High-strength high-elongation 1060h18 aluminum alloy foil for power battery and preparation method thereof

Abstract

The application belongs to the technical field of aluminum-based materials, and particularly relates to a high-strength and high-elongation 1060H18 aluminum alloy foil for power batteries and a preparation method thereof. Through the synergy of components and the whole process, especially the fine control of the warm rolling process as the core, the traditional intermediate annealing is successfully replaced, and the unification of performance and efficiency is realized. The aluminum alloy foil prepared by the application has stable comprehensive performance and high reliability, and fully meets or even exceeds the high requirements of new energy automobile power batteries on material performance.

Description

Technical Field

[0001] This invention belongs to the field of aluminum-based materials technology, specifically relating to a high-strength, high-elongation 1060H18 aluminum alloy foil for power batteries and its preparation method. Background Technology

[0002] With the global energy structure shifting towards green and low-carbon development, and the rapid growth of the new energy vehicle industry, the performance, safety, and cost of power batteries, as the "heart" of new energy vehicles, directly determine the depth and breadth of the industry's development. Among the various structural forms of power batteries, aluminum-cased batteries occupy a mainstream position in the market due to their advantages such as light weight, good formability, excellent thermal conductivity, and relatively low cost. The battery casing and cover, as key structural components protecting the internal cells and electrolyte, not only need excellent sealing, corrosion resistance, and thermal conductivity, but also place extremely high demands on the strength, plasticity, and fatigue performance of the materials. 1060 aluminum alloy, as a commercially available pure aluminum with high purity and excellent electrical conductivity, is widely considered for the manufacture of battery casings and covers due to its good processing performance and cost advantages.

[0003] However, traditional 1060 aluminum alloy faces a key technical dilemma when applied to the demanding application of power batteries: the difficulty of balancing strength and plasticity (elongation). According to the theory of work hardening, cold deformation (such as cold rolling) can significantly improve the strength of materials, enabling them to reach H18 (ultra-hard state) or similar high-strength states. However, drastic cold working leads to a high density of dislocations in the material's crystal lattice, a sharp increase in internal energy, and a significant decrease in plasticity reserve (elongation), resulting in a brittle and hard material. This low-plasticity material is highly susceptible to defects such as edge cracking, wrinkling, or uneven thickness during the subsequent stamping and forming of the battery casing, severely impacting yield and battery safety.

[0004] To alleviate this contradiction, the commonly used process in existing technologies involves introducing an "intermediate annealing" step during cold rolling. The typical process flow is: hot rolling → cold rolling (to achieve a certain deformation) → intermediate annealing → further cold rolling / foil rolling to the finished product. The purpose of intermediate annealing is to eliminate the internal stress and work hardening effects accumulated during the initial cold rolling process through recrystallization, restoring the material's plasticity so that it can withstand subsequent rolling with large deformations without cracking. However, this traditional process route has several inherent and insurmountable drawbacks:

[0005] First, there is a significant increase in production efficiency and energy costs. The intermediate annealing process typically requires holding at hundreds of degrees Celsius for several hours, which not only greatly extends the entire production cycle and reduces production efficiency, but also consumes a large amount of electricity or gas, directly driving up the manufacturing cost of the product. This contradicts the overall trend of cost reduction and efficiency improvement in the new energy vehicle industry.

[0006] Secondly, there are challenges in product quality control. The intermediate annealing process is a dynamic recrystallization and grain growth process. Even slight deviations in process parameters (such as temperature, time, and atmosphere) can easily lead to uneven grain structure, abnormal growth, or the formation of coarse grains. This uneven structure directly results in fluctuations in the mechanical properties of the final product, poor sheet shape, and even "orange peel" surface defects in subsequent processing, severely affecting the product's appearance and consistency. Furthermore, surface oxidation during annealing requires additional surface treatment, increasing process complexity.

[0007] Furthermore, from the perspective of material properties, intermediate annealing inevitably "sacrifices" the strength accumulated in the previous cold rolling processes while restoring plasticity. This is essentially a roundabout path of "strengthening first, then softening, and then strengthening again," resulting in a microstructure that is a mixture of multiple "fracture-recovery" processes when the final product reaches the target strength. Its strength potential is often not optimally tapped, and the combination of strength and plasticity (strength-plasticity product) has a ceiling.

