Method for preparing metal bipolar plate of fuel cell, and metal bipolar plate multi-step forming production line

Abstract

A method for preparing a metal bipolar plate of a fuel cell, and a metal bipolar plate multi-step forming production line. The method for preparing a metal bipolar plate of a fuel cell comprises: a feeding procedure: feeding a metal substrate to a first-stage stamping device, wherein the thickness of the metal substrate is less than 0.2 mm; a first-stage forming procedure: utilizing the first-stage stamping device to perform first-stage stamping pre-forming on the metal substrate to form a pre-formed metal bipolar plate; a transfer and electric treatment procedure: controlling a transfer and electric treatment device to move the pre-formed metal bipolar plate to an electric treatment station on the transfer and electric treatment device for electric treatment, and taking out an electrically-treated metal bipolar plate after the electric treatment is finished; a second-stage forming procedure: utilizing a second-stage stamping device to perform second-stage stamping forming on the electrically-treated metal bipolar plate to obtain a completely-formed metal bipolar plate; and a discharging procedure: removing the completely-formed metal bipolar plate from the second-stage stamping device.

Description

Method for manufacturing fuel cell metal bipolar plate and multi-step forming production line of metal bipolar plate TECHNICAL FIELD

[0001] The present application relates to the field of fuel cells, in particular to a multi-step forming production line of metal bipolar plate based on the effect of electro-processing modification and a process thereof, and particularly relates to a method for manufacturing fuel cell metal bipolar plate and a multi-step forming production line of metal bipolar plate. BACKGROUND

[0002] Hydrogen energy is an important strategic means to promote the green transformation of the world's energy industry, and proton exchange membrane fuel cells are the key technology for hydrogen energy utilization. High power, long service life and high performance are the development trend of fuel cells. As one of the core components of fuel cells, bipolar plates have micro-channel characteristics of sub-millimeter level, and the fine degree of flow channel has an important influence 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, excellent electrical and thermal conductivity, etc., and have become one of the mainstream trends in the manufacturing technology of fuel cells.

[0003] However, as the fuel cell's demand for reaction gas and product water transport efficiency continues to increase, the bipolar plate needs to have a more fine flow channel structure and a higher flow channel aspect ratio. The forming performance bottleneck of ultra-thin metal substrates will cause them to crack prematurely during stamping forming, which restricts the development of high-performance fuel cells. In recent years, extensive innovation has been made on the forming method of metal bipolar plates at home and abroad. Although laboratory-level new processes such as electromagnetic high-speed forming and high-temperature forming can effectively improve the forming limit of metal bipolar plates, they all have the problems of low production efficiency and poor compatibility with existing bipolar plate production lines, which limits their application in actual production. Therefore, it is urgent to develop a high-performance fuel cell metal bipolar plate manufacturing method that is both efficient and simple to be compatible with existing metal bipolar plate production lines.

[0004] Patent document CN112974642A (a fuel cell metal bipolar plate electric auxiliary forming device and process) discloses an electric auxiliary forming process of a fuel cell metal bipolar plate. By passing an electric current through the metal bipolar plate in the mold during stamping forming, the forming force of the bipolar plate is reduced by using Joule heat and electroplastic effect, and the forming precision and consistency are improved. However, the electric auxiliary forming process of the invention focuses on improving the manufacturing precision of single-step stamping forming of metal bipolar plates, and has no significant effect on improving the forming limit of metal bipolar plates.

[0005] The patent document CN111842611A (a titanium alloy bipolar plate forming device and method based on multi-time pulse current) proposes an electromagnetic-thermal composite forming method for titanium alloy bipolar plates. Through multi-stage time sequential pulse current discharge, the thermal effect, electroplastic effect and high strain rate effect of pulse electromagnetic force are utilized to improve the forming limit of titanium alloy bipolar plates. However, the electromagnetic forming device included in this technology is complex, requires high cost and has low production efficiency, which is not suitable for practical production applications.

[0006] The patent document CN116154208B (high-precision and high-corrosion-resistant titanium bipolar plate for fuel cells, preparation method and mold assembly) proposes a hot assisted forming process for ultra-thin titanium bipolar plates of fuel cells. By adding an annealing heat treatment process between the two-step stamping forming processes, the internal stress of the titanium bipolar plate after the first forming process is released and the work hardening is eliminated, thereby improving the re-deformation performance and increasing the forming limit. However, the heat treatment process in this invention takes a long time (2-30 min), which affects the production efficiency of the titanium bipolar plate. In addition, during the static recovery process of heat treatment, grain growth often occurs, which limits the improvement effect of the forming limit of the bipolar plate. SUMMARY

[0007] In view of the above-mentioned deficiencies of the prior art, the present invention aims to provide a metal bipolar plate multi-step forming production line and process based on electrical treatment modification, which can significantly improve the forming limit and forming precision of the metal bipolar plate, to solve the problems of insufficient micro-channel depth, channel cracking and poor dimensional accuracy in the existing metal bipolar plate forming process, and does not affect the production efficiency.

[0008] To achieve the above-mentioned purpose, the present invention provides a preparation method of a fuel cell metal bipolar plate based on electrical treatment modification and a metal bipolar plate multi-step forming production line. The metal bipolar plate multi-step forming production line sequentially includes a feeding robot (feeding equipment), a first sequence stamping device, a transfer electrical treatment device, an electrical treatment device, a second sequence stamping device and a discharging robot (discharging equipment).

