8-series aluminum alloy foil, its preparation method and application

Abstract

This invention provides an 8-series aluminum alloy foil, its preparation method, and its application. The preparation method includes: step S1, melting and casting the raw material of the 8-series aluminum alloy foil to obtain a sheet; step S2, cold rolling the sheet to obtain an aluminum foil blank; step S3, cold rolling the aluminum foil blank at 30 N / mm². 2 ~45N / mm 2 Foil was rolled at a rolling tension of 500 m / min to 800 m / min to obtain 8-series aluminum alloy foil; the rolling oil used for foil rolling had a viscosity of 1.5 mm. 2 / s~2.5mm 2 This invention is based on the control of aluminum foil blank rolling process, and combined with the specific viscosity of rolling oil, thereby effectively reducing the number of oil pits and pinhole defects caused by microcracks generated during the rolling process on the surface of 8-series aluminum alloy foil, and significantly optimizing its surface morphology.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy foil and its processing technology, and more specifically, to an 8-series aluminum alloy foil, its preparation method and application. Background Technology

[0002] Aluminum foil has a wide range of applications, covering multiple fields and industries. Packaging aluminum foil, due to its moisture-proof, airtight, light-blocking, and abrasion-resistant properties, is widely used in industrial and civilian fields such as aluminum-plastic film foil for new energy lithium batteries, functional aluminum foil for new energy components, and pharmaceutical packaging. Battery aluminum foil serves as a current collector material for the positive electrode of lithium-ion batteries, playing a crucial role in battery manufacturing due to its excellent conductivity and cost-effectiveness. Air conditioning aluminum foil is used to manufacture the fins of air conditioner heat exchangers; early versions used plain foil, but later hydrophilic and hydrophobic foils were developed to improve fin surface properties and prevent condensation adhesion. Electronic aluminum foil is a key material used in the electronics industry to manufacture wires, cables, and capacitors. Decorative aluminum foil is used as gold and silver thread, wallpaper, and decorative trademarks for various stationery and light industrial products. Insulating aluminum foil, due to its low solar absorptivity (solar radiation absorption coefficient), can reflect over 93% of radiant heat and can be used as insulation material in buildings, vehicles, and ships.

[0003] Currently, commercially available aluminum foil grades mainly include 1xxx, 3xxx, 5xxx, and 8xxx (i.e., 1-series, 3-series, 5-series, and 8-series). Among commonly used aluminum alloy foil products, 8-series aluminum alloy foil has become a hot spot for high-tech products and new product development in fields such as new energy lithium batteries, new energy components, pharmaceuticals, and food packaging due to its lightweight, high strength, high conductivity, good processing performance, and environmental protection characteristics. Typical grades include 8021, 8079, 8006, 8011, and 8111. Among them, 8021 aluminum alloy foil has excellent moisture resistance, strong light-blocking effect, and strong blocking ability. It is safe and hygienic, has good heat resistance, and has a certain resistance to stress corrosion cracking, making it suitable for lithium battery soft-pack aluminum foil. 8079 aluminum alloy foil, due to its high strength, good elongation, and good compressibility, is widely used in pharmaceuticals, food packaging, and lithium battery soft-pack applications. 8011 aluminum alloy foil has excellent moisture resistance, light blocking and extremely high barrier properties. It is non-toxic, odorless, safe and hygienic, and suitable for use in pharmaceuticals, food packaging and radiators.

[0004] 8-series aluminum alloy foils are primarily manufactured by adjusting the composition and process of the Al-Fe-Si alloy to make foil processing easier and less costly, while maintaining the required strength, cold deformation resistance, diffusion resistance, sealing properties, and coatability. The main alloying elements in commercial 8xxx series aluminum alloy foils are Fe and Si, with Fe content reaching up to 2.0% (wt.)% and Si content reaching up to 1.1% (wt.)%. This facilitates the formation of AlFeSi phase compounds, resulting in high foil strength. However, during production, microcracks can easily lead to defects such as oil pits and pinholes.

[0005] Therefore, optimizing the preparation method of 8-series aluminum alloy foil to significantly reduce oil pit and pinhole defects on its surface, thereby reducing its pinhole rate and improving surface performance, is one of the important technical problems that need to be solved in this field. Summary of the Invention

[0006] The main objective of this invention is to provide an 8-series aluminum alloy foil, its surface morphology optimization method, and its application, in order to solve the problem of poor surface morphology and limited application caused by excessive oil pits and pinhole defects on the surface of existing 8-series aluminum alloy foils.

