Method for preparing fuel cell packaging box

Abstract

The invention relates to the technical field of fuel cell preparation, in particular to a method for preparing a fuel cell packaging box. The method comprises the following steps: preparing a plurality of single parts according to the structure of the fuel cell packaging box body; a preset lap joint face is arranged at the contact position of the single part; lapping the preset lapping surfaces to obtain a to-be-welded box frame; the to-be-welded box frame is subjected to friction stir welding, so that a welding seam is formed in the to-be-welded position of the to-be-welded box frame, and a welded box frame is obtained; carrying out heat treatment on the fuel cell packaging box body frame to obtain a heat treatment box body frame; a bonding point is arranged on the outer side of the heat treatment box body frame, and a machining box body containing the bonding point is obtained; and plugging the bonding point of the processing box body by using a plugging bolt to obtain a primary fuel cell packaging box body. According to the method, the preset lap joint surface for friction stir welding is designed, and the bonding point is blocked by the blocking bolt, 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 in particular to a method for preparing a fuel cell packaging box. Background Art

[0002] With the continuous acceleration of fuel cell product updates and iterative upgrades, the fuel cell packaging box needs to undergo multiple design changes frequently, and the multiple fuel cell packaging box models generated by multiple design changes will exist for a long time. At present, the most widely used material for fuel cell packaging boxes is aluminum alloy, which generally requires the use of dedicated molds in the die-casting or gravity casting process to form. This results in the need to equip multiple dedicated molds for multiple fuel cell packaging box models, which will increase the production cost of the entire fuel cell; in addition, the fuel cell packaging box can also be directly formed by machining with aluminum ingots as raw materials, but the machining process requires the addition of a large amount of aluminum ingot blanks and a long process flow, resulting in a surge in the cost of the aluminum ingot machining process and the investment cost of the fixture, and the raw material utilization rate of the machining process is low, which will cause a large degree of waste.

[0003] In the process of processing the aluminum alloy fuel cell packaging box obtained by the above two processing methods, the threaded holes are directly processed on the aluminum alloy fuel cell packaging box. Due to the ductility of the aluminum alloy material, such threaded holes are not conducive to multiple disassembly and assembly, and the threaded threads will be damaged by the threads of the installation bolts in the case of multiple disassembly and assembly, which will affect the integrity of the fuel cell packaging box structure and result in poor stability of the prepared aluminum alloy fuel cell packaging box. Summary of the invention

[0004] The present application provides a method for preparing a fuel cell packaging box to solve the following technical problem: 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 monomer parts are prepared;

[0007] Designing a preset overlap surface at the contact position of two adjacent monomer parts;

[0008] Overlapping a plurality of the preset overlapping surfaces to obtain a box frame to be welded;

[0009] The box frame to be welded is subjected to friction stir welding to form a weld at a location to be welded of the box frame to be welded, thereby obtaining a welded box frame; wherein the penetration depth of the weld corresponds to the depth of the preset overlap surface;

[0010] The welded box frame is heat treated to obtain a heat-treated box frame;

[0011] Arranging a grounding point on the outer side of the heat treatment box frame to obtain a processing box containing the grounding point; and

[0012] The grounding points of the processed box body are sealed with sealing bolts to obtain a primary fuel cell packaging box body.

[0013] Optionally, the parameters of the friction stir welding also include: a rotation speed of the friction stir welding needle ≥ 800 r / min, and a feed speed of the single component ≥ 300 mm / min.

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

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

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

[0017] Optionally, overlapping a plurality of the preset overlapping surfaces to obtain a box frame to be welded comprises the following steps:

[0018] According to the shape of the preset overlapping surface, the preset overlapping surfaces of two adjacent single parts are overlapped to prepare a box frame for welding; wherein the depth of the preset overlapping surface is the same as the thickness of the single part.

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

[0020] Optionally, the heat treatment includes a heating section and a heat preservation section, the temperature of the heating section is 120° C. to 160° C., and the time of the heat preservation section is 2 h to 4 h.

