A method for producing a battery aluminum can

Abstract

The present application relates to the technical field of battery shell production, and particularly relates to a production method of a battery aluminum shell.The present application discloses a production method of a battery aluminum shell, which comprises the following steps: after 6-series aluminum alloy is subjected to melting, degassing, continuous casting and rolling forming, the aluminum alloy is subjected to two-stage ball milling together with zirconium diboride and modified lignin to prepare a composite plate; after pretreatment through alkali washing and acid etching, the plate is coated with a lignin-zinc compound coating and solidified; after preheating, the plate is pulled through a gradient temperature mold to perform hot draw forming, and an interface reaction occurs simultaneously; after laser repair welding of defects, the plate is subjected to preheating, cooling and stabilization heat treatment; finally, the plate is subjected to precise machining such as milling and polishing to obtain a finished product.The present application can make the aluminum shell have stable microstructure and optimized interface bonding, excellent mechanical properties and corrosion resistance by means of phase composite, gradient coating and heat treatment regulation, and the process is controllable, so the present application is suitable for large-scale production of battery aluminum shells.

Description

Technical Field

[0001] This invention relates to the field of battery casing manufacturing technology, and in particular to a method for producing an aluminum battery casing. Background Technology

[0002] As a core structural component of power batteries, the aluminum casing directly affects the battery's safety, stability, and lifespan. It must simultaneously meet stringent requirements such as high strength, high corrosion resistance, high dimensional accuracy, and long cycle life. Currently, in the forming process of battery aluminum casings, the "drawing through a die" method has become the mainstream technology for metal sheet forming due to its advantages such as high processing efficiency, good forming consistency, and controllable production costs. It is widely used in deep drawing processing of metal sheets of limited length. However, existing technologies using this drawing method to produce battery aluminum casings still face many technical bottlenecks, making it difficult to match the high-performance requirements of power batteries for aluminum casings.

[0003] Chinese patent CN107583999B discloses a method for producing aluminum battery casings for new energy vehicles and the battery casing itself. The core of this patent's technical solution involves preparing an aluminum alloy plate and a drawing die. The aluminum alloy plate is placed between the lower die and the ring die of the mold, and the battery casing is produced using either cold drawing or hot drawing processes. Hot drawing requires preheating and heat preservation of the aluminum alloy plate and the mold. During the drawing process, the temperature and drawing speed are controlled, and the blank holder force is adjusted according to the rule of "increase, constant, decrease, constant, decrease" as the upper die stroke is completed. After drawing, the upper die is lifted to remove the part, and cracks can be repaired by welding. The hot-drawn casing can also undergo quenching treatment. The resulting concave battery casing is divided into several grooves by horizontal and vertical partitions, with protrusions with through holes extending from both sides. Welding points are provided at the connection points between the partitions and the perimeter of the aluminum casing. While this patent provides preliminary control over the temperature, drawing speed, and blank holder force of hot drawing, the lack of a zoned temperature control design in the mold makes it impossible to precisely match the different flow characteristics of different parts of the aluminum sheet (corners, sidewalls, bottom). This can easily lead to insufficient material supply or excessively rapid flow in certain areas, causing problems such as uneven wall thickness and corner thinning and cracking. Furthermore, the absence of interfacial reactions during the drawing process prevents the formation of a stable gradient interface layer and a three-dimensional interwoven network structure, making it difficult to effectively disperse stress. This results in a tendency for the aluminum shell to spring back and deform, limiting dimensional accuracy and surface flatness. Directly using conventional aluminum alloy sheets for drawing without modifying the building phase, introducing hard ceramic building phases and modified organic building phases, and lacking a building phase gradient dispersion process, relies solely on drawing and quenching processes to improve performance. The lack of strengthening effect of the building phase on the matrix and improvement of interfacial compatibility limits the improvement of mechanical properties such as hardness, yield strength, and elongation at break, making it difficult to meet the high load-bearing capacity and impact resistance requirements of battery aluminum shells. Without a systematic surface pretreatment process (such as alkaline ultrasonic degreasing, mixed acid etching activation, etc.), the basic pre-drawing preparation alone cannot completely remove the oxide layer and impurities on the aluminum alloy plate surface, affecting the subsequent possible surface adhesion. At the same time, without the use of protective measures such as organic-inorganic hybrid coatings, relying solely on the aluminum alloy itself and basic processing technology, there is no dense protective layer on the surface, and corrosive media can easily penetrate into the substrate, resulting in insufficient corrosion resistance of the aluminum shell and a service life that is greatly affected by environmental factors.

[0004] Chinese patent CN106784419A discloses a corrosion-resistant aluminum shell for power lithium batteries and its preparation method. The aluminum shell body is constructed by sequentially laminating an aluminum substrate, aluminum foil, and copper foil from the outside in. The aluminum foil and aluminum substrate are laminated using a cold rolling forging method, while the copper foil and aluminum foil are laminated using an explosive rolling process. First, an aluminum substrate is prepared using a thick, soft aluminum plate. Second, an aluminum foil and copper foil composite plate is prepared by first producing a rolled blank using an explosive lamination method, and then rolling it into a composite plate. Next, an aluminum shell sheet is prepared by attaching the aluminum foil side of the composite plate to the aluminum substrate and continuously rolling it using a cold rolling process. Finally, the composite plate is stretched and formed into an aluminum shell using a cold stretching process. This patent uses a cold stretching process to form the aluminum shell, lacking both temperature control design for the mold (such as zoned temperature control) to match the flow characteristics of different parts of the material and dynamic adjustment of the blank holder force to adapt to changes in material inflow resistance at different stages of the stretching process. Cold stretching is prone to problems such as poor material flowability, stress concentration, and springback deformation, and lacks effective control methods, resulting in defects such as uneven wall thickness, large dimensional deviations, and insufficient surface flatness in the final aluminum shell, making it difficult to guarantee forming quality. Performance is improved solely through a multi-layer composite structure of "aluminum substrate, aluminum foil, and copper foil," without introducing key reinforcing components such as hard building phases or modified organic building phases, nor is the composite layer subjected to interface compatibility modification. The reinforcement system is singular, relying solely on the physical composite of multiple metals, failing to create a synergistic strengthening effect and unable to effectively improve key mechanical properties such as material hardness, tensile strength, and elongation at break, making it difficult to meet the high strength and high toughness requirements of power battery aluminum shells. While addressing internal corrosion by using inner copper foil to prevent lithium-aluminum contact reaction, a comprehensive surface protection system is lacking. On one hand, no special pretreatment is performed on the outer side of the aluminum substrate, failing to remove the surface oxide layer and microscopic defects; on the other hand, no external protective coating is applied, leaving the outer side of the aluminum substrate directly exposed to the environment, susceptible to corrosion from external corrosive media such as humidity, heat, and salt spray. Meanwhile, if the multi-layered composite structure is not tightly bonded, crevice corrosion may occur, further reducing the overall corrosion resistance. The manufacturing process does not include any defect repair procedures; micro-cracks and interlayer delamination that may occur during stretching cannot be precisely repaired, easily leading to stress concentration at defect locations and affecting structural integrity. Furthermore, no targeted heat treatment process was designed after forming, making it impossible to stabilize the microstructure and optimize interfacial bonding strength through phase transformation or recrystallization. The interfacial stability of the multi-layered composite structure depends on the rolling composite process, and long-term use may result in interlayer separation and mechanical property degradation, limiting the service life of the aluminum shell.

