A process for casting, cold rolling and annealing an aluminum alloy foil

Abstract

This invention discloses a casting, cold rolling, and annealing process for aluminum alloy foil. By controlling the Cu and V content in the melt to extremely low levels and adjusting the ratio of Mg, Na, and Ca, these elements are directionally segregated on the surface of the cast-rolled sheet during the subsequent casting and annealing process at 300-450℃, forming an easily removable segregated layer. The sheet is then mechanically polished to remove the segregated layer, and the cleaned sheet is cold-rolled with a total reduction of not less than 94.7%, controlling the parameters of the final pass to create a deformation energy storage gradient in the foil blank. Finally, a two-stage annealing process is used: first, holding at 150-190℃ to promote recovery and dispersion precipitation, then raising the temperature to 240-260℃ to complete recrystallization and microstructure homogenization. This invention effectively maintains a high strength level while improving the foil elongation, making it suitable for aluminum foil production with high requirements for comprehensive performance.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy foil production and processing, specifically to a casting, cold rolling and annealing process for aluminum alloy foil. Background Technology

[0002] Aluminum alloy foil is one of the base materials used in industries such as packaging and electronics. Among them, 8079 alloy, as a typical aluminum-iron-silicon alloy, relies mainly on cold rolling work hardening and the dispersed intermetallic compounds formed by Fe / Si elements for its strength. Therefore, it has good work hardening ability, strength, barrier properties, and economy, and is widely used.

[0003] Traditionally produced 8079 alloy foil achieves strength and pinhole resistance through large-deformation cold rolling, but its plasticity often becomes a bottleneck. While plasticity is restored during subsequent full annealing, strength decreases simultaneously, resulting in elongation typically only within the 2%-5% range, making it difficult to achieve an ideal balance between strength and plasticity. This makes the material unsuitable for applications with increasingly demanding processing and forming requirements.

[0004] International patent application WO2025 / 160047A1 discloses a 3xxx series aluminum alloy for food packaging can lids and its preparation method. By adjusting the content of main alloying elements such as Mn and Mg, and using a final annealing process at about 255°C, a combination of strength and formability suitable for can lids is obtained.

[0005] Given that the 8079 series is a non-heat-treatable strengthening alloy, its performance regulation mainly relies on the control of cold rolling deformation and annealing processes. This is different from the 3xxx series alloys, which can be fine-tuned by precipitation strengthening in terms of strengthening mechanism and process window. Specifically, the strengthening second phase of 3xxx series aluminum alloys is a dispersed Mn phase, while that of 8079 is a coarser Al-Fe-Si phase. This leads to differences in work hardening behavior, recrystallization kinetics, and texture evolution between the two.

[0006] Therefore, how to control the recovery and recrystallization process of 8079 series alloys under the constraint of non-heat-treatable strengthening, so as to ultimately improve the elongation and maintain a high strength level as much as possible, has not yet been effectively solved. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings shown in the background art and to improve the 8079 series aluminum alloy.

[0008] To achieve the above objectives, the technical solution provided by the present invention is as follows.

[0009] A casting, cold rolling, and annealing process for aluminum alloy foil includes the following steps: S1. Provide aluminum alloy melt, refine the aluminum alloy melt and then cast it to obtain aluminum alloy ingot; S2. At room temperature, the aluminum alloy ingot is cast and rolled into a cast plate. After the temperature of the cast plate drops below 100°C, it is heated to 300-450°C for casting and annealing. The casting and annealing is held for 1-12 hours. The thickness of the cast plate is 7.0-7.5 mm. S3. The cast-rolled plate that has undergone casting and rolling annealing is subjected to multiple cold rolling passes to make the total reduction rate of the cast-rolled plate not less than 94.7% to obtain foil blank; S4. Place the foil blank in an environment of 240-260℃ for finished product annealing, and keep the finished product annealing at the temperature for 1-6 hours.

[0010] As a preferred technical solution, in S1, the aluminum alloy ingot, by mass percentage, includes Si, 0.15-0.25%; Fe, 0.70-0.90%; the balance being aluminum and unavoidable impurities, wherein V≤0.010% and Cu≤0.020%.

[0011] As a preferred technical solution, in S1, the aluminum alloy melt contains 0.005%-0.05% Mg by mass percentage, and the mass ratio of Na to Ca is 1.2-2.0, so that the Mg, Na, and Ca elements preferentially agglomerate in the sub-surface area of ​​the cast-rolled plate during the casting and rolling annealing process, forming an agglomeration layer.

[0012] As a preferred technical solution, in S1, the mass ratio of Fe to Si is ≥3.5.

[0013] As a preferred technical solution, after the casting and rolling annealing in S2, a surface treatment is further included, in which the casting and rolling plate is mechanically polished to remove a layer with a surface thickness of 5-30 μm, so as to remove the segregation layer.

[0014] As a preferred technical solution, in step S1, the refining operation includes: firstly, a mixture of argon and chlorine gas is introduced into the melt for rotary spray refining, wherein the chlorine gas fraction is 1-5%, and the refining time is 15-40 minutes; then, a refining agent containing Na3AlF6 and NaCl is added for covering and settling; after the melt stabilizes, it is allowed to stand for 20-60 minutes, and the time from the start of casting to the end of standing is controlled not to exceed 30 minutes.

[0015] As a preferred technical solution, the casting and rolling annealing process of S2 needs to control the heating rate to 30-80℃ / h, and a nitrogen protective atmosphere is introduced during the heat preservation stage above 350℃, wherein the nitrogen protective atmosphere contains chlorine gas with a volume fraction of 0.1%-0.5%.

[0016] As a preferred technical solution, in the cold rolling operation of S3, the reduction rate of the last three passes decreases in a gradient manner; and the reduction rate of the last pass does not exceed 10%, and the rolling speed of the last pass does not exceed 100m / min, forming a deformation energy storage gradient distribution that increases from the surface to the core in the thickness direction of the foil blank.