[0021] Optionally, after the grounding point of the processed box is sealed with a sealing bolt to obtain a preliminary fuel cell packaging box, the method further includes:

[0022] Chemically polishing the primary fuel cell packaging box, and then hard-oxidizing the chemically polished plugging box to obtain a first surface-treated box containing an oxide film;

[0023] The first surface treatment box containing the oxide film is sealed to optimize the structure and performance of the oxide film layer of the surface treatment box to obtain a second surface treatment box;

[0024] The second surface treatment box is cleaned, and then the blocking bolts in the cleaned second surface treatment box are removed to obtain a second surface treatment box having a plurality of threaded holes;

[0025] Filling the threaded hole of the second surface treatment box with an inlaid screw sleeve to obtain a third surface treatment box containing an inlaid screw sleeve;

[0026] The third surface-treated box body containing the embedded screw sleeve is subjected to resistance detection and sealing detection to obtain a qualified fuel cell packaging box body.

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

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

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

[0030] Optionally, the sealing liquid used for the sealing treatment includes 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; and / or

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

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

[0033] The embodiment of the present application provides a method for preparing a fuel cell packaging box. The method sets a preset overlap surface at the contact position between the single monomer parts of the fuel cell packaging box, and stir-friction welds two adjacent monomer parts according to the preset overlap surface. The preset overlap surface can increase the contact area of ​​the two adjacent monomer parts within a limited contact space. The two monomer parts with increased contact areas can disperse the stress on the fuel cell packaging box during the stir-friction welding process on the one hand, and reduce the possibility of stress concentration during the stir-friction welding process on the other hand, so as to improve the stability of the monomer parts during the stir-friction welding process and obtain a sufficient depth of weld penetration, thereby improving the stability of the fuel cell packaging box; in addition, the welded box frame is heat-treated, and the linear expansion coefficient between the monomer parts is increased by heat treatment to offset the welding stress generated by the welded box frame during the stir-friction welding process, thereby further improving the stability of the fuel cell packaging box during the processing process, thereby improving the stability of the fuel cell packaging box; in addition, the processed box body containing the grounding point after fine processing is blocked by a blocking bolt, and the stability of the grounding point can be improved by the rigidity of the blocking bolt, so as to avoid the fuel cell packaging box being disassembled and assembled multiple times to affect the stability of the threaded hole structure, thereby improving the stability of the fuel cell packaging box. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0036] Figure 1 A schematic flow chart of a method for preparing a fuel cell packaging box provided in an embodiment of the present application;

[0037] Figure 2 A detailed schematic diagram of a method for preparing a fuel cell packaging box provided in an embodiment of the present application;

[0038] Figure 3 A schematic diagram of the actual process of a method for preparing a fuel cell packaging box provided in an embodiment of the present application;

[0039] Figure 4 A schematic structural diagram of a preset overlap surface in a method for preparing a fuel cell packaging box provided in an embodiment of the present application;

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

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

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

[0043] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0044] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be understood as a rigid limitation on the scope of the present application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within 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., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which applies regardless of the range; in addition, whenever a numerical range is indicated in this document, it is meant to include any cited numbers (fractions or integers) within the indicated range.

[0045] In this document, the terms including "including" and "including" mean "including but not limited to". Relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. "And / or" describes the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone; where A and B can be singular or plural. "At least one" means one or more, and "plurality" means two or more; "at least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items; for example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple. "Parts" such as parts by weight and parts by mass indicate the proportional relationship between the components. In the proportional relationship involved in this article, the parameters that need to be described by proportion should be understood as the first term of the proportional formula in the order of description, and the proportional numbers should be understood as the second term of the proportional formula. For example, if the mass ratio of substance A, substance B and substance C is 1:2:3, then substance A, substance B and substance C should correspond to the proportional numbers in the proportional formula in the order of description, that is, the mass of substance A: the mass of substance B: the mass of substance C = 1:2:3.

[0046] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this article can be purchased from the market or prepared by existing methods.

[0047] It should be noted that the current processing methods for fuel cell packaging boxes require the design of grounding points on the aluminum alloy fuel cell packaging box, and the grounding points need to have good conductivity to ensure the safety of electricity use during the processing process. However, in the subsequent hard oxidation process, the contact surfaces of these grounding points are prone to oxidation corrosion and form metal corrosion points. These metal corrosion points will not only affect the safety of electricity use during the processing process, but also cause structural instability at these grounding points. In addition, the grounding point annular surface will involve a surface treatment stage during the processing process, and after the surface treatment, the grounding point annular surface needs to be cleaned of the oxide film to reduce the contact resistance of the aluminum alloy fuel cell packaging box. However, in the case of poor stability of the aluminum alloy fuel cell packaging box, part of the oxide film will remain on the grounding point annular surface. These residual oxide films will significantly increase the contact resistance of the grounding 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 safety of electricity use of the fuel cell packaging box.