[0005] In summary, the existing technology for producing battery aluminum casings using the "drawing through a mold" method has shortcomings in terms of precise control of the drawing process, phase modification and dispersion, surface protection system construction, defect repair, and microstructure stabilization. As a result, the product's dimensional accuracy, mechanical properties, corrosion resistance, and service life cannot meet the high-performance requirements of power batteries, and the above-mentioned technical problems urgently need to be solved. Summary of the Invention

[0006] To address the aforementioned problems, the present invention aims to provide a method for producing an aluminum battery casing, specifically comprising the following steps:

[0007] S001, aluminum alloy raw materials are added to an induction furnace for melting and treatment, argon gas is introduced for degassing, aluminum-titanium-boron wire is added for stirring and continuous casting to obtain an aluminum alloy billet. The aluminum alloy billet is hot-rolled to obtain a hot-rolled plate. The hot-rolled plate is solution-treated, water-quenched, cold-rolled, and polished to obtain a cold-rolled plate. The cold-rolled plate and coarse-grade building phase dispersion are subjected to a first-stage ball milling treatment, followed by the addition of fine-grade filler phase dispersion and additives for a second-stage ball milling treatment to obtain an aluminum-based composite plate constructed from zirconium diboride and modified lignin, denoted as the composite plate.

[0008] S002, the composite board is immersed in an alkaline solution and ultrasonically treated, then transferred to a mixed acid solution and acid etched to obtain a pretreated board. The coating liquid is applied to the surface of the pretreated board and cured to obtain an aluminum-based composite board with a lignin-zinc compound coating, which is denoted as a coated composite board.

[0009] S003, heat-treat the coated composite sheet to obtain a preheated sheet, place the preheated sheet in a preheated mold, and perform drawing by pulling through the mold, that is, deep drawing through the mold and perform interface reaction to obtain an aluminum-based composite component with a three-dimensional interwoven network structure and a gradient interface layer formed by hot drawing, denoted as composite component.

[0010] S004, the cracked area of ​​the composite component is repaired by laser welding, and then preheated, shaped, cooled and stabilized by heat treatment to obtain an aluminum-based composite component with stable microstructure and optimized interface after defect repair and heat treatment control, which is referred to as a stable composite component.

[0011] S005, the stable composite component is milled, surface polished, perforated and electrolytic polished to obtain the battery aluminum shell.

[0012] In step S001, the aluminum alloy raw material is a 6-series aluminum alloy, consisting of 96.5 wt% aluminum, 0.8 wt% magnesium, 0.6 wt% silicon, 0.3 wt% copper, and 0.15 wt% iron, with the remaining 1.65 wt% being impurities and other trace elements. The melting treatment is performed in a 200 kW medium-frequency induction furnace, heating to 720 ℃ and holding for 30 min. The degassing treatment involves introducing argon gas at a flow rate of 5 L / min for 15 min. The amount of aluminum-titanium-boron wire added is 0.15 wt%, with a titanium to boron mass ratio of 5:1. The stirring treatment is performed at 300 r / min for 10 min. The continuous casting treatment is performed with a crystallizer water temperature of 30 ℃ and a casting speed of 800 mm / min. The aluminum alloy billet size is 1000 mm × 500 mm × 20 mm. The hot rolling treatment is performed in a 480 ℃ four-roll mill with multiple passes, the first pass having a reduction rate of 30% (from 20 mm to 14 mm). The subsequent passes were 20% (14 mm to 11.2 mm), 18% (11.2 mm to 9.2 mm), and 15% (9.2 mm to 7.8 mm), with water spray cooling between each pass to control the board temperature at 450~500 ℃; solution treatment was performed at 530 ℃ for 2 h; water quenching was performed at a cooling rate of 180 ℃ / s to rapidly reduce to room temperature; cold rolling was performed at room temperature with a reduction rate of 33% to a thickness of 4 mm; grinding was performed using 800-mesh abrasive belt at a speed of 15 m / min to achieve a surface roughness of 0.6 μm; the coarse-grade building phase dispersion consisted of 120 nm hydroxylated zirconium diboride and maleic anhydride grafted lignin, at 1.2 wt% and 0.6 wt% respectively, with isopropanol added at a solid-liquid mass ratio of 1:5, and ultrasonically dispersed at 1200 W for 40 min; the fine-grade filling phase dispersion consisted of 30 The mixture consisted of 0.6 wt% hydroxylated zirconium diboride and maleic anhydride-grafted lignin, with isopropanol added at a solid-liquid mass ratio of 1:8 and ultrasonically dispersed at 1000 W for 50 min. The additives consisted of 0.8 wt% 15 nm KH-550 modified wollastonite and 0.012 wt% epoxy chain extender ADR-4370, mixed together. The first-stage ball milling treatment was carried out at a ball-to-material mass ratio of 12:1, under argon protection at a speed of 200 r / min with assisted ultrasonic treatment at 500 W for 30 min. The second-stage ball milling treatment was carried out at a speed of 180 r / min with assisted ultrasonic treatment at 400 W for 60 min.

[0013] Hydroxylated zirconium diboride was prepared by mixing zirconium diboride of different specifications with hydrogen peroxide, followed by hydroxylation, filtration, washing, and drying. The hydrogen peroxide was added at a solid-liquid ratio of 1:10, and the hydrogen peroxide content was 5 wt%. The hydroxylation reaction was carried out with a reflux condenser, stirred at 80 °C and 300 r / min for 2 h, and then cooled to room temperature. The filtration was performed using a Buchner funnel to collect the solid product. The washing process involved washing three times with 500 mL of deionized water each time until the pH of the filtrate was neutral. The drying process was carried out at 60 °C and an absolute pressure of 0.01 MPa for 6 h.

[0014] Maleic anhydride-grafted lignin is prepared by mixing lignin with acetone, followed by reflux, centrifugation, and rotary evaporation to obtain purified lignin. The purified lignin is then mixed with ethylenediamine for amination, followed by washing and drying to obtain amination lignin. The amination lignin is then mixed with maleic anhydride, an initiator is added, and a grafting reaction is carried out, followed by precipitation and purification. In this process, acetone is mixed at a solid-liquid ratio of 1:12; reflux treatment involves using a reflux apparatus and refluxing at 70 °C for 3 h; centrifugation is performed at 8000 r / min for 20 min; rotary evaporation is performed at 60 °C, 0.01 MPa, and 60 r / min; ethylenediamine is mixed at a mass ratio of 1:4; the amination reaction is carried out at 130 °C under nitrogen protection for 5 h; and the washing and drying process involves cooling to room temperature, washing three times with 500 mL of deionized water each time, and drying at 80 °C and 0.01 MPa for 24 hours. h; maleic anhydride was mixed at a mass ratio of 10:1; the initiator was dicumyl peroxide, with an addition amount of 0.5 wt%; the grafting reaction was carried out at 160 ℃ under nitrogen protection for 40 min; the precipitation purification treatment was carried out by first adding anhydrous ethanol at a liquid-solid ratio of 10 mL:1 g, stirring at 600 r / min for 30 min, then letting it stand for 10 min, centrifuging at 8000 r / min for 15 min, discarding the supernatant, adding anhydrous ethanol at a liquid-solid ratio of 5 mL:1 g, stirring at 600 r / min for 30 min, then letting it stand for 10 min, centrifuging at 8000 r / min for 15 min, discarding the supernatant, adding anhydrous ethanol at a liquid-solid ratio of 5 mL:1 g, stirring at 600 r / min for 30 min, then letting it stand for 10 min, centrifuging at 8000 r / min for 15 min, collecting the precipitate, and drying it at 55 ℃ and an absolute pressure of 0.01 MPa for 12 h.