[0008] Furthermore, with the continuous improvement of power battery energy density and the extreme pursuit of lightweight battery packs, the thickness of battery casing covers is trending towards thinner dimensions (e.g., below 15μm). This places almost stringent requirements on the uniformity of foil thickness, the fineness and uniformity of microstructure, and the consistency of longitudinal and transverse properties. Any minute structural inhomogeneity or performance fluctuations will be amplified at such a thin scale, thus affecting the stamping quality and the long-term reliability of the battery. Traditional process routes involving intermediate annealing, due to the inherent uncontrollability of heat treatment, are increasingly inadequate in meeting these high-end, thin-specification demands.

[0009] Therefore, there is an urgent need in this field for an innovative technological solution that can directly produce 1060 series aluminum alloy foils with high strength (meeting H18 temper requirements), high elongation, and high microstructure uniformity without relying on intermediate annealing processes, through process optimization and innovation. Such a technological breakthrough will fundamentally solve the high cost, low efficiency, and performance bottlenecks of traditional processes, providing crucial material support for cost reduction, efficiency improvement, and reliability enhancement in high-performance power batteries. This is both an urgent need for the development of the power battery industry chain and an important direction for the evolution of aluminum processing technology. The present invention arose precisely from this profound technological background and industrial demand. Summary of the Invention

[0010] The purpose of this invention is to overcome the shortcomings of the prior art and provide a high-strength, high-elongation 1060H18 aluminum alloy foil for power batteries and its preparation method.

[0011] The objective of this invention is achieved through the following technical solution:

[0012] A method for preparing high-strength, high-elongation 1060H18 aluminum alloy foil for power batteries, wherein the composition of the aluminum alloy foil, by mass percentage, includes: Fe: 0.15%–0.20%, Cu: 0.010%–0.016%, Ti: 0.025%–0.030%, Si≤0.08%, Al≥99.60%, with the balance being unavoidable impurities;

[0013] The preparation method includes the following steps:

[0014] a) Smelting and casting: Smelting is carried out according to the above composition. After the melt is filtered, Ti3B wire is added to refine the grains and then cast to obtain an ingot.

[0015] b) Milling and ingot heating: Mill the surface of the ingot from step a), and then heat it at 380-460°C for 6-24 hours;

[0016] c) Warm rolling: The heated ingot is warm rolled, and the warm rolling process includes multiple rolling passes; the starting temperature of the warm rolling is the ingot heating temperature in step b), and the temperature of the final pass is controlled at 260-280℃.

[0017] d) Cold rolling and foil rolling: After the warm rolled coil is cold rolled to an intermediate thickness, it is directly foil rolled without any intermediate annealing to a finished thickness of 10-15μm.

[0018] Furthermore, in step c), the final pass temperature is actively adjusted by controlling the rolling speed in stages, specifically including:

[0019] In the early and middle passes of warm rolling, a rolling speed of 1.4 m / s to 2.0 m / s is used to delay the temperature drop by utilizing deformation heat.

[0020] In the later passes of warm rolling, the rolling speed is reduced to 0.8–1.2 m / s, and the interval between passes is extended to enhance heat dissipation, thereby forcing the final rolling temperature to be precisely controlled within the target range of 260–280°C.

[0021] Furthermore, the total number of passes in the warm rolling process is 24 to 26, with specific pass control as follows:

[0022] In the first and second passes, the deformation is 2% to 3%, the rolling speed is 1.4 to 1.6 m / s, and the cumulative ingot thickness is rolled to 24 to 26 mm;

[0023] For passes 3 to 17, the deformation is 4% to 21%, and the rolling speed is 1.8 to 2.0 m / s;

[0024] For passes 18 to 21, the deformation is 22%–34%, and the rolling speed is 0.8–1.2 m / s.

[0025] From the 22nd to the final pass, the intermediate billet is rolled to an exit thickness of 4 mm at a rolling speed of 0.8–1.2 m / s.

[0026] Further, in step d), the cold rolling step is: rolling the warm-rolled coil to an intermediate thickness of 0.18-0.22 mm in two passes.

[0027] Furthermore, the foil rolling process employs a three-stage foil rolling mill consisting of roughing, intermediate, and finishing mills.

