A method of manufacturing a fuel cell package

Abstract

The application relates to the technical field of fuel cell preparation, and particularly relates to a method for preparing a fuel cell packaging box body; the method comprises the following steps: according to the structure of the fuel cell packaging box body, a plurality of single parts are prepared; a preset lap joint surface is arranged at a contact position of the single part; the preset lap joint surface is lap jointed to obtain a to-be-welded box body frame; the to-be-welded box body frame is friction stir welded to form a weld at a to-be-welded position of the to-be-welded box body frame, so that a welded box body frame is obtained; the fuel cell packaging box body frame is subjected to heat treatment to obtain a heat-treated box body frame; a grounding point is arranged on the outer side of the heat-treated box body frame to obtain a processed box body containing the grounding point; and the grounding point of the processed box body is plugged by using a plugging bolt to obtain a preliminary fuel cell packaging box body. The method designs the preset lap joint surface of the friction stir welding and the plugging bolt for plugging the grounding point, so that the stability of the fuel cell packaging box body is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fuel cell preparation, and particularly relates to a method for preparing a fuel cell packaging box. BACKGROUND

[0002] With the continuous acceleration of fuel cell product updates and iterative upgrades, the fuel cell packaging box needs to be frequently designed and changed, and the state of multiple fuel cell packaging box models generated by multiple design changes will exist for a long time. At present, the material widely used in the fuel cell packaging box is an aluminum alloy material, which generally needs to be formed by using a special mold in the process of die casting or gravity casting, which leads to the need for multiple special molds for multiple fuel cell packaging box models, thereby increasing the production cost of the entire fuel cell; in addition, the fuel cell packaging box can also be directly formed by machining process using aluminum ingots as raw materials, but the machining process requires a large amount of aluminum ingot blank and a long process flow, which leads to a sharp increase in the cost of aluminum ingot machining process and the cost of jig investment, and the utilization rate of raw materials in the machining process is low, which will cause a large degree of waste.

[0003] In the process of the aluminum alloy fuel cell packaging box processed by the above two methods, the threaded holes are directly processed on the aluminum alloy fuel cell packaging box. Based on the ductility of the aluminum alloy material, such threaded holes are not conducive to multiple disassembly and assembly, and the threaded screw will be damaged by the mounting bolt thread under the condition of multiple disassembly and assembly, which affects the integrity of the fuel cell packaging box structure and leads to poor stability of the prepared aluminum alloy fuel cell packaging box. SUMMARY

[0004] The present application provides a method for preparing a fuel cell packaging box to solve the technical problem of how to improve the stability of the fuel cell packaging box.

[0005] In a first aspect, the present application provides a method for preparing a fuel cell packaging box, the method comprising:

[0006] According to the structure of the fuel cell packaging box, a plurality of single parts are prepared;

[0007] A preset lap joint surface is designed at the contact position of two adjacent single parts;

[0008] The plurality of preset lap joint surfaces are lap jointed to obtain a to-be-welded box frame;

[0009] The to-be-welded box frame is friction stir welded to form a weld at the to-be-welded position of the to-be-welded box frame, thereby obtaining a welded box frame; wherein the penetration depth of the weld corresponds to the depth of the preset lap joint surface;

[0010] heat treating the welded box frame to obtain a heat treated box frame;

[0011] setting a flash point on the outer side of the heat treated box frame to obtain a processed box containing a flash point; and

[0012] plugging the flash point of the processed box using a plugging bolt to obtain a primary fuel cell packaging box.

[0013] Optionally, the parameters of the friction stir welding further include that the rotation speed of the welding pin is ≥800 r / min, and the feeding speed of the single part is ≥300 mm / min.

[0014] Optionally, the rotation speed of the welding pin is 800 r / min-1200 r / min, and the feeding speed of the single part is 300 mm / min-600 mm / min.

[0015] Optionally, the weld penetration depth is 6 mm-8 mm.

[0016] Optionally, the weld penetration depth h1 and the thickness h2 of the single part satisfy the relationship h1:h2=(0.6-1):1.

[0017] Optionally, the plurality of the preset lap surfaces are overlapped to obtain a box frame to be welded, including the steps of:

[0018] The preset lap surfaces of the adjacent two single parts are overlapped according to the shape of the preset lap surface to obtain a box frame to be welded; wherein the depth of the preset lap surface is the same as the thickness of the single part.

[0019] Optionally, the preset lap surface includes a plurality of trapezoidal surfaces, and the length of a single trapezoidal surface is 3 mm-50 mm.

[0020] Optionally, the heat treatment includes a heating section and a holding section, the temperature of the heating section is 120℃-160℃, and the time of the holding section is 2 h-4 h.

[0021] Optionally, after the flash point of the processed box is plugged using the plugging bolt to obtain the primary fuel cell packaging box, the method further includes:

[0022] The primary fuel cell packaging box is chemically polished, and then the plugging box after chemical polishing is hard oxidized to obtain a first surface treatment box containing an oxide film.

[0023] The first surface treatment box containing the oxide film is subjected to a sealing treatment to optimize the structure and performance of the oxide film layer of the surface treatment box, thereby obtaining a second surface treatment box;

[0024] The second surface treatment box is cleaned, and then the sealing bolts in the second surface treatment box after cleaning are disassembled, thereby obtaining a second surface treatment box containing a plurality of threaded holes;

[0025] The threaded holes of the second surface treatment box are filled with inlaid screw sleeves, thereby obtaining a third surface treatment box containing inlaid screw sleeves;

[0026] The third surface treatment box containing the inlaid screw sleeves is subjected to resistance detection and sealing detection, thereby obtaining a qualified fuel cell packaging box.