[0009] Meanwhile, the present invention proposes a metal bipolar plate multi-step forming production process based on electrical treatment modification around the aforementioned production line as follows:

[0010] S1, material acquisition process, acquiring titanium base material or ferritic stainless steel base material with a thickness of 0.05 mm or more and 0.2 mm or less;

[0011] S2, an electric treatment parameter acquisition procedure. The electric treatment refers to a material modification process of repairing internal defects of a metal plate by passing direct current into the metal plate to stimulate plasticity. Compared with traditional furnace annealing heat treatment, the ultra-short-time electric treatment can release internal stress, eliminate deformation twin and dislocation accumulation generated in the pre-deformation process of the ultra-thin metal plate, and significantly promote static recrystallization, thereby improving the re-deformation performance of the pre-deformed metal plate and increasing the forming limit. The electric treatment device can provide constant-voltage direct current or pulse direct current with any waveform, and the output voltage amplitude is 0-300V, the duty cycle is 0-100%, and the frequency is 100-4000Hz.

[0012] For metal plates of different sizes, the input electric energy required to treat defects is also different, and the temperature rise of the metal plate caused by the electric treatment Joule heat effect is easy to measure, which can be used as a simple means to determine the electric energy input level and to determine the electric treatment parameter threshold. The target temperature range of the electric treatment is 500-1200℃, and the power-on time needs to be controlled within 0.5-10 seconds. In actual production, the electric treatment time should be selected based on the beat demand of production, and then the output voltage, duty cycle and frequency of the electric treatment process parameters are determined based on the target heating temperature;

[0013] S3, a feeding procedure, in which a feeding robot automatically transfers the sheet to the first sequence stamping equipment through a vacuum chuck and positions the sheet in the first sequence forming die;

[0014] S4, a first sequence forming procedure, in which a punch machine goes down and pre-forms the metal sheet through the first sequence forming die to obtain a metal plate;

[0015] S5, a transfer and electric treatment procedure, in which a transfer and electric treatment device sucks up the pre-formed metal plate through a vacuum chuck, moves it out of the first sequence stamping equipment first. Then, it moves to the electric treatment clamp position integrated on the transfer and electric treatment device, the upper clamp of the electric treatment clamp is lowered to clamp at both ends of the pre-formed metal plate, and the vacuum chuck stops working and moves up. The transfer of the pre-deformed metal plate between the two sequence stamping equipment is completed by clamping the pre-deformed metal plate with the electric treatment clamp, and the pre-deformed metal plate is electrically treated and modified, and it is ensured that the metal plate has completed the electric treatment modification and cooled to room temperature before reaching the second sequence stamping equipment. Finally, the vacuum chuck moves down to suck the metal plate, the electric treatment clamp is released and retreats, and the metal plate is transferred to the second sequence stamping equipment and positioned;

[0016] S6, a second sequence forming procedure, in which a punch machine goes down and fully stamps and forms the pre-formed metal plate after the electric treatment through a second sequence forming die;

[0017] S7, a discharging procedure, in which a discharging robot transfers the fully formed metal plate out of the second sequence stamping equipment.

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

[0019] a first-sequencing stamping process for performing first-sequencing stamping preforming on the metal substrate by using the first-sequencing stamping equipment to form a preformed metal bipolar plate;

[0020] a first-sequencing stamping process for performing first-sequencing stamping preforming on the metal substrate by using the first-sequencing stamping equipment to form a preformed metal bipolar plate;

[0021] a transferring and electro-processing process for moving the preformed metal bipolar plate to an electro-processing station on the transferring and electro-processing equipment to perform electro-processing, and taking out the electro-processed metal bipolar plate after the electro-processing is completed; the electro-processing clamping area is > 500 mm 2 ; further, the electro-processing clamping area is > 1500 mm 2 ; further, the electro-processing clamping area is > 2000 mm 2 .

[0022] a second-sequencing stamping process for performing second-sequencing stamping forming on the electro-processed metal bipolar plate by using the second-sequencing stamping equipment to obtain a fully formed metal bipolar plate;

[0023] a discharging process for discharging the fully formed metal bipolar plate from the second-sequencing stamping equipment.

[0024] As a preferred aspect, the first-sequencing stamping process and the second-sequencing stamping process further comprise at least one intermediate-sequencing stamping process for performing stamping forming on the metal bipolar plate, and the electro-processing process is arranged between the two stamping processes.

[0025] As a preferred aspect, the transferring and electro-processing equipment comprises an electro-processing bearing platform and a transferring platform arranged above the electro-processing bearing platform; the electro-processing bearing platform comprises oppositely arranged electrode units; the electrode units comprise openable and closable electrode clamps; the transferring platform is installed above the electro-processing bearing platform by a vertical moving support; the transferring platform is arranged on the vertical moving support in a vertically movable manner; the transferring platform comprises a rectangular frame and a suction disc assembly arranged on the rectangular frame in a horizontally movable manner; the suction disc assembly is used for sucking the metal substrate or the metal bipolar plate;

[0026] the suction disc assembly has a first horizontal position (initial position) and a second horizontal position relative to the rectangular frame in a horizontal direction; the transferring platform has a first height position and a second height position above the first height position on the vertical moving support 5.