[0028] Rough rolling: inlet thickness: 0.18~0.22mm, outlet thickness: 0.05mm, deformation 70%~80%, speed 700~750m / min;

[0029] Intermediate rolling mill: inlet thickness: 0.05mm, outlet thickness: 0.02mm, deformation 55%~65%, speed 800~880m / min;

[0030] Finishing rolling: entrance thickness: 0.02 mm, exit thickness: 10-15 μm, deformation: 25%-50%, speed: 950-1100 m / min.

[0031] This invention provides an aluminum alloy foil prepared by the above-described preparation method.

[0032] Due to the adoption of the above technical solution, the beneficial effects of the present invention are as follows:

[0033] The 1060H18 aluminum alloy foil prepared by this invention successfully achieves an excellent combination of high strength and high elongation. Through precise alloy composition design and innovative preparation process, the tensile strength of the finished product is stable at over 220MPa, while the elongation is between 3.47% and 3.81%, fully meeting the stringent requirements of power battery casing cover plates for material mechanical properties.

[0034] The key to achieving the aforementioned performance and successfully eliminating the "intermediate annealing" process lies in the innovative warm rolling process. This process, through staged variable-speed rolling and precise control of the final rolling temperature at 260-280℃, enables the material to obtain a uniform and stable work-hardened structure and refined grains after warm rolling. It is this optimized microstructure that allows the coil material to directly enter subsequent cold rolling and foil rolling without the traditionally necessary intermediate annealing, thus laying the technological foundation for the anneal-free process.

[0035] "No intermediate annealing" directly brings significant technical and economic benefits. It not only greatly shortens the production cycle and reduces energy consumption and costs, but more importantly, it completely preserves the work hardening effect accumulated during warm rolling and avoids material softening caused by annealing, thus directly achieving high strength in the final product.

[0036] While achieving high strength and elongation, the method of this invention also endows the material with excellent electrical conductivity, all exceeding 60% IACS. This is also due to the pure alloy composition and the uniform microstructure obtained by warm rolling and subsequent rolling, ensuring that the product meets the good conductivity requirements of power batteries.

[0037] In summary, this invention, through the synergy of composition and the entire process, particularly with the core of a precisely controlled warm rolling process, successfully replaces traditional intermediate annealing, achieving a balance between performance and efficiency. The aluminum alloy foil prepared by this invention exhibits stable overall performance and high reliability, fully meeting and even exceeding the high performance requirements of new energy vehicle power batteries. Attached Figure Description

[0038] Figure 1 This is a metallographic image of the microstructure of the 1060H18 aluminum alloy foil prepared in Example 1 of this invention. Detailed Implementation

[0039] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] Example 1

[0041] Aluminum alloy composition (mass percentage): Fe: 0.15%, Cu: 0.010%, Ti: 0.025%, Si: 0.05%, Al: 99.60%, balance being unavoidable impurities;

[0042] Preparation steps:

[0043] a) Smelting and casting: Smelting is carried out according to the above composition, and the hydrogen content of the melt is controlled at 0.10ml / 100gAl. After two-stage filtration (plate filter + RB-level tubular filter), MQP super Ti3B wire (0.6kg / ton of aluminum) is added to refine the grains. The ingot is obtained by DC casting method.

[0044] b) Milling and ingot heating: Mill the ingot from the lowest point, with 15mm milled on each of the top and bottom surfaces. Do not mill the sides. Heat the milled ingot at 380℃ for 24 hours.

[0045] c) Warm rolling: Total number of passes: 24; Starting temperature for warm rolling: 380℃; Specific pass control:

[0046] Passes 1 to 2: Deformation amount 2%, rolling speed 1.4m / s, cumulatively rolling the ingot thickness to 24mm;

[0047] Passes 3 to 17: Deformation amount 4% to 21% (specifically 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 16%, 18%, 20%, 21%), rolling speed 1.8m / s;

[0048] Passes 18 to 21: Deformation amount 22%–34% (specifically 22%, 26%, 30%, 34% respectively), rolling speed 0.8 m / s;

[0049] Passes 22 to 24: Roll the intermediate billet to an exit thickness of 4 mm at a rolling speed of 0.8 m / s; the temperature of the final pass is controlled at 260℃.

[0050] d) Cold rolling and foil rolling: The warm-rolled coil is cold-rolled twice to an intermediate thickness of 0.18mm, without any intermediate annealing, and then directly subjected to foil rolling.