[0027] Optionally, the temperature of the chemical polishing is 90-105 DEG C, and the time of the chemical polishing is 3-6 min; and / or

[0028] The temperature of the hard oxidation is 10-15 DEG C, the voltage of the hard oxidation is 12-22 V, the current density of the hard oxidation is 1 A / dm 2 ~ 2 A / dm 2 , and the time of the hard oxidation is 70-120 min; and / or

[0029] The temperature of the sealing treatment is 25-60 DEG C, and the time of the sealing treatment is 10-15 min.

[0030] Optionally, the sealing liquid used in the sealing treatment includes nickel acetate, sodium fluoride, a surfactant and an additive, the weight m1 of the nickel acetate, the weight m2 of the sodium fluoride, the weight m3 of the surfactant and the weight m4 of the additive satisfy the relationship: m1:m2:m3:m4=(5-8):(1-1.5):(0.3-0.5):3; and / or

[0031] The pH value of the sealing liquid used in the sealing treatment is 5.5-6.5.

[0032] The above technical solution provided by the embodiments of the present application has the following advantages compared with the prior art:

[0033] The method for preparing the fuel cell packaging box provided by the embodiment of the application sets a preset lap joint surface at the contact position between single parts of the fuel cell packaging box, and the adjacent two single parts are friction stir welded according to the preset lap joint surface. The preset lap joint surface can increase the contact area of the adjacent two single parts in the limited contact space, and the two single parts with the increased contact area can disperse the stress received by the fuel cell packaging box during the friction stir welding process and reduce the possibility of stress concentration during the friction stir welding process, so as to improve the stability of the single parts during the friction stir welding process and obtain a weld seam with sufficient depth, thereby improving the stability of the fuel cell packaging box. In addition, the welded box frame is subjected to heat treatment, the linear expansion coefficient between the single parts is improved through the heat treatment, so as to offset the welding stress of the welded box frame during the friction stir welding process, thereby further improving the stability of the fuel cell packaging box during the processing process, and improving the stability of the fuel cell packaging box. In addition, the machining box with the tacking point after finishing is plugged by a plugging bolt, and the rigidity of the plugging bolt can improve the stability of the tacking point, so as to avoid the influence of the stability of the threaded hole structure of the fuel cell packaging box caused by multiple disassembly and assembly, thereby improving the stability of the fuel cell packaging box. BRIEF DESCRIPTION OF DRAWINGS

[0034] The accompanying drawings, which are incorporated herein and constitute part of the specification, illustrate embodiments consistent with the application and, together with the description, serve to explain the principles of the application.

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the accompanying drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, for those skilled in the art, other drawings can also be obtained based on these drawings without any creative labor.

[0036] Figure 1 A flowchart of a method for preparing a fuel cell packaging box provided by an embodiment of the application is shown in the figure.

[0037] Figure 2 A detailed flowchart of a method for preparing a fuel cell packaging box provided by an embodiment of the application is shown in the figure.

[0038] Figure 3 An actual flowchart of a method for preparing a fuel cell packaging box provided by an embodiment of the application is shown in the figure.

[0039] Figure 4 A structure diagram of a preset lap joint surface in a method for preparing a fuel cell packaging box provided by an embodiment of the application is shown in the figure.

[0040] Figure 5 A schematic diagram of a lapping mode of a preset lapping surface in a method for preparing a fuel cell packaging box provided by an embodiment of the present application;

[0041] Figure 6 A schematic diagram of a fuel cell packaging box structure involved in a method for preparing a fuel cell packaging box provided by Embodiment 1 of the present application;

[0042] Figure 7 A schematic diagram of a structure of a plugging bolt in a method for preparing a fuel cell packaging box provided by an embodiment of the present application. DETAILED DESCRIPTION

[0043] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0044] Various embodiments of the present application can exist in the form of a range; it should be understood that the description in the form of a range is merely for the convenience and brevity, and should not be understood as a hard limitation on the scope of the present application; therefore, it should be considered that the described range has specifically disclosed all possible sub-ranges and single values in the range; for example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers in the range, such as 1, 2, 3, 4, 5 and 6, which is applicable to any range; in addition, whenever a numerical range is indicated in the present application, it refers to any cited number (fraction or integer) in the indicated range.

[0045] In this document, the terms "comprises", "comprising", "includes", "including" or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises, includes or includes elements or steps do not include only those elements or steps but can include other elements or steps not expressly listed or inherent to such process, method, article, or apparatus. The terms "first", "second", "third", "fourth", "fifth", "sixth", etc. are used merely to distinguish one element or step from another, without necessarily requiring or implying any actual relationship or order between such elements or steps. The term "and / or" describes association between or among multiple components such that (i) a first component can be associated with a second component, (ii) more than two components can be associated with each other, and (iii) the association can be direct or indirect. The term "at least one" means one or more. The term "multiple" means two or more. The term "at least one of" followed by a list of two or more items means any one of the listed items individually, or any combination of two or more of the listed items. For example, "at least one of a, b, and c" means a, b, c, a-b, a-c, b-c, or a-b-c. The term "parts" such as weight parts, mass parts, etc. means a ratio relationship between components. In the ratio relationship described herein, the parameters that need to be described by the ratio should be understood as the front item of the ratio formula in the order of description, and the ratio number should be understood as the rear item of the ratio formula. For example, the mass ratio of substance A, substance B and substance C is 1:2:3, then substance A, substance B and substance C should be corresponding to the ratio number in the ratio formula in the order of description, i.e. the mass of substance A: the mass of substance B: the mass of substance C = 1:2:3.

[0046] Unless otherwise specifically stated, all raw materials, reagents, instruments and equipment used in this document can be purchased on the market or prepared by existing methods.

