.35. Fig.10 The displayed results show that pure electrical treatment has a significant effect on improving the forming limit of sheet metal. It can be seen that the specimens without electrical treatment using the traditional process are completely cracked, which means that the forming limit is completely exceeded. However, the cracking of the specimens after electrical treatment is significantly improved, which shows the effect of electrical treatment on improving the local forming limit.

[0095] The present invention is further described below through several specific embodiments to facilitate a better understanding of the present invention.

[0096] Example 1

[0097] This embodiment provides a new method for improving the forming limit and uniformity of the cross-sectional thickness distribution of the metal plate. The target plate flow channel period to be formed is 1.2 mm, the draft angle is 5°, the fillet radius is 0.1 mm, and the aspect ratio is 0.79. The specific steps are as follows:

[0098] S1. Raw material selection

[0099] In this embodiment, the sample substrate is selected from TA1 industrial pure titanium with a thickness of 0.1 mm and a titanium content higher than 99.5% produced by a steel plant. The industrial pure titanium is a titanium substrate with an α-phase structure obtained by annealing heat treatment after cold rolling.

[0100] S2. Obtaining electrical processing parameters

[0101] In order to obtain the electrical treatment parameters, a titanium plate that has been preformed is used to monitor the temperature of the preformed titanium plate under electrical treatment conditions using an infrared thermal imager. The electrical treatment time is selected as 2 seconds, and the maximum temperature of the titanium plate is ensured to reach 750°C when the power is turned off after 2 seconds of electrical treatment. Figure 1 For the preformed titanium plate with a width of 100 mm in this embodiment, the output voltage of the power box obtained is 120 V, the duty cycle is 70%, and the pulse frequency is 300 Hz.

[0102] S3, loading

[0103] The ultra-thin titanium substrate obtained in S1 is transferred to the first-order stamping equipment and positioned using a loading robot.

[0104] S4, first order forming

[0105] Use Figure 2 The first-order forming die shown in a performs the first-order stamping forming on the blank after loading in S3.

[0106] S5. Transport and electrical treatment

[0107] The pre-deformed titanium plate obtained in S4 is sucked from the first-order stamping die by the vacuum suction cup integrated in the integrated fixture of the transfer electrical treatment equipment, and is moved to the electrical treatment station in the integrated fixture. After recognizing that the pre-deformed titanium plate has reached the specified position, the servo motor drives the upper chuck of the electrode to move downward to clamp the titanium plate. Subsequently, the vacuum pump stops working and the suction cup moves upward. The pulse current calibrated in S2 is passed through the pre-deformed titanium plate, and at the same time, the mechanical arm of the transfer electrical treatment equipment moves, driving the entire integrated fixture to move to the second-order stamping station. After the electrical treatment is completed, the suction cup moves down and the vacuum pump is turned on again. The upper chuck moves upward to release the titanium plate, and the titanium plate is transferred to the second-order stamping equipment by the vacuum suction cup and the positioning is completed.

[0108] S6, Second Order Forming

[0109] Use Figure 2 The second forming die shown in b performs second stamping forming on the titanium electrode plate after the electrical treatment in S5.

[0110] S7, unloading

[0111] The formed titanium plate is transferred out of the second-stage stamping equipment by the unloading equipment.

[0112] like Figure 3 The figures show the titanium plate microchannels formed by the conventional room temperature multi-step forming process and the new method proposed in the present disclosure. The new method proposed in the present invention can break through the forming limit of the titanium plate and obtain the target plate without cracking. Figure 4As shown in the figure, the thickness distribution uniformity of the plate flow channel is evaluated by the range method, that is, 9 characteristic positions (the ridge, groove and side wall midpoint and the maximum thinning position of the fillet) are selected on each flow channel line cycle to measure the thickness of the substrate. It can be found that the thickness range of the titanium plate microflow channel manufactured by the traditional multi-step forming process is large (27.8μm), and the excessive thinning of the weakest fillet position (P6) eventually causes the flow channel to crack. The method proposed in the present invention can promote the uniform deformation of the material during the forming process, thereby improving the uniformity of the flow channel thickness and reducing the range of the flow channel thickness to about 21.8μm.

[0113] Example 2

[0114] This embodiment uses TA1 industrial pure titanium with a thickness of 0.1 mm, the same as in Example 1, and the target plate flow channel period to be formed is 1.18 mm, and the flow channel depth is 0.38 mm. The conventional multi-step stamping can produce a titanium plate without cracking, but the flow channel dimensional accuracy is poor.