[0048] Therefore, improving the corrosion resistance of the grounding point and reducing the thickness of the oxide film on the annular surface of the grounding point are beneficial to improving the stability of the fuel cell packaging box and the safety of electricity use.

[0049] Figure 1 A schematic flow chart of a method for preparing a fuel cell packaging box provided in an embodiment of the present application is exemplarily shown;

[0050] Figure 3 The actual process diagram of a method for preparing a fuel cell packaging box provided in an embodiment of the present application is exemplarily shown;

[0051] like Figure 1 and Figure 3 As shown, an embodiment of the present application provides a method for preparing a fuel cell packaging box, the method comprising:

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

[0053] S2. Setting a preset overlap surface at the contact position of two adjacent monomer parts;

[0054] S3. Overlapping the plurality of preset overlapping surfaces to obtain a box frame to be welded;

[0055] S4. Stir friction welding the box frame to be welded to form a weld at the welding position of the box frame to be welded to obtain a welded box frame; wherein the penetration depth of the weld corresponds to the depth of the preset overlap surface;

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

[0057] S6. A grounding point is set on the outer side of the heat treatment box frame to obtain a processing box containing a grounding point; and

[0058] S7. Use sealing bolts to seal the grounding points of the processed box body containing the grounding points to obtain a primary fuel cell packaging box body.

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

[0060] It should be noted that the grounding point is formed on the heat treatment box frame by fine machining. In addition to the grounding point, the fine machining also requires machining of product appearance structures such as threaded holes, mounting surfaces and sealing grooves; the machining accuracy of the fine machining can be in the range of -0.02mm to 0.02mm.

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

[0062] It should be noted that, in the design process of the preset overlap surface, the inner hole positions and mounting surfaces of the single part also need to be designed; and then the corresponding inner hole positions and mounting surfaces are prepared on the single part through a CNC machining center.

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

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

[0065] It should be noted that the sealing bolt can not only improve the stability of the grounding point through its rigid characteristics, but also serve as a covering member to protect the annular surface of the grounding point. In the post-processing process, it can reduce the probability of the annular surface of the grounding point of the fuel cell packaging box being covered with an oxide film, thereby reducing the thickness of the oxide film covering the annular surface of the grounding point, thereby reducing the contact resistance of the fuel cell packaging box, thereby improving the electrical safety of the fuel cell packaging box.

[0066] Figure 6 The schematic diagram of the structure of a fuel cell packaging box body involved in a method for preparing a fuel cell packaging box body provided in Example 1 of the present application is exemplarily shown;

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

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

[0069] In these embodiments, the parameters of the friction stir welding may also include: the welding needle rotation speed of the friction stir welding is ≥800r / min, and the feed speed of the single part is ≥300mm / min. The welding needle rotation speed and the feed speed of the single part of the friction stir welding can form a deeper and firmer weld on the preset lap surface, and the obtained weld penetration depth is above 6mm.

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

[0071] In these embodiments, the welding needle speed of the stir friction welding can be 800r / min~1200r / min, and the feed speed of the single part can be 300mm / min~600mm / min. The welding needle speed of the stir friction welding and the feed speed of the single part can form a deeper and firm weld on the preset lap surface, and the two single parts can be firmly fixed together, thereby improving the stability of the single part during the stir friction welding process.

[0072] The welding needle rotation speed 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 feed speed of the single part can be 300mm / min, 350mm / min, 400mm / min, 450mm / min, 500mm / min, 550mm / min or 600mm / min.