[0047] It should be noted that the current processing method of the fuel cell packaging box needs to design the riveting point on the aluminum alloy fuel cell packaging box, and the riveting point needs to have good electrical conductivity to ensure the electrical safety of the processing process, but in the subsequent hard oxidation process, the contact surface of the riveting point is easy to be oxidized and corroded to form metal corrosion points, which not only affects the electrical safety of the processing process, but also causes the structure of the riveting point to be unstable. In addition, the riveting point ring surface will involve the surface treatment stage in the processing process, and after the surface treatment, the oxide film of the riveting point ring surface needs to be cleaned to reduce the contact resistance of the aluminum alloy fuel cell packaging box, but in the case of poor stability of the aluminum alloy fuel cell packaging box, part of the oxide film will remain on the riveting point ring surface, which will significantly increase the contact resistance of the riveting point, and the fuel cell packaging box with increased contact resistance will increase the local voltage in the subsequent use stage, which will cause arc discharge and affect the electrical safety of the fuel cell packaging box.

[0048] Therefore, improving the corrosion resistance of the bonding point and reducing the thickness of the oxide film of the bonding point, is beneficial to improve the stability and safety of the fuel cell packaging box.

[0049] Figure 1 An example of a method for preparing a fuel cell packaging box is shown in the flow chart;

[0050] Figure 3 An example of a method for preparing a fuel cell packaging box is shown in the flow chart;

[0051] As Figure 1 and Figure 3 The method for preparing a fuel cell packaging box provided by the embodiment of the application comprises:

[0052] S1. According to the structure of the fuel cell packaging box, a plurality of single parts are prepared;

[0053] S2. A preset lap joint surface is arranged at the contact position of two adjacent single parts;

[0054] S3. A plurality of preset lap joint surfaces are lap jointed to obtain a to-be-welded box frame;

[0055] S4. The to-be-welded box frame is friction stir welded to form a weld at the to-be-welded position of the to-be-welded box frame, to obtain a welded box frame; wherein the penetration depth of the weld corresponds to the depth of the preset lap joint surface;

[0056] S5. The welded box frame is heat treated to obtain a heat treated box frame;

[0057] S6. A bonding point is arranged on the outer side of the heat treated box frame to obtain a processing box containing a bonding point; and

[0058] S7. The bonding point of the processing box containing a bonding point is plugged using a plugging bolt to obtain a primary fuel cell packaging box.

[0059] It should be noted that the penetration depth of the weld can be the same as the depth of the preset lap joint surface, or less than the depth of the preset lap joint surface and greater than or equal to half the depth of the preset lap joint surface.

[0060] It should be noted that the bonding point is formed on the heat treated box frame by fine machining, and in addition to the bonding point, threaded holes, mounting surfaces and sealing grooves and other product external structures also need to be machined. The machining precision of the fine machining can be in the range of -0.02mm to 0.02mm.

[0061] It should be noted that after the finishing, the residual metal chips and impurities on the surface of the processing box containing the bonding point can be washed off by cleaning.

[0062] It should be noted that the design process of the preset lap surface also needs to design the inner hole position and the mounting surface of the single part; and the corresponding inner hole position and mounting surface are prepared on the single part by the numerical control machining center.

[0063] It should be noted that the single part can be a 6061T5 aluminum plate.

[0064] It should be noted that after the post-processing, the fuel cell packaging box is immediately packaged with a PVC film to avoid foreign matter from entering.

[0065] It should be noted that the plugging bolt can not only improve the stability of the bonding point through its rigidity, but also can serve as a cover to protect the annular surface of the bonding point. In the post-processing process, the probability of covering the annular surface of the bonding point with an oxide film can be reduced, so as to reduce the thickness of the oxide film covered by the annular surface of the bonding point, thereby reducing the contact resistance of the fuel cell packaging box and improving the electrical safety of the fuel cell packaging box.

[0066] Figure 6 An exemplary structure diagram of a fuel cell packaging box involved in a method for preparing a fuel cell packaging box provided by Embodiment 1 of the present application is shown;

[0067] It should be noted that the structure of the fuel cell packaging box can be as shown in Figure 5 .

[0068] In some optional embodiments, the parameters of the friction stir welding further include: the rotation speed of the welding pin of the friction stir welding is ≥800 r / min, and the feeding speed of the single part is ≥300 mm / min.

[0069] In these embodiments, the parameters of the friction stir welding can further include: the rotation speed of the welding pin of the friction stir welding is ≥800 r / min, and the feeding speed of the single part is ≥300 mm / min. Through the rotation speed of the welding pin of the friction stir welding and the feeding speed of the single part, a deeper and firmer weld can be formed on the preset lap surface, and the weld penetration is more than 6 mm.

[0070] In some optional embodiments, the rotation speed of the welding pin of the friction stir welding is 800 r / min-1200 r / min, and the feeding speed of the single part is 300 mm / min-600 mm / min.

[0071] In the embodiments, the rotation speed of the welding pin of the friction stir welding can be 800-1200 r / min, and the feeding speed of the single part can be 300-600 mm / min. The rotation speed of the welding pin and the feeding speed of the single part can form a deep and firm weld on the preset lap joint surface, and the two single parts can be firmly fixed together, thereby improving the stability of the single part in the friction stir welding process.

[0072] The rotation speed of the welding pin of the friction stir welding can be 800 r / min, 850 r / min, 900 r / min, 950 r / min, 1050 r / min, 1100 r / min, 1150 r / min, or 1200 r / min.

[0073] The feeding speed of the single part can be 300 mm / min, 350 mm / min, 400 mm / min, 450 mm / min, 500 mm / min, 550 mm / min, or 600 mm / min.

[0074] Figure 4 An exemplary schematic diagram of a lap joint mode of a preset lap joint surface in a method for preparing a fuel cell packaging box body is shown;

[0075] In some optional embodiments, the penetration depth h1 of the weld and the thickness h2 of the single part satisfy the relationship h1:h2=(0.6-1):1.