[0115] Using the new method provided by the present invention, the preformed titanium plate is first subjected to an electrical treatment. The electrical treatment time is selected to be 2 seconds to ensure that the maximum temperature of the flow channel area of ​​the titanium plate reaches 730°C when the power is turned off 2 seconds after the electrical treatment. At this time, the calibrated output voltage of the power box is 190V, the duty cycle is 100%, and the pulse frequency is 4000Hz. The flow channel depth of the titanium plate formed by the new method of the present invention is about 10μm higher than that of the titanium plate formed by multi-step cold stamping, and the formed flow channel cross-section is closer to the design value, which proves that the new method of the present invention can also be used as an effective means to improve the dimensional accuracy of the flow channel of the target metal plate.

[0116] Example 3

[0117] In this embodiment, the sample substrate is selected from TA1 industrial pure titanium with a thickness of 0.1 mm and a titanium content higher than 99.5% produced by a steel plant, with the goal of increasing the elongation at break of the titanium plate.

[0118] The new method provided by the present invention is used to pre-stretch the titanium plate to 15% elongation, and then perform electrical treatment for 10 seconds to ensure that the maximum temperature reaches 550°C when the power is turned off after 10 seconds of electrical treatment. Finally, the plate is loaded and stretched again until it breaks. The tensile test results show that the elongation of the titanium plate is increased by about 23% compared with that under normal temperature stretching conditions.

[0119] Example 4

[0120] In this embodiment, the sample substrate is selected from 446 ferritic stainless steel with a thickness of 0.1 mm produced by a domestic steel plant. Based on uniaxial stretching, the feasibility of migrating the new method proposed in the present invention to ultra-thin stainless steel substrates is explored.

[0121] By using the new method provided by the present invention, the ferritic stainless steel plate is pre-stretched to an elongation of 15%, and then subjected to an electrical treatment for 2 seconds to ensure that the maximum temperature reaches 1000°C when the power is turned off after 2 seconds of electrical treatment, and finally loaded and stretched again until it breaks. The tensile test results show that the elongation of the ferritic stainless steel is increased by about 32% compared with the normal temperature tensile condition, proving that the new method of the present invention can improve the formability of ferritic stainless steel.

[0122] Any numerical value cited herein includes all values ​​of lower and upper values ​​that increase by one unit from the lower limit to the upper limit, and there is at least a two-unit interval between any lower value and any higher value. For example, if the value of the quantity of a component or a process variable (such as temperature, pressure, time, etc.) is stated to be from 1 to 90, preferably from 20 to 80, and more preferably from 30 to 70, the purpose is to illustrate that values ​​such as 15 to 85, 22 to 68, 43 to 51, 30 to 32 are also explicitly listed in the specification. For values ​​less than 1, one unit is appropriately considered to be 0.0001, 0.001, 0.01, 0.1. These are merely examples that are intended to be clearly expressed, and it can be considered that all possible combinations of numerical values ​​listed between the lowest value and the highest value are clearly stated in the specification in a similar manner.

[0123] Unless otherwise indicated, all ranges include the endpoints and all numbers between the endpoints. "About" or "approximately" used with a range applies to both endpoints of the range. Thus, "about 20 to 30" is intended to cover "about 20 to about 30", including at least the specified endpoints.

[0124] It should be understood that the above description is for illustration and not for limitation. Many embodiments and many applications beyond the examples provided will be apparent to those skilled in the art upon reading the above description. Therefore, the scope of the present teachings should not be determined with reference to the above description, but should be determined with reference to the appended claims and the full scope of equivalents possessed by such claims. For the purpose of comprehensiveness, all articles and references, including disclosures of patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein in the preceding claims is not intended to be a waiver of the subject matter, nor should it be considered that the inventors did not consider the subject matter to be part of the disclosed inventive subject matter.

Claims

1. A method for preparing a fuel cell metal plate, characterized in that: include: A feeding step of feeding a metal substrate having a thickness of not less than 0.05 mm and not more than 0.2 mm to a first-order stamping device having a first-order forming die; A first forming step, using a first stamping device to perform a first stamping pre-forming on the metal substrate to form a pre-formed metal plate; The transfer and electrical treatment process controls the transfer electrical treatment equipment to move the preformed metal electrode plate to the electrical treatment station on the transfer electrical treatment equipment for electrical treatment, and takes out the electrically treated metal electrode plate after the electrical treatment; the electrical treatment clamping area is >500mm 2 ; A second forming step, using a second stamping device to perform a second stamping forming on the metal plate after the electrical treatment to obtain a fully formed metal plate; A blanking step, removing the fully formed metal plate from the second-order stamping equipment; The transport electric treatment equipment comprises an electric treatment carrying platform and a transport platform located above the electric treatment carrying platform; the electric treatment carrying platform comprises electrode units arranged opposite to each other; the electrode units comprise electrode clamps which can be operated to be pressed and opened; the transport platform is installed above the electric treatment carrying platform through a vertical movable bracket; the transport platform can be operated to be moved up and down on the vertical movable bracket; the transport platform comprises a rectangular frame and a suction cup assembly which can be operated to be moved in a horizontal direction on the rectangular frame; the suction cup assembly is used to absorb a metal substrate or a metal electrode plate; The suction cup assembly has a first horizontal position and a second horizontal position in a horizontal direction relative to the rectangular frame; the transfer platform has a first height position and a second height position located above the first height position on the vertical movable bracket.