[0074] Figure 4 A schematic diagram of a lap joint method of a preset lap joint surface in a method for preparing a fuel cell packaging box provided in an embodiment of the present application is exemplarily shown;

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

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

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

[0078] In some optional embodiments, such as Figure 4 As shown, overlapping a plurality of the preset overlapping surfaces to obtain a box frame to be welded comprises the steps of:

[0079] S301. According to the shape of the preset overlap surface, overlap the preset overlap surfaces of two adjacent monomer parts to be welded to the box frame; wherein the depth of the preset overlap surface is the same as the thickness of the monomer part;

[0080] In these embodiments, the overlap may include overlapping two adjacent monomer parts according to the shape of a preset overlap surface, and the depth of the preset overlap surface is the same as the thickness of the monomer parts. By clarifying the size of the overlapping area of ​​the two adjacent monomer parts on the overlap surface, on the one hand, the guiding effect of the preset overlap surface can make it easier to connect the two adjacent monomer parts during the stir friction welding process, so as to improve the accuracy of stir friction welding. On the other hand, the overlap surface can clarify that the weld penetration depth of the subsequent stir friction welding is within the range of 6mm to 8mm, so as to form a weld of sufficient thickness on the preset overlap surface, thereby improving the stability of the connection between the two adjacent monomer parts and improving the stability of the fuel cell packaging box.

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

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

[0083] In these embodiments, the preset overlapping surface may include multiple trapezoidal surfaces, and the length of a single trapezoidal surface is ≥3mm. Multiple trapezoidal surfaces are arranged on the preset overlapping surface to ensure that the contact area between two adjacent monomer parts has sufficient area, thereby improving the stability of the monomer parts during the stir friction welding process; in addition, the length of a single trapezoidal surface may be 3mm to 50mm. The trapezoidal surface of sufficient length can, on the one hand, play a guiding role, which can facilitate the docking of two adjacent monomer parts during the stir friction welding process to improve the accuracy of the stir friction welding, and on the other hand, can also provide a certain friction force to avoid displacement between two adjacent monomer parts during the stir friction welding process to improve the stability of the stir friction welding process; in addition, the trapezoidal surface of sufficient length can also cause the weld formed by the stir friction welding to have sufficient length, and the weld of sufficient length can improve the stability of the two adjacent monomer parts to improve the stability of the fuel cell packaging box.

[0084] Figure 4 A schematic structural diagram of a preset overlap surface in a method for preparing a fuel cell packaging box provided in an embodiment of the present application is exemplarily shown;

[0085] It should be noted that the trapezoidal surface can be as follows Figure 4 The three-layer stepped trapezoidal structure shown.

[0086] The length of the single trapezoidal face may be 3 mm, 5 mm, 10 mm, 20 mm, 30 mm, 40 mm or 50 mm.

[0087] In some optional embodiments, the heat treatment includes a heating section and a heat preservation section, the temperature of the heating section is 120° C. to 160° C., and the time of the heat preservation section is 2 h to 4 h;

[0088] In these embodiments, the heat treatment may include a heating section and a heat preservation section, and the temperature of the heating section may be 120°C to 160°C, and the time of the heat preservation section may be 2h to 4h. The heat treatment may promote the weld formed by the stir friction welding to further complete the phase change transformation to offset the stress of the two adjacent monomer parts at the weld, thereby improving the stability of the weld structure and improving the stability of the fuel cell packaging box.

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

[0090] The insulation period can be 2.0h, 2.5h, 3.0h, 3.5h or 4.0h.

[0091] Figure 2 A detailed flow chart of a method for preparing a fuel cell packaging box provided in an embodiment of the present application is exemplarily shown;

[0092] In some optional embodiments, such as Figure 2 As shown, after the grounding point of the processed box body is sealed with a sealing bolt to obtain a preliminary fuel cell packaging box body, the method further includes:

[0093] S8. chemically polishing the primary fuel cell packaging box, and then hard-oxidizing the plugging box after chemical polishing to obtain a first surface-treated box containing an oxide film;

[0094] S9. The first surface treatment box containing the oxide film is sealed 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 then the sealing bolts in the second surface treatment box after cleaning are removed to obtain a second surface treatment box containing a plurality of threaded holes;

[0096] S11. Use the embedded screw sleeve to fill the threaded hole of the second surface treatment housing to obtain a third surface treatment housing containing an embedded screw sleeve;

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

[0098] In these embodiments, the post-treatment first forms a dense oxide film on the surface of the sealing box through chemical polishing and hard oxidation. Since the sealing box has been sealed in advance with the sealing bolts, oxidation corrosion can be avoided on the annular surface of the grounding point on the subsequent box, thereby improving the corrosion resistance of the sealing box; in addition, the first surface box is sealed to optimize the structure and performance of the oxide film, so that the oxide film can 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 bolts are disassembled to remove the residual solution of the second surface treatment box and expose the grounding point without the oxide film, so as to facilitate the subsequent embedding of the embedded screw sleeve, so as to support the threaded structure of the grounding point through the embedded screw sleeve, thereby improving the stability of the subsequent fuel cell packaging box; finally, through resistance detection and sealing detection, a target fuel cell packaging box with low resistance and good sealing can be obtained.