[0076] In the embodiments, the penetration depth h1 of the weld and the thickness h2 of the single part can satisfy the relationship h1:h2=(0.6-1):1, so that the friction stir welding can form a weld with sufficient penetration depth on the box body frame to be welded, thereby improving the stability of the connection between the box body frames to be welded and improving the stability of the fuel cell packaging box body.

[0077] The penetration depth h1 of the weld can be 0.6, 0.7, 0.8, 0.9, or 1.0, and the thickness h2 of the single part can be 1.0.

[0078] In some optional embodiments, as shown in Figure 4 The method for preparing the fuel cell packaging box body comprises the steps of:

[0079] S301. According to the shape of the preset lap joint surface, the preset lap joint surfaces of the two adjacent single parts are overlapped to obtain a box body frame to be welded; wherein the depth of the preset lap joint surface is the same as the thickness of the single part.

[0080] In the embodiments, the lapping can include lapping the two adjacent single parts according to the shape of the preset lapping surface, and the depth of the preset lapping surface is the same as the thickness of the single part. By defining the size of the overlapping area of the two adjacent single parts on the lapping surface, on the one hand, the lapping surface can guide the abutting of the two adjacent single parts in the friction stir welding process, thereby improving the accuracy of the friction stir welding. On the other hand, the lapping surface can define that the weld penetration of the subsequent friction stir welding is in the range of 6mm to 8mm, so that a weld with sufficient thickness is formed on the preset lapping surface, thereby improving the stability of the connection between the two adjacent single parts and the stability of the fuel cell packaging box.

[0081] It should be noted that when the thickness h2 of the single part is 6mm to 10mm, the weld penetration h1 can be 6mm to 8mm.

[0082] In some optional embodiments, the preset lapping surface includes a plurality of trapezoidal surfaces, and the length of each trapezoidal surface is 3mm to 50mm.

[0083] In the embodiments, the preset lapping surface can include a plurality of trapezoidal surfaces, and the length of each trapezoidal surface is greater than or equal to 3mm. The plurality of trapezoidal surfaces on the preset lapping surface ensure that the contact area of the two adjacent single parts has sufficient area, thereby improving the stability of the single part in the friction stir welding process. In addition, the length of each trapezoidal surface can be 3mm to 50mm. The trapezoidal surface with sufficient length can guide the abutting of the two adjacent single parts in the friction stir welding process, thereby improving the accuracy of the friction stir welding. In addition, the trapezoidal surface with sufficient length can also provide a certain friction force to prevent displacement between the two adjacent single parts in the friction stir welding process, thereby improving the stability of the friction stir welding process. In addition, the trapezoidal surface with sufficient length can also promote the weld formed by the friction stir welding to have sufficient length, and the weld with sufficient length can improve the stability of the two adjacent single parts, thereby improving the stability of the fuel cell packaging box.

[0084] Figure 4 An exemplary structure diagram of a preset lapping surface in a method for preparing a fuel cell packaging box provided by the embodiments of the present application is shown;

[0085] It should be noted that the trapezoidal surface can be a three-step trapezoidal structure as shown in Figure 4 .

[0086] The length of each trapezoidal surface can be 3mm, 5mm, 10mm, 20mm, 30mm, 40mm or 50mm.

[0087] In some optional embodiments, the heat treatment comprises a heating section and a holding section, the temperature of the heating section is 120-160°C, and the holding section is 2-4 hours.

[0088] In these embodiments, the heat treatment can comprise a heating section and a holding section, the temperature of the heating section can be 120-160°C, and the holding section can be 2-4 hours. The heat treatment can promote the phase transformation of the weld formed by the friction stir welding to offset the stress between the two adjacent monomer parts at the weld, thereby improving the stability of the weld structure and the stability of the fuel cell packaging box.

[0089] The temperature of the heating section can be 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, or 160°C.

[0090] The holding section can be 2.0h, 2.5h, 3.0h, 3.5h, or 4.0h.

[0091] Figure 2 An exemplary detailed flowchart of a method for preparing a fuel cell packaging box is shown;

[0092] In some optional embodiments, as shown in Figure 2 After the use of the plugging bolt to plug the bonding point of the processing box to obtain a preliminary fuel cell packaging box, the method further comprises:

[0093] S8. The preliminary fuel cell packaging box is chemically polished, and the plugging box after chemical polishing is hard oxidized to obtain a first surface treatment box containing an oxide film;

[0094] S9. The first surface treatment box containing an oxide film is subjected to a sealing treatment to optimize the structure and performance of the oxide film layer of the surface treatment box, to obtain a second surface treatment box;

[0095] S10. The second surface treatment box is cleaned, and the second surface treatment box after cleaning is disassembled to obtain a second surface treatment box containing a plurality of threaded holes;

[0096] S11. The threaded holes of the second surface treatment box are filled with inlaid screw sleeves to obtain a third surface treatment box containing inlaid screw sleeves;

[0097] S12. The third surface treatment box containing inlaid screw sleeves is subjected to resistance detection and sealing detection to obtain a target fuel cell packaging box;

[0098] In the embodiments, the post-processing first forms a dense oxide film on the surface of the sealing box through chemical polishing and hard oxidation, and since the sealing box has been sealed in advance by the sealing bolt, the subsequent oxidation corrosion of the ring surface of the box can be avoided, thereby improving the corrosion resistance of the sealing box. In addition, the first surface box is closed for treatment to optimize the structure and performance of the oxide film, so as to make the oxide film better resist environmental erosion, thereby improving the corrosion resistance of the fuel cell packaging box. In addition, the second surface treatment box is cleaned and the sealing bolt is removed, which can remove the residual solution of the second surface treatment box and expose the lug point without the oxide film, so as to facilitate the subsequent embedding of the inlaid nut, so as to support the thread structure of the lug point through the inlaid nut, thereby improving the stability of the subsequent fuel cell packaging box. Finally, through resistance detection and sealing detection, the target fuel cell packaging box with low resistance and good sealing can be obtained.