[0027] As a preferred aspect, in the transferring and electric treatment process, the chuck assembly is controlled to suck the preformed metal plate in the second horizontal position and the second height position, then the electrode clamp is opened, the chuck 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 plate is sent into the electrode clamp, the chuck assembly is controlled to release the preformed metal plate and the electrode clamp is controlled to press and electrically treat the preformed metal plate, finally, the electrode clamp is opened, the chuck assembly is controlled to suck the electrically treated metal plate from the first horizontal position to the second horizontal position, and then the electrically treated metal plate is moved upward to the second height position.

[0028] As a preferred aspect, in the feeding process, the robot is controlled to feed the metal substrate to the first sequence punching device, and after the first sequence forming process is completed, the preformed metal plate is removed from the first sequence punching device;

[0029] After the transferring and electric treatment process is completed, the electrically treated metal plate is also transferred to the second sequence punching device by the robot;

[0030] In the discharging process, the robot is controlled to remove the completely formed metal plate from the second sequence punching device.

[0031] As a preferred aspect, it further includes an electric treatment parameter acquisition process, and the electric treatment parameter is acquired when the highest temperature of the preformed metal plate reaches 500-1200°C when the power is turned off at the end of the electric treatment time; the electric treatment time is 0.5-10 seconds.

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

[0033] As a preferred aspect, the electric 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.

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

[0035] As a preferred aspect, a first electric drive guide rail is arranged on the electric treatment bearing platform, the electrode clamp includes a lower electrode fixedly connected to both ends of the first electric drive guide rail and an upper electrode movably connected to both ends of the electric drive guide rail, and the first electric drive guide rail can drive the upper electrode to move up and down to open and close the electrode clamp.

[0036] The transfer platform comprises electrically-driven telescopic guide rails arranged at the lower side of the rectangular frame; the suction cup assembly is connected between the two electrically-driven telescopic guide rails and is driven to switch between a first horizontal position (initial position) and a second horizontal position.

[0037] The vertical moving bracket 5 comprises two second electrically-driven guide rails vertically arranged on the electrically-processed carrying platform, and the rectangular frame is vertically connected between the two second electrically-driven guide rails and is driven to switch between a first height position and a second height position.

[0038] A metal pole multi-step forming production line for implementing the preparation method of the fuel cell metal pole as described above, comprising: a feeding device, a first sequence punching device, a transfer electric processing device, a second sequence punching device, and a discharging device; wherein,

[0039] The feeding device is used for feeding the metal base material to the first sequence punching device with a first sequence forming die;

[0040] The first sequence punching device is used for first sequence punching pre-forming on the metal base material to form a pre-formed metal pole;

[0041] The transfer electric processing device is used for moving the pre-formed metal pole to an electric processing station on the transfer electric processing device for electric processing, and taking out the electrically-processed metal pole after the electric processing is completed;

[0042] The second sequence punching device is used for second sequence punching forming on the electrically-processed metal pole to obtain a completely formed metal pole;

[0043] The discharging device takes down the completely formed metal pole from the second sequence punching device.

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

[0045] 1. The preparation method of the fuel cell metal pole and the metal pole multi-step forming production line add an electric processing procedure between two punching procedures, can release the internal stress of the pre-formed metal pole in a very short processing time, eliminate deformation twin crystals and dislocation accumulation, and finally significantly improve the forming limit and forming precision of the metal pole;

[0046] 2. The preparation method of the fuel cell metal pole and the metal pole multi-step forming production line integrate the electric processing device on the transfer electric processing device, can electrically process the pre-formed metal pole to eliminate deformation twin crystals and dislocation accumulation while transferring the pre-formed metal pole to the next punching procedure, and does not affect the production efficiency;

[0047] 3. The preparation method of the fuel cell metal polar plate and the multi-step forming production line of the metal polar plate of the present application propose that the multi-step forming production line of the metal polar plate based on the electric treatment modification effect can be obtained based on the simple modification of the existing series punch automatic production line, and the investment cost is low and the application range is wide.

[0048] Specific embodiments of the present application are disclosed below with reference to the drawings, which show, by way of example, the principles of the present application. It should be understood that the embodiments of the present application are not limited in scope to the specific embodiments described herein.

[0049] Features described and / or illustrated with respect to one embodiment can be used in the same or similar manner in one or more other embodiments, in combination with features of other embodiments, or in place of features of other embodiments.

[0050] It should be emphasized that the term "comprises / comprising" when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof. BRIEF DESCRIPTION OF DRAWINGS

[0051] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed to be used in the following embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0052] Fig. 1 is the temperature distribution and local temperature history during the electric treatment of the micro-channel of the target polar plate in Example 1;

[0053] Fig. 2 is the flow channel cross-sectional design parameters of (a) the first sequence forming die and (b) the second sequence forming die in Example 1;

[0054] Fig. 3 is (a) the titanium polar plate formed by the conventional normal temperature multi-step punch forming and (b) the titanium polar plate formed by the new method of the present application in Example 1;

[0055] Fig. 4 is the flow channel thickness distribution of (a) the titanium polar plate formed by the conventional normal temperature multi-step punch forming and (b) the titanium polar plate formed by the new method of the present application in Example 1;

[0056] Fig. 5 is the total elongation column chart of the sample under the electric treatment at 550°C for a long time;

[0057] Fig. 6 and Fig. 7 are the total elongation column charts of the sample under the electric treatment at 500°C (E10.5%) / 600°C (E13.5%) / 700°C (E16.8%) for 2 seconds, 3 seconds, 5 seconds or 10 seconds, respectively;

[0058] Figure 8 is a bar chart of total elongation for samples subjected to 2 seconds of rapid heating to different target temperatures;

[0059] Figure 9 is a bar chart of total elongation for samples subjected to different pre-strains and heated to different target temperatures.