[0051] Rough rolling: inlet thickness: 0.18 mm, outlet thickness: 0.05 mm, deformation: 72.2%, speed: 750 m / min;

[0052] Intermediate rolling mill: inlet thickness: 0.05mm, outlet thickness: 0.02mm, deformation amount: 60%, speed: 850m / min;

[0053] Finishing rolling: Inlet thickness: 0.02 mm, outlet thickness: 10 μm, deformation amount: 50%, speed: 950 m / min.

[0054] Figure 1 This is a metallographic image of the microstructure of the 1060H18 aluminum alloy foil prepared by the method described in Example 1. Figure 1 As can be seen, through the specific composition design and warm rolling process of this invention, the material obtains a uniform and fine equiaxed grain structure with a narrow grain size distribution range and no obvious coarse grains or textured banded structures. This excellent microstructure is the fundamental reason why this invention achieves high strength, high elongation, and stable performance, and it also intuitively proves that the warm rolling process of this invention successfully achieves the effects of grain refinement and microstructure homogenization while replacing traditional intermediate annealing.

[0055] Example 2

[0056] Aluminum alloy composition (mass percentage): Fe: 0.18%, Cu: 0.013%, Ti: 0.028%, Si: 0.06%, Al: 99.65%, balance being unavoidable impurities;

[0057] Preparation steps:

[0058] a) Smelting and casting: Smelting is carried out according to the above composition, and the hydrogen content of the melt is controlled at 0.10ml / 100gAl. After two-stage filtration (plate filter + RB-level tubular filter), MQP super Ti3B wire (0.6kg / ton of aluminum) is added to refine the grains. The ingot is obtained by DC casting method.

[0059] b) Milling and ingot heating: Mill the ingot from the lowest point, with 15mm milled on each of the top and bottom surfaces. Do not mill the sides. Heat the milled ingot at 400℃ for 18 hours.

[0060] c) Warm rolling: Total number of passes: 24; Starting temperature for warm rolling: 400℃; Specific pass control:

[0061] Passes 1 to 2: Deformation amount 2.5%, rolling speed 1.5m / s, cumulatively rolling the ingot thickness to 25mm;

[0062] Passes 3 to 17: Deformation amount 4% to 21% (specifically 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 15%, 17%, 19%, 20%, 21%), rolling speed 1.9 m / s;

[0063] Passes 18 to 21: Deformation amount 22%–34% (specifically 22%, 26%, 30%, 34% respectively), rolling speed 1.0 m / s;

[0064] Passes 22 to 24: Roll the intermediate billet to an exit thickness of 4 mm at a rolling speed of 1.0 m / s; the temperature of the final pass is controlled at 270℃.

[0065] d) Cold rolling and foil rolling: The warm-rolled coil is cold-rolled twice to an intermediate thickness of 0.20mm, without any intermediate annealing, and then directly subjected to foil rolling.

[0066] Rough rolling: inlet thickness: 0.20 mm, outlet thickness: 0.05 mm, deformation: 75%, speed: 700 m / min;

[0067] Intermediate rolling mill: inlet thickness: 0.05mm, outlet thickness: 0.02mm, deformation amount: 60%, speed: 800m / min;

[0068] Finishing rolling: inlet thickness: 0.02 mm, outlet thickness: 12 μm, deformation amount: 40%, speed: 1000 m / min.

[0069] Example 3

[0070] Aluminum alloy composition (mass percentage): Fe: 0.20%, Cu: 0.016%, Ti: 0.030%, Si: 0.08%, Al: 99.60%, balance being unavoidable impurities;

[0071] Preparation steps:

[0072] a) Smelting and casting: Smelting is carried out according to the above composition, and the hydrogen content of the melt is controlled at 0.10ml / 100gAl. After two-stage filtration (plate filter + RB-level tubular filter), MQP super Ti3B wire (0.6kg / ton of aluminum) is added to refine the grains. The ingot is obtained by DC casting method.

[0073] b) Milling and ingot heating: Mill the ingot from the lowest point, with 15mm milled on each of the top and bottom surfaces, without side milling. Then heat the milled ingot at 460℃ for 6 hours.