[0015] In step S002, the alkaline solution is a 5 wt% sodium hydroxide solution; the ultrasonic treatment is performed at 60 ℃ and 350 W for 12 min; the mixed acid solution consists of hydrofluoric acid and nitric acid, at 2 wt% and 5 wt% respectively; the acid etching treatment involves etching at 25 ℃ for 30 s, followed by rinsing with deionized water until the pH is neutral, and drying at 50 ℃ for 1 h; the coating solution consists of maleic anhydride grafted lignin, zinc chloride, polyvinylpyrrolidone, and anhydrous ethanol, at 5 wt%, 2 wt%, 0.5 wt%, and 92.5 wt% respectively, prepared by magnetic stirring at 800 r / min for 50 min until completely dissolved, and then filtered through a 0.2 μm filter membrane; the coating conditions are: using a slot coater with a width of 15 mm, a gap of 0.1 mm, a speed of 10 m / min, and a back roller heated to 60 ℃; the curing treatment uses an infrared drying tunnel, heated in steps of 60 ℃, 70 ℃, and 60 ℃, each step for 30 s, followed by 65 ℃. Dry at ℃ and absolute pressure 0.01 MPa for 20 min.

[0016] In step S003, the heating treatment is preheating at 290 ℃ for 10 min; the preheating mold is an H13 steel nitriding mold, with 4 independent heating modules preheating to 280 ℃ at the corner, 290 ℃ at the side wall, and 300 ℃ at the bottom, and holding at that temperature for 40 min; during the drawing process, the blank holder force is controlled by pulling through the mold, with a stroke of 250 kN for 0~30 mm, 280 kN for 30~90 mm, and 220 kN for 90~120 mm, and the servo hydraulic press speed is 20 mm / min; the interface reaction is an interface reaction at 300 ℃ for 6 min.

[0017] In step S004, laser repair welding is performed in argon gas containing 5% nitrogen at a flow rate of 15 L / min using aluminum-5% silicon-0.2% magnesium welding wire; preheating and shaping treatment is performed in deionized water at 65 ℃ at 50 r / min for 6 min; cooling treatment is performed by rapidly placing the device in a 20 ℃ cold water bath with 500 W and 1 m / s ultrasonic turbulence for 10 min, and then rapidly cooling it to room temperature; stabilization heat treatment is performed by holding the device in an 85 ℃ oven for 4 h, followed by natural cooling to room temperature.

[0018] In step S005, the milling process is performed at a speed of 15000 r / min and a feed rate of 0.15 mm / r; the surface polishing process uses 1000-grit abrasive belt; the piercing process is performed by electrical discharge machining with an 8 A, 50 μs pulse; the electropolishing process is performed by immersion in a 10% sulfuric acid solution, electropolishing at 1 A / dm² for 30 s, followed by rinsing with deionized water and drying at 60 ℃ for 30 min.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] 1. This invention employs a hot drawing forming process. By placing the preheated composite sheet in a preheating mold with zoned temperature control and using segmented edge pressure control, an interfacial reaction is introduced, systematically solving the technical problems of poor material flowability, easy cracking, large springback, and uneven wall thickness in deep drawing forming. The zoned temperature control of the mold allows for precise matching of material flow characteristics in different areas, enhancing material plasticity in high-temperature regions and guiding differentiated material flow. This enhances deep-drawing capability and prevents thinning and cracking in stress concentration areas such as corners. Simultaneously, the blank holder force is dynamically adjusted based on the inflow resistance of the sheet metal at different drawing stages. Moderate pressure is used in the initial stage to initiate flow, pressure is increased in the middle stage to suppress wrinkling, and pressure is reduced in the final stage to avoid sidewall cracking. This combination of blank holder force control and low-speed servo forming ensures stable and uniform material flow into the mold cavity, resulting in high-quality deep-drawn parts with uniform wall thickness. Under specific thermal conditions, the active components of the coating diffuse and react with the aluminum matrix, forming a gradient interface layer in situ and promoting the generation of a three-dimensional interwoven network structure. This structure not only strengthens the interface bonding but also effectively transfers and disperses stress, thereby synergistically improving the overall integrity, impact resistance, and lifespan of the component. This integrated process system, combining gradient temperature field, dynamic blank holder force, and interface reaction, enables high-quality, high-precision deep-drawing of aluminum-based composite materials under non-cutting conditions.

[0021] 2. This invention uses zirconium diboride and modified lignin as building phases, which are uniformly dispersed in an aluminum matrix through a multi-stage ball milling process to form a nanocomposite structure. Zirconium diboride, as a hard ceramic phase, can effectively improve the strength and hardness of the material, while modified lignin, through chemical grafting, improves the interfacial compatibility with the aluminum matrix, promotes the dispersion and bonding of the building phases, thereby enhancing the overall mechanical properties and stability of the composite board.

[0022] 3. This invention forms a dense protective layer on the surface of aluminum-based composite panels by combining alkaline ultrasonic treatment and acid etching pretreatment with a lignin-zinc compound coating. The pretreatment removes surface oxides and impurities, improving coating adhesion, while the lignin-zinc coating, through a curing reaction, forms an organic-inorganic hybrid structure, giving the aluminum shell excellent corrosion resistance and surface hardness, thus extending its service life.

[0023] 4. This invention introduces laser welding and stabilization heat treatment to repair defects and stabilize the microstructure of formed components. Laser welding precisely repairs microcracks and reduces stress concentration, while preheating and stabilization heat treatment stabilize the microstructure through phase transformation and recrystallization processes, enhance interfacial bonding strength, and ensure the dimensional stability and reliability of components in harsh environments.

[0024] 5. This invention optimizes the dimensional accuracy and surface finish of the battery aluminum casing through subsequent processing such as machining and electropolishing. High-precision machining reduces surface defects, and electropolishing forms a uniform oxide layer, further improving corrosion resistance and sealing performance to meet the requirements of the battery casing. Detailed Implementation

[0025] The present invention will be further described below with reference to specific embodiments.

[0026] Example

[0027] A method for producing an aluminum battery casing specifically includes the following steps:

[0028] Preparation of 30 nm and 120 nm hydroxylated zirconium diboride: 100 g of 30 nm and 100 g of 120 nm zirconium diboride were added to 1000 mL of 5 wt% hydrogen peroxide and mixed evenly. After mixing, a reflux condenser was installed, and the mixture was stirred at 80 °C and 300 r / min for 2 h. After cooling to room temperature, the solid product was collected by suction filtration using a Buchner funnel. The solid product was washed three times with 500 mL of deionized water each time until the pH of the filtrate was neutral. The solid product was then dried at 60 °C and 0.01 MPa absolute pressure for 6 h.

[0029] Preparation of maleic anhydride-grafted lignin: 50 g of lignin was mixed with 600 mL of acetone, refluxed at 70 °C for 3 h, centrifuged at 8000 r / min for 20 min, and evaporated at 60 °C, 0.01 MPa, and 60 r / min to obtain purified lignin. 45 g of purified lignin was mixed with 180 g of ethylenediamine and reacted at 130 °C under nitrogen protection for 5 h. After cooling to room temperature, it was washed three times with 500 mL of deionized water each time, and dried at 80 °C and 0.01 MPa for 24 h to obtain aminated lignin. 200 g of aminated lignin was mixed with 20 g of maleic anhydride, 1.1 g of initiator was added, and grafting reaction was carried out at 160 °C under nitrogen protection for 40 min. 2200 mL of anhydrous ethanol was added, and stirring was carried out at 600 r / min for 30 min. After standing for 10 min, the mixture was evaporated at 8000 r / min. Centrifuge at 600 r / min for 15 min, discard the supernatant, add 1100 mL of anhydrous ethanol, stir at 600 r / min for 30 min, let stand for 10 min, then centrifuge at 8000 r / min for 15 min, discard the supernatant, add 1100 mL of anhydrous ethanol, stir at 600 r / min for 30 min, let stand for 10 min, then centrifuge at 8000 r / min for 15 min, collect the precipitate, and dry at 55 ℃ and 0.01 MPa absolute pressure for 12 h.