[0099] Figure 7 The schematic diagram of the structure of the sealing bolt in the method for preparing a fuel cell packaging box provided in an embodiment of the present application is exemplarily shown;

[0100] It should be noted that, through Figure 7 The sealing bolt shown covers and protects the annular surface of the grounding point, which can reduce the probability of the annular surface of the grounding point of the fuel cell packaging box being covered with an oxide film during the post-processing process, thereby reducing the thickness of the oxide film covered by the annular surface of the grounding point, thereby reducing the contact resistance of the fuel cell packaging box. Combined with resistance detection, the contact resistance of the fuel cell packaging box can be controlled within a lower value to improve the electrical safety of the fuel cell packaging box.

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

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

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

[0104] It should be noted that the cleaning can be carried out by high-pressure cleaning, and the pressure of the high-pressure cleaning is generally ≥40 kPa.

[0105] It should be noted that the process of the sealing test can be: the third surface treatment box is sealed with a special sealing fixture, and then nitrogen is introduced into the cavity inlet of the third surface treatment box. The pressure of the introduced nitrogen is set to 100 kPa and maintained for 5 minutes. When the pressure drop value at the test outlet is less than 3 kPa, the third surface treatment box is regarded as a qualified product. When the pressure drop value at the test outlet is ≥3 kPa, the third surface treatment box is regarded as an unqualified product. For the unqualified third surface treatment box, it is necessary to find the leakage point and perform corresponding treatment.

[0106] It should be noted that the material of the inlaid screw sleeve can be 316L stainless steel.

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

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

[0109] The temperature of the sealing treatment is 25°C to 60°C, and the time of the sealing treatment is 10min to 15min;

[0110] In these embodiments, the temperature of chemical polishing can be 90°C to 105°C, and the time of chemical polishing can be 3min to 6min. The surface impurities and metal debris of the plugging box can be cleaned by chemical polishing to facilitate the subsequent hard oxidation to form a uniform oxide film, thereby improving the corrosion resistance of the fuel cell packaging box; in addition, the temperature of hard oxidation can be 10°C to 15°C, the voltage of hard oxidation can be 12V to 22V, and the current density of hard oxidation can be 1A / dm 2 ~2A / dm 2, and the hard oxidation time can be 70min~120min. Through hard oxidation, a dense oxide film can be formed on the surface of the sealing box to avoid corrosion of the fuel cell packaging box in subsequent processes; in addition, the sealing treatment temperature can be 25℃~60℃, and the sealing treatment time can be 10min~15min. Through sealing treatment, the oxide film structure and performance formed by hard oxidation can be optimized to further improve the corrosion resistance of the fuel cell packaging box.

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

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

[0113] The hard anodizing temperature may be 10°C, 11°C, 12°C, 13°C, 14°C or 15°C.

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

[0115] The current density of the hard anodizing 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 hard anodizing time can be 70 min, 80 min, 90 min, 100 min, 110 min or 120 min.

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

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

[0119] In some optional embodiments, the sealing liquid used for the sealing treatment includes 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; and / or

[0120] The pH value of the sealing solution used in the sealing treatment is 5.5 to 6.5;

[0121] In these embodiments, the sealing liquid used for the sealing treatment may include nickel acetate, sodium fluoride, a surfactant and an additive, and the weight m1 of nickel acetate, the weight m2 of 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 the oxide film formed by the first surface treatment box is optimized through the interaction between nickel acetate, sodium fluoride, the surfactant and the additive to optimize the structure and performance of the oxide film, and obtain a second surface treatment box with stable corrosion resistance; in addition, the pH value of the sealing liquid used for the sealing treatment may be 5.5-6.5, which promotes the normal interaction between nickel acetate, sodium fluoride, the surfactant and the additive to further optimize the structure and performance of the oxide film, and obtain a 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 present application is further described below in conjunction with specific examples. The experimental methods in the following examples where specific conditions are not specified are usually measured in accordance with national standards / industry standards; if there are no corresponding national standards / industry standards, they are measured in accordance with common international standards, conventional conditions or conditions recommended by the manufacturer.