[0074] c) Warm rolling: Total number of passes: 26; Starting temperature for warm rolling: 460℃; Specific pass control:

[0075] Passes 1 to 2: Deformation amount 3%, rolling speed 1.6m / s, cumulatively rolling the ingot thickness to 26mm;

[0076] Passes 3 to 17: Deformation amount 4% to 21% (specifically 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 14%, 16%, 17%, 18%, 19%, 21%), rolling speed 2.0 m / s;

[0077] Passes 18 to 21: Deformation amount 22%–34% (specifically 22%, 26%, 30%, 34% respectively), rolling speed 1.2 m / s;

[0078] Passes 22 to 26: Roll the intermediate billet to an exit thickness of 4 mm at a rolling speed of 1.2 m / s; the temperature of the final pass is controlled at 280℃.

[0079] d) Cold rolling and foil rolling: The warm-rolled coil is cold-rolled twice to an intermediate thickness of 0.22mm, without any intermediate annealing, and then directly subjected to foil rolling.

[0080] Rough rolling: inlet thickness: 0.22mm, outlet thickness: 0.05mm, deformation: 77.3%, speed: 750m / min;

[0081] Intermediate rolling mill: inlet thickness: 0.05mm, outlet thickness: 0.02mm, deformation amount: 60%, speed: 850m / min;

[0082] Finishing rolling: inlet thickness: 0.02 mm, outlet thickness: 15 μm, deformation amount: 25%, speed: 950 m / min.

[0083] Example 4

[0084] Aluminum alloy composition (mass percentage): Fe: 0.16%, Cu: 0.012%, Ti: 0.026%, Si: 0.04%, Al: 99.70%, balance being unavoidable impurities;

[0085] Preparation steps:

[0086] a) Smelting and casting: Smelting is carried out according to the above composition, and the hydrogen content of the melt is controlled at 0.10ml / 100gAl. After two-stage filtration (plate filter + RB-level tubular filter), MQP super Ti3B wire (0.6kg / ton of aluminum) is added to refine the grains. The ingot is obtained by DC casting method.

[0087] b) Milling and ingot heating: Mill the ingot from the lowest point, with a milling amount of 15mm on each of the top and bottom surfaces. Do not mill the sides. Heat the milled ingot at 420℃ for 12 hours.

[0088] c) Warm rolling: Total number of passes: 25; Starting temperature for warm rolling: 420℃; Specific pass control:

[0089] Passes 1 to 2: Deformation amount 2%, rolling speed 1.4m / s, cumulatively rolling the ingot thickness to 25mm;

[0090] Passes 3 to 17: Deformation amount 4% to 21% (specifically 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 16%, 18%, 20%, 21%), rolling speed 1.8m / s;

[0091] Passes 18 to 21: Deformation amount 22%–34% (specifically 22%, 26%, 30%, 34% respectively), rolling speed 0.9 m / s;

[0092] Passes 22 to 25: Roll the intermediate billet to an exit thickness of 4 mm at a rolling speed of 0.9 m / s; the temperature of the final pass is controlled at 265℃.

[0093] d) Cold rolling and foil rolling: The warm-rolled coil is cold-rolled twice to an intermediate thickness of 0.19mm, without any intermediate annealing, and then directly subjected to foil rolling.

[0094] Rough rolling: inlet thickness: 0.19 mm, outlet thickness: 0.05 mm, deformation: 73.7%, speed: 700 m / min;

[0095] Intermediate rolling mill: inlet thickness: 0.05mm, outlet thickness: 0.02mm, deformation amount: 60%, speed: 850m / min;

[0096] Finishing rolling: inlet thickness: 0.02 mm, outlet thickness: 11 μm, deformation amount: 45%, speed: 1000 m / min.

[0097] Example 5

[0098] Aluminum alloy composition (mass percentage): Fe: 0.19%, Cu: 0.015%, Ti: 0.029%, Si: 0.07%, Al: 99.65%, balance being unavoidable impurities;

[0099] Preparation steps:

[0100] a) Smelting and casting: Smelting is carried out according to the above composition, and the hydrogen content of the melt is controlled at 0.10ml / 100gAl. After two-stage filtration (plate filter + RB-level tubular filter), MQP super Ti3B wire (0.6kg / ton of aluminum) is added to refine the grains. The ingot is obtained by DC casting method.