[0030] Preparation of coarse construct phase dispersion: Weigh 144 g of 120 nm hydroxylated zirconium diboride and 72 g of maleic anhydride grafted lignin, add 1080 mL of isopropanol, and disperse by ultrasonication at 1200 W for 40 min.

[0031] Preparation of fine-grade packed phase dispersion: Weigh 72 g of 30 nm hydroxylated zirconium diboride and 72 g of maleic anhydride grafted lignin, add 1152 mL of isopropanol, and disperse by ultrasonication at 1000 W for 50 min.

[0032] Preparation of additives: Weigh 96 g of 15 nm KH-550 modified wollastonite and 1.44 g of epoxy chain extender ADR-4370 and mix them evenly.

[0033] S001: Weigh 12000 g of 6-series aluminum alloy raw material and put it into a 200 kW medium-frequency induction furnace. Heat the furnace to 720 ℃ for melting and hold for 30 min to ensure complete melting. Introduce argon gas at a flow rate of 5 L / min for 15 min. Add 18 g of aluminum-titanium-boron wire and stir at 300 r / min for 10 min. Pour the molten aluminum into a crystallizer. Control the water temperature in the crystallizer at 30 ℃ and the drawing speed at 800 mm / min to cast an aluminum alloy billet with dimensions of 1000 mm × 500 mm × 20 mm. The resulting aluminum alloy billet is then fed into a 480 ℃ four-roll mill for multi-pass rolling. The first pass has a reduction rate of 30%, rolling from 20 mm to 14 mm. The second pass has a reduction rate of 20%, rolling to 11.2 mm. The third pass has a reduction rate of 18%, rolling to 9.2 mm. The fourth pass has a reduction rate of 15%, rolling to 7.8 mm. The sheet is cooled by water spraying between each pass, and the sheet temperature is controlled at 450~500 ℃ to obtain hot-rolled sheet. It is then placed in an oven and solidified at 530 ℃ for 2 h. Subsequently, it is subjected to water quenching treatment at a cooling rate of 180 ℃ / s to rapidly reduce to room temperature. At room temperature, it is rolled to a thickness of 4 mm with a reduction rate of 33%. The surface of the sheet is polished with an 800-mesh abrasive belt at a speed of 15 m / min to achieve a surface roughness of 0.6 μm, resulting in cold-rolled sheet. The cold-rolled sheet and coarse-grade building phase dispersion are added to a ball mill, along with 14.4 kg of grinding balls. Under argon protection, the mill is ultrasonically treated at 200 r / min with 500 W for 30 min. Fine-grade filling phase dispersion and additives are added to the ball mill, and the mill is ultrasonically treated at 180 r / min with 400 W for 60 min to obtain an aluminum-based composite sheet constructed from zirconium diboride and modified lignin, denoted as composite sheet.

[0034] Preparation of coating solution: Weigh 50 g maleic anhydride grafted lignin, 20 g zinc chloride, 5 g polyvinylpyrrolidone, and 925 g anhydrous ethanol, add them to a magnetic stirrer, stir magnetically at 800 r / min for 50 min until completely dissolved, and filter through a 0.2 μm filter membrane.

[0035] S002: The composite board is immersed in a 5 wt% sodium hydroxide solution and ultrasonically treated at 60 ℃ and 350 W for 12 min. Then it is transferred to a mixed acid solution containing 2 wt% hydrofluoric acid and 5 wt% nitric acid and acid etched at 25 ℃ for 30 s. After that, it is rinsed with deionized water until the pH is neutral and dried at 50 ℃ for 1 h to obtain a pretreated board. A slot coater with a width of 15 mm, a gap of 0.1 mm, and a speed of 10 m / min is used. The back roller is heated at 60 ℃ to coat the surface of the pretreated board with the coating liquid. An infrared drying tunnel is used, and the board is heated in steps of 60 ℃, 70 ℃, and 60 ℃ for 30 s each. Then it is dried at 65 ℃ and an absolute pressure of 0.01 MPa for 20 min to obtain an aluminum-based composite board with a lignin-zinc compound coating, which is referred to as the coated composite board.

[0036] S003: Place the coated composite sheet in an oven and preheat it to 290 ℃ for 10 min to obtain a preheated sheet. Preheat the H13 steel nitriding mold to 280 ℃ at the corner, 290 ℃ at the side wall, and 300 ℃ at the bottom using 4 independent heating modules, and keep it at that temperature for 40 min to obtain a preheated mold. Place the preheated sheet in the preheated mold and control the blank holder force by pulling it through the mold. The blank holder force is 250 kN for a stroke of 0~30 mm, 280 kN for a stroke of 30~90 mm, and 220 kN for a stroke of 90~120 mm. The speed of the servo hydraulic press is 20 mm / min. The interface reaction is carried out at 300 ℃ for 6 min to obtain an aluminum-based composite component with a three-dimensional interwoven network structure and a gradient interface layer formed by hot drawing, which is referred to as the composite component.

[0037] S004: In argon gas containing 5% nitrogen at a flow rate of 15 L / min, the cracked area of ​​the composite component was laser-welded using aluminum-5% silicon-0.2% magnesium welding wire. The component was then preheated and shaped in 65 ℃ deionized water at 50 r / min for 6 min, and then rapidly placed in a 20 ℃ cold water bath with 500 W and 1 m / s ultrasonic turbulence for 10 min. After cooling, the component was rapidly cooled to room temperature and then kept at 85 ℃ in an oven for 4 h. Finally, it was allowed to cool naturally to room temperature, resulting in an aluminum-based composite component with stable microstructure and optimized interface bonding after defect repair and heat treatment. This component is referred to as the stable composite component.

[0038] S005: The stable composite component was milled at 15000 r / min and 0.15 mm / r feed. The surface was polished with 1000-grit abrasive belt, followed by electrical discharge machining (EDM) with an 8 A, 50 μs pulse. The component was then immersed in a 10% sulfuric acid solution and electropolished at 1 A / dm² for 30 s. After rinsing with deionized water, the component was dried at 60 ℃ for 30 min to obtain the aluminum battery casing, which was designated as the test sample.

[0039] Comparative Example 1

[0040] A method for producing a battery aluminum casing with non-zoned temperature control and fixed edge pressing force specifically includes the following steps:

[0041] The difference from the embodiment is that in S003, the preheating mold adopts an overall constant temperature of 290 ℃, without zoned temperature control, and the blank holder force is fixed at 250 kN throughout the drawing process without stroke adjustment; the remaining steps are the same as in the embodiment, thus obtaining control product 1.

[0042] Comparative Example 2

[0043] A method for producing battery aluminum casings that involves alkali-free ultrasonic treatment, acid etching, and ordinary zinc coating specifically includes the following steps:

[0044] The difference from the example is that in S002, only 800-mesh sandpaper was used for polishing for 5 minutes, without alkaline ultrasonic treatment and acid etching. Pure zinc chloride coating (20 g zinc chloride dissolved in 980 g anhydrous ethanol) was used to replace the coating liquid, and the coating was directly dried at 65 °C for 20 minutes, with no step curing. The remaining steps are the same as in the example, thus obtaining control product 2.