[0099] Figure 7 Exemplarily, a structure schematic diagram of a sealing bolt in a method for preparing a fuel cell packaging box provided by the embodiments of the present application is shown;

[0100] It should be noted that the ring surface of the lug point is covered and protected by the sealing bolt as shown in Figure 7 In the post-processing process, the probability of covering the oxide film on the ring surface of the lug point of the fuel cell packaging box can be reduced, the thickness of the oxide film covered on the ring surface of the lug point can be reduced, and the contact resistance of the fuel cell packaging box can be reduced. In combination with the resistance detection, the contact resistance of the fuel cell packaging box can be controlled within a lower value, so as to improve the power safety of the fuel cell packaging box.

[0101] It should be noted that the resistance detection can be the detection of the contact resistance of the ring surface of the lug point by using a multimeter. In the case that the contact resistance of any point on the ring surface of the lug point is less than 0.5Ω, the third surface treatment box is considered to be a qualified product. In the case that the contact resistance of any point on the ring surface of the lug point is greater than or equal to 0.5Ω, the third surface treatment box is considered to be an unqualified product. For the unqualified lug point ring surface, the entire post-processing process needs to be performed again until the contact resistance is less than 0.5Ω.

[0102] It should be noted that the chemical polishing can use an acid solution as a polishing agent. The acid solution can be a mixed solution composed of phosphoric acid with a weight content of 70%, sulfuric acid with a weight content of 21%, and nitric acid with a weight content of 9%.

[0103] It should be noted that the electrolyte solution used in the hard oxidation can be sulfuric acid with a weight content of 15% to 20%.

[0104] It should be noted that this cleaning can be done using high-pressure cleaning, with a pressure generally ≥40kPa.

[0105] It should be noted that the sealing test procedure can be as follows: the third surface treatment chamber is sealed using a special sealing fixture, and then nitrogen gas is introduced into the inlet of the third surface treatment chamber at a pressure of 100 kPa for 5 minutes. If the pressure drop at the test outlet is less than 3 kPa, the third surface treatment chamber is considered a qualified product. If the pressure drop at the test outlet is greater than or equal to 3 kPa, the third surface treatment chamber is considered a unqualified product. For unqualified third surface treatment chambers, the leak point needs to be located and corresponding treatment needs to be carried out.

[0106] It should be noted that the insert can be made of 316L stainless steel.

[0107] In some optional embodiments, the chemical polishing temperature is 90°C to 105°C, and the chemical polishing time is 3 min to 6 min; and / or

[0108] The hard anodizing temperature is 10℃~15℃, the hard anodizing voltage is 12V~22V, and the hard anodizing current density is 1A / dm³. 2 ~2A / dm 2 The hard oxidation time is 70 min to 120 min; and / or

[0109] The temperature of the sealing treatment is 25℃~60℃, and the sealing treatment time is 10min~15min;

[0110] In these embodiments, the chemical polishing temperature can be 90°C to 105°C, and the chemical polishing time can be 3 min to 6 min. Chemical polishing can clean the surface impurities and metal debris of the sealing casing, facilitating the subsequent hard oxidation to form a uniform oxide film, thereby improving the corrosion resistance of the fuel cell packaging casing. Furthermore, the hard oxidation temperature can be 10°C to 15°C, the hard oxidation voltage can be 12V to 22V, and the hard oxidation current density can be 1A / dm³. 2 ~2A / dm 2The temperature of the hard oxidation can be 10°C, 11°C, 12°C, 13°C, 14°C, or 15°C.

[0112] The time of the hard oxidation can be 70 min to 120 min. By the hard oxidation, a dense oxide film can be formed on the surface of the sealing box to avoid corrosion of the fuel cell sealing box in subsequent processes. In addition, the temperature of the sealing treatment can be 25°C to 60°C, and the time of the sealing treatment can be 10 min to 15 min. By the sealing treatment, the structure and performance of the oxide film formed by the hard oxidation can be optimized to further improve the corrosion resistance of the fuel cell sealing box.

[0111] The temperature of the chemical polishing can be 90°C, 95°C, 100°C, or 105°C.

[0112] The time of the chemical polishing can be 3 min, 4 min, 5 min, or 6 min.

[0113] The temperature of the hard oxidation can be 10°C, 11°C, 12°C, 13°C, 14°C, or 15°C.

[0114] The voltage of the hard oxidation can be 12V, 14V, 16V, 18V, 20V, or 22V.

[0115] The current density of the hard oxidation can be 1A / dm 2 , 1.1A / dm 2 , 1.2A / dm 2 , 1.3A / dm 2 , 1.4A / dm 2 , 1.5A / dm 2 , 1.6A / dm 2 , 1.7A / dm 2 , 1.8A / dm 2 , 1.9A / dm 2 , or 2.0A / dm 2 .

[0116] The time of the hard oxidation can be 70 min, 80 min, 90 min, 100 min, 110 min, or 120 min.

[0117] The temperature of the sealing treatment can be 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, or 60°C.

[0118] The time of the sealing treatment can be 10 min, 11 min, 12 min, 13 min, 14 min, or 15 min.

[0119] In some alternative embodiments, the sealing liquid used in the sealing process comprises nickel acetate, sodium fluoride, a surfactant and an additive, the weight m1 of the nickel acetate, the weight m2 of the sodium fluoride, the weight m3 of the surfactant and the weight m4 of the additive satisfy the relationship: m1:m2:m3:m4=(5-8):(1-1.5):(0.3-0.5):3; and / or

[0120] The pH value of the sealing liquid used in the sealing process is 5.5-6.5.