[0124] Example 1

[0125] Use as Figure 6 The fuel cell packaging box shown is formed by welding four aluminum plates in total, namely, the upper, lower, left and right.

[0126] like Figure 2 As shown, a method for preparing a fuel cell packaging box comprises:

[0127] S1. According to the structure of the fuel cell packaging box, the six-sided monomer parts are split and the more economical billet thickness is calculated for cutting. The economical billet thickness is generally the size of the finished monomer part plus 3mm of the plate billet to prepare multiple monomer parts;

[0128] S2. A preset overlap surface is set at the contact position of two adjacent monomer parts. The preset overlap surface is as follows: Figure 4 As shown, it presents a three-layer stepped trapezoidal structure;

[0129] S301. On a three-coordinate measuring machine, inspect the inner hole position, mounting surface and dimensions of the preset overlap surface of the single part. When the processing dimensions of the entire structure meet the requirements of the fuel cell packaging box product, then align the two adjacent single parts with the preset overlap surface as follows: Figure 5 The method shown is to overlap according to the shape of the preset overlap surface to obtain the box frame to be welded;

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

[0131] S5. The fuel cell packaging box frame is heat treated and then cooled under air conditions to obtain a heat treated box frame;

[0132] S6. The heat treatment box frame is finished to set a grounding point on the outside of the heat treatment box frame, and then the heat treatment box after finishing is cleaned to obtain a processed box containing a grounding point;

[0133] S7. Use a three-coordinate measuring machine to measure the dimensions of the mounting holes, mounting surfaces, grounding points, sealing grooves, and other structures of the processed box to ensure that the dimensions of each structure meet the design dimensions of the fuel cell packaging box product, and then use Figure 7 The plugging bolts shown are used to plug the grounding points of the processed box body to obtain a primary fuel cell packaging box body; and

[0134] S8. 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-treated box containing an oxide film;

[0135] S9. The first surface treatment box containing the oxide film is sealed 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 sealing bolts in the cleaned second surface treatment box are removed to obtain a second surface treatment box containing a plurality of threaded holes;

[0137] S11. Use the inlaid screw sleeve to fill the threaded hole of the second surface treatment housing to obtain a third surface treatment housing containing an inlaid screw sleeve;

[0138] S12. Conduct resistance testing and sealing testing on the third surface-treated box body containing the embedded screw sleeve to obtain a qualified fuel cell packaging box body.

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

[0140] The overlapping includes overlapping two adjacent single parts according to the shape of a preset overlapping surface, and the depth of the preset overlapping surface is the same as the thickness of the single parts.

[0141] The preset overlapping surface includes a plurality of trapezoidal surfaces, and the lengths of a single trapezoidal surface are 3 mm, 5 mm, 22 mm and 27 mm.

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

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

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

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

[0146] The sealing liquid used for the sealing treatment includes nickel acetate, sodium fluoride, a surfactant and an additive. The weight m1 of nickel acetate, the weight m2 of 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 blocking solution used for the blocking treatment is 6.5.

[0148] Example 2

[0149] Based on the contents disclosed in Example 1, the following modifications are further made:

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

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

[0152] The temperature of the heating section is 120°C and the time of the insulation section is 2.5h.

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

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

[0155] The temperature of the sealing treatment was 40°C and the time of the sealing treatment was 12 minutes.

[0156] The weight m1 of nickel acetate, the weight m2 of 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 value of the blocking solution used for the blocking treatment is 5.5.

[0158] Example 3

[0159] Based on the contents disclosed in Example 1, the following modifications are further made:

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

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

[0162] The temperature of the heating section is 160°C and the time of the insulation section is 3.5h.

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

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

[0165] The temperature of the sealing treatment was 55°C and the time of the sealing treatment was 10 minutes.

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

[0167] The pH value of the blocking solution used for the blocking treatment is 6.0.

[0168] Comparative Example 1

[0169] Based on the contents disclosed in Example 1, the following modifications are further made:

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

[0171] Comparative Example 2

[0172] Based on the contents disclosed in Example 1, the following modifications are further made:

[0173] The friction stir welding needle speed is 600r / min, and the single part feed speed is 200mm / min.