[0045] Comparative Example 3

[0046] A method for producing a battery aluminum casing with conventional building phases, without hydroxylated zirconium diboride and without grafted lignin, specifically includes the following steps:

[0047] The difference from the example is that, in the preparation of the coarse building phase dispersion, zirconium diboride is replaced with hydroxylated zirconium diboride, and lignin is replaced with maleic anhydride-grafted lignin; the preparation steps of 30 nm and 120 nm hydroxylated zirconium diboride, maleic anhydride-grafted lignin, and fine-grade filled phase dispersion are not performed; only the first-stage ball milling treatment is performed in S001, and the second-stage ball milling treatment is not performed; the remaining steps are the same as in the example, thus obtaining control product 3.

[0048] Comparative Example 4

[0049] A method for producing battery aluminum casings without laser welding or stabilization heat treatment specifically includes the following steps:

[0050] The difference from the embodiment is that S004 is not performed, there is no laser welding, no preheating and shaping, no cooling, and no stabilization heat treatment; the remaining steps are the same as in the embodiment, thus obtaining control product 4.

[0051] Experimental Example 1

[0052] This experimental example compares the drawing quality of the test sample in the comparative example with that of the control sample in Comparative Example 1, and specifically includes the following steps:

[0053] Sample pretreatment: Wipe the surfaces of the test sample and reference standard 1 with acetone. Each sample 3 is parallel, and the sample dimensions are as follows:

[0054] Dimensional accuracy: 120 mm × 100 mm × 4 mm;

[0055] Surface quality and roughness: 50 mm × 50 mm × 4 mm;

[0056] Mechanical properties: Hardness: 15 mm × 15 mm × 4 mm;

[0057] Tensile mechanical properties: gauge length 50 mm, width 10 mm, thickness 4 mm;

[0058] After cutting, polish the cut with 400-grit sandpaper, sonicate with anhydrous ethanol at 300 W for 5 min, and bake at 60 ℃ for 10 min.

[0059] 1. Dimensional accuracy testing

[0060] Wall thickness, dimensional deviation, and flatness were measured using a coordinate measuring machine. Three measurement points were selected for each sample.

[0061] Wall thickness measurement: The actual wall thickness at each point was recorded using the contact probe of a coordinate measuring machine. The average value and standard deviation were calculated, and the wall thickness uniformity of the two measurements was compared (coefficient of variation = standard deviation / average value × 100%). The measurement results are shown in Table 1-1.

[0062] Dimensional deviation: Measure the actual length (drawing direction) and width (perpendicular to the drawing direction) of the sample and compare them with the design dimensions (120 mm × 100 mm). Calculate the average value and the absolute dimensional deviation (absolute deviation = actual size - design size). The measurement results are shown in Table 1-1.

[0063] Flatness measurement: The flatness method is used. The sample is placed on a standard flat crystal and the maximum gap is measured. The flatness error is the result of the measurement. The results are shown in Table 1-1.

[0064] Table 1-1 Dimensional accuracy test results

[0065]

[0066] As can be seen from Table 1-1, the wall thickness uniformity (coefficient of variation) of the embodiment is 0.25%, while that of Comparative Example 1 is 0.57%, indicating that the wall thickness distribution of its aluminum-based composite component is more uniform. This is because the segmented gradient blank holder force and the mold zone temperature control work together to regulate the material flow behavior during the hot drawing process of the sheet metal, effectively reducing the local wall thickness deviation during the forming process.

[0067] In the embodiment, the absolute deviation of the length in the drawing direction is 0.08 mm, and the absolute deviation of the width in the perpendicular drawing direction is 0.09 mm. In Comparative Example 1, the absolute deviations of the dimensions in the corresponding directions are 0.30 mm and 0.31 mm, respectively. The actual dimensions of the embodiment are extremely close to the design dimensions, which improves the dimensional accuracy of the component and effectively suppresses the dimensional deviation problem in the hot drawing process.

[0068] The flatness error of the embodiment is 0.04±0.002 mm, and the flatness error of Comparative Example 1 is 0.09±0.004 mm. The component has excellent surface flatness and small molding deformation, indicating that the process of mold zone temperature control combined with segmented gradient blank holder force can effectively reduce local stress concentration during molding and reduce warping deformation.

[0069] In summary, the embodiment optimizes the hot drawing process and adopts a mold zone temperature control combined with segmented gradient blank holder force control method, which significantly improves the three core forming indicators of wall thickness uniformity, dimensional accuracy, and flatness. Compared with Comparative Example 1, which uses a traditional overall constant temperature and fixed blank holder force process, the aluminum-based composite component formed in the embodiment has better dimensional stability and forming quality, providing a reliable foundation for the subsequent precision machining of the battery aluminum shell.

[0070] 2. Surface quality and roughness testing

[0071] The surface defects (cracks, wrinkles, coating peeling, scratches), quantity, and size (length, width) were observed using a stereomicroscope (50×, 200×). The defect rate was calculated (defect rate = number of defective samples / total number of samples × 100%). The results are shown in Table 1-2.

[0072] The surface roughness Ra value was measured by a roughness tester along three lines in the drawing direction and three lines in the perpendicular direction. Each line was 10 mm long. The average value and standard deviation were calculated. The measurement results are shown in Table 1-2.

[0073] Table 1-2 Surface Quality and Roughness Test Results

[0074]

[0075] As can be seen from Tables 1-2, the Example 1 is superior to Comparative Example 1 in terms of surface quality and roughness. The defect rate of the Example 1 is 0%, while the defect rate of Comparative Example 1 is as high as 66.7%, indicating that the component formed by the partitioned temperature-controlled mold and segmented blank holder hot drawing process has no surface defects and the forming quality stability is far superior to that of Comparative Example 1, which uses the traditional process.

[0076] The roughness of the example in the drawing direction was 0.59±0.01 μm, while that of Comparative Example 1 was 0.76±0.02 μm. The roughness of the example was only 77.6% of that of Comparative Example 1. The roughness of the example perpendicular to the drawing direction was 0.58±0.01 μm, while that of Comparative Example 1 was 0.74±0.02 μm. The roughness of the example was only 78.4% of that of Comparative Example 1.

[0077] In summary, the embodiments showed no surface defects and significantly lower roughness, indicating that the zoned temperature-controlled mold and segmented edge-pressing hot drawing process can effectively improve the surface forming quality of aluminum-based composite components and optimize surface precision.

[0078] 3. Mechanical property testing

[0079] Five points were measured using a Vickers hardness tester (100 g test force, 10 s holding time). The average hardness and standard deviation were taken. The results are shown in Table 1-3.

[0080] Tensile properties were measured using a universal testing machine (speed 0.5 mm / min), and the yield strength, tensile strength, and elongation at break were recorded. The results are shown in Table 1-3.

[0081] Table 1-3 Mechanical property test results

[0082]

[0083] As can be seen from Tables 1-3, the mechanical properties of the embodiments are comprehensively superior to those of Comparative Example 1. The Vickers hardness of the embodiments is 124.5 ± 1.1 HV, while that of Comparative Example 1 is 105.1 ± 1.1 HV. The higher hardness and smaller fluctuation of the embodiments indicate that their material has better hardness stability and strength.

[0084] The yield strength of the embodiment is 332 MPa, while that of Comparative Example 1 is 292 MPa. The yield strength of the embodiment is 13.7% higher than that of Comparative Example 1, and the component has a stronger ability to resist plastic deformation.