2. The method for preparing a fuel cell metal plate according to claim 1, characterized in that: At least one intermediate forming step is included between the first forming step and the second forming step to perform stamping on the metal plate, and the electrical treatment step is provided between the two forming steps.

3. The method for preparing a fuel cell metal plate according to claim 1, characterized in that: During the transfer and electrical treatment process, the suction cup assembly is controlled to absorb the preformed metal electrode plate at the second horizontal position and the second height position, then the electrode clamp is opened, the suction cup assembly is controlled to descend to the first height position and then move from the second horizontal position to the first horizontal position, the preformed metal electrode plate is delivered between the electrode clamps, the suction cup assembly is controlled to release the preformed metal electrode plate and the electrode clamp is controlled to press the preformed metal electrode plate for electrical treatment, finally, the electrode clamp is opened and the suction cup assembly is controlled to re-absorb the electrically treated metal electrode plate and move from the first horizontal position to the second horizontal position, and then the electrically treated metal is moved upward to the second height position.

4. The method for preparing a fuel cell metal plate according to claim 1, characterized in that: During the loading process, the robot is controlled to load the metal substrate to the first-order stamping equipment, and after the first-order forming process is completed, the preformed metal plate is removed from the first-order stamping equipment; After the transfer and electrical treatment process is completed, the electrically treated metal plate is transferred to the second-order stamping equipment by a robot; During the unloading process, the robot is controlled to remove the fully formed metal plate from the second-order stamping equipment.

5. The method for preparing a fuel cell metal plate according to claim 1, characterized in that: It also includes an electrical processing parameter acquisition step, which acquires the electrical processing parameters when the maximum temperature of the preformed metal plate reaches 500-1200°C when the power is turned off at the end of the electrical processing time; the electrical processing time is 0.5-10 seconds.

6. The method for preparing a fuel cell metal plate according to claim 1, characterized in that: The temperature of the preformed metal plates under electrical treatment conditions was monitored by an infrared thermal imager.

7. The method for preparing a fuel cell metal plate according to claim 1, characterized in that: The electrical treatment adopts constant voltage direct current or pulse direct current; wherein the output voltage amplitude is 0-300V, the duty cycle is 0-100%, and the frequency is 100Hz-4000Hz.

8. The method for preparing a fuel cell metal plate according to claim 1, characterized in that: A first electric drive rail is provided on the electrical processing carrying platform, and the electrode fixture comprises a lower electrode whose two ends are fixedly connected to the first electric drive rail and an upper electrode whose two ends are movably connected to the first electric drive rail, and the first electric drive rail can drive the upper electrode to move up and down to open and close the electrode fixture; The transfer platform includes an electrically driven telescopic rail disposed on the lower side of the rectangular frame; the suction cup assembly is connected between the two electrically driven telescopic rails and is driven to switch between a first horizontal position and a second horizontal position; The vertical movable bracket includes two second electrically driven guide rails vertically arranged on the electrical processing bearing platform, and the rectangular frame vertically connects the two second electrically driven guide rails and is driven to switch between a first height position and a second height position.

9. A metal plate multi-step forming production line for implementing the method for preparing a fuel cell metal plate as claimed in claim 1, characterized in that: include: Loading equipment, first-order stamping equipment, transfer electrical processing equipment, second-order stamping equipment, unloading equipment; among them, The feeding device is used to feed the metal substrate to a first-order stamping device having a first-order forming die; The first-order stamping equipment is used to perform first-order stamping pre-forming on the metal substrate to form a pre-formed metal plate; The transport electrical treatment equipment is used to move the preformed metal electrode plate to the electrical treatment station on the transport electrical treatment equipment for electrical treatment, and to take out the electrically treated metal electrode plate after the electrical treatment is completed; The second-order stamping equipment is used to perform second-order stamping on the metal plate after the electrical treatment to obtain a fully formed metal plate; The unloading equipment removes the fully formed metal plate from the second-order stamping equipment.

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