[0121] In these embodiments, the sealing liquid used in the sealing process can comprise nickel acetate, sodium fluoride, a surfactant and an additive, and the weight m1 of the nickel acetate, the weight m2 of the sodium fluoride, the weight m3 of the surfactant and the weight m4 of the additive satisfy the relationship: m1:m2:m3:m4=(5-8):(1-1.5):(0.3-0.5):3, the oxide film formed by the first surface treatment box is optimized by the action between the nickel acetate, the sodium fluoride, the surfactant and the additive, so as to optimize the structure and performance of the oxide film, and obtain the second surface treatment box with stable corrosion resistance; in addition, the pH value of the sealing liquid used in the sealing process can be 5.5-6.5, so as to promote the normal action between the nickel acetate, the sodium fluoride, the surfactant and the additive, further optimize the structure and performance of the oxide film, and obtain the second surface treatment box with stable corrosion resistance.

[0122] The weight m1 of the nickel acetate can be 5, 6, 7 or 8, the weight m2 of the sodium fluoride can be 1.0, 1.1, 1.2, 1.3, 1.4 or 1.5, and the weight m3 of the surfactant can be 0.3, 0.4 or 0.5.

[0123] The application will be further described below in conjunction with specific examples. The experimental methods in the following examples are generally determined according to the national standards / industry standards; if there is no corresponding national standard / industry standard, the general international standards, conventional conditions or the conditions suggested by the manufacturers are used.

[0124] Example 1

[0125] A fuel cell packaging box as shown in Figure 6 is used, which is formed by welding four aluminum plates in total.

[0126] A method for preparing a fuel cell packaging box as shown in Figure 2 is used, which comprises:

[0127] S1. According to the structure of the fuel cell packaging box, six surface single parts are split, and the economic blank thickness is calculated for blanking, and the economic blank thickness is generally the size of the single part product plus 3mm plate blank, and a plurality of single parts are prepared;

[0128] S2. A preset lap joint surface is arranged at the contact position of the two adjacent single parts, which is shown in Figure 4 , and presents a three-step trapezoidal structure;

[0129] S301. The dimensions of the inner hole, mounting surface and preset lap joint surface of the single part are detected on the three-coordinate detector, and when the processing dimensions of all structures meet the requirements of the fuel cell packaging box product, then the two adjacent single parts containing the preset lap joint surface are lap jointed according to the shape of the preset lap joint surface as shown in Figure 5 , to obtain a to-be-welded box frame;

[0130] S4. The obtained to-be-welded box frame is friction stir welded to form a weld at the to-be-welded position of the to-be-welded box frame, to obtain a welded box frame; wherein the penetration depth of the weld is the same as the depth of the preset lap joint surface;

[0131] S5. The fuel cell packaging box frame is subjected to heat treatment, and then cooled in air to obtain a heat-treated box frame;

[0132] S6. The heat-treated box frame is subjected to finishing machining to set a tacking point on the outside of the heat-treated box frame, and then the finished heat-treated box is cleaned to obtain a machining box containing a tacking point;

[0133] S7. The dimensions of the mounting hole, mounting surface, tacking point and sealing groove of the machining box are detected on the three-coordinate measuring instrument to ensure that the dimensions of each structure meet the design dimensions of the fuel cell packaging box product, and then the tacking point of the machining box is plugged using a plugging screw as shown in Figure 7 , to obtain a primary fuel cell packaging box; and

[0134] S8. The primary fuel cell packaging box is subjected to chemical polishing, and then the plugged box after chemical polishing is subjected to hard oxidation to obtain a first surface treatment box containing an oxide film;

[0135] S9. The first surface treatment box containing the oxide film is subjected to sealing treatment to optimize the structure and performance of the oxide film layer of the surface treatment box, to obtain a second surface treatment box;

[0136] S10. The second surface treatment box is cleaned, and then the second surface treatment box after cleaning is disassembled to obtain a second surface treatment box containing a plurality of threaded holes.

[0137] S11. Fill the threaded hole of the second surface treatment box with the mosaic screw sleeve to obtain a third surface treatment box containing the mosaic screw sleeve;

[0138] S12. Perform resistance detection and sealing detection on the third surface treatment box containing the mosaic screw sleeve to obtain a qualified fuel cell packaging box.

[0139] The parameters of the friction stir welding include the rotation speed of the friction stir welding needle, the feeding speed of the single part, and the weld penetration depth. The rotation speed of the friction stir welding needle is 900 r / min, and the feeding speed of the single part is 400 mm / min. The weld penetration depth h1 is 7 mm, and the thickness h2 of the single part is 10 mm.

[0140] The lapping includes lapping the two adjacent single parts according to the shape of the preset lapping surface. The depth of the preset lapping surface is the same as the thickness of the single part.

[0141] The preset lapping surface includes a plurality of trapezoidal surfaces. The length of a single trapezoidal surface is 3 mm, 5 mm, 22 mm, or 27 mm.

[0142] The heat treatment includes a heating section and a holding section. The temperature of the heating section is 150°C, and the holding time of the holding section is 3 h.

[0143] The temperature of the chemical polishing is 100°C, and the time of the chemical polishing is 5 min.

[0144] The temperature of the hard oxidation is 15°C, the voltage of the hard oxidation is 15V, the current density of the hard oxidation is 1.5 A / dm2, and the time of the hard oxidation is 90 min. 2

[0145] The temperature of the sealing treatment is 50°C, and the time of the sealing treatment is 15 min.

[0146] The sealing liquid used in the sealing treatment includes nickel acetate, sodium fluoride, a surfactant, and an additive. The weight m1 of the nickel acetate, the weight m2 of the sodium fluoride, the weight m3 of the surfactant, and the weight m4 of the additive satisfy the relationship: m1:m2:m3:m4=8:1.5:0.5:3.