[0085] The tensile strength of the example is 392 MPa, while that of Comparative Example 1 is 352 MPa. The tensile strength of the example is increased by 11.4%, and the ability of the component to withstand the maximum tensile stress is enhanced.

[0086] The elongation at break of the example was 13.5%, while that of Comparative Example 1 was 10.5%. The plasticity of the example was improved by 28.6% compared with that of Comparative Example 1, and the deformation toughness of the component was better.

[0087] In summary, the embodiment using zoned temperature-controlled molds and segmented blank holder force hot drawing process exhibits excellent mechanical properties in Vickers hardness, yield strength, tensile strength, and elongation at break, indicating that the process effectively improves the comprehensive mechanical properties of aluminum-based composite components.

[0088] Experiment Example 2

[0089] This experimental example illustrates the difference in corrosion resistance between the test sample in the comparative example and the control sample in Comparative Example 2, and specifically includes the following steps:

[0090] Five parallel samples were cut from the test sample and the reference sample 2 respectively. Each sample was 100 mm × 50 mm × 4 mm in size. The edges of the sample were gently sanded with a 1000-mesh sandpaper, rinsed with deionized water, immersed in anhydrous ethanol for 10 min, ultrasonically cleaned at 300 W for 5 min, dried with nitrogen, placed in an oven at 60 ℃ for 30 min, and cooled to room temperature to obtain the test sample.

[0091] The thickness of each test sample was measured with vernier calipers at three evenly distributed points 20 mm from the edge. The average value was recorded as the initial thickness. The sample was placed in a salt spray test chamber and sprayed continuously with a 5% sodium chloride solution at pH 6.8 for 480 h. After that, the spraying was stopped. The sample surface was gently rinsed with 25 °C deionized water. The area around the corrosion points was brushed with a soft brush. The sample was then dried with nitrogen gas. The thickness was measured at three evenly distributed points 20 mm from the edge. The average value was recorded as the final thickness.

[0092] The corrosion thickness was calculated based on the difference between the initial thickness and the final thickness. The corrosion rate was then calculated by multiplying the corrosion rate by the number of days in a year (365), the number of hours in a day (24), and the reciprocal of the test duration. The results are shown in Table 2.

[0093] Table 2 Results of Corrosion Resistance Differences

[0094]

[0095] As shown in Table 2, the corrosion rate of the aluminum battery casing in the embodiment was 0.15 mm / a, while that in Comparative Example 2 was 1.24 mm / a. The difference in corrosion rates was 1.09 mm / a, indicating that the corrosion resistance of the embodiment was significantly better than that of Comparative Example 2. This demonstrates that the surface pretreatment and coating formulation used in the experiment effectively improved the corrosion resistance of the aluminum battery casing, while Comparative Example 2, lacking key process or material support, exhibited poor corrosion resistance. In conclusion, this experiment fully verified the effectiveness of the embodiment in enhancing the corrosion resistance of the aluminum battery casing.

[0096] Experimental Example 3

[0097] This experimental example is a lifespan test of the test sample in the comparative example and the control samples in comparative examples 1-4, specifically including the following steps:

[0098] 1. Cyclic fatigue test

[0099] Five parallel samples were taken from each of the test sample, reference sample 1, reference sample 2, reference sample 3, and reference sample 4 for cyclic fatigue testing. The test was conducted under the conditions of 25 ℃ and 50 RH, with axial tensile-compressive fatigue, a stress ratio of -1 symmetrical cycle, a maximum stress of 232 MPa, and a cycle frequency of 20 Hz. After the sample fractured, the test was stopped, the number of fracture cycles was recorded, and the average number of fracture cycles and the standard deviation were calculated. The test results are shown in Table 3.

[0100] 2. Corrosion fatigue test

[0101] Five parallel samples were taken from each of the test sample, reference 1, reference 2, reference 3, and reference 4. They were placed in a 35 ℃ salt spray chamber and continuously sprayed with 5 wt% sodium chloride solution. After 2 h of pre-corrosion, axial tensile-compressive fatigue, symmetrical cycle with a stress ratio of -1, maximum stress of 232 MPa, and cycle frequency of 10 Hz were performed. After the sample fractured, the test was stopped, the number of corrosion fracture cycles was recorded, and the average number of corrosion fracture cycles and standard deviation were calculated. The test results are shown in Table 3.

[0102] Table 3 Service life test results

[0103]

[0104] As shown in Table 3, the aluminum casing of the embodiment outperforms Comparative Examples 1-4 in both cyclic fatigue performance and corrosion fatigue performance. The fracture cycle count of the embodiment is 8,400,000 ± 200,000, the highest among all samples, indicating optimal mechanical cyclic performance under dry conditions. The fracture cycle counts of Comparative Example 1 (without zoned temperature-controlled hot drawing), Comparative Example 2 (without alkaline etching-composite coating), Comparative Example 3 (without construct phase modification), and Comparative Example 4 (without laser welding and heat stabilization) are 7,040,000 ± 207,364, 5,500,000 ± 158,114, 4,020,000 ± 192,354, and 2,500,000 ± 158,114, respectively, showing a stepwise decrease. This indicates that the manufacturing process of the embodiment can significantly improve the cyclic fatigue resistance of the aluminum casing, and the degree of impact of the absence of different process steps on fatigue life varies.

[0105] The corrosion fracture cycle count of the example was 5,400,000 ± 158,114 cycles, maintaining the highest lifespan even under corrosive conditions, indicating excellent synergistic performance of corrosion resistance and fatigue resistance. The corrosion fracture cycle counts of Comparative Examples 1-4 were 4,400,000 ± 158,114, 2,900,000 ± 158,114, 2,100,000 ± 158,114, and 1,300,000 ± 158,114 cycles, respectively, showing a greater decrease than in the cyclic fatigue test. Under corrosive conditions, the cycle count of all samples was lower than that of conventional cyclic fatigue tests, but the corrosion fatigue resistance advantage of the example was still significant, indicating superior synergistic performance of corrosion resistance and fatigue resistance.

[0106] Comparative Example 1 omits the "mold zone temperature control" and "segmented blank holder force" of the previous example, and adopts "overall constant temperature and fixed blank holder force". Data shows that its two indicators are only 16%~18.5% lower than those of the previous example, indicating that this process mainly affects molding accuracy and interface bonding uniformity, and has a relatively mild impact on lifespan.

[0107] Comparative Example 2 eliminated the pretreatment of "alkaline ultrasonic cleaning and mixed acid etching" and replaced the "maleic anhydride grafted lignin, zinc chloride, and polyvinylpyrrolidone composite coating" of the previous example with "pure zinc chloride coating". Its corrosion fracture cycle count decreased by 46%, higher than the conventional fatigue reduction (34.5%), indicating that the pretreatment can improve coating adhesion, and the composite coating can form a more effective corrosion protection barrier, which is a key guarantee for corrosion fatigue resistance.

[0108] Comparative Example 3 did not use "hydroxylated zirconium diboride" or "maleic anhydride-grafted lignin," and omitted "fine-grade filler phase dispersion" and "two-stage ball milling and ultrasonic dispersion." Both of its indicators showed a reduction of over 50%, indicating that the hydroxylation modification of zirconium diboride and the maleic anhydride grafting modification of lignin can improve the compatibility of the building phase with the aluminum matrix. The reinforcing effect of the gradient dispersion of the coarse-grade building phase and the fine-grade filler phase is far superior to the simple mixing of a single building phase, and is the core of improving matrix strength and fatigue life.