[0101] b) Milling and ingot heating: Mill the ingot from the lowest point, with a milling amount of 15mm on each of the top and bottom surfaces. Do not mill the sides. Heat the milled ingot at 440℃ for 10 hours.

[0102] c) Warm rolling: Total number of passes: 24; Starting temperature for warm rolling: 440℃; Specific pass control:

[0103] Passes 1 to 2: Deformation amount 2.5%, rolling speed 1.5m / s, cumulatively rolling the ingot thickness to 25mm;

[0104] Passes 3 to 17: Deformation amount 4% to 21% (specifically 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 15%, 17%, 19%, 20%, 21%), rolling speed 1.9 m / s;

[0105] Passes 18 to 21: Deformation amount 22%–34% (specifically 22%, 26%, 30%, 34% respectively), rolling speed 1.1 m / s;

[0106] Passes 22 to 24: Roll the intermediate billet to an exit thickness of 4 mm at a rolling speed of 1.1 m / s; the temperature of the final pass is controlled at 275℃.

[0107] d) Cold rolling and foil rolling: The warm-rolled coil is cold-rolled twice to an intermediate thickness of 0.21mm, without any intermediate annealing, and then directly subjected to foil rolling.

[0108] Rough rolling: inlet thickness: 0.21 mm, outlet thickness: 0.05 mm, deformation: 76.2%, speed: 710 m / min;

[0109] Intermediate rolling mill: inlet thickness: 0.05mm, outlet thickness: 0.02mm, deformation amount: 60%, speed: 880m / min;

[0110] Finishing rolling: inlet thickness: 0.02 mm, outlet thickness: 13 μm, deformation amount: 35%, speed: 1100 m / min.

[0111] To illustrate the technical effects of the present invention, the inventors have provided the following comparative examples:

[0112] Comparative Example 1: Changing the starting temperature of warm rolling

[0113] Change point: Change the starting temperature of warm rolling from 380℃ to 470℃ (too high temperature).

[0114] Detailed parameters:

[0115] Aluminum alloy composition: Same as in Example 1.

[0116] Smelting and casting: Same as in Example 1.

[0117] Sawing and milling and ingot heating: The ingot is heated at 470°C for 24 hours (instead of 380°C).

[0118] Warm rolling: Total 24 passes; initial temperature 470℃; pass control same as in Example 1 (passes 1-2: deformation 2%, speed 1.4m / s; passes 3-17: deformation 4%-21%, speed 1.8m / s; passes 18-21: deformation 22%-34%, speed 0.8m / s; passes 22-24: rolling to 4mm, speed 0.8m / s). Final pass temperature controlled at 260℃.

[0119] Cold rolling and foil rolling: Same as Example 1.

[0120] Results: Due to the excessively high initial temperature, the ingot underwent grain coarsening during heating. The excessively high recrystallization temperature during warm rolling resulted in uneven grain size, decreased mechanical properties (strength), and oxide scale and hot cracks on the surface of the final foil.

[0121] Comparative Example 2: Changing the deformation distribution of each pass (uniform deformation)

[0122] Change: The deformation amount per pass in the warm rolling process is changed to a uniform distribution instead of the incremental distribution in Example 1.

[0123] Detailed parameters:

[0124] Aluminum alloy composition: Same as in Example 1.

[0125] Smelting and casting: Same as in Example 1.

[0126] Sawing and milling and ingot heating: Same as Example 1 (heating at 380℃ for 24 hours).

[0127] Warm rolling: a total of 24 passes; initial temperature of 380℃; uniform deformation in all passes (10% deformation per pass), and a constant rolling speed of 1.8m / s (ignoring speed variations). The final pass temperature is controlled at 260℃.

[0128] Cold rolling and foil rolling: Same as Example 1.

[0129] Results: The uniform deformation amount could not effectively control the synergy between work hardening and recrystallization, leading to stress concentration within the material, uneven grain structure after warm rolling, and cracks and edge cracking during cold rolling. The foil produced after foil rolling exhibited poor thickness uniformity and reduced elongation.

[0130] Comparative Example 3: Changing the rolling speed (constant high speed)

[0131] Change: Change the rolling speed of the warm rolling to a constant high speed instead of the variable speed control in Example 1.

[0132] Detailed parameters:

[0133] Aluminum alloy composition: Same as in Example 1.

[0134] Smelting and casting: Same as in Example 1.