[0147] The pH value of the sealing liquid used in the sealing treatment is 6.5.

[0148] Example 2

[0149] Based on the disclosure of Example 1, the following modifications are further made:

[0150] The rotation speed of the friction stir welding needle is 850 r / min, and the feeding speed of the single part is 600 mm / min. The weld penetration depth h1 is 6 mm. ​

[0151] The length of the single trapezoidal face is 8 mm.

[0152] The temperature of the heating section is 120℃, and the time of the holding section is 2.5 h.

[0153] The temperature of the chemical polishing is 90℃, and the time of the chemical polishing is 3 min;

[0154] The temperature of the hard oxidation is 10℃, the voltage of the hard oxidation is 12V, the current density of the hard oxidation is 1A / dm 2 , and the time of the hard oxidation is 70 min;

[0155] The temperature of the sealing treatment is 40℃, and the time of the sealing treatment is 12 min.

[0156] The weight m1 of the nickel acetate, the weight m2 of the sodium fluoride, the weight m3 of the surfactant, and the weight m4 of the additive satisfy the relationship: m1:m2:m3:m4=6:1.2:0.3:3;

[0157] The pH of the sealing liquid used in the sealing treatment is 5.5.

[0158] Example 3

[0159] Based on the disclosure of Example 1, the following modifications are further made:

[0160] The rotational speed of the friction stir welding needle is 1150r / min, and the feeding speed of the single part is 300mm / min; the penetration depth h1 of the weld is 8mm.

[0161] The length of the single trapezoidal face is 22 mm.

[0162] The temperature of the heating section is 160℃, and the time of the holding section is 3.5 h.

[0163] The temperature of the chemical polishing is 105℃, and the time of the chemical polishing is 6 min;

[0164] The temperature of the hard oxidation is 15℃, the voltage of the hard oxidation is 22V, the current density of the hard oxidation is 2A / dm 2 , and the time of the hard oxidation is 100 min;

[0165] The temperature of the sealing treatment is 55℃, and the time of the sealing treatment is 10 min.

[0166] The weight m1 of the nickel acetate, the weight m2 of the sodium fluoride, the weight m3 of the surfactant, and the weight m4 of the additive satisfy the relationship: m1:m2:m3:m4=5:1:0.4:3;

[0167] The pH of the sealing liquid used in the sealing treatment is 6.0.

[0168] Comparative Example 1

[0169] On the basis of the disclosure of Example 1, the following modifications are further made:

[0170] Without using the preset lap surface, holes are directly punched on the single-piece parts, and positioning pins are used to position and fix between the two adjacent single-piece parts, and then friction stir welding is performed.

[0171] Comparative Example 2

[0172] On the basis of the disclosure of Example 1, the following modifications are further made:

[0173] The rotation speed of the friction stir welding needle is 600 r / min, and the feeding speed of the single-piece part is 200 mm / min.

[0174] Comparative Example 3

[0175] On the basis of the disclosure of Example 1, the following modifications are further made:

[0176] The rotation speed of the friction stir welding needle is 1500 r / min, and the feeding speed of the single-piece part is 800 mm / min.

[0177] Comparative Example 4

[0178] On the basis of the disclosure of Example 1, the following modifications are further made:

[0179] The penetration depth h1 of the weld is 4 mm.

[0180] Comparative Example 5

[0181] On the basis of the disclosure of Example 1, the following modifications are further made:

[0182] The penetration depth h2 of the weld is 10 mm.

[0183] Comparative Example 6

[0184] On the basis of the disclosure of Example 1, the following modifications are further made:

[0185] The plugging bolt is not used.

[0186] Related experiments and effect data:

[0187] 1. The fuel cell packaging box obtained in Example 3 is subjected to stability, corrosion resistance and constant humidity and heat detection, and the results show that the tensile strength of the fuel cell packaging box can be as high as 223.5 MPa, and it meets the requirements of 500h neutral salt spray test, and the stable duration in the constant humidity and heat test under the condition of 40℃ and relative humidity of 90% to 95% is 48h.

[0188] 2. The fuel cell package boxes obtained in each of the examples and the comparative examples were collected, and the tensile strength and constant damp heat test of each fuel cell package box were counted, and the results are shown in Table 1.

[0189] Table 1: Tensile strength and constant damp heat test results of each fuel cell package box

[0190]

[0191]

[0192] As shown in Table 1, the method for preparing a fuel cell package box provided in the present application sets a preset lap joint surface at the contact position between single monomer parts, so as to improve the stability of the single monomer parts in the friction stir welding process; then the welding box frame obtained by the friction stir welding is subjected to heat treatment and sealing by sealing bolts, so as to improve the tensile strength of the fuel cell package box to above 220 MPa, and to stabilize for more than 48 h under the condition of 40℃ and relative humidity of 90% to 95%.

[0193] In addition, compared with Examples 1 to 3, although the tensile strength and the stabilization time under the condition of 40℃ and relative humidity of 90% to 95% of Comparative Example 6 are close, the contact resistance of Comparative Example 6 is as high as kΩ level or above, while the contact resistance of each of Examples 1 to 5 and Comparative Example 6 is controlled within 0.5Ω.

[0194] In summary, the method for preparing a fuel cell package box provided in the present application sets a preset lap joint surface at the contact position between single monomer parts of the fuel cell package box, so as to improve the stability of the single monomer parts in the friction stir welding process, thereby improving the stability of the fuel cell package box; in addition, the welding box frame obtained by the friction stir welding is subjected to heat treatment, so as to improve the stability of the fuel cell package box in the processing process, thereby improving the stability of the fuel cell package box; furthermore, the bonding point is sealed by sealing bolts, which avoids the influence of the stability of the threaded hole structure of the fuel cell package box caused by multiple disassembly and assembly, thereby improving the stability of the fuel cell package box.