[0109] Comparative Example 4 omitted the processes of "laser welding to repair cracks" and "preheating, ultrasonic turbulent cooling, and heat stabilization," and its two indicators showed a reduction of 69% to 76%, making it the worst among all comparative examples. This indicates that microcracks generated during the forming process can severely weaken structural integrity, while laser welding can repair defects; heat treatment control can optimize the microstructure and interfacial bonding state, improve structural stability, and is a key factor in ensuring long service life.

[0110] In summary, the embodiments achieved optimal cyclic fatigue life and corrosion fatigue life through the optimization of the entire process of "modified building phase gradient dispersion, composite coating protection, zoned molding control, defect repair and heat treatment", verifying the scientificity and effectiveness of the production process. The weight of each process step in terms of lifespan, from largest to smallest, is: defect repair and heat treatment, building phase modification and dispersion, surface pretreatment and coating, and mold temperature control and blank holder force control. In corrosive environments, the role of surface coating and pretreatment is more prominent, and the corrosion fatigue reduction in Comparative Example 2 is greater than that in conventional fatigue. In conventional cyclic fatigue, the influence of the building phase system and heat treatment is more critical, and the conventional fatigue reduction in Comparative Examples 3 and 4 is significant.

[0111] Experiment Example 4

[0112] This experimental example is a long-term simulated stability test of the test sample in the comparative example and the control samples 1-4, specifically including the following steps:

[0113] Take six parallel samples from each of the test sample, reference 1, reference 2, reference 3, and reference 4. The sample dimensions are as follows:

[0114] Dimensional accuracy: 120 mm × 100 mm × 4 mm;

[0115] Mechanical properties: Hardness: 15 mm × 15 mm × 4 mm;

[0116] Tensile mechanical properties: gauge length 50 mm, width 10 mm, thickness 4 mm;

[0117] After cutting, polish the cut with 400-grit sandpaper, sonicate with anhydrous ethanol at 300 W for 5 min, and bake at 60 ℃ for 10 min.

[0118] Take three parallel specimens from each sample, and test them according to the dimensional accuracy test method and mechanical property test method in Experiment Example 1. Record the dimensional accuracy results and mechanical property results in the initial state.

[0119] The remaining samples were placed in a constant temperature and humidity chamber at 60 ℃ and 80% RH for 2000 h. The samples were then removed and left to stand naturally for 30 min to test the dimensional accuracy and mechanical properties after aging.

[0120] The following parameters were calculated: dimensional change rate (dimensional change rate = (initial size - aged size) / initial size × 100%), hardness retention rate (hardness retention rate = aged Vickers hardness / initial Vickers hardness × 100%), tensile strength retention rate (tensile strength retention rate = aged tensile strength / initial tensile strength × 100%), and elongation at break retention rate (elongation at break retention rate = aged elongation at break / initial elongation at break × 100%). The results are shown in Tables 4-1 and 4-2.

[0121] Table 4-1 Dimensional Accuracy Test Results

[0122]

[0123] As shown in Table 4-1, the aluminum-based composite components for battery aluminum shells prepared by different processes exhibit varying dimensional stability after being placed in a constant temperature and humidity environment of 60 ℃ and 80% RH for 2000 h. The example showed the smallest dimensional change rates in length, width, and thickness, at 0.3% (length), 0.4% (width), and 0.2% respectively, all below 1%, indicating almost no significant dimensional deformation under long-term humid and hot aging conditions, demonstrating extremely strong dimensional stability and effectively maintaining the initial design dimensional accuracy. Comparative Example 1 (no zoned temperature control, fixed blank holder force) showed a dimensional change rate of 1.3% in length, 1.5% in width, and 1.4% in thickness, 4-5 times that of the example. Its process lacked coordinated control of zoned temperature control molds and segmented blank holder forces, leading to uneven stress distribution within the component during molding. The stress was slowly released under long-term humid and hot conditions, causing dimensional deviations. Comparative Example 2 (no alkaline ultrasonic treatment, acid etching pretreatment, ordinary zinc coating) showed a dimensional change rate of 2.3% in length, 2.4% in width, and 2.2% in thickness, 5-6 times that of the example. Due to the lack of effective surface pretreatment (alkaline washing for degreasing, mixed acid etching for activation) and the use of a single zinc chloride coating (without the synergistic protection of maleic anhydride grafted lignin and polyvinylpyrrolidone), the coating has weak adhesion to the substrate. Under humid and hot conditions, the coating is prone to aging and peeling off, and slight corrosion occurs on the substrate surface, leading to dimensional deformation. Comparative Example 3 (conventional building phase, without hydroxylated zirconium diboride and grafted lignin) has a length of 3.3%, a width of 3.1%, and a thickness of 3.1%, with a dimensional change rate 8 to 11 times that of the examples. It did not use hydroxylated modified zirconium diboride (lacking surface hydroxyl groups to bind to the substrate) and maleic anhydride grafted lignin (lacking the bridging effect of amination groups), resulting in a loose bond between the building phase and the aluminum substrate interface. During aging, micro-cracks were generated at the interface, causing overall dimensional fluctuations. Comparative Example 4 (without laser welding and stabilization heat treatment) has a length of 4.3%, a width of 4.0%, and a thickness of 4.1%, with a dimensional change rate 10 to 14 times that of the examples, making it the sample with the worst dimensional stability. Because laser welding was not used to repair microcracks that may have occurred during the molding process, and because stabilizing heat treatment was lacking to stabilize and control the microstructure, there were hidden cracks and structural stress inside the component. Under long-term humid and hot conditions, the cracks expanded and the stress was released, resulting in severe dimensional deformation.

[0124] Therefore, the embodiments, through the synergistic process of zoned temperature control, segmented edge-pressing hot drawing (optimizing forming stress), hydroxylated zirconium diboride, maleic anhydride grafted lignin gradient reinforcement (strengthening interface bonding), alkali washing, acid etching pretreatment, composite coating (improving surface protection), laser welding, and heat treatment (repairing defects and stabilizing the structure), suppress dimensional deformation under long-term humid and hot conditions from multiple dimensions of forming, reinforcement, protection, and post-treatment, and ultimately achieve dimensional stability far exceeding that of traditional processes (each comparative example).

[0125] In summary, the process design of the embodiments can effectively ensure the dimensional reliability of the battery aluminum shell during long-term use. However, the comparative examples have a significant decrease in dimensional stability due to the lack of key process steps. Among them, the impact of defect-free repair and heat treatment (Comparative Example 4) and unmodified building phase (Comparative Example 3) is the most significant.

[0126] Table 4-2 Mechanical property test results

[0127]

[0128] As shown in Table 4-2, the aluminum-based composite components for battery aluminum shells prepared by different processes exhibit differences in the retention rate of mechanical properties. The retention rates of hardness (96.5%), tensile strength (95.8%), and elongation at break (94.3%) in the Example were significantly higher than those in all comparative examples, exceeding 94% for all three indicators. This indicates that its mechanical properties showed almost no significant degradation under conditions such as long-term damp heat aging tests, demonstrating extremely strong performance stability. The retention rates of all mechanical properties in Comparative Examples 1-4 continuously decreased: hardness retention rate dropped from 86.3% to 56.6%; tensile strength retention rate from 85.5% to 54.8%; and elongation at break retention rate from 83.5% to 50.4%. The performance retention rates of each comparative example were significantly lower than those of the Example, and the more critical the missing process step, such as Comparative Example 4 lacking laser welding and stabilization heat treatment, the greater the performance degradation.