[0060] Figure 10 is a comparison chart of intermediate electro-processing results for two shaping of a sample by a single die;

[0061] Figure 11 is a perspective view of a transport electro-processing apparatus according to an embodiment of the present application;

[0062] Figure 12 is another view of Figure 11 ;

[0063] Figure 13 is a side view of Figure 11 ;

[0064] Figure 14 is a process view of transport electro-processing using the transport electro-processing apparatus of Figure 11. DETAILED DESCRIPTION

[0065] In order to make the technical solution in the present application better understood by those skilled in the art, the technical solution in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work should belong to the scope of protection of the present application.

[0066] It should be noted that when an element is referred to as being "on" another element, it can be directly on the other element or there can be another element between them. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or there can be another element between them. The terms "vertical", "horizontal", "left", "right", and similar expressions used herein are only for the purpose of illustration and do not represent the only implementation.

[0067] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0068] Referring to FIGS. 1-14, in one embodiment, a method for manufacturing a metal bipolar plate for a fuel cell is provided. To implement the method, a multi-step forming production line for the metal bipolar plate is also provided. The multi-step forming production line includes a feeding device, a first sequence of stamping devices, a transfer and electro-processing device, a second sequence of stamping devices, and a discharging device.

[0069] The feeding device is configured to feed the metal substrate to the first sequence of stamping devices with a first sequence of forming dies. The feeding device employs a feeding robot, specifically a manipulator. The first sequence of stamping devices is configured to perform a first sequence of stamping pre-forming on the metal substrate to form a pre-formed metal bipolar plate. The transfer and electro-processing device is configured to move the pre-formed metal bipolar plate to an electro-processing station on the transfer and electro-processing device for electro-processing, and to take out the electro-processed metal bipolar plate after the electro-processing is completed. The second sequence of stamping devices is configured to perform a second sequence of stamping forming on the electro-processed metal bipolar plate to obtain a fully formed metal bipolar plate. The discharging device is configured to take out the fully formed metal bipolar plate from the second sequence of stamping devices. The discharging device employs a discharging robot, specifically a manipulator. The feeding manipulator and the discharging manipulator are different manipulators, which are arranged along the process steps of the production line. Of course, as a feasible option, the feeding device and the discharging device can employ the same manipulator.

[0070] The stamping devices each include a stamping machine and a die. The die structure can employ the die disclosed in Patent Publication No. CN116154208A entitled “High-precision and high-corrosion-resistant titanium bipolar plate for fuel cell, preparation method thereof, and die assembly”, and the repeated description is omitted. The stamping machine employs a precision press machine, such as a YKP-630 precision press machine. The electro-processing device includes a direct current power supply, a copper electrode, and an insulating wood clamp. The electrode and the insulating clamp are integrated into the transfer and electro-processing device for grabbing and transferring the pre-formed metal bipolar plate.

[0071] As shown in FIGS. 11-14, the embodiment also provides a transfer and electro-processing device. The transfer and electro-processing device includes an electro-processing bearing platform 1 and a transfer platform 3 above the electro-processing bearing platform 1. The electro-processing bearing platform 1 includes oppositely arranged electrode units 4, and the electrode units 4 include open electrode clamps that can be operatively pressed together. The transfer platform 3 is installed above the electro-processing bearing platform 1 by a vertical moving support 5, and the transfer platform 3 can be operatively moved up and down on the vertical moving support 5. The transfer platform 3 includes a rectangular frame and a suction cup assembly 2 that can be operatively moved in a horizontal direction on the rectangular frame, and the suction cup assembly 2 is configured to suck the metal substrate or the metal bipolar 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 above the first height position on the vertical moving support 5. The first horizontal position in the second height position is the initial position of the suction cup assembly 2.

[0073] Specifically, the electro-processing carrying platform 1 is provided with a first electric drive rail 40. The electrode clamp includes a lower electrode 42 fixedly connected to both ends of the first electric drive rail 40 and an upper electrode 41 movably connected to both ends of 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 clamp. The lower electrode 42 and the upper electrode 41 are copper electrodes.

[0074] The transfer platform 3 includes an electric drive telescopic rail 31 arranged on the lower side of the rectangular frame. The suction cup assembly 2 is connected between two parallel electric drive telescopic rails 31 and is driven to switch between the first horizontal position and the second horizontal position. The vertical moving support 5 includes two second electric drive rails 51 vertically arranged on the electro-processing carrying platform 1, and the rectangular frame is vertically connected to the two second electric drive rails 51 and is driven to switch between the first height position and the second height position.