[0135] Sawing and milling and ingot heating: Same as Example 1 (heating at 380℃ for 24 hours).

[0136] Warm rolling: a total of 24 passes; initial temperature of 380℃; all passes use a constant rolling speed of 1.8m / s (high speed), and the deformation distribution is the same as in Example 1. The temperature of the final pass is controlled at 260℃.

[0137] Cold rolling and foil rolling: Same as Example 1.

[0138] Results: Constant high-speed rolling led to excessive heat accumulation during deformation, and temperature runaway during warm rolling (exceeding 300℃), causing excessive dynamic recrystallization and grain coarsening. Ultimately, the strength and toughness of the foil were mismatched, and the surface quality deteriorated (pitting and warping appeared).

[0139] Comparative Example 4: Changing the final pass temperature (too high temperature)

[0140] Change: Change the final pass temperature of the warm rolling from 260°C to 300°C (too high temperature), and the other steps are the same as in Example 1.

[0141] Detailed parameters:

[0142] Aluminum alloy composition: Same as in Example 1.

[0143] Smelting and casting: Same as in Example 1.

[0144] Sawing and milling and ingot heating: Same as Example 1 (heating at 380℃ for 24 hours).

[0145] Warm rolling: Total number of passes: 24; starting temperature: 380℃; pass control is the same as in Example 1. However, the final pass temperature is controlled at 300℃ (achieved by adjusting the cooling or pass interval).

[0146] Cold rolling and foil rolling: Same as Example 1.

[0147] Result: The excessively high temperature of the final pass caused the material to be above the recrystallization temperature at the end of the warm rolling process. Grains continued to grow before cold rolling, resulting in insufficient work hardening during cold rolling and foil rolling. As a result, the foil material had low strength and poor plasticity, and the foil strip broke during foil rolling.

[0148] Comparative Example 5: Using conventional hot rolling instead of warm rolling

[0149] Changes: Completely omit warm rolling, adopt traditional hot rolling processes (such as high-temperature rolling), and then directly cold roll.

[0150] Detailed parameters:

[0151] Aluminum alloy composition: Same as in Example 1.

[0152] Smelting and casting: Same as in Example 1.

[0153] Sawing and milling and ingot heating: The ingot is heated at 500℃ for 12 hours (typical hot rolling process).

[0154] Hot rolling: Hot rolling is carried out at 500℃, with a total of 15 passes, rolling from the ingot thickness to 4mm, with uniform deformation distribution (12% per pass), and a constant rolling speed of 1.5m / s. The final hot rolling temperature is approximately 350℃.

[0155] Cold rolling and foil rolling: Same as Example 1 (directly cold rolled to 0.18 mm, then foil rolled).

[0156] Results: Traditional hot rolling at high temperatures leads to coarse grains and severe surface oxidation, resulting in the loss of the fine grain effect of warm rolling. After cold rolling, residual stress remains inside the material, making it prone to thickness fluctuations and surface defects during foil rolling. Ultimately, the mechanical properties of the foil (such as fatigue strength) are significantly lower than those in Example 1.

[0157] Experimental Example

[0158] Performance testing

[0159] Tensile strength: Tested using a universal testing machine according to GB / T 228.1—2021 standard, with a specimen size of [missing information] and a tensile speed of 5 mm / min;

[0160] Elongation: Same as the above standard, test the elongation at break of the specimen;

[0161] Conductivity: Tested according to GB / T 3048.2-2007 standard using an eddy current conductivity meter (model: SigmaTest 2.0) at a test frequency of 60kHz.

[0162] The performance test results of all embodiments and comparative examples are shown in Table 1:

[0163] Table 1 Comparison of Performance Test Results

[0164]

[0165] The performance test results clearly show that the overall performance of Examples 1 to 5 of the present invention is significantly better than that of all comparative examples. The tensile strength of the examples is consistently between 223.7 and 236.4 MPa, the elongation is between 3.47% and 3.81%, and the electrical conductivity remains above 60.2% IACS. This excellent performance is fundamentally due to the synergistic effect of a series of optimized warm rolling process parameters in the examples.