[0017] As a preferred technical solution, the S4 finished product annealing includes two sequential holding stages: in the first stage, the foil blank is heated to a first temperature at a rate of 1.0-5.0℃ / min and held at the first temperature for 0.5-2 hours; in the second stage, the foil blank is heated to a second temperature at a rate of 5.0-20.0℃ / min and held at the second temperature for 1-4 hours; the first temperature is 150-190℃ and the second temperature is 240-260℃.

[0018] As a preferred technical solution, the composition of the aluminum alloy melt in S1 satisfies the following condition: after the casting and rolling annealing process in S2 is completed, the sum of the mass fractions of Mg, Na, and Ca elements detected by instrument analysis in the subsurface of the cast and rolled plate within a depth range of 5-30 μm is at least 50% higher than that at the center position in the thickness direction of the cast and rolled plate.

[0019] The advantages and beneficial effects of this invention are as follows: The content of impurities such as copper and vanadium is controlled to extremely low levels, while the proportions of elements such as magnesium, sodium, and calcium are adjusted. These elements are then allowed to actively migrate and accumulate near the surface of the sheet during the subsequent casting, rolling, and annealing process. This impurity-rich surface layer can be directly removed through a single polishing process, effectively performing an additional refining of the material and thus improving the purity of the matrix. The sheet with a purified surface can withstand relatively intense cold rolling with reduced risk of cracking. This greater degree of deformation stores sufficient energy within the material, and through the final few rolling passes, a gradient of energy is created in the thickness direction of the sheet, gradually decreasing from the surface to the interior.

[0020] In terms of process route, this invention achieves component segregation through specific casting-rolling annealing; the clean surface obtained after polishing and delamination is beneficial for withstanding extremely high cold rolling deformation and avoids the expansion of surface defects under extreme deformation; simultaneously, by controlling the deformation energy storage gradient formed in the final cold rolling pass, combined with the staged annealing response, dislocation reorganization and possible dispersion phase precipitation are promoted, and recrystallization and microstructure homogenization are completed on this optimized matrix. This invention produces foils for non-heat-treatable aluminum alloys, which retain higher strength levels while possessing good plasticity, and can be adapted to the production of aluminum foils with higher requirements. Detailed Implementation

[0022] The terms “comprising” and “having”, and any variations thereof, used in this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such process, method, product, or apparatus.

[0023] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly or implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0024] This invention provides a casting, cold rolling, and annealing process for aluminum alloy foil, comprising the following steps: S1. Provide aluminum alloy melt, refine the aluminum alloy melt and then cast it to obtain aluminum alloy ingot; S2. At room temperature, the aluminum alloy ingot is cast and rolled into a cast plate. After the temperature of the cast plate drops below 100°C, it is heated to 300-450°C for casting and annealing. The casting and annealing is held for 1-12 hours. The thickness of the cast plate is 7.0-7.5 mm. S3. The cast-rolled plate that has undergone casting and rolling annealing is subjected to multiple cold rolling passes to make the total reduction rate of the cast-rolled plate not less than 94.7% to obtain foil blank; S4. Place the foil blank in an environment of 240-260℃ for finished product annealing, and keep the finished product annealing at the temperature for 1-6 hours.

[0025] This process is applicable to 8079 series aluminum alloys that cannot be strengthened by heat treatment. By controlling the composition, casting and rolling annealing and surface treatment, cold rolling control and gradient annealing, it solves the problem of difficulty in balancing strength and plasticity in traditional processes, and achieves the goal of maintaining a high strength level while improving the elongation of aluminum foil.

[0026] In some embodiments, the chemical composition of the aluminum alloy melt provided in step S1 needs to be strictly controlled, especially the restriction of impurity elements such as Cu and V. Specifically, the aluminum alloy ingot, by mass percentage, contains Si: 0.15-0.25%; Fe: 0.70-0.90%; Mg: 0.005%-0.05%, and the mass ratio of Na to Ca is controlled at 1.2-2.0; the remainder is aluminum and unavoidable impurities, of which V≤0.010% and Cu≤0.020%. The strengthening phase of the 8079 series alloy is mainly an Al-Fe-Si intermetallic compound. The mass ratio of Fe to Si is required to be ≥3.5 to ensure the formation of a sufficient quantity and appropriately sized dispersed phase.

[0027] Cu and V are prone to segregation, easily forming brittle phases at grain boundaries, reducing the material's plasticity and processing performance. Therefore, their content must be controlled at extremely low levels. The addition of trace amounts of Mg, Na, and Ca, unlike the solid solution strengthening used in 3XXX series aluminum alloys, primarily utilizes the low solid solubility and high diffusion coefficient of these elements in the aluminum matrix. During subsequent casting, rolling, and annealing processes, driven by thermodynamic forces, these elements migrate and accumulate to the surface and subsurface regions of the plate, forming an easily removable segregated layer.

[0028] In some embodiments, in order to achieve efficient purification of the melt and control the impurity content, the refining operation in S1 includes two stages: first, a mixture of argon and chlorine is introduced into the melt for rotary spray refining, wherein the chlorine gas fraction is 1-5% and the refining time is 15-40 minutes; then, a refining agent containing cryolite and NaCl is added for covering and settling, and after the melt stabilizes, it is allowed to stand for 20-60 minutes, and the total time from the start of pouring to the end of standing is controlled not to exceed 30 minutes.

[0029] Rotary jet refining utilizes the stirring effect of argon gas and the chemical reaction of chlorine gas with impurities such as hydrogen and alkali metals to effectively remove gases and some inclusions from the melt. A chlorine content below 1% results in insufficient impurity removal, while a content above 5% exacerbates equipment corrosion and increases environmental pressure. The subsequently added composite refining agent further adsorbs non-metallic inclusions such as oxides, and the resulting molten salt coating prevents secondary gas absorption and oxidation of the melt. Strict control of settling time and casting intervals aims to promote the full floating or sinking of inclusions while avoiding excessive temperature drop or macroscopic component segregation caused by prolonged melt residence.