[0075] As shown in Fig. 14a, the suction cup assembly 2 is located in the second horizontal position and in the second height position for sucking or unloading the metal substrate or metal plate. When the suction cup assembly 2 is located in the second horizontal position, it is used to switch and move between the first height position and the second height position, as shown in Fig. 15b. As shown in Fig. 14b, when the suction cup assembly 2 is located in the second horizontal position and in the first height position, it can be moved to the first horizontal position to send the metal substrate or metal plate into the opened electrode clamp.

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

[0077] The feeding process feeds a metal substrate with a thickness of 0.05 mm or more and 0.2 mm or less to a first sequence stamping device with a first sequence forming die;

[0078] The first sequence forming process uses the first sequence stamping device to perform first sequence stamping pre-forming on the metal substrate to form a pre-formed metal plate;

[0079] The transfer and electro-processing process controls the transfer and electro-processing device to move the pre-formed metal plate to the electro-processing station on the transfer and electro-processing device for electro-processing, and takes out the electro-processed metal plate after the electro-processing is completed; the electro-processing clamping area is > 500 mm2 ;

[0080] A second sequence forming process, using a second sequence stamping device to stamp and form the metal plate after the electrical treatment to obtain a completely formed metal plate;

[0081] A discharging process, taking the completely formed metal plate from the second sequence stamping device. The completely formed metal plate has a flow channel thickness range less than 24 μm and a flow channel aspect ratio greater than 0.79.

[0082] In other embodiments, the method for preparing the fuel cell metal plate is not limited to two stamping forming processes and one intermediate electrical treatment process. It can be multiple stamping processes and multiple electrical treatment processes. Thus, the first sequence forming process and the second sequence forming process further include at least one intermediate sequence forming process to stamp and form the metal plate, and the electrical treatment process is arranged between the two forming processes. Through multiple electrical treatments, the metal plate can finally achieve a higher forming limit.

[0083] As shown in FIG. 14, in the transferring and electrical treatment process, first, as shown in FIG. 14a, the suction cup assembly 2 is controlled to suck the pre-formed metal plate at the second horizontal position and the second height position, then, as shown in FIG. 14b 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 pre-formed metal plate is sent into the electrode clamp, the suction cup assembly 2 is controlled to release the pre-formed metal plate, then as shown in FIG. 14d, the electrode clamp is controlled to press and combine the pre-formed metal plate for electrical treatment, the suction cup assembly 2 is lifted to the initial position (the second horizontal position of the second height position). Finally, the electrode clamp is opened and the suction cup assembly 2 is controlled to return to the position shown in FIG. 14d to suck the metal plate after the electrical treatment from the first horizontal position to the second horizontal position, and then move the metal plate after the electrical treatment upward to the second height position.

[0084] In the feeding process, the robot is controlled to feed the metal substrate to the first sequence stamping device, and after the first sequence forming process is completed, the pre-formed metal plate is taken off from the first sequence stamping device. After the transferring and electrical treatment process is completed, the metal plate after the electrical treatment is also transferred to the second sequence stamping device by the robot. In the discharging process, the robot is controlled to take the completely formed metal plate from the second sequence stamping device.

[0085] The method for preparing the fuel cell metal pole plate further comprises an electric treatment parameter acquisition process, in which an electric treatment parameter is acquired when the highest temperature of the preformed metal pole plate reaches 500-1200 DEG C at the time of power-off at the end of the electric treatment time; and the electric treatment time is 0.5-10 seconds.

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

[0087] In the embodiment, considering that the bipolar plate is small in thickness (<0.2 mm) but large in electric treatment clamping area (>500 mm 2 , generally >2000 mm 2 ), the contact quality between the copper electrode and the metal pole plate is high, but the stress distribution of the clamped surface of the bipolar plate in the electrode closing state can be non-uniform due to the surface flatness error in the electrode processing process, the assembly error between the upper and lower electrodes and the electrode clamp, and the movement error of the upper electrode during downward movement, which can cause problems in the electric treatment process of the preformed pole plate: uneven current density due to local contact resistance difference, even electric erosion damage on the contact surface; local bending deformation of the clamped section; and sliding due to uneven and effective application of clamping force.

[0088] To solve such problems, a rubber pad is additionally arranged on the surface of the upper electrode towards the lower electrode, so as to improve the stress transmission and increase the actual contact area, so that the conduction is more uniform and the clamping is 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. Among 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 greater than the lower surface area of the rubber pad. The end of the metal pole plate is clamped between the rubber pad and the upper surface of the lower electrode.

[0089] The method for preparing the fuel cell metal pole plate and the metal pole plate multi-step forming production line provided by the embodiment can release the internal stress of the preformed metal pole plate in a very short treatment time, eliminate the deformation twin and dislocation accumulation, and finally significantly improve the forming limit and forming precision of the metal pole plate.

[0090] The embodiments of the present application are particularly for the electrical treatment of pre-shaped metal plates, especially titanium plates, which is a means of adding a step of material modification in the process of material to part shaping, aiming to improve the processability of the material (manufacturability of the part), and thus the ductility (elongation), as verified in Figures 5 to 11. The electrical treatment of the metal plates (titanium plates) of the present application hopes to, in the most ideal case, completely eliminate defects such as dislocations and twins, and complete recrystallization, replacing deformed grains with brand new equiaxed grains, and thus maximally improving the ductility of the material, thereby achieving a higher forming limit of the metal plates.

[0091] Figures 5 to 10 are verification result graphs obtained by the inventor to verify the effect of electrical treatment in the process of metal plate shaping.

[0092] Among them, Figure 5 is the result of multi-step stretching of a 0.1 mm thick titanium base material produced by a certain steel plant and measuring the total elongation (i.e. the scenario described in Example 3 below). Specifically, the titanium base material is first stretched to 15% along the rolling direction, then subjected to electrical treatment under different electrical treatment conditions shown in Figure 5 (5s@550℃, i.e. electrical treatment for 5 seconds, the highest temperature of the plate material when the power is off reaches 550℃. The highest temperature of this group of experiments is all 550℃, but the electrical treatment time varies), and finally stretched again to break. Calculate the total elongation of the titanium base material after two stretches, and compare it with the sample that is also stretched twice but without electrical treatment in between (i.e. the position marked by the green dotted line in Figure 5, the elongation of this sample is about 35.8%), the elongation of the sample under each electrical treatment condition is improved to varying degrees. Elongation is an important indicator for evaluating the ductility of the sample, the higher the elongation, the more the material can withstand before breaking, thus proving the ability of electrical treatment to improve the forming limit of titanium base material.

[0093] Figures 6, 7 and 8 are also stretching experiment results of similar titanium plates, only the electrical treatment parameters are changed. It can also be seen that the elongation of the samples under different electrical treatment conditions is improved to varying degrees. Figure 9 is a comparison of the total elongation after changing the pre-deformation amount (originally only 15%, now 10%, 15% and 20% are compared together), and then respectively subjected to 2sec@500℃, 600℃ and 700℃ electrical treatment. It can also be seen that for samples with different pre-deformation amounts, electrical treatment is also effective, and the overall trend of the effect is the same.

[0094] Figure 10 is a comparative result diagram of two forming processes by controlling the punch depth directly in the second sequence forming die without using the first sequence forming die in Figure 2. Compared with the traditional simple multi-step punch forming (upper picture in Figure 10), the improved process is (lower picture in Figure 10) to control the punch depth to about 0.25 mm at the first forming time, at which time the pole plate still does not appear to crack, and then the pole plate is electrically treated and then put back into the die to be fully punched to a final depth of 0.35 mm. As can be seen from the results shown in Figure 10, pure electrical treatment has a great effect on improving the forming limit of the sheet metal, and it can be seen that the sample without electrical treatment in the traditional process is completely cracked, which indicates that it is completely beyond the forming limit, while the sample after electrical treatment has a significant improvement in cracking, which indicates the improvement effect of electrical treatment on the local forming limit.

[0095] The present application will be further described below through several specific examples in order to better understand the present application.

[0096] Example 1

[0097] This example provides a new method capable of improving the forming limit and cross-sectional thickness distribution uniformity of a metal pole plate, the target pole plate flow passage period to be formed is 1.2 mm, the draft angle is 5°, the fillet radius is 0.1 mm, and the depth-width ratio is 0.79, and the specific steps are as follows:

[0098] S1, raw material selection

[0099] In this example, the sample substrate is TA1 industrial pure titanium produced by a certain steel plant, with a thickness of 0.1 mm and a titanium element content of more than 99.5%, and the industrial pure titanium is a titanium substrate with an α phase after annealing heat treatment after cold rolling.

[0100] S2, electrical treatment parameter acquisition

[0101] In order to obtain the electrical treatment parameters, a piece of pre-formed titanium pole plate is used to monitor the temperature of the pre-formed titanium pole plate under the electrical treatment condition by using an infrared thermal imager. The electrical treatment time is selected as 2 seconds, and the highest temperature of the titanium pole plate after 2 seconds of electrical treatment and power-off is ensured to reach 750°C, as shown in Figure 1. For the pre-formed titanium pole plate with a width of 100 mm in this example, the obtained output voltage of the power supply box is 120V, the duty cycle is 70%, and the pulse frequency is 300Hz.

[0102] S3, feeding

[0103] The feeding robot is used to transfer the ultra-thin titanium substrate obtained in S1 to the first sequence punch equipment and position it.

[0104] S4, first sequence forming

[0105] The first sequence forming die as shown in Fig. 2a is used to perform first sequence stamping forming on the material sheet after feeding in S3.

[0106] S5, transfer and electro-processing

[0107] The pre-deformed titanium electrode plate obtained in S4 is sucked from the first sequence stamping die by the vacuum chuck integrated in the integrated clamp of the transfer and electro-processing device, and is moved to the electro-processing station in the integrated clamp. After recognizing that the pre-deformed titanium electrode plate reaches the designated position, the servo motor drives the upper clamp to move downward to clamp the titanium electrode plate. Then, the vacuum pump is temporarily stopped, and the vacuum chuck moves upward. The pulse current calibrated in S2 is applied to the pre-deformed titanium electrode plate, while the mechanical arm of the transfer and electro-processing device moves to drive the entire integrated clamp to move to the second sequence stamping station. After the electro-processing is completed, the vacuum chuck moves downward and the vacuum pump is restarted, and the upper clamp moves upward to release the titanium electrode plate. The titanium electrode plate is transferred to the second sequence stamping device by the vacuum chuck and is positioned.