[0166] A detailed analysis of the reasons for the performance degradation in each comparative example reveals that every modification deviating from the core process of this invention leads to serious consequences. Comparative Example 1, due to its excessively high initial warm rolling temperature, experienced grain coarsening, thereby impairing its strength, plasticity, and electrical conductivity. Comparative Example 2, employing uniform deformation instead of incremental deformation, resulted in stress concentration and increased defects within the material, similarly causing a decline in various performance indicators. Comparative Example 3, using constant high-speed rolling, led to heat accumulation during deformation and temperature runaway, causing grain coarsening and severely impacting the material's toughness and strength. Comparative Example 4, with its excessively high final pass temperature, caused recrystallization and grain growth at the end of processing, weakening the work hardening effect and resulting in one of the weakest strengths among the comparisons. The most typical comparative example, Comparative Example 5, completely abandoned warm rolling and adopted traditional hot rolling. Its high-temperature process caused the most severe grain coarsening and structural defects, resulting in the lowest tensile strength, elongation, and electrical conductivity among all groups. This, conversely, fully demonstrates the necessity and inventiveness of the "warm rolling" process used in this invention.

[0167] In summary, the key to the success of this invention lies in the precise control of the warm rolling process, including a complete set of parameters such as the initial temperature, the distribution of deformation per pass, the rolling speed, and the final pass temperature. Deviation from any single parameter will disrupt the balance between work hardening and recrystallization, leading to microstructural deterioration and performance degradation. Therefore, it is through this innovative, parameter-coordinated warm rolling technology that high-performance aluminum alloy foils possessing both high strength and good electrical conductivity have been successfully prepared.

[0168] The above description is a detailed description of the preferred embodiments of the present invention. However, the embodiments are not intended to limit the scope of the patent application of the present invention. All equivalent changes or modifications made under the technical spirit of the present invention should fall within the patent scope covered by the present invention.

Claims

1. A method for preparing high-strength, high-elongation 1060H18 aluminum alloy foil for power batteries, characterized in that, The aluminum alloy foil comprises, by mass percentage: Fe: 0.15%–0.20%, Cu: 0.010%–0.016%, Ti: 0.025%–0.030%, Si≤0.08%, Al≥99.60%, with the balance being unavoidable impurities; The preparation method includes the following steps: a) Smelting and casting: Smelting is carried out according to the above composition. After the melt is filtered, Ti3B wire is added to refine the grains and then cast to obtain an ingot. b) Milling and ingot heating: Mill the surface of the ingot from step a), and then heat it at 380-460°C for 6-24 hours; c) Warm rolling: The heated ingot is warm rolled, and the warm rolling process includes multiple rolling passes; the starting temperature of the warm rolling is the ingot heating temperature in step b), and the temperature of the final pass is controlled at 260-280℃; the temperature of the final pass is actively adjusted by controlling the rolling speed in stages, specifically including: the total number of passes in the warm rolling process is 24-26, and the specific pass control is: for the first and second passes, the deformation is 2%-3%, and the rolling speed is 1.4-1. The rolling speed is 6 m / s, gradually rolling the ingot to a thickness of 24–26 mm; from the 3rd to the 17th pass, the deformation is 4%–21%, with the deformation increasing in each pass, and the rolling speed is 1.8–2.0 m / s; from the 18th to the 21st pass, the deformation is 22%–34%, with the deformation increasing in each pass, and the rolling speed is 0.8–1.2 m / s; from the 22nd to the final pass, the intermediate billet is rolled to an exit thickness of 4 mm, with a rolling speed of 0.8–1.2 m / s. d) Cold rolling and foil rolling: After the warm-rolled coil is rolled to an intermediate thickness of 0.18-0.22 mm in two passes, it is directly rolled into foil without any intermediate annealing, and the finished thickness is 10-15 μm. The foil rolling adopts a three-stage foil rolling mill: roughing-intermediate rolling-finishing. Roughing: entrance thickness: 0.18-0.22 mm, exit thickness: 0.05 mm, deformation: 72.2%-77.3%, speed: 700-750 m / min; Intermediate rolling: entrance thickness: 0.05 mm, exit thickness: 0.02 mm, deformation: 60%, speed: 800-880 m / min; Finishing rolling: entrance thickness: 0.02 mm, exit thickness: 10-15 μm, deformation: 25%-50%, speed: 950-1100 m / min.

2. An aluminum alloy foil, characterized in that, It is prepared by the preparation method described in claim 1.

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