[0174] Comparative Example 3

[0175] Based on the contents disclosed in Example 1, the following modifications are further made:

[0176] The friction stir welding needle speed is 1500r / min, and the single part feed speed is 800mm / min.

[0177] Comparative Example 4

[0178] Based on the contents disclosed in Example 1, the following modifications are further made:

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

[0180] Comparative Example 5

[0181] Based on the contents disclosed in Example 1, the following modifications are further made:

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

[0183] Comparative Example 6

[0184] Based on the contents disclosed in Example 1, the following modifications are further made:

[0185] No plugging bolts are used.

[0186] Related experiments and effect data:

[0187] 1. The fuel cell packaging box obtained in Example 3 was subjected to stability, corrosion resistance and constant humidity and heat tests. The results showed that the tensile strength of the fuel cell packaging box can be as high as 223.5 MPa, and meets the requirements of a 500-h neutral salt spray test, as well as a stable time of 48 h in a constant humidity and heat test at 40°C and a relative humidity of 90% to 95%.

[0188] 2. The fuel cell packaging boxes obtained in various embodiments and comparative examples were collected, and the tensile strength and constant humidity and heat tests of each fuel cell packaging box were statistically analyzed. The results are shown in Table 1.

[0189] Table 1 Tensile strength and constant humidity test results of various fuel cell packaging boxes

[0190]

[0191]

[0192] As can be seen from Table 1, an embodiment of the present application provides a method for preparing a fuel cell packaging box, which sets a preset overlap surface at the contact position between single monomer parts to improve the stability of the monomer parts during the stir friction welding process; then heat treatment and sealing bolts are performed to increase the tensile strength of the fuel cell packaging box to more than 220 MPa, and stabilize it at 40°C and a relative humidity of 90% to 95% for more than 48 hours.

[0193] In addition, compared with Examples 1 to 3, although the tensile strength and the stable time at 40°C and a relative humidity of 90% to 95% of Example 6 are similar, the contact resistance of Example 6 is as high as above kΩ level, while the contact resistance of each embodiment and Examples 1 to 5 is controlled within 0.5Ω.

[0194] In summary, an embodiment of the present application provides a method for preparing a fuel cell packaging box, which sets a preset overlap surface at the contact position between the single monomer parts of the fuel cell packaging box to improve the stability of the monomer parts during the stir friction welding process, thereby improving the stability of the fuel cell packaging box; in addition, the welded box frame obtained by stir friction welding is heat treated to improve the stability of the fuel cell packaging box during the processing process to improve the stability of the fuel cell packaging box; in addition, the grounding point is sealed with a sealing bolt to avoid multiple disassembly and assembly of the fuel cell packaging box to affect the stability of the threaded hole structure, thereby improving the stability of the fuel cell packaging box.

[0195] In addition, an embodiment of the present application provides a method for preparing a fuel cell packaging box, in which the grounding point is sealed by a sealing bolt. In the subsequent hard oxidation and sealing process, the probability of the annular surface of the grounding point of the fuel cell packaging box being covered with an oxide film can be reduced, so as to reduce the thickness of the oxide film covered by the annular surface of the grounding point, thereby reducing the contact resistance of the fuel cell packaging box and improving the electrical safety of the fuel cell packaging box; in addition, the sealing bolt can avoid the oxide film cleaning operation on the annular surface of the grounding point, and maintain the integrity and corrosion resistance of the oxide film of the fuel cell packaging box, so that the sealing bolt can improve the surface quality, electrical safety and corrosion resistance of the fuel cell packaging box.

[0196] In addition, an embodiment of the present application provides a method for preparing a fuel cell packaging box. This method seals the grounding point by a sealing bolt, and combined with subsequent resistance detection, can keep the contact resistance of the annular surface of the grounding point at a low value, thereby avoiding the failure of poor grounding in the integrated fuel cell packaging box.

[0197] In addition, an embodiment of the present application provides a method for preparing a fuel cell packaging box. This method protects the annular surface of the grounding point by embedding a screw sleeve, thereby improving the wear resistance of the bolt connection inside the grounding point of the fuel cell packaging box and avoiding damage to the grounding point connection thread, thereby effectively improving the strength of the threaded hole of the grounding point and the wear resistance of the thread.