[0030] Specifically, the mass ratio of cryolite to NaCl is 1:1, and the amount added is 0.02~0.05% of the melt mass.

[0031] In some embodiments, in S2, the refined melt is formed into a cast-rolled plate with a thickness of 7.0-7.5 mm using a casting and rolling machine. After casting and rolling, especially continuous casting and rolling, the plate temperature needs to be allowed to cool naturally to below 100°C before reheating for casting and rolling annealing. This annealing is carried out in the temperature range of 300-450°C and held for 1-12 hours.

[0032] Cast-roll annealing differs from homogenization annealing in that it is used to induce the directional segregation of elements such as Mg, Na, and Ca. Thermodynamically, the solid solubility of these elements in the aluminum matrix decreases sharply with decreasing temperature, and they also have lower interfacial energies at grain boundaries, phase boundaries, and free surfaces. Within the temperature range of 300-450℃, they acquire sufficient diffusion kinetic energy and migrate towards the free surface (and near-surface region) of the sheet material driven by concentration and chemical potential gradients. To control the uniformity and efficiency of the segregation process, the heating rate should be controlled between 30-80℃ / h. Too low a rate results in low production efficiency; too high a rate may lead to excessive temperature differences between the inside and outside of the sheet material, causing thermal stress or even cracking, while also resulting in insufficient element migration and an uneven segregated layer.

[0033] In some embodiments, to further optimize the annealing environment and protect the plate surface, during the S2 casting-rolling annealing process, when the temperature rises above 350°C, a nitrogen protective atmosphere containing 0.1%-0.5% chlorine by volume is introduced. The introduction of trace amounts of chlorine can react with residual active metals such as magnesium, further cleaning the plate surface; it can also slightly corrode the oxide film, exposing fresh aluminum substrate and providing more favorable interfacial conditions for the surface segregation of elements such as Mg, Na, and Ca. In addition, it suppresses severe oxidation of the plate surface at high temperatures.

[0034] In some embodiments, the composition design of the aluminum alloy melt in S1 must meet the following requirements: after the S2 casting and rolling annealing process, the sum of the mass fractions of Mg, Na, and Ca elements detectable at a depth of 5-30 μm on the subsurface of the cast-rolled plate, as analyzed by instruments such as electron probe microanalysis (EPMA) or glow discharge spectroscopy (GDOES), must be at least 50% higher than the content at the center of the cast-rolled plate in the thickness direction. This compositional gradient indicates that a large number of impurities and trace additives have been driven away and enriched in the subsurface layer, thus facilitating the purification of the aluminum matrix.

[0035] In some embodiments, after completing the casting and rolling annealing in S2, the casting and rolling plate is further mechanically polished to remove a layer with a surface thickness of 5-30 μm. This step removes the segregated layer rich in elements such as Mg, Na, and Ca formed during the aforementioned high-temperature annealing process. Typically, trace impurities or added elements in aluminum alloys tend to segregate at grain boundaries or defects during hot working. This segregation is often difficult to control and is diffusely distributed. Traditional processes can only mitigate its negative effects through extreme purification of the overall composition, but this is costly and has limited effectiveness.

[0036] This invention takes the opposite approach, actively guiding these elements to undergo high-intensity directional enrichment within a controllable subsurface depth, forming a sacrificial layer with a composition and structure different from the matrix. This segregated layer is essentially a high-impurity region, with mechanical properties and interfacial bonding strength far weaker than the pure matrix. Removing it through subsequent mechanical polishing is equivalent to a localized refining or surface purification of the board. This operation firstly improves the purity of the near-surface region of the board, eliminating surface brittleness or weak interfaces that may be caused by impurity segregation; secondly, it removes potential surface defects, resulting in a clean, homogeneous surface with superior mechanical properties.

[0037] Most importantly, this purified surface can withstand subsequent extreme cold rolling deformation, reducing the risk of surface crack initiation and propagation under high strain. Without this step, the segregated layer is very likely to become a crack source in subsequent large deformation cold rolling, leading to rolling failure or an increased product defect rate.

[0038] In some embodiments, after mechanical polishing, given the good atmospheric corrosion resistance of aluminum and its alloys and the immediate commencement of subsequent cold rolling, no special passivation treatment is required to avoid introducing additional process steps or coatings that may adversely affect subsequent rolling. The natural oxide film that forms on the surface of the sheet during short turnover periods is sufficient to provide the necessary short-term corrosion protection. If the workshop environment has extremely high humidity or the turnover time is long, simple protection can be achieved by purging with dry air or low-humidity nitrogen.

[0039] In some embodiments, the cold rolling operation of S3 requires multiple passes of rolling the surface-treated cast-rolled sheet, with a total reduction rate of not less than 94.7%. For example, a 7.2 mm thick cast-rolled sheet can be rolled through multiple passes such as primary rolling and intermediate rolling to a foil blank thickness of approximately 220 μm. The relatively high plastic deformation rate allows for the storage of high-density dislocations within the material, accumulating sufficient deformation energy to provide a driving force for recrystallization during subsequent annealing. The clean surface obtained after removing the segregation layer enables the sheet to withstand such extreme deformation without easily cracking, breaking through the surface quality control bottleneck of traditional processes under large deformation, thus benefiting aluminum foil rolling.