[0007] To achieve the above objectives, a first aspect of the present invention provides a method for preparing 8-series aluminum alloy foil, comprising: step S1, melting and casting the raw material of 8-series aluminum alloy foil to obtain a sheet; step S2, cold rolling the sheet to obtain an aluminum foil blank; and step S3, cold rolling the aluminum foil blank at 30 N / mm². 2 ~45N / mm 2 Foil was rolled at a rolling tension of 500 m / min to 800 m / min to obtain 8-series aluminum alloy foil; the rolling oil used for foil rolling had a viscosity of 1.5 mm. 2 / s~2.5mm 2 / s.

[0008] Further, in step S2, the metallographic structure of the aluminum foil blank includes a matrix phase and a second phase, wherein the area of ​​the second phase with a gauge diameter > 5 μm accounts for 2.0% to 4.0% of the metallographic structure, and the area of ​​the second phase with a gauge diameter > 3 μm accounts for 6.0% to 10.0% of the metallographic structure; preferably, the second phase is an AlFe phase and / or an AlFeSi phase.

[0009] Further, in step S3, the foil rolling includes the following sequential processes: first foil rolling to obtain a first aluminum foil; second foil rolling to obtain a second aluminum foil; and third foil rolling to obtain a third aluminum foil. Preferably, the reduction rate of the first foil rolling, the second foil rolling, and the third foil rolling is independently 40% to 55%.

[0010] Furthermore, the roll surface roughness used for rolling the first foil and the second foil is independently 0.15μm to 0.20μm, and the roll surface roughness used for rolling the third foil is 0.10μm to 0.12μm.

[0011] Furthermore, the maximum microcrack depth on the surfaces of the first, second, and third foils is 1.30 μm; the maximum microcrack width on the surfaces of the first, second, and third foils is 21.5 μm; and the maximum microcrack area ratio on the surfaces of the first, second, and third foils is 13.0%.

[0012] Furthermore, the rolling oil includes base oil, acid compounds, ester compounds and alcohol compounds, with the content of acid compounds being 0.08% to 0.12%, the content of ester compounds being 3.00% to 5.00%, and the content of alcohol compounds being 0.50% to 12.00%.

[0013] Furthermore, step S2 also includes annealing the cold-rolled sheet to obtain aluminum foil blank; preferably, the annealing temperature is 200℃~270℃, the heating rate is 30℃ / h~65℃ / h, and the holding time is 1.5h~6h; more preferably, the heating method of the annealing is furnace heating.

[0014] A second aspect of the present invention provides an 8-series aluminum alloy foil, which is prepared by the above-described method for preparing 8-series aluminum alloy foil, and the thickness of the 8-series aluminum alloy foil is 35 μm to 45 μm.

[0015] Furthermore, the number of pinholes on the surface of the 8-series aluminum alloy foil is 2 per 10,000 m². 2 ~4 per 10,000 m 2 The diameter of the pinhole is ≤0.05mm.

[0016] A third aspect of the present invention provides an application of the above-mentioned 8-series aluminum alloy foil as a packaging aluminum foil material in the fields of new energy, industrial and civil electrical equipment, food and pharmaceuticals.

[0017] By applying the technical solution of this invention, based on the foil rolling process control of aluminum foil blanks, the limit depth, maximum width and area ratio of microcracks on the aluminum foil surface are controlled within a specified range. At the same time, combined with the specific viscosity of the rolling oil, the number of oil pits and pinhole defects caused by microcracks generated during the rolling process on the surface of 8-series aluminum alloy foil is effectively reduced, and its surface morphology is significantly optimized so that its surface quality meets the product requirements of various fields. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0019] Figure 1 The image shown is a scanning electron microscope (SEM) image of the surface of the 8-series aluminum alloy foil obtained in Example 1. Detailed Implementation

[0020] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0021] As described in the background section, existing 8-series aluminum alloy foils suffer from poor surface morphology and limited applications due to excessive oil pits and pinholes. To address these technical problems, the first aspect of this invention provides a method for preparing 8-series aluminum alloy foil, comprising: step S1, melting and casting the raw material of the 8-series aluminum alloy foil to obtain a sheet; step S2, cold rolling the sheet to obtain an aluminum foil blank; and step S3, cold rolling the aluminum foil blank at 30 N / mm². 2 ~45N / mm 2 Foil was rolled at a rolling tension of 500 m / min to 800 m / min to obtain 8-series aluminum alloy foil; the rolling oil used for foil rolling had a viscosity of 1.5 mm. 2 / s~2.5mm 2 / s.

[0022] This invention is based on the control of process parameters during the rolling process of 8-series aluminum alloy foil, combined with adjusting the viscosity of the rolling oil used in the rolling process to 1.5 mm. 2 / s~2.5mm 2 Within this specