Electrode electro-hydraulic forming device and method for metal bipolar plate

Abstract

The invention belongs to the technical field of metal bipolar plate forming, and particularly relates to an electrode electro-hydraulic forming device and method for a metal bipolar plate, the electrode electro-hydraulic forming device comprises a charging and discharging loop and a forming structure, the forming structure comprises a liquid chamber and a female die, liquid is arranged in the liquid chamber, and a metal plate is located between the liquid chamber and the female die. A sealing cavity is defined by the liquid chamber and the female die; the side wall of the liquid chamber is provided with at least two electrodes which are oppositely and horizontally arranged, the positive electrode and the negative electrode of the charging and discharging loop are connected with the two electrodes respectively, and the electrodes are located below the metal plate; horizontally arranged metal wires are connected among the end parts of the plurality of electrodes; the forming limit of the metal bipolar plate can be improved, the residual stress of the bipolar plate is reduced, the problems of cracking and springback warping of the bipolar plate are avoided, and the forming quality is guaranteed.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal bipolar plate forming, and in particular relates to an electrode electro-hydraulic forming device and a forming method for metal bipolar plates. Background Art

[0002] Bipolar plates, also known as current collector plates, are widely used in aviation, aerospace, automobile, communication, power and other industries. Fuel cell bipolar plates are one of them, with excellent electrical and thermal conductivity, machinability, compactness, gas barrier and other advantages. They are one of the important components in fuel cells and have good application prospects.

[0003] Fuel cell bipolar plates are generally composed of inlet and outlet, flow field distribution area and flow field reaction area. Among them, the inlet and outlet introduce hydrogen, oxygen / air and coolant into the bipolar plate to provide working fluid for the electrochemical reaction, and adjust the reaction temperature through the coolant; the distribution area mainly distributes hydrogen, oxygen / air and coolant evenly to the flow channel of the flow field reaction area to ensure the consistency of the electrochemical reaction; the flow field reaction area is in uniform contact with the membrane electrode, supplies hydrogen, oxygen / air, takes away the reaction products, and conducts electrons and reaction heat. Fuel cell bipolar plates can be divided into three categories according to the material: one is graphite bipolar plates, which have strong corrosion resistance, high thermal conductivity and electrical conductivity, and mature manufacturing process, but poor mechanical properties, large mass and volume, and high processing cost; the second is metal bipolar plates, which have good thermal and electrical conductivity, superior mechanical properties, low manufacturing cost, good structural durability, strong impact and vibration resistance, and metals such as titanium have good corrosion resistance; the third is composite material bipolar plates, which are corrosion-resistant, light in weight and volume, and high in strength, but poor in mechanical strength, low in electrical conductivity, and high in cost. The use of metals to prepare fuel cell bipolar plates can effectively improve the battery's capacity density, service life, charging speed, and performance under low temperature conditions.

[0004] During the operation of the fuel cell bipolar plate, the forming quality of the bipolar plate is an important factor to ensure the normal operation of the bipolar plate. At present, domestic metal bipolar plates mainly use materials such as stainless steel, titanium and nickel. Among them, stainless steel is the most widely used and most cost-effective metal. Its forming methods include soft mold forming, roll forming, liquid filling forming, stamping forming, etc. However, stainless steel is easily corroded in the proton exchange membrane fuel cell (PEMFC) cell environment, while titanium has better corrosion resistance than stainless steel in the PEMFC environment, and has high specific strength, which can significantly reduce the weight of the bipolar plate. It is an ideal material for fuel cell bipolar plates. Compared with stainless steel, titanium is similar to light alloys, with poor forming performance and poor plasticity at room temperature. The use of traditional forming processes will cause residual stress, small forming limit, poor flatness, cracking, and rebound warping problems in the bipolar plate. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide an electrode electro-hydraulic forming device and forming method for metal bipolar plates, which can improve the forming limit of metal bipolar plates, reduce the residual stress of bipolar plates, avoid cracking and rebound warping of bipolar plates, and ensure the forming quality.

[0006] An embodiment of the present invention provides an electrode electro-hydraulic forming device for a metal bipolar plate, comprising a charge-discharge circuit and a forming structure, wherein the forming structure comprises a liquid chamber and a concave die, wherein a liquid is arranged in the liquid chamber, wherein the metal plate is located between the liquid chamber and the concave die, and wherein the liquid chamber and the concave die enclose a sealed cavity; At least two electrodes arranged horizontally and opposite to each other are arranged on the side wall of the liquid chamber, the positive and negative electrodes of the charge and discharge circuit are respectively connected to the two electrodes, and the electrodes are located below the metal plate; and metal wires arranged horizontally are connected between the ends of the plurality of electrodes; A through hole is arranged on the side wall of the liquid chamber, and an electrode bushing is arranged in the through hole. The electrode bushing includes a conical electrode bushing a and a columnar electrode bushing b. The electrode is located in the electrode bushing, and also includes a limit block for fixing the electrode bushing on the liquid chamber.

[0007] Optionally, the number of the electrodes is 4, all located on the side walls of the liquid chamber, the electrodes are arranged opposite to each other in pairs, the electrodes on the same side wall of the liquid chamber are connected to the positive pole of the charge and discharge circuit, and the electrodes on the opposite side walls of the liquid chamber are connected to the negative pole of the charge and discharge circuit.

[0008] Optionally, the metal wire connects two electrodes on the same side or different sides.

[0009] Optionally, relative to the electrode bushing b, the electrode bushing a is closer to the sealing cavity.

[0010] Optionally, the limit block is located outside the electrode bushing b, and both the limit block and the liquid chamber are provided with threads, and also include bolts located in the threaded holes for fixing the electrode bushing on the liquid chamber.

[0011] Optionally, a groove is provided on the electrode bushing a, and a convex feature matching the groove is provided at a corresponding position of the electrode.

[0012] Optionally, the charging and discharging circuit includes a charging circuit and a discharging circuit, and the charging circuit includes a charging switch, a step-up transformer, a high-voltage rectifier, a current-limiting resistor and a capacitor; One end of the primary coil of the step-up transformer is connected to one end of the AC voltage source through a charging switch, the other end of the primary coil of the step-up transformer is connected to the other end of the AC voltage source, the two ends of the secondary coil of the step-up transformer are respectively connected to the two ends of the high-voltage rectifier, one end of the high-voltage rectifier is connected to one end of the capacitor through a current limiting resistor, and the other end of the high-voltage rectifier is connected to the other end of the capacitor; The discharge circuit includes a capacitor, one end of the capacitor is connected to an electrode through a discharge switch, and the other end of the capacitor is connected to another opposite electrode.

[0013] Optionally, a drainage hole is provided at the bottom of the liquid chamber, and also includes a positioning pin for locating the position of the die.

[0014] The side wall of the liquid chamber of the present invention is provided with at least two (preferably four) through holes for placing electrodes, and the through holes are divided into two sections, one of which is a conical hole, and the outer wall of the liquid chamber from the conical hole to the liquid chamber is a cylindrical hole, which is used to place a conical electrode bushing a and a columnar electrode bushing b respectively. The two electrodes are opposite to each other, and preferably two pairs of electrodes are provided. The bottom of the liquid chamber is designed to be connected with the surroundings at a rounded transition, so that the wall reflection of the shock wave during the forming process is more uniform, thereby making the forming characteristics more uniform. A drainage hole (preferably a threaded hole) is opened in the center of the bottom and sealed with bolts. After the electro-hydraulic forming is completed, the bolts are removed to discharge the water in the liquid chamber, and there is no need to move the liquid chamber to change the water during the whole process.

[0015] The electrode bushing includes electrode bushing a and electrode bushing b. The part of electrode bushing a in contact with water (i.e., the end face) is cylindrical, and the part in contact with the liquid chamber cavity is conical. Electrode bushing b is a stepped cylinder. Electrode bushing a and electrode bushing b respectively cooperate with the conical hole and cylindrical hole of the liquid chamber cavity. A groove (preferably a stepped hole) is opened inside the bushing to cooperate with the electrode. Electrode bushing a forms an interference fit with the liquid chamber and the electrode, and electrode bushing b forms a transition fit with the electrode, the liquid chamber, and the limit block.

[0016] The middle part of the electrode is a protrusion (preferably a stepped cylinder) which is used to form an interference fit and positioning with the electrode bushing. The stepped cylinder allows the bushing to provide axial constraints for the electrode. Metal wires are pre-set between the electrodes before electrohydraulic forming begins. The two sets of electrode pairs are connected in parallel and are connected to the positive and negative poles of the charge and discharge circuit through wires.

[0017] The limit block is matched with the liquid chamber through bolts to provide axial constraint for the electrode bushing; a gasket is placed in the groove at the end of the electrode bushing a to provide radial constraint for the electrode bushing and increase the sealing performance.

[0018] The die is provided with threaded holes, pin holes and air holes. The two holes on the diagonal are pin holes for installing positioning pins, and the remaining holes are threaded holes. Bolts are used to remove the die after the electro-hydraulic forming is completed. The air holes are used to discharge the air in the gap between the sheet and the die during the electro-hydraulic forming process to increase the film adhesion.

[0019] The electrode bushing a and the electrode form an interference fit through the transition of the stepped cylinder and the conical surface, and provide axial and radial constraints for the electrode. The electrode and the electrode bushing a as a whole form an interference fit with the liquid chamber. A gasket is added to the groove of the electrode bushing a to impose radial constraints on the bushing. The electrode bushing b is a transition fit with the electrode, the limit block, and the liquid chamber. The limit block and the liquid chamber are positioned and fastened with bolts to impose axial constraints on the bushing. The die is positioned using a locating pin during the assembly process.

[0020] The present invention can realize two discharge forms, one is the simultaneous discharge of two electrode pairs, and the other is the discharge of a single electrode pair. The former is suitable for forming metal bipolar plates with a large forming depth, complex features, and large size, while the latter is suitable for forming metal bipolar plates with a small forming depth, simple features, and small size.

[0021] In the charging circuit of the present invention, electric energy is stored in a capacitor via a step-up transformer, a high-voltage rectifier, and a current-limiting resistor; after charging is completed, the charging circuit is in an open circuit state, and the discharge switch of the discharge circuit is closed, and the electric energy is instantly released on the electrode pair. When the electric energy flows through the electrode pair, the preset metal wire undergoes a rapid phase change under the action of Joule heating, and finally forms a plasma channel to generate a strong shock wave pressure in the liquid chamber. When the shock wave pressure is greater than the yield limit of the sheet material, the sheet material undergoes plastic deformation, and electro-hydraulic forming occurs in the die forming area.

[0022] When a single electrode pair is used for discharge, the electrode pair is composed of two adjacent parallel electrodes on the same side, and the number of preset metal wires is changed from two to one. The discharge process is basically the same as that of the double electrode pair discharge. When electric energy flows through the electrode pair, the preset metal wire undergoes a sharp phase change under the action of Joule heating, and finally forms a plasma channel to generate a strong shock wave pressure in the liquid chamber. When the shock wave pressure is greater than the yield limit of the sheet, the sheet undergoes plastic deformation, and electro-hydraulic forming occurs in the die forming area. Since only one pair of electrodes is discharged, the shock wave pressure generated is smaller than the shock wave pressure generated by the double electrode pair discharge.

[0023] Whether single-electrode pair discharge or multi-electrode pair discharge is used, metal bipolar plates can be electro-hydraulically formed. When the metal bipolar plate features are more complex and the forming depth requirements are higher, multi-electrode pair discharge can be used; when the metal bipolar plate features are relatively simple and the forming depth requirements are not high, single-electrode pair discharge can be used.

[0024] The embodiment of the present invention provides a forming method of a metal bipolar plate, which is formed by using the electrode electro-hydraulic forming device for a metal bipolar plate, and includes the following steps: The liquid chamber is filled with water, the metal part to be formed is placed between the liquid chamber and the die, and the electrodes are installed; The charge-discharge circuit is charged first, and after charging is completed, the charge switch is disconnected and the discharge switch is closed, and the discharge in the sealed cavity generates a liquid-electric effect to generate shock wave pressure, so that the metal to-be-formed part is formed to obtain a metal bipolar plate.

[0025] Optionally, the metal part to be formed is located directly above the liquid surface, and the center of the metal part to be formed coincides with the center of the liquid surface.

[0026] Specifically, the forming method of the metal bipolar plate includes the following steps: Step 1: Prepare the metal sheet blank, remove rust and oil from the die surface and the blank to ensure that the forming area is smooth, clean and undamaged; Step 2: Put the electrode bushing on the outside of the electrode, use a gasket to impose radial constraints and increase sealing, and apply high vacuum silicone grease on the contact surface between the electrode and the electrode bushing to increase sealing; Step 3, placing the electrode and the bushing as a whole inside the liquid chamber, installing a limit block on the bushing, and connecting the limit block and the liquid chamber by bolts; Step 4, connecting the electrodes to the discharge circuit, two electrodes are connected to the positive electrode at the same time, and two electrodes are connected to the negative electrode at the same time to form a multi-electrode discharge pair, at this time the discharge switch is not closed; Step 5: Pre-place a metal wire between the electrodes, seal the threaded holes at the bottom of the liquid chamber with bolts, apply high vacuum silicone grease to the contact area between the bottom of the liquid chamber and the bolts and the contact area between the entire liquid chamber in step 2 to increase the sealing performance, and add water to the liquid chamber cavity; Step 6: Place the metal sheet blank in step 1 just above the liquid level in the liquid chamber, and apply high vacuum silicone grease to the contact area between the sheet and the liquid chamber to prevent leakage; Step 7: Position the die with the positioning pins and place the die directly above the sheet. The upper and lower surfaces of the sheet are in contact with the die and water respectively, and a press is used to apply pressure to the die to apply a blanking force; Step 8, close the charging switch, the alternating voltage is boosted by the step-up transformer, the current is converted from AC to DC through the high-voltage rectifier, the current limiting resistor reduces the current in the charging circuit, the rectified DC charges the capacitor, the charging switch is disconnected, the discharge switch is closed, the capacitor applies electrical energy to the electrode, the metal wire quickly melts under high energy and forms a plasma channel, instantly generating a huge shock wave pressure, so that the sheet metal is formed.

[0027] Step 9, release the pressure of the press, take out the die and the formed metal sheet to check the forming quality, repeat steps 5 to 8, and discharge forming under different energies can be performed.

[0028] The beneficial effects of the present invention are: 1. The present invention belongs to high-efficiency forming, which can improve the forming limit of materials and solve the problems that pure titanium, titanium alloys, etc. are difficult to form at room temperature and are prone to springback and wrinkling when formed using traditional methods.

[0029] 2. There is no punch in the forming process, which reduces the friction between the punch and the sheet, improves the surface quality of the metal sheet, has simple tooling, low cost, and can achieve mass production.

[0030] 3. Electrohydraulic forming does not require a high frequency of magnetic pulse equipment, and low-energy forming can be achieved by pre-setting metal wires before forming. Compared with existing electrohydraulic forming devices, multi-electrode electrohydraulic forming devices have an increased number of electrode pairs, and the shock wave pressure generated under the same discharge energy is greater, and the film-laminating effect of metal sheets is better. It significantly improves the processing flexibility of thin-plate electrohydraulic forming, and can be applied to thin-plate forming with a larger forming depth, and has good application prospects.

[0031] 4. The liquid chamber contains water, and the liquid chamber and the plate form a sealed chamber, and the die is placed on the upper part of the plate. At least two adjacent or oppositely arranged electrodes are arranged on both sides of the liquid chamber. Metal wires are connected between the ends of the multiple electrodes, and the arrangement direction of the metal wires is related to the distribution of the forming characteristics. The present invention can improve the forming limit of light alloy metal bipolar plates such as titanium at room temperature. The present invention uses an electro-hydraulic forming process to form metal bipolar plates. The electro-hydraulic forming process uses water as a force transmission medium, and generates shock waves through the underwater liquid-electric effect to provide forming pressure. There are no requirements for the conductivity of the material, so it can be applied to the forming of any material. At the same time, the electro-hydraulic forming process belongs to high-speed forming, which can greatly improve the forming performance of materials such as titanium and aluminum at room temperature, and reduce warping rebound and cracking problems. In addition, the electro-hydraulic forming process can flexibly control the forming effect of the plate by adjusting the discharge energy, the position of the metal wire, and the number of electrodes to meet the needs of flexible processing.

[0032] 5. The present invention sets electrodes on the side walls of the liquid chamber instead of the bottom, and the electrodes are arranged horizontally, and the metal wires on the electrodes are also arranged horizontally. The inventor found that after the metal wire explodes, a cylindrical shock wave spreads to both sides, and the width direction of the flow channel feature on the sheet is tensile deformation, and the mechanical properties of the sheet parallel to the rolling direction are the best. Therefore, the horizontal arrangement of the metal wire can make the cylindrical shock wave after the metal wire explodes during electro-hydraulic forming perpendicular to the flow channel direction, so the axial direction of the metal wire is parallel to the flow channel, and at the same time, it is also parallel to the axial direction of the electrode, which can significantly improve the forming quality of the sheet, improve the forming limit of the metal bipolar plate, reduce the residual stress of the bipolar plate, avoid the cracking and rebound warping of the bipolar plate, and ensure the forming quality. Compared with conventional electro-hydraulic forming devices, the present invention can provide greater shock wave pressure under the same discharge energy, and can be applied to formed parts with deeper feature depths and larger feature area areas. For the same forming feature parts, the use of the multi-electrode electro-hydraulic forming tooling proposed by the present invention can make the plate mold-attaching effect better.

[0033] 6. The thickness of the titanium bipolar plate prepared by the present invention can be as small as 0.1mm, the channel depth can be as small as 0.4mm, and the width can be as small as 0.32mm. The thickness of the conventional titanium bipolar plate is currently as small as 0.15mm, the channel depth is between 0.35-0.4mm, and the width is more than 1mm. The bipolar plate of the present invention has better effect. With the increasing requirements for lightweight automobiles, the thickness requirements for fuel cell metal bipolar plates are becoming more and more stringent. The lower the thickness requirements for fuel cell bipolar plates, the better, and the channel width and channel depth are also more refined.

[0034] The patent of the present invention is not only applicable to the preparation of titanium bipolar plates, but also to the preparation of coated stainless steel bipolar plates. Stainless steel bipolar plates are low in price, but have poor corrosion resistance and often require coating. When stainless steel bipolar plates are formed using processes such as stamping and rolling, the coating often cracks. Using the present invention to prepare stainless steel bipolar plates can avoid coating cracking, and can also greatly reduce the warping and rebound of stainless steel bipolar plates and improve assembly accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A schematic diagram of the structural principle of an electrode electro-hydraulic forming device for metal bipolar plates; Figure 2 for Figure 1 A schematic top view of the middle electrode electrohydraulic forming device; Figure 3 for Figure 2 The AA sectional view shown; Figure 4 for Figure 2 The BB cross-sectional view is shown.

[0036] Figure 5 1 is a diagram of the arrangement of metal wires in an embodiment of the present application, wherein ah represents different arrangements of the metal wires.

[0037] In the figure: 1. charging switch; 2. step-up transformer; 3. high-voltage rectifier; 4. current-limiting resistor; 5. capacitor; 6. discharge switch; 7. liquid chamber; 8. metal plate; 9. electrode bushing a; 10. electrode bushing b; 11. electrode; 12. limit block; 13. die; 14. metal wire. DETAILED DESCRIPTION

[0038] The technical solution of the present invention is further specifically described below in conjunction with the accompanying drawings and specific embodiments.

[0039] Example 1 An electrode electro-hydraulic forming device for a metal bipolar plate, comprising a charge-discharge circuit and a forming structure, wherein the forming structure comprises a liquid chamber 7 and a die 13, wherein the liquid chamber 7 is provided with liquid, wherein the metal plate 8 is located between the liquid chamber 7 and the die 13, and wherein the liquid chamber 7 and the die 13 enclose a sealed cavity; At least two electrodes 11 arranged horizontally and opposite to each other are provided on the side wall of the liquid chamber 7. The positive and negative electrodes of the charge-discharge circuit are connected to the two electrodes 11 respectively. The electrodes 11 are located below the metal plate 8. Horizontally arranged metal wires 14 are connected between the ends of the plurality of electrodes 11. A through hole is provided on the side wall of the liquid chamber 7, and an electrode bushing is provided in the through hole. The electrode bushing includes a conical electrode bushing a9 and a columnar electrode bushing b10. The electrode 11 is located in the electrode bushing, and also includes a limit block 12 for fixing the electrode bushing on the liquid chamber 7.

[0040] There are four electrodes 11, all located on the side walls of the liquid chamber 7. The electrodes 11 are arranged opposite to each other in pairs. The electrodes on the same side wall of the liquid chamber 7 are connected to the positive pole of the charge and discharge circuit, and the electrodes on the opposite side walls of the liquid chamber 7 are connected to the negative pole of the charge and discharge circuit.

[0041] The metal wire connects two electrodes 11 on the same side or different sides.

[0042] Compared with the electrode bushing b10, the electrode bushing a9 is closer to the sealing chamber.

[0043] The limit block 12 is located outside the electrode bushing b10 . The limit block 12 and the liquid chamber 7 are both provided with screw holes, and also include bolts located in the screw holes for fixing the electrode bushing on the liquid chamber 7 .

[0044] The electrode bushing a9 is provided with a groove, and the corresponding position of the electrode 11 is provided with a protrusion matching with the groove.

[0045] The charging and discharging circuit includes a charging circuit and a discharging circuit, and the charging circuit includes a charging switch 1, a step-up transformer 2, a high-voltage rectifier 3, a current-limiting resistor 4 and a capacitor 5; One end of the primary coil of the step-up transformer 2 is connected to one end of the AC voltage source through the charging switch 1, the other end of the primary coil of the step-up transformer 2 is connected to the other end of the AC voltage source, the two ends of the secondary coil of the step-up transformer 2 are respectively connected to the two ends of the high-voltage rectifier 3, one end of the high-voltage rectifier 3 is connected to one end of the capacitor 5 through the current limiting resistor 4, and the other end of the high-voltage rectifier 3 is connected to the other end of the capacitor 5; The discharge circuit includes a capacitor 5 , one end of the capacitor 5 is connected to an electrode 11 via a discharge switch 6 , and the other end of the capacitor 5 is connected to another opposite electrode 11 .

[0046] The bottom of the liquid chamber 7 is provided with a drainage hole and also includes a positioning pin for positioning the position of the die 13 .

[0047] Specifically, Figure 1 As shown, the charging switch 1 is closed, and the step-up transformer 2 increases the AC voltage in the power grid to several thousand volts. The high-voltage rectifier 3 converts the AC in the circuit into DC. The current-limiting resistor 4 reduces the current in the loop. After the current is reduced, it finally flows to the capacitor 5 for charging. When the capacitor 5 is charged to the threshold value, the charging switch 1 is disconnected, and the discharge switch 6 is closed. The extremely high voltage acts on the electrode 11 to generate a strong current. The metal wire 14 preset on the electrode pair is quickly melted at a high energy rate to form a plasma channel. A strong shock wave pressure is instantly generated in the liquid chamber 7. The shock wave transmits pressure through the liquid medium to drive the metal sheet 8 to move upward at a high speed to fit the die 13. When the shock wave pressure is greater than the yield limit of the metal sheet 8, the metal sheet 8 undergoes plastic deformation. When the shock wave pressure is large enough, the metal sheet 8 undergoes electro-hydraulic forming in the forming area of ​​the die 13.

[0048] See also Figure 2-3 The liquid chamber 7 is provided with four conical holes for placing electrodes. The electrode 11 forms an interference fit and a transition fit with the electrode bushing a9 and the electrode bushing b10 respectively and is placed in the conical hole of the liquid chamber 7 as a whole. The whole forms an interference fit with the liquid chamber 7. The contact surfaces of the electrode 11 and the electrode bushing a9, the electrode bushing b10 and the contact surface of the electrode bushing a9 and the liquid chamber 7 are coated with high vacuum silicone grease to enhance the sealing.

[0049] See also Figure 3 The limit block 12 and the electrode bushing b10 form a transition fit, and the limit block 12 and the liquid chamber 7 are fastened with bolts to provide axial constraints for the electrode bushing a9, the electrode bushing b10 and the electrode 11 as a whole.

[0050] See also Figure 3 Every two electrodes facing each other in the liquid chamber 7 form an electrode pair. A maximum of two electrode pairs can be used for simultaneous discharge. Before electro-hydraulic forming, a metal wire 14 is pre-placed in the electrode pair.

[0051] See also Figure 3 , add water into the liquid chamber 7 until the inner wall of the liquid chamber 7 is filled, and evenly apply high vacuum silicone grease around the liquid surface and in contact with the metal plate 8 to increase the sealing during the electro-hydraulic forming process.

[0052] See also Figure 2-4 , place the metal plate 8 just above the liquid surface, with the center of the metal plate 8 coinciding with the center of the liquid surface, use the positioning pin to position the die 13, place the die 13 just above the liquid surface, with the center of the die 13 coinciding with the center of the metal plate 8, the upper surface of the metal plate 8 contacts the die 13, and the lower surface contacts the liquid surface and the liquid chamber 7 at the same time, use wires to connect the electrodes on the same side of the liquid chamber 7 to the same pole of the charge and discharge circuit, such as the electrodes on the left are connected to the positive pole of the charge and discharge circuit, and the electrodes on the right are connected to the negative pole of the charge and discharge circuit.

[0053] like Figure 3 The electrode 11 is made of chromium zirconium copper, and threads are processed on both ends for pre-setting the metal wire 14 and fastening the wire with nuts. The metal wire 14 is made of aluminum. The electrode bushing a9 and the electrode bushing b10 are made of phenolic plastic. The metal plate 8 is made of TA1 industrial pure titanium, with a length of 150 mm, a width of 120 mm, and a thickness of 0.1 mm. The liquid chamber 7 and the die 13 are made of 45 steel and mold steel respectively. The die 13 is a parallel flow channel, and the characteristic area dimensions are 136.5 mm in length, 76.5 mm in width, 0.6 mm in flow channel width, 0.4 mm in flow channel depth, 0.3 mm in upper fillet, 0.2 mm in lower fillet, 45° in flow channel inclination, and 12 kJ in discharge energy.

[0054] Place the liquid chamber 7 on the working platform of the press, install the electrode 11 into the electrode bushing a9 and the electrode bushing b10, add a gasket to the groove at the end of the electrode bushing a9 to provide radial constraint and increase the sealing, apply high vacuum silicone grease on the contact surface of the electrode 11 and the electrode bushing a9 and the electrode bushing b10 to increase the sealing, assemble the electrode 11 and the electrode bushing a9 and the electrode bushing b10 into a conical hole that is placed in the liquid chamber 7 as a whole, and the liquid chamber 7 is provided with 4 conical holes for placing electrodes, and 4 groups of electrodes and electrode bushings are placed to form 2 groups of electrode pairs, and the limit block 12 forms a transition fit with the electrode bushing b10 and is fastened with bolts between the liquid chamber 7 to provide axial constraint for the electrode 11 and the electrode bushing a9 and the electrode bushing b10 as a whole, pre-set the metal wire 14 on the 2 groups of electrode pairs and add water to the liquid chamber 7. Until the inner wall of the liquid chamber 7 is filled, the metal plate 8 is placed just above the liquid surface, the center of the metal plate 8 coincides with the center of the liquid surface, the positioning pin is used to position the die 13, the die 13 is placed just above the liquid surface, the center of the die 13 coincides with the center of the metal plate 8, the upper surface of the metal plate 8 contacts the die 13, and the lower surface contacts the liquid surface and the liquid chamber 7 at the same time, high vacuum silicone grease is evenly applied to the contact area around the liquid surface and the metal plate 8 to increase the sealing, 4 groups of electrodes are distributed on the left and right sides of the liquid chamber 7, the left electrode and the right electrode are horizontally opposite, and an electrode pair is formed between the two, and the electrodes on the same side of the liquid chamber 7 are connected to the same pole of the charge and discharge circuit using wires, such as connecting the 2 groups of electrodes on the left to the negative pole and the 2 groups of electrodes on the right to the negative pole, and a press is used to apply sufficient pressure on the die to complete the assembly of the entire tooling.

[0055] Example 2 A forming method of a metal bipolar plate, using the electrode electro-hydraulic forming device for a metal bipolar plate to form the metal bipolar plate, comprises the following steps: The liquid chamber 7 is filled with water, the metal part to be formed is placed between the liquid chamber 7 and the die 13, and the electrode 11 is installed; The charge-discharge circuit is charged first, and after the charging is completed, the charging switch 1 is disconnected, and the discharging switch 6 is closed, so that a shock wave is generated in the sealed cavity to form the metal part to be formed, thereby forming a metal bipolar plate.

[0056] The metal part to be formed is located directly above the liquid surface, and the center of the metal part to be formed coincides with the center of the liquid surface.

[0057] Specifically, the following steps are included: Step 1: Prepare metal sheets of appropriate size, remove rust and oil from the die surface and the forming area of ​​the metal sheet to ensure that the forming area is smooth, clean and free of damage; Step 2, place the liquid chamber 7 on the working platform of the press, install the electrode 11 into the electrode bushing a9 and the electrode bushing b10, add a gasket to the groove at the end of the electrode bushing a9 to provide radial constraint and increase sealing, and apply high vacuum silicone grease on the contact surface between the electrode 11 and the electrode bushing a9 and the electrode bushing b10 to increase sealing; Step 3, placing the electrode 11, electrode bushing a9 and electrode bushing b10 formed by step 2 into the conical hole in the liquid chamber 7. The liquid chamber 7 has 4 conical holes, and a total of 4 groups of electrodes and electrode bushings are placed to form 2 groups of electrode pairs; Step 4, the limit block 12 forms a transition fit with the electrode bushing b10 and is fastened with the liquid chamber 7 using bolts to provide axial constraints for the electrode 11 and the electrode bushing a9 and the electrode bushing b10 as a whole; Step 5, pre-place metal wires 14 on the two sets of electrode pairs and add water into the liquid chamber 7 until the inner wall of the liquid chamber 7 is filled, place the metal plate 8 just above the liquid surface, the center of the metal plate 8 coincides with the center of the liquid surface, and seal the threaded holes at the bottom of the liquid chamber 7 with bolts, and apply high vacuum silicone grease to the contact area between the bottom of the liquid chamber 7 and the bolts and the contact area between the entirety of step 2 and the liquid chamber 7 to increase the sealing performance; Step 6: Use the positioning pins to position the die 13, place the die 13 just above the liquid surface, the center of the die 13 coincides with the center of the metal plate 8, the upper surface of the metal plate 8 contacts the die 13, and the lower surface contacts the liquid surface and the liquid chamber 7 at the same time; Step 7, 4 groups of electrodes are distributed on the left and right sides of the liquid chamber 7, the left electrode and the right electrode are horizontally opposite to each other, and an electrode pair is formed between the two electrodes. The electrodes on the same side of the liquid chamber 7 are connected to the same pole of the charge and discharge circuit using a wire, such as connecting the two groups of electrodes on the left to the negative pole and the two groups of electrodes on the right to the negative pole, and a press is used to apply sufficient pressure on the die; Step 8, close the charging switch 1, the alternating voltage is boosted by the step-up transformer 2, the current is converted from AC to DC through the high-voltage rectifier 3, the current limiting resistor 4 reduces the current in the charging circuit, the rectified DC charges the capacitor 5, the charging switch 1 is disconnected, the discharge switch 6 is closed, the capacitor 5 applies electrical energy to the electrode 11, the metal wire 14 quickly melts under high energy and forms a plasma channel, instantly generating a huge shock wave pressure, when the shock wave pressure is greater than the yield limit of the metal plate 8, the metal plate undergoes plastic deformation to form a titanium bipolar plate.

[0058] Step 9, release the pressure of the press, take out the die and the formed metal sheet to check the forming quality, repeat steps 5 to 8, and discharge forming under different energies can be performed.

[0059] Example 3 The technical solution provided in this embodiment is basically the same as that in the first embodiment, except that: only two groups of electrodes on the same side of the liquid chamber 7 are used to form an electrode pair, and the two groups of electrodes are respectively connected to the positive and negative poles of the charge and discharge circuit, and the bipolar plates formed have different size parameters, which changes the discharge capacity.

[0060] Specifically, the electrode 11 is made of chromium zirconium copper, and threads are processed on both ends for pre-setting the metal wire 14 and fastening the wire with nuts. The metal wire 14 is made of aluminum. The electrode bushing a9 and the electrode bushing b10 are both made of phenolic plastic. The metal plate 8 is made of TA1 industrial pure titanium, with a length of 150 mm, a width of 120 mm, and a thickness of 0.1 mm. The liquid chamber 7 and the die 13 are made of 45 steel and mold steel respectively. The die 13 is a parallel flow channel, and the characteristic area dimensions are 136.5 mm in length, 76.5 mm in width, 0.32 mm in flow channel width, 0.1 mm in flow channel depth, 0.05 mm in upper fillet, 0.04 mm in lower fillet, 11° in flow channel inclination, and 6 kJ in discharge energy.

[0061] Specifically, the charging switch 1 is closed, the alternating voltage is boosted by the step-up transformer 2, the current is converted from AC to DC by the high-voltage rectifier 3, the current limiting resistor 4 reduces the current in the charging circuit, and the rectified DC charges the capacitor 5, the charging switch 1 is disconnected, and the discharge switch 6 is closed, the capacitor 5 applies electric energy to the electrode 11, the metal wire 14 is quickly melted under high energy and forms a plasma channel, instantly generating a huge shock wave pressure, and when the shock wave pressure is greater than the yield limit of the metal plate 8, the metal plate undergoes plastic deformation to produce an electro-hydraulic formed titanium bipolar plate.

[0062] Example 4 like Figure 5 As shown, the embodiment of the present invention is provided with two pairs of electrodes, both arranged on the side wall of the liquid chamber and arranged opposite to each other. These two pairs of electrodes can be connected to 6 capacitors for discharge at the same time, or each pair of electrodes can be connected to 3 capacitors for discharge to improve the uniformity of energy distribution.

[0063] Generally speaking, the arrangement of the metal wire 14 of the traditional single-electrode electro-hydraulic forming tooling is fixed, which means that the shock wave pressure distribution after each discharge is consistent. When the forming feature distribution areas are large and the features are complex, the single shock wave pressure distribution will not match the forming feature areas, resulting in insufficient forming depth and poor mold adhesion in some areas, affecting the performance of the formed parts.

[0064] The present invention has two pairs of electrodes, and there are many options for arranging the metal wire 14. Figure 5. The winding arrangement of the metal wire 14 can be selected according to the actual forming feature position of the metal bipolar plate. It is worth noting that the present invention is not limited to two pairs of electrodes. Using the design method or idea of ​​the present invention, the number of electrode pairs can be flexibly increased to three or more piles and the winding method of the metal wire 14 can be changed according to the regional area, distribution, and depth requirements of the forming features, greatly improving the processing flexibility of actual industrial production.

[0065] For example, if the features of the formed part are distributed on both sides of the sheet and the length direction of the features is parallel to the electrode axis, then a bimetallic wire 14 can be used for winding, and the axis of the metal wire 14 is consistent with the axis of the electrode, such as Figure 5 As shown in g.

[0066] A person skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of protection of the present application is limited to these examples. In line with the concept of the present application, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of different aspects of one or more embodiments of the present application as described above, which are not provided in detail for the sake of simplicity.

[0067] One or more embodiments of the present application are intended to cover all such substitutions, modifications and variations that fall within the broad scope of the present application. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of one or more embodiments of the present application should be included in the protection scope of the present application.

Claims

1. An electrode electro-hydraulic forming device for a metal bipolar plate, characterized in that: The invention comprises a charge-discharge circuit and a forming structure, wherein the forming structure comprises a liquid chamber (7) and a concave mold (13), wherein a liquid is arranged in the liquid chamber (7), wherein the metal plate (8) is located between the liquid chamber (7) and the concave mold (13), and wherein the liquid chamber (7) and the concave mold (13) enclose each other to form a sealed cavity; At least two electrodes (11) arranged horizontally and arranged opposite to each other are provided on the side wall of the liquid chamber (7); the positive and negative electrodes of the charge-discharge circuit are respectively connected to the two electrodes (11); the electrodes (11) are located below the metal plate (8); and horizontally arranged metal wires (14) are connected between the ends of the plurality of electrodes (11); A through hole is provided on the side wall of the liquid chamber (7), an electrode bushing is provided in the through hole, the electrode bushing comprises a conical electrode bushing a (9) and a columnar electrode bushing b (10), the electrode (11) is located in the electrode bushing, and also comprises a limit block (12) for fixing the electrode bushing on the liquid chamber (7).

2. The electrode electro-hydraulic forming device for metal bipolar plates according to claim 1, characterized in that: The number of the electrodes (11) is four, all of which are located on the side walls of the liquid chamber (7). The electrodes (11) are arranged opposite to each other in pairs, the electrodes on the same side wall of the liquid chamber (7) are connected to the positive electrode of the charge-discharge circuit, and the electrodes on the opposite side walls of the liquid chamber (7) are connected to the negative electrode of the charge-discharge circuit.

3. The electrode electro-hydraulic forming device for metal bipolar plates according to claim 2, characterized in that: The metal wire (14) connects two electrodes (11) on the same side or on different sides.

4. The electrode electro-hydraulic forming device for metal bipolar plates according to any one of claims 1 to 3, characterized in that: Compared with the electrode bushing b (10), the electrode bushing a (9) is closer to the sealing chamber.

5. The electrode electro-hydraulic forming device for metal bipolar plates according to any one of claims 1 to 3, characterized in that: The limit block (12) is located outside the electrode bushing b (10), and threaded holes are provided on the limit block (12) and the liquid chamber (7), and also includes bolts located in the threaded holes for fixing the electrode bushing on the liquid chamber (7).

6. The electrode electro-hydraulic forming device for metal bipolar plates according to any one of claims 1 to 3, characterized in that: The electrode bushing a (9) is provided with a groove, and a corresponding position of the electrode (11) is provided with a protruding feature that matches the groove.

7. The electrode electro-hydraulic forming device for metal bipolar plates according to any one of claims 1 to 3, characterized in that: The charging and discharging circuit comprises a charging circuit and a discharging circuit, and the charging circuit comprises a charging switch (1), a step-up transformer (2), a high-voltage rectifier (3), a current-limiting resistor (4) and a capacitor (5); One end of the primary coil of the step-up transformer (2) is connected to one end of an AC voltage source via a charging switch (1), the other end of the primary coil of the step-up transformer (2) is connected to the other end of the AC voltage source, the two ends of the secondary coil of the step-up transformer (2) are respectively connected to the two ends of a high-voltage rectifier (3), one end of the high-voltage rectifier (3) is connected to one end of a capacitor (5) via a current limiting resistor (4), and the other end of the high-voltage rectifier (3) is connected to the other end of the capacitor (5); The discharge circuit comprises a capacitor (5), one end of the capacitor (5) is connected to an electrode (11) via a discharge switch (6), and the other end of the capacitor (5) is connected to another opposite electrode (11).

8. The electrode electro-hydraulic forming device for metal bipolar plates according to any one of claims 1 to 3, characterized in that: The bottom of the liquid chamber (7) is provided with a liquid drain hole, and also includes a positioning pin for positioning the position of the concave mold (13).

9. A method for forming a metal bipolar plate, characterized in that: The forming is performed using the electrode electro-hydraulic forming device for metal bipolar plates according to any one of claims 1 to 8, comprising the following steps: The liquid chamber (7) is filled with water, a metal part to be formed is placed between the liquid chamber (7) and the die (13), and an electrode (11) is installed; The charging and discharging circuit is first charged, and after the charging is completed, the charging switch (1) is disconnected and the discharging switch (6) is closed, so that the discharge in the sealed cavity generates a liquid-electric effect to generate shock wave pressure, thereby forming the metal part to be formed, thereby obtaining a metal bipolar plate.

10. The forming method according to claim 9, characterized in that: The metal part to be formed is located directly above the liquid surface, and the center of the metal part to be formed coincides with the center of the liquid surface.

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