[0129] In summary, the embodiments effectively suppressed the degradation of mechanical properties through the synergistic process of molding process control (zoned temperature control, segmented edge pressure), building phase modification (hydroxylated zirconium diboride, grafted lignin), surface protection (composite pretreatment, coating), defect repair and microstructure stabilization (laser welding, heat treatment); while the comparative examples, due to the lack of the above key process steps, resulted in a significant reduction in the retention rate of mechanical properties, and the higher the level of process deficiency, the worse the performance stability.

[0130] The above description is only used to illustrate the technical solution of the present invention and is not intended to limit it. Equal modifications and variations made by those skilled in the art to the technical solution of the present invention, as long as they do not depart from the overall concept of the present invention, shall still fall within the scope of the present invention.

Claims

1. A method for producing an aluminum battery casing, characterized in that, The method for producing the aluminum casing of the battery specifically includes the following steps: S001, aluminum alloy raw materials are added to an induction furnace for melting and treatment, argon gas is introduced for degassing, aluminum-titanium-boron wire is added for stirring and continuous casting to obtain an aluminum alloy billet. The aluminum alloy billet is hot-rolled to obtain a hot-rolled plate. The hot-rolled plate is solution-treated, water-quenched, cold-rolled, and polished to obtain a cold-rolled plate. The cold-rolled plate and coarse-grade building phase dispersion are subjected to a first-stage ball milling treatment, followed by the addition of fine-grade filler phase dispersion and additives for a second-stage ball milling treatment to obtain an aluminum-based composite plate constructed from zirconium diboride and modified lignin, denoted as the composite plate. S002, the composite board is immersed in an alkaline solution and ultrasonically treated, then transferred to a mixed acid solution and acid etched to obtain a pretreated board. The coating liquid is applied to the surface of the pretreated board and cured to obtain an aluminum-based composite board with a lignin-zinc compound coating, which is denoted as a coated composite board. S003, heat-treat the coated composite sheet to obtain a preheated sheet, place the preheated sheet in a preheated mold, and perform drawing by pulling through the mold, that is, deep drawing through the mold and perform interface reaction to obtain an aluminum-based composite component with a three-dimensional interwoven network structure and a gradient interface layer formed by hot drawing, denoted as composite component. S004, the cracked area of ​​the composite component is repaired by laser welding, and then preheated, shaped, cooled and stabilized by heat treatment to obtain an aluminum-based composite component with stable microstructure and optimized interface after defect repair and heat treatment control, which is referred to as a stable composite component. S005, the stable composite component is milled, surface polished, perforated and electrolytic polished to obtain the battery aluminum shell.

2. The method for producing the aluminum casing of a battery according to claim 1, characterized in that, In step S001, the aluminum alloy raw material is a 6-series aluminum alloy, consisting of 96.5 wt% aluminum, 0.8 wt% magnesium, 0.6 wt% silicon, 0.3 wt% copper, and 0.15 wt% iron, with the remaining 1.65 wt% being impurities and other trace elements; the amount of aluminum-titanium-boron wire added is 0.15 wt%, with a titanium to boron mass ratio of 5:1; the aluminum alloy billet size is 1000 mm × 500 mm × 20 mm.

3. The method for producing the aluminum battery casing according to claim 1, characterized in that, In step S001, the coarse-grade building phase dispersion consists of 120 nm hydroxylated zirconium diboride and maleic anhydride-grafted lignin, at 1.2 wt% and 0.6 wt% respectively, with isopropanol added at a solid-liquid mass ratio of 1:5, and ultrasonically dispersed at 1200 W for 40 min. The fine-grade filling phase dispersion consists of 30 nm hydroxylated zirconium diboride and maleic anhydride-grafted lignin, both at 0.6 wt%, with isopropanol added at a solid-liquid mass ratio of 1:8, and ultrasonically dispersed at 1000 W for 50 min. The additive consists of 15 nm KH-550 modified wollastonite and epoxy chain extender ADR-4370, at 0.8 wt% and 0.012 wt% respectively, prepared by mixing the two. The first-stage ball milling treatment is performed at a ball-to-material mass ratio of 12:1, under argon protection at 200 r / min with assisted ultrasonic treatment at 500 W for 30 min. The second-stage ball milling treatment is performed at 180 r / min with assisted ultrasonic treatment at 400 W for 60 min. min.

4. The method for producing the aluminum battery casing according to claim 3, characterized in that, Hydroxylated zirconium diboride is prepared by adding zirconium diboride of different specifications to hydrogen peroxide, mixing them evenly, and then performing a hydroxylation reaction, filtration, washing, and drying. The hydrogen peroxide is added at a solid-liquid ratio of 1:10, and the amount of hydrogen peroxide is 5 wt%.

5. The method for producing the aluminum battery casing according to claim 3, characterized in that, Maleic anhydride-grafted lignin is prepared by mixing lignin with acetone, followed by reflux, centrifugation, and rotary evaporation to obtain purified lignin. The purified lignin is then mixed with ethylenediamine and subjected to an amination reaction. After washing and drying, amination lignin is obtained. The amination lignin is then mixed with maleic anhydride, an initiator is added, and a grafting reaction is carried out. After precipitation and purification, the lignin is obtained. In this process, acetone is mixed at a solid-liquid ratio of 1:12; ethylenediamine is mixed at a mass ratio of 1:4; maleic anhydride is mixed at a mass ratio of 10:1; and the initiator is dicumyl peroxide, added at 0.5 wt%.

6. The method for producing the aluminum battery casing according to claim 1, characterized in that, In step S002, the alkaline solution is a 5 wt% sodium hydroxide solution; the ultrasonic treatment is performed at 60 ℃ and 350 W for 12 min; the mixed acid solution consists of hydrofluoric acid and nitric acid, at 2 wt% and 5 wt% respectively; the acid etching treatment is performed by first etching at 25 ℃ for 30 s, then rinsing with deionized water until the pH is neutral, and drying at 50 ℃ for 1 h; the coating solution consists of maleic anhydride grafted lignin, zinc chloride, polyvinylpyrrolidone, and anhydrous ethanol, at 5 wt%, 2 wt%, 0.5 wt%, and 92.5 wt% respectively, and is prepared by magnetic stirring at 800 r / min for 50 min until completely dissolved, and then filtered through a 0.2 μm filter membrane.

7. The method for producing the aluminum battery casing according to claim 1, characterized in that, In step S003, the preheating mold is an H13 steel nitriding mold. Four independent heating modules preheat the mold to 280 ℃ at the corner, 290 ℃ at the side wall, and 300 ℃ at the bottom, and hold the temperature for 40 minutes. During the drawing process, the blank holder force is controlled by pulling the mold through the die. The blank holder force is 250 kN for the 0~30 mm stroke, 280 kN for the 30~90 mm stroke, and 220 kN for the 90~120 mm stroke. The servo hydraulic press speed is 20 mm / min.

8. The method for producing the aluminum casing of a battery according to claim 1, characterized in that, In step S004, laser repair welding is performed in argon gas containing 5% nitrogen at a flow rate of 15 L / min using aluminum-5% silicon-0.2% magnesium welding wire; preheating and shaping treatment is performed in deionized water at 65 ℃ at 50 r / min for 6 min; cooling treatment is performed by rapidly placing the device in a 20 ℃ cold water bath with 500 W and 1 m / s ultrasonic turbulence for 10 min, and then rapidly cooling it to room temperature; stabilization heat treatment is performed by holding the device in an 85 ℃ oven for 4 h, followed by natural cooling to room temperature.

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