[0040] In some embodiments, to construct a specific, non-uniform microstructure in the foil blank to improve plasticity, the reduction rate of the last three passes in the S3 cold rolling operation needs to decrease gradually, with the reduction rate of the last pass not exceeding 10% and the rolling speed not exceeding 100 m / min. In the later stages of cold rolling, as the sheet thins, deformation becomes increasingly difficult. By designing a decreasing reduction rate in the last few passes (e.g., the reduction rates of the last three passes being 25%, 15%, and 8%, respectively), the increase in strain experienced by the material on the surface of the sheet gradually decreases in each pass, ultimately resulting in a lower cumulative strain and dislocation density on the surface compared to the core. The core material, having experienced greater overall strain in the earlier and middle passes, maintains a higher level of dislocation density and stored deformation energy. Therefore, a continuous gradient distribution of increasing deformation energy (mainly contributed by dislocation density) is formed from the surface to the core. The construction of this gradient structure provides a driving force distribution for recrystallization in subsequent heat treatment.

[0041] An exemplary four-pass aluminum foil finishing process can be set as follows: the entry roll gap (or billet thickness) is successively 220μm, 105μm, 45μm, and 20μm, with the final exit thickness controlled at 13-15μm. This is for illustrative purposes; in actual implementation, rolling pressure and speed can be configured according to existing technologies. Based on the above control of the cast-rolled plate, the fixed and reinforced gradient energy storage structure of this invention avoids energy storage homogenization caused by over-rolling. The construction of the energy storage gradient allows a single material to possess different microstructure evolution potentials in the thickness direction.

[0042] In some embodiments, the finished product annealing of S4 includes two sequential holding stages: In the first stage, the foil blank is heated to 150-190°C at a rate of 1.0-5.0°C / min and held at this temperature for 0.5-2 hours; in the second stage, it is subsequently heated to 240-260°C at a rate of 5.0-20.0°C / min and held for 1-4 hours. This two-stage annealing process is a responsive heat treatment for the aforementioned blank characteristics, utilizing temperature and time control to stepwise regulate the recovery, precipitation, and recrystallization processes. The first stage mainly involves recovery and low-temperature precipitation. At the lower temperature of 150-190°C, some dislocations inside the material (especially the high-energy-storage core) begin to rearrange and annihilate, forming a subcrystalline structure and releasing some elastic strain energy, but this is insufficient to trigger large-scale recrystallization nucleation. Simultaneously, this temperature range falls within the kinetic window for the precipitation of certain dispersed phases (such as α-Al(Fe,Mn)Si or β-AlFeSi) in Al-Fe-Si alloys. Fe and Si elements have sufficient time to diffuse, precipitating fine, dispersed intermetallic compound particles on existing dislocation lines or subgrain boundaries. These nanoscale precipitates effectively hinder further dislocation movement and rearrangement, stabilizing the substructure. In subsequent high-temperature stages, they strongly pin the migrating grain boundaries, inhibiting abnormal growth of recrystallized grains and promoting the acquisition of fine and uniform recrystallized grains. If the temperature or time in this stage is too high or too long, recrystallization nucleation may be prematurely triggered in local high-energy storage regions, disrupting the predetermined gradient energy storage distribution and leading to an inhomogeneous final structure. Conversely, if the temperature is too low or the time is too short, recovery is insufficient, resulting in an inadequate number and small size of precipitates, and a weak pinning effect.

[0043] The second stage completes recrystallization and microstructure homogenization. After heating to 240-260℃ at a relatively rapid rate, the recrystallization behavior of different regions within the material varies depending on their energy storage levels. The core region, with the highest deformation energy storage, reaches the critical energy condition required for recrystallization nucleation first, resulting in a large number of nuclei that grow rapidly, forming fine equiaxed recrystallized grains. In contrast, the surface region, due to its lower energy storage, has a weaker nucleation driving force and a lower nucleation rate, leading to a significantly delayed recrystallization process. It may only undergo complete recrystallization or retain some deformed structures. During the subsequent holding process, the recrystallized grains in the core gradually grow, while the recrystallization front may slowly advance towards the surface. By controlling the holding time, sufficient recrystallization and moderate grain growth in the core can be achieved, while sufficient recovery or partial recrystallization of the surface microstructure can occur, ultimately forming a gradient / composite microstructure with fine equiaxed recrystallized grains in the core and a recovered or relatively fine recrystallized grain structure on the surface.

[0044] The present invention will now be clearly and thoroughly described in conjunction with specific embodiments and comparative examples.

[0045] Example 1 A casting, cold rolling, and annealing process for aluminum alloy foil includes the following steps: S1. Provide an aluminum alloy melt, wherein the aluminum alloy melt, by mass percentage, has the following composition: Si 0.18%, Fe 0.75%, with the balance being aluminum and unavoidable impurities, wherein the V content is 0.008% and the Cu content is 0.015%. The aluminum alloy melt is refined and then cast to obtain an aluminum alloy ingot. S2. The aluminum alloy ingot is cast and rolled into a 7.1mm thick cast and rolled plate. After the temperature of the cast and rolled plate drops to 60℃, it is heated to 320℃ for casting and rolling annealing. The casting and rolling annealing is held at the temperature for 3 hours. S3. The cast-rolled plate that has undergone casting and rolling annealing is subjected to multiple cold rolling passes, with a total reduction rate of 95.0%, to obtain foil blanks; S4. Place the foil blank in an environment of 245°C for finished product annealing, and keep the finished product annealed for 2 hours.

[0046] The aluminum foil produced had an elongation of 6.5% and a tensile strength of 235 MPa.

[0047] Example 2 A casting, cold rolling, and annealing process for aluminum alloy foil includes the following steps: S1. Provide an aluminum alloy melt, wherein the aluminum alloy melt, by mass percentage, has the following composition: Si 0.22%, Fe 0.85%, with the balance being aluminum and unavoidable impurities, wherein the V content is 0.009% and the Cu content is 0.018%. The aluminum alloy melt is refined and then cast to obtain an aluminum alloy ingot. S2. The aluminum alloy ingot is cast and rolled into a 7.4mm thick plate. After the temperature of the plate drops to 80℃, it is heated to 420℃ for casting and annealing, and the casting and annealing is held for 10 hours. S3. The cast-rolled plate that has undergone casting and rolling annealing is subjected to multiple cold rolling passes, with a total reduction rate of 95.2%, to obtain foil blanks; S4. Place the foil blank in an environment of 255°C for finished product annealing, and keep the finished product annealing at the temperature for 5 hours.

[0048] The aluminum foil produced had an elongation of 7.8% and a tensile strength of 238 MPa.

[0049] Example 3 A casting, cold rolling, and annealing process for aluminum alloy foil includes the following steps: S1. Provide an aluminum alloy melt, the composition of which, by mass percentage, is: Si 0.16%, Fe 0.72%, Mg 0.008%, Na 0.0015%, Ca 0.0010%, with the balance being aluminum and unavoidable impurities, wherein V≤0.005%, Cu≤0.010%, and the mass ratio of Fe to Si is 4.5. The aluminum alloy melt is refined and then cast to obtain an aluminum alloy ingot. The refining operation includes: firstly, a mixture of argon and chlorine gas is introduced into the melt for rotary spray refining, wherein the chlorine gas fraction is 2%, and the refining time is 25 minutes; subsequently, a refining agent containing Na3AlF6 and NaCl is added for covering and settling; after the melt stabilizes, it is allowed to stand for 35 minutes, and the time from the start of casting to the end of standing is controlled to be 25 minutes. S2. The aluminum alloy ingot is cast and rolled into a 7.2 mm thick cast and rolled plate. After the temperature of the cast and rolled plate drops to 50°C, it is heated to 380°C for casting and rolling annealing, and held at that temperature for 6 hours. The heating rate during the casting and rolling annealing process is controlled at 50°C / h, and a nitrogen protective atmosphere is introduced during the holding stage above 350°C. The nitrogen protective atmosphere contains 0.3% chlorine gas by volume. After the casting and rolling annealing is completed, the cast and rolled plate is mechanically polished to remove a 10 μm thick layer from the surface. S3. The cast-rolled plate that has undergone casting, rolling annealing and polishing is subjected to multiple cold rolling passes, with a total reduction rate of 95.5%, to obtain foil blanks. In the cold rolling operation, the reduction rate of the last three passes decreases in a gradient, and the reduction rate of the last pass is 8%, with a rolling speed of 80 m / min. S4. The foil blank is subjected to finished product annealing. Finished product annealing includes two sequential heat preservation stages: in the first stage, the foil blank is heated to 170°C at a rate of 3.0°C / min and held at 170°C for 1 hour; in the second stage, the foil blank is heated to 250°C at a rate of 12.0°C / min and held at 250°C for 2.5 hours.

[0050] The composition of the aluminum alloy melt in S1 meets the requirements. After the casting and rolling annealing process in S2 is completed, instrumental analysis shows that the sum of the mass fractions of Mg, Na, and Ca elements detected within a depth of 10 μm on the subsurface of the cast and rolled plate is 65% higher than that at the center position in the thickness direction of the cast and rolled plate.

[0051] The aluminum foil produced had an elongation of 8.2% and a tensile strength of 240 MPa.

[0052] Example 4 A casting, cold rolling, and annealing process for aluminum alloy foil includes the following steps: S1. Provide an aluminum alloy melt, the composition of which, by mass percentage, is: Si 0.24%, Fe 0.88%, Mg 0.03%, Na 0.0024%, Ca 0.0015%, with the balance being aluminum and unavoidable impurities, wherein V≤0.009%, Cu≤0.019%, and the mass ratio of Fe to Si is 3.67. The aluminum alloy melt is refined and then cast to obtain an aluminum alloy ingot. The refining operation includes: firstly, introducing a mixture of argon and chlorine gas into the melt for rotary spray refining, wherein the chlorine gas fraction is 4%, and the refining time is 35 minutes; subsequently, adding a refining agent containing Na3AlF6 and NaCl for covering and settling; after the melt stabilizes, allowing it to stand for 50 minutes, and controlling the time from the start of casting to the end of standing for 28 minutes. S2. The aluminum alloy ingot is cast and rolled into a 7.3 mm thick plate. After the temperature of the plate drops to 70°C, it is heated to 400°C for casting and annealing, and held at that temperature for 8 hours. The heating rate during the casting and annealing process is controlled at 70°C / h, and a nitrogen protective atmosphere containing 0.4% chlorine gas by volume is introduced during the holding stage above 350°C. After the casting and annealing is completed, the plate is mechanically polished to remove a 22 μm thick layer from the surface. S3. The cast-rolled plate that has undergone casting, rolling, annealing and polishing is subjected to multiple cold rolling passes, with a total reduction rate of 95.8%, to obtain foil blanks. In the cold rolling operation, the reduction rate of the last three passes decreases in a gradient, and the reduction rate of the last pass is 6%, with a rolling speed of 60 m / min. S4. The foil blank is subjected to finished product annealing. Finished product annealing includes two sequential heat preservation stages: in the first stage, the foil blank is heated to 180°C at a rate of 2.0°C / min and held at 180°C for 1.5 hours; in the second stage, the foil blank is heated to 255°C at a rate of 15.0°C / min and held at 255°C for 3 hours.

[0053] The composition of the aluminum alloy melt in S1 meets the requirements. After the casting and rolling annealing process in S2 is completed, instrumental analysis shows that the sum of the mass fractions of Mg, Na, and Ca elements detected within a depth range of 20 μm on the subsurface of the cast and rolled plate is 80% higher than that at the center position in the thickness direction of the cast and rolled plate.

[0054] The aluminum foil produced had an elongation of 9.5% and a tensile strength of 242 MPa.