[0198] In addition, an embodiment of the present application provides a method for preparing a fuel cell packaging box. The method only requires the design of a preset lap joint and a sealing bolt on the annular surface of the grounding point. The overall preparation cost of the method is low and can be well adapted to the current small-batch and multi-model production needs of fuel cell packaging boxes to achieve flexible production of fuel cell packaging boxes.

[0199] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. It will be apparent to those skilled in the art that various modifications to these embodiments are possible, 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 the embodiments shown in the present application, but will conform to the widest range consistent with the principles and novel features applied for by the present application.

Claims

1. A method for preparing a fuel cell packaging box, the method comprising: According to the structure of the fuel cell packaging box, a plurality of monomer parts are prepared; Setting a preset overlap surface at the contact position of two adjacent monomer parts; Overlapping a plurality of the preset overlapping surfaces to obtain a box frame to be welded; The box frame to be welded is subjected to friction stir welding to form a weld at a location to be welded of the box frame to be welded, thereby obtaining a welded box frame; wherein the penetration depth of the weld corresponds to the depth of the preset overlap surface; The welded box frame is heat treated to obtain a heat treated box frame; Arranging a grounding point on the outer side of the heat treatment box frame to obtain a processing box containing the grounding point; and The grounding point of the processed box body is sealed with a sealing bolt to obtain a primary fuel cell packaging box body.

2. The method according to claim 1, wherein the parameters of the friction stir welding further include: The welding needle rotation speed of the stir friction welding is ≥800r / min, and the feeding speed of the single component is ≥300mm / min.

3. According to the method of claim 2, the rotation speed of the friction stir welding needle is 800r / min to 1200r / min, and the feeding speed of the single part is 300mm / min to 600mm / min.

4. According to the method of claim 1, the penetration depth h1 of the weld and the thickness h2 of the single component satisfy the relationship: h1:h2=(0.6-1):

1.

5. The method according to claim 1, wherein overlapping the plurality of preset overlapping surfaces to obtain a box frame to be welded comprises the steps of: According to the shape of the preset overlap surface, the preset overlap surfaces of two adjacent monomer parts are overlapped to be welded to the box frame; wherein, The depth of the preset overlapping surface is the same as the thickness of the single component.

6. According to the method of claim 1, the preset overlapping surface comprises a plurality of trapezoidal surfaces, and the length of each of the trapezoidal surfaces is 3 mm to 50 mm.

7. The method according to claim 1, wherein the heat treatment comprises a heating section and a heat preservation section, the temperature of the heating section is 120°C to 160°C, and the time of the heat preservation section is 2h to 4h.

8. The method according to claim 1, after the grounding point of the processed box is sealed with a sealing bolt to obtain a preliminary fuel cell packaging box, further comprising: The plugging box is chemically polished, and then the plugging box after chemical polishing is hard-oxidized to obtain a first surface-treated box containing an oxide film; The first surface treatment box containing the oxide film is sealed to optimize the structure and performance of the oxide film layer of the surface treatment box to obtain a second surface treatment box; The second surface treatment box is cleaned, and then the blocking bolts in the cleaned second surface treatment box are removed to obtain a second surface treatment box having a plurality of threaded holes; Filling the threaded hole of the second surface treatment box with an inlaid screw sleeve to obtain a third surface treatment box containing an inlaid screw sleeve; The third surface-treated box body containing the embedded screw sleeve is subjected to resistance detection and sealing detection to obtain a target fuel cell packaging box body.

9. The method according to claim 8, characterized in that The temperature of the chemical polishing is 90°C to 105°C, and the time of the chemical polishing is 3min to 6min; and / or The temperature of the hard oxidation is 10°C to 15°C, the voltage of the hard oxidation is 12V to 22V, and the current density of the hard oxidation is 1A / dm 2 ~2A / dm 2 , the hard oxidation time is 70min to 120min; and / or The temperature of the sealing treatment is 25° C. to 60° C., and the time of the sealing treatment is 10 min to 15 min.

10. The method according to claim 8, characterized in that The sealing liquid used for the sealing treatment comprises nickel acetate, sodium fluoride, a surfactant and an additive, wherein 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 The pH value of the sealing solution used in the sealing treatment is 5.5-6.5.

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