[0195] In addition, the method for manufacturing the fuel cell packaging box provided in the embodiment of the present application blocks the bonding point by the blocking bolt, so that the probability of the annular surface of the bonding point being covered with the oxidation film can be reduced in the subsequent hard oxidation and sealing process, the thickness of the oxidation film covered by the annular surface of the bonding point can be reduced, the contact resistance of the fuel cell packaging box can be reduced, and the electrical safety of the fuel cell packaging box can be improved. In addition, the oxidation film cleaning operation of the annular surface of the bonding point can be avoided by the blocking bolt, the integrity and corrosion resistance of the oxidation film of the fuel cell packaging box can be maintained, and thus the surface quality, electrical safety and corrosion resistance of the fuel cell packaging box can be improved by the blocking bolt.

[0196] In addition, the method for manufacturing the fuel cell packaging box provided in the embodiment of the present application blocks the bonding point by the blocking bolt, and then cooperates with the subsequent resistance detection, so that the contact resistance of the annular surface of the bonding point can be kept at a lower value, and the fault of poor bonding of the integrated fuel cell packaging box can be avoided.

[0197] In addition, the method for manufacturing the fuel cell packaging box provided in the embodiment of the present application protects the annular surface of the bonding point by the inlaying screw sleeve, so that the wear resistance of the bonding point inner bolt connection can be improved, the damage of the bonding point connecting thread can be avoided, and thus the strength of the thread hole of the bonding point and the wear resistance of the thread can be effectively improved.

[0198] In addition, the method for manufacturing the fuel cell packaging box provided in the embodiment of the present application only needs to involve the design of the preset bonding surface and the blocking bolt of the annular surface of the bonding point, the overall manufacturing cost is low, the production demand of small batch and multiple types of fuel cell packaging boxes can be well met, and flexible production of the fuel cell packaging box can be realized.

[0199] The above only describes the specific embodiments of the present application, so that those skilled in the art can understand or implement the present application. Various modifications of these embodiments will be apparent to those skilled in the art, and the general principles defined in the present application can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown in the present application, but will conform to the widest scope consistent with the principles and novel features of the present application.

Claims

1. A method for preparing a fuel cell packaging box, the method comprising: preparing a plurality of single parts according to the structure of the fuel cell packaging box; arranging a preset overlapping surface at the contact position of two adjacent single parts, the preset overlapping surface comprising a plurality of trapezoidal surfaces, and the length of each trapezoidal surface being 3 mm to 50 mm; overlapping a plurality of preset overlapping surfaces to obtain a to-be-welded box frame; friction stir welding the to-be-welded box frame to form a weld at the to-be-welded position of the to-be-welded box frame, thereby obtaining a welded box frame, wherein the penetration depth of the weld corresponds to the depth of the preset overlapping surface, and the penetration depth h1 of the weld and the thickness h2 of the single part satisfy the relationship h1: h2 = (0.6-1) : 1; heat treating the welded box frame to obtain a heat-treated box frame; arranging a grounding point on the outer side of the heat-treated box frame to obtain a processed box containing a grounding point; and plugging the grounding point of the processed box using a plugging bolt to obtain a primary fuel cell packaging box; sequentially performing chemical polishing and hard oxidation on the primary fuel cell packaging box to obtain a first surface-treated box containing an oxide film; after the first surface-treated box is subjected to sealing treatment and cleaning, the plugging bolt is removed to obtain a second surface-treated box containing a plurality of threaded holes; filling the threaded holes of the second surface-treated box with an inlaid screw sleeve to obtain a third surface-treated box containing an inlaid screw sleeve; and performing resistance detection and sealing property detection on the third surface-treated box to obtain a target fuel cell packaging box. The rotation speed of the welding pin of the friction stir welding is ≥800 r / min, and the feeding speed of the single part is ≥300 mm / min. 3.The method of claim 2, wherein the rotation speed of the welding pin of the friction stir welding is 800 r / min to 1200 r / min, and the feeding speed of the single part is 300 mm / min to 600 mm / min. 4.The method of claim 1, wherein the step of overlapping a plurality of preset overlapping surfaces to obtain a to-be-welded box frame comprises: the depth of the preset overlapping surface is the same as the thickness of the single part. 5.The method of claim 1, wherein the heat treatment comprises a heating section and a holding section, the temperature of the heating section is 120 ℃ to 160 ℃, and the holding time of the holding section is 2 h to 4 h. The temperature of the chemical polishing is 90 ℃ to 105 ℃, and the time of the chemical polishing is 3 min to 6 min; and / or the temperature of the sealing treatment is 25 ℃ to 60 ℃, and the time of the sealing treatment is 10 min to 15 min. The sealing liquid used in the sealing treatment comprises nickel acetate, sodium fluoride, a surfactant and an additive, the weight m1 of the nickel acetate, the weight m2 of the sodium fluoride, the weight m3 of the surfactant and the weight m4 of the additive satisfy the relationship m1: m2: m3: m4 = (5-8) : (1-1.5) : (0.3-0.5) : 3; and / or ​ ​ ​ ​ ​ 2. The method of claim 1, the parameters of the friction stir welding further comprising: ​ ​ ​ The two adjacent single parts are overlapped according to the shape of the preset overlapping surface, and the box frame is welded. ​ ​ 6. The method of claim 1, wherein, ​ The hard anodizing temperature is 10℃~15℃, the hard anodizing voltage is 12V~22V, and the hard anodizing current density is 1A / dm³. 2 ~2A / dm 2 The hard oxidation time is 70 min to 120 min; and / or ​ 7. The method of claim 1, wherein, ​ The pH of the sealing liquid used in the sealing process is 5.5-6.

5. The pH of the sealing liquid used in the sealing process is 5.5-6.5.

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