[0055] Example 5 A casting, cold rolling, and annealing process for aluminum alloy foil includes the following steps: S1. Provide an aluminum alloy melt, the composition of which, by mass percentage, is: Si 0.20%, Fe 0.80%, Mg 0.04%, Na 0.0030%, Ca 0.0018%, with the balance being aluminum and unavoidable impurities, wherein V≤0.006%, Cu≤0.012%, and the mass ratio of Fe to Si is 4.0. The aluminum alloy melt is refined and then cast to obtain an aluminum alloy ingot. The refining operation includes: firstly, introducing a mixture of argon and chlorine gas into the melt for rotary spray refining, wherein the chlorine gas fraction is 3%, and the refining time is 30 minutes; subsequently, adding a refining agent containing Na3AlF6 and NaCl for covering and settling; after the melt stabilizes, allowing it to stand for 45 minutes, and controlling the time from the start of casting to the end of standing for 22 minutes. S2. The aluminum alloy ingot is cast and rolled into a 7.25mm thick plate. After the temperature of the plate drops to 40℃, it is heated to 350℃ for casting and annealing, and held at that temperature for 4 hours. The heating rate is controlled at 40℃ / h during the casting and annealing process, and a nitrogen protective atmosphere containing 0.2% chlorine gas by volume is introduced during the holding stage above 350℃. After the casting and annealing is completed, the plate is mechanically polished to remove a 15μm thick layer from the surface. S3. The cast-rolled plate that has undergone casting, rolling, annealing and polishing is subjected to multiple cold rolling passes, with a total reduction rate of 95.3%, to obtain foil blanks. In the cold rolling operation, the reduction rate of the last three passes decreases in a gradient, and the reduction rate of the last pass is 9%, with a rolling speed of 90 m / min. S4. The foil blank is subjected to finished product annealing. Finished product annealing includes two sequential heat preservation stages: in the first stage, the foil blank is heated to 160°C at a rate of 4.0°C / min and held at 160°C for 0.8 hours; in the second stage, the foil blank is heated to 242°C at a rate of 8.0°C / min and held at 242°C for 2 hours.

[0056] The composition of the aluminum alloy melt in S1 meets the requirements. After the casting and rolling annealing process in S2 is completed, instrumental analysis shows that the sum of the mass fractions of Mg, Na, and Ca elements detected within an 8μm depth range on the subsurface of the cast and rolled plate is 55% higher than that at the center position in the thickness direction of the cast and rolled plate.

[0057] The aluminum foil produced had an elongation of 7.5% and a tensile strength of 237 MPa.

[0058] Example 6 A casting, cold rolling, and annealing process for aluminum alloy foil includes the following steps: S1. Provide an aluminum alloy melt, wherein the aluminum alloy melt, by mass percentage, has the following composition: Si 0.17%, Fe 0.78%, Mg 0.01%, Na content 0.0018%, Ca content 0.0012%, and the balance being aluminum and unavoidable impurities, wherein V ≤ 0.007%, Cu ≤ 0.014%, and the mass ratio of Fe to Si is 4.59. The aluminum alloy melt is refined and then cast to obtain an aluminum alloy ingot. S2. The aluminum alloy ingot is cast and rolled into a 7.15mm thick plate. After the temperature of the plate drops to 55℃, it is heated to 330℃ for casting and annealing. The casting and annealing is held at the temperature for 2 hours. S3. The cast-rolled plate that has undergone casting and rolling annealing is subjected to multiple cold rolling passes, with a total reduction rate of 95.1%, to obtain foil blanks. In the cold rolling operation, the reduction rate of the last three passes decreases in a gradient manner, and the reduction rate of the last pass is 7%, with a rolling speed of 95 m / min. S4. The foil blank is subjected to finished product annealing. Finished product annealing includes two sequential heat preservation stages: in the first stage, the foil blank is heated to 155°C at a rate of 1.5°C / min and held at 155°C for 1.2 hours; in the second stage, the foil blank is heated to 248°C at a rate of 6.0°C / min and held at 248°C for 3.5 hours.

[0059] The composition of the aluminum alloy melt in S1 meets the requirements. After the casting and rolling annealing process in S2 is completed, instrumental analysis shows that the sum of the mass fractions of Mg, Na, and Ca elements detected within a depth range of 12 μm on the subsurface of the cast and rolled plate is 70% higher than that at the center position in the thickness direction of the cast and rolled plate.

[0060] The aluminum foil produced had an elongation of 8.8% and a tensile strength of 239 MPa.

[0061] Example 7 A casting, cold rolling, and annealing process for aluminum alloy foil includes the following steps: S1. Provide an aluminum alloy melt, wherein the aluminum alloy melt, by mass percentage, has the following composition: Si 0.23%, Fe 0.86%, Mg 0.045%, Na content 0.0027%, Ca content 0.0016%, and the balance being aluminum and unavoidable impurities, wherein V ≤ 0.010%, Cu ≤ 0.020%, and the mass ratio of Fe to Si is 3.74. The aluminum alloy melt is refined and then cast to obtain an aluminum alloy ingot. S2. The aluminum alloy ingot is cast and rolled into a 7.45mm thick plate. After the temperature of the plate drops to 90℃, it is heated to 440℃ for casting and annealing, and the casting and annealing is held for 11 hours. S3. The cast-rolled plate that has undergone casting and rolling annealing is subjected to multiple cold rolling passes, with a total reduction rate of 96.0%, to obtain foil blanks. In the cold rolling operation, the reduction rate of the last three passes decreases in a gradient manner, and the reduction rate of the last pass is 5%, with a rolling speed of 70 m / min. S4. The foil blank is subjected to finished product annealing. Finished product annealing includes two sequential heat preservation stages: in the first stage, the foil blank is heated to 185°C at a rate of 4.5°C / min and held at 185°C for 1.8 hours; in the second stage, the foil blank is heated to 258°C at a rate of 18.0°C / min and held at 258°C for 3.8 hours.

[0062] The composition of the aluminum alloy melt in S1 meets the requirements. After the casting and rolling annealing process in S2 is completed, instrumental analysis shows that the sum of the mass fractions of Mg, Na, and Ca elements detected within a depth range of 25 μm on the subsurface of the cast and rolled plate is 90% higher than that at the center position in the thickness direction of the cast and rolled plate.

[0063] The aluminum foil produced had an elongation of 10.5% and a tensile strength of 243 MPa.

[0064] Example 8 A casting, cold rolling, and annealing process for aluminum alloy foil includes the following steps: S1. Provide an aluminum alloy melt, wherein the aluminum alloy melt, by mass percentage, has the following composition: Si 0.19%, Fe 0.82%, Mg 0.02%, Na content 0.0021%, Ca content 0.0013%, and the balance being aluminum and unavoidable impurities, wherein V ≤ 0.008%, Cu ≤ 0.016%, and the mass ratio of Fe to Si is 4.32. The aluminum alloy melt is refined and then cast to obtain an aluminum alloy ingot. S2. The aluminum alloy ingot is cast and rolled into a 7.35mm thick plate. After the temperature of the plate drops to 75℃, it is heated to 390℃ for casting and annealing. The casting and annealing is held for 7 hours. S3. The cast-rolled plate after casting and rolling annealing is subjected to multiple cold rolling passes, with a total reduction rate of 95.6%, to obtain foil blanks. In the cold rolling operation, the reduction rate of the last three passes decreases in a gradient, and the reduction rate of the last pass is 4.5%, with a rolling speed of 85 m / min. S4. The foil blank is subjected to finished product annealing. Finished product annealing includes two sequential holding stages: in the first stage, the foil blank is heated to 175°C at a rate of 2.5°C / min and held at 175°C for 0.6 hours; in the second stage, the foil blank is heated to 252°C at a rate of 10.0°C / min and held at 252°C for 1.5 hours.

[0065] The composition of the aluminum alloy melt in S1 meets the requirements. After the casting and rolling annealing process in S2 is completed, instrumental analysis shows that the sum of the mass fractions of Mg, Na, and Ca elements detected within a depth range of 18 μm on the subsurface of the cast and rolled plate is 75% higher than that at the center position in the thickness direction of the cast and rolled plate.

[0066] The aluminum foil produced had an elongation of 9.0% and a tensile strength of 241 MPa.

[0067] Example 9 A casting, cold rolling, and annealing process for aluminum alloy foil includes the following steps: S1. Provide an aluminum alloy melt, wherein the aluminum alloy melt, by mass percentage, has the following composition: Si 0.25%, Fe 0.90%, Mg 0.05%, Na content 0.0036%, Ca content 0.0020%, and the balance being aluminum and unavoidable impurities, wherein V ≤ 0.010%, Cu ≤ 0.020%, and the mass ratio of Fe to Si is 3.6. The aluminum alloy melt is refined and then cast to obtain an aluminum alloy ingot. S2. The aluminum alloy ingot is cast and rolled into a 7.5mm thick plate. After the temperature of the plate drops to 95℃, it is heated to 450℃ for casting and annealing, and the casting and annealing is held for 12 hours. S3. The cast-rolled plate that has undergone casting and rolling annealing is subjected to multiple cold rolling passes, with a total reduction rate of 96.2%, to obtain foil blanks. In the cold rolling operation, the reduction rate of the last three passes decreases in a gradient, and the reduction rate of the last pass is 3%, with a rolling speed of 50 m / min. S4. The foil blank is subjected to finished product annealing. Finished product annealing includes two sequential heat preservation stages: in the first stage, the foil blank is heated to 190°C at a rate of 5.0°C / min and held at 190°C for 2 hours; in the second stage, the foil blank is heated to 260°C at a rate of 20.0°C / min and held at 260°C for 4 hours.

[0068] The composition of the aluminum alloy melt in S1 meets the requirements. After the casting and rolling annealing process in S2 is completed, instrumental analysis shows that the sum of the mass fractions of Mg, Na, and Ca elements detected within a depth range of 28 μm on the subsurface of the cast and rolled plate is 95% higher than that at the center position in the thickness direction of the cast and rolled plate.

[0069] The aluminum foil produced had an elongation of 11.5% and a tensile strength of 245 MPa.

[0070] Comparative Example 1 A casting, cold rolling, and annealing process for aluminum alloy foil includes the following steps: S1. Provide an aluminum alloy melt, wherein the aluminum alloy melt, by mass percentage, has the following composition: Si 0.12%, Fe 0.65%, with the balance being aluminum and unavoidable impurities, wherein the V content is 0.015% and the Cu content is 0.030%. The aluminum alloy melt is refined and then cast to obtain an aluminum alloy ingot. S2. The aluminum alloy ingot is cast and rolled into a cast and rolled plate with a thickness of 6.8 mm. After the temperature of the cast and rolled plate drops to 50°C, it is heated to 280°C for casting and rolling annealing, and the casting and rolling annealing is held at the temperature for 0.5 hours. S3. The cast-rolled plate that has undergone casting and rolling annealing is subjected to multiple cold rolling passes, with a total reduction rate of 92.0%, to obtain foil blanks; S4. The foil blank is placed in an environment of 230°C for finished product annealing, and the finished product is kept at the annealing temperature for 0.5 hours.

[0071] The aluminum foil produced had an elongation of 3.2% and a tensile strength of 198 MPa.

[0072] Comparative Example 2 A casting, cold rolling, and annealing process for aluminum alloy foil includes the following steps: S1. Provide an aluminum alloy melt, wherein the aluminum alloy melt, by mass percentage, has the following composition: Si 0.20%, Fe 0.80%, Mg 0.03%, Na content 0.002%, Ca content 0.0015%, and the balance being aluminum and unavoidable impurities, wherein V ≤ 0.010%, Cu ≤ 0.020%, and the mass ratio of Fe to Si is 4.0. The aluminum alloy melt is refined and then cast to obtain an aluminum alloy ingot. S2. The aluminum alloy ingot is cast and rolled into a 7.2mm thick plate (naturally cooled after casting and rolling, without casting and rolling annealing or mechanical polishing). S3. The cast-rolled plate is subjected to multiple cold rolling passes, with a total reduction rate of 95.0%, to obtain foil blanks; S4. Place the foil blank in an environment of 250°C for finished product annealing, and keep the finished product annealed at this temperature for 2 hours.