[0108] S6, second sequence forming

[0109] The second sequence forming die as shown in Fig. 2b is used to perform second sequence stamping forming on the titanium electrode plate after the electro-processing in S5.

[0110] S7, discharging

[0111] The formed titanium electrode plate is transferred out of the second sequence stamping device by the discharging device.

[0112] As shown in Fig. 3, the micro-channels of the titanium electrode plate formed by the conventional normal temperature multi-step forming process and the new method proposed in the present disclosure are shown respectively. The new method proposed in the present disclosure can break through the forming limit of the titanium electrode plate and obtain a target electrode plate without cracking. As shown in Fig. 4, the thickness distribution uniformity of the electrode plate channel is evaluated by the range method, that is, the thickness of the base material is measured at 9 characteristic positions (the midpoints of the ridge, groove and side wall, and the maximum thinning position of the fillet) on each channel profile period. It can be found that the thickness range of the micro-channel of the titanium electrode plate manufactured by the conventional multi-step forming process is large (27.8 μm), and the excessive thinning at the weakest fillet position (P6) eventually causes the channel to crack. The method proposed in the present disclosure can promote uniform deformation of the material during the forming process, thereby improving the thickness uniformity of the channel and reducing the thickness range of the channel to about 21.8 μm.

[0113] Example 2

[0114] In this example, TA1 industrial pure titanium with a thickness of 0.1 mm is used, the target electrode plate channel to be formed has a period of 1.18 mm and a channel depth of 0.38 mm. The titanium electrode plate without cracking can be manufactured by the conventional multi-step stamping forming, but the channel size precision is poor.

[0115] The new method provided by the application is used to perform first electric treatment on the pre-shaped titanium plate. The electric treatment time is selected as 2 seconds, so that the highest temperature of the flow channel area of the titanium plate is 730 DEG C when the power is turned off after the electric treatment for 2 seconds. At this time, the output voltage of the power supply box is 190 V, the duty cycle is 100%, and the pulse frequency is 4000 Hz. The flow channel depth of the titanium plate formed by the new method is about 10 um higher than that of the titanium plate formed by the multi-step cold stamping, and the cross section of the formed flow channel is closer to the design value, which proves that the new method can also be used as an effective means to improve the dimensional accuracy of the target metal plate.

[0116] Example 3

[0117] In this embodiment, the sample substrate is selected as TA1 industrial pure titanium with a thickness of 0.1 mm and a titanium element content higher than 99.5% produced by a certain steel plant, and the target is to improve the fracture elongation of the titanium plate.

[0118] The new method provided by the application is used to pre-stretch the titanium plate to 15% elongation, then perform 10-second electric treatment, so that the highest temperature reaches 550 DEG C when the power is turned off after the electric treatment for 10 seconds, and finally load stretching to fracture again. The stretching test result shows that the elongation of the titanium plate is improved by about 23% compared with the normal temperature stretching condition.

[0119] Example 4

[0120] In this embodiment, the sample substrate is selected as 446 ferritic stainless steel with a thickness of 0.1 mm produced by a certain steel plant in China, and the feasibility of the new method proposed by the application for migrating to the ultra-thin stainless steel substrate is explored based on the uniaxial stretching.

[0121] The new method provided by the application is used to pre-stretch the ferritic stainless steel plate to 15% elongation, then perform 2-second electric treatment, so that the highest temperature reaches 1000 DEG C when the power is turned off after the electric treatment for 2 seconds, and finally load stretching to fracture again. The stretching test result shows that the elongation of the ferritic stainless steel is improved by about 32% compared with the normal temperature stretching condition, which proves that the new method can improve the formability of the ferritic stainless steel.

[0122] Any numerical values recited herein include all values from the lower to the upper value inclusive of the lower and higher values, and are inclusive of any intervening values as well as any other intervening endpoints. For example, if a range is stated as 1 to 90, preferably 20 to 80, more preferably 30 to 70, it is intended that values such as 15 to 85, 22 to 68, 43 to 51, and 30 to 32 are expressly enumerated in this specification. For values which are less than one, one unit is considered to be 0.0001, 0.001, 0.01, 0.1. These are only examples of what is specifically enumerated herein and are not the only examples of equivalent values which are considered to be within the scope of the present teachings. Other such examples are expressly contemplated as falling within the scope of the present teachings.

[0123] Unless otherwise stated, all ranges include the endpoints and all numbers between the endpoints. The use of "about" or "approximately" in connection with a range applies to both ends 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 is to be understood that the above description is intended to be illustrative, and not restrictive. Many embodiments and applications other than the examples provided would be apparent to those of skill in the art upon reading the above description. The scope of the teachings should, therefore, be determined not with reference to the above description, but should instead be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. The disclosures of all articles and references, including patent applications and publications, are incorporated by reference for the purpose of the present teachings. The omission of any aspect of the subject matter disclosed herein does not preclude coverage of that aspect, whether from a prior claim or from the written description.