[0073] The aluminum foil produced had an elongation of 4.1% and a tensile strength of 205 MPa, and edge cracks appeared during the cold rolling process.

[0074] Comparative Example 3 A casting, cold rolling, and annealing process for aluminum-manganese alloy foil includes the following steps: S1. Provide an aluminum-manganese alloy melt, wherein the alloy melt, by mass percentage, has the following composition: Mn 1.2%, Mg 0.8%, Cu 0.1%, with the balance being aluminum and unavoidable impurities. The alloy melt is refined and then cast to obtain an ingot. S2. The ingot is cast and rolled into a 7.0 mm thick plate. After the temperature of the cast and rolled plate drops below 100°C, it is heated to 350°C for casting and rolling annealing and held for 5 hours. S3. The cast-rolled plate that has undergone casting and rolling annealing is subjected to multiple cold rolling passes, with a total reduction rate of 94.8%, to obtain foil blanks; S4. Place the foil blank in an environment of 255°C for finished product annealing, and keep the finished product annealing at the temperature for 3 hours.

[0075] The aluminum foil produced had an elongation of 15.0% and a tensile strength of 175 MPa.

[0076] Comparative Example 4 A casting, cold rolling, and annealing process for an aluminum-magnesium-silicon alloy foil includes the following steps: S1. Provide an aluminum-magnesium-silicon alloy melt, wherein the alloy melt, by mass percentage, comprises: Mg 0.8%, Si 0.7%, Cu 0.2%, with the balance being aluminum and unavoidable impurities. The alloy melt is refined and then cast to obtain an ingot. S2. The ingot is cast and rolled into a 7.2mm thick plate. After the temperature of the plate drops below 100℃, it is heated to 420℃ for casting and annealing and held for 6 hours. S3. The cast-rolled plate that has undergone casting and rolling annealing is subjected to multiple cold rolling passes, with a total reduction rate of 95.0%, to obtain foil blanks; S4. Place the foil blank in an environment of 250°C for finished product annealing, and keep the finished product annealed at this temperature for 2 hours.

[0077] The aluminum foil produced had an elongation of 18.0% and a tensile strength of 165 MPa.

[0078] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A casting, cold rolling, and annealing process for aluminum alloy foil, characterized in that, Includes the following steps: S1. Provide aluminum alloy melt, refine the aluminum alloy melt and then cast it to obtain aluminum alloy ingot; S2. At room temperature, the aluminum alloy ingot is cast and rolled into a cast plate. After the temperature of the cast plate drops below 100°C, it is heated to 300-450°C for casting and annealing. The casting and annealing is held for 1-12 hours. The thickness of the cast plate is 7.0-7.5 mm. S3. The cast-rolled plate that has undergone casting and rolling annealing is subjected to multiple cold rolling passes to make the total reduction rate of the cast-rolled plate not less than 94.7% to obtain foil blank; S4. Place the foil blank in an environment of 240-260℃ for finished product annealing, and keep the finished product annealing at the temperature for 1-6 hours.

2. The process according to claim 1, characterized in that, In S1, the aluminum alloy ingot, by mass percentage, includes 0.15-0.25% Si, 0.70-0.90% Fe, and the balance being aluminum and unavoidable impurities, wherein V≤0.010% and Cu≤0.020%.

3. The process according to claim 2, characterized in that, In S1, the aluminum alloy melt contains 0.005%-0.05% Mg by mass percentage, and the mass ratio of Na to Ca is 1.2-2.

0.

4. The process according to claim 3, characterized in that, In S1, the mass ratio of Fe to Si is ≥3.

5.

5. The process according to claim 3 or 4, characterized in that, The casting and rolling annealing process of S2 needs to control the heating rate to 30-80℃ / h, and a nitrogen protective atmosphere is introduced during the holding stage above 350℃. The nitrogen protective atmosphere contains chlorine gas with a volume fraction of 0.1%-0.5%.

6. The process according to claim 5, characterized in that, After the casting and rolling annealing in S2, surface treatment is also included, in which the cast and rolled plate is mechanically polished to remove a layer with a surface thickness of 5-30 μm.

7. The process according to claim 1, characterized in that, In S1, the refining operation includes: first, a mixture of argon and chlorine gas is introduced into the melt for rotary spray refining, wherein the chlorine gas fraction is 1-5%, and the refining time is 15-40 minutes; then, a refining agent containing Na3AlF6 and NaCl is added for covering and settling; after the melt stabilizes, it is allowed to stand for 20-60 minutes, and the time from the start of casting to the end of standing is controlled not to exceed 30 minutes.

8. The process according to claim 1, characterized in that, In the cold rolling operation of S3, the reduction rate of the last three passes decreases in a gradient manner, and the reduction rate of the last pass does not exceed 10%, and the rolling speed does not exceed 100m / min.

9. The process according to claim 1, characterized in that, The S4 finished product annealing includes two sequential holding stages: in the first stage, the foil blank is heated to a first temperature at a rate of 1.0-5.0℃ / min and held at the first temperature for 0.5-2 hours; in the second stage, the foil blank is heated to a second temperature at a rate of 5.0-20.0℃ / min and held at the second temperature for 1-4 hours; the first temperature is 150-190℃ and the second temperature is 240-260℃.

10. The process according to claim 1, characterized in that, The composition of the aluminum alloy melt in S1 meets the requirement that, after the casting and rolling annealing process in S2 is completed, the sum of the mass fractions of Mg, Na, and Ca elements detected by instrument analysis in the subsurface of the cast and rolled plate within a depth range of 5-30 μm is at least 50% higher than that at the center position in the thickness direction of the cast and rolled plate.