Claims

1. A method for manufacturing a fuel cell metal bipolar plate, comprising: a feeding step of feeding a metal substrate having a thickness of 0.05 mm or more and 0.2 mm or less to a first sequence punching device having a first sequence forming die; a first sequence forming step of performing first sequence punching preforming on the metal substrate by the first sequence punching device to form a preformed metal bipolar plate; The transport and electric treatment process controls the transport and electric treatment equipment to move the preformed metal plate to the electric treatment station on the transport and electric treatment equipment for electric treatment, and takes out the metal plate after electric treatment; the electric treatment clamping area is > 500 mm 2 ; a second sequence forming step of performing second sequence punching forming on the electrically treated metal bipolar plate by a second sequence punching device to obtain a completely formed metal bipolar plate; a discharging step of discharging the completely formed metal bipolar plate from the second sequence punching device.

2. The method of making a fuel cell metal bipolar plate of claim 1, wherein, The first sequence forming step and the second sequence forming step further comprise at least one intermediate sequence forming step of punching forming on the metal bipolar plate, and the electric treatment step is arranged between the two forming steps.

3. The method of making a fuel cell metal bipolar plate of claim 1, wherein, The transfer and electric treatment device comprises an electric treatment supporting platform and a transfer platform arranged above the electric treatment supporting platform; the electric treatment supporting platform comprises oppositely arranged electrode units; the electrode units comprise openable and closable electrode clamps; the transfer platform is installed above the electric treatment supporting platform by a vertical moving support; the transfer platform is arranged on the vertical moving support in a controllable up-and-down movement; the transfer platform comprises a rectangular frame and a suction disc assembly arranged on the rectangular frame in a controllable horizontal movement; the suction disc assembly is used for sucking the metal substrate or the metal bipolar plate; The suction disc assembly has a first horizontal position and a second horizontal position relative to the rectangular frame in a horizontal direction; the transfer platform has a first height position and a second height position above the first height position on the vertical moving support.

4. The method of making a fuel cell metal bipolar plate of claim 3, wherein, In the transfer and electric treatment step, the suction disc assembly sucks the preformed metal bipolar plate at the second horizontal position and the second height position, then the electrode clamps are opened, the suction disc assembly is controlled to move from the second horizontal position to the first horizontal position after descending to the first height position, the preformed metal bipolar plate is sent into the electrode clamps, the suction disc assembly is controlled to release the preformed metal bipolar plate and the electrode clamps are controlled to press and close the preformed metal bipolar plate for electric treatment, finally, the electrode clamps are opened again, the suction disc assembly is controlled to suck the electrically treated metal bipolar plate again from the first horizontal position to the second horizontal position, and the electrically treated metal is moved upward to the second height position.

5. The method of making a fuel cell metal bipolar plate of claim 3, wherein, In the feeding step, a manipulator is controlled to feed the metal substrate to the first sequence punching device, and the preformed metal bipolar plate is discharged from the first sequence punching device after the first sequence forming step; After the transfer and electric treatment step, the electrically treated metal bipolar plate is further transferred to the second sequence punching device by the manipulator; In the discharging step, a manipulator is controlled to discharge the completely formed metal bipolar plate from the second sequence punching device.

6. The method of making a fuel cell metal bipolar plate of claim 3, wherein, The method further comprises an electric treatment parameter acquisition step of acquiring an electric treatment parameter when the highest temperature of the preformed metal bipolar plate reaches 500-1200℃ at the time of power-off at the end of the electric treatment time; the electric treatment time is 0.5-10 seconds.

7. The method of making a fuel cell metal bipolar plate of claim 1, wherein, The temperature of the preformed metal plate under the electric treatment is monitored by an infrared thermal imager.

8. The method of making a fuel cell metal bipolar plate of claim 1, wherein, The electric 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.

9. The method of making a fuel cell metal bipolar plate of claim 3, wherein, The first electric drive guide rail is arranged on the electric treatment bearing platform, the electrode clamp includes a lower electrode fixedly connected to both ends of the first electric drive guide rail and an upper electrode movably connected to both ends of the electric drive guide rail, and the first electric drive guide rail can drive the upper electrode to move up and down to open and close the electrode clamp. The transfer platform includes electric drive telescopic guide rails arranged on the lower side of the rectangular frame, and the suction cup assembly is connected between the two electric drive telescopic guide rails and is driven to switch between the first horizontal position and the second horizontal position. The vertical moving bracket includes two second electric drive guide rails vertically arranged on the electric treatment bearing platform, and the rectangular frame is vertically connected to the two second electric drive guide rails and is driven to switch between the first height position and the second height position.

10. A multi-step forming production line of metal bipolar plates implementing the method of producing the fuel cell metal bipolar plates as claimed in claim 1, wherein, It comprises: a feeding device, a first sequence stamping device, a transfer electric treatment device, a second sequence stamping device, and a discharging device; wherein, the feeding device is used to feed the metal substrate to the first sequence stamping device with a first sequence forming die; the first sequence stamping device is used to perform first sequence stamping preforming on the metal substrate to form a preformed metal plate; the transfer electric treatment device is used to move the preformed metal plate to the electric treatment station on the transfer electric treatment device for electric treatment, and take out the metal plate after electric treatment; the second sequence stamping device is used to perform second sequence stamping forming on the metal plate after electric treatment to obtain a completely formed metal plate; the discharging device takes down the completely formed metal plate from the second sequence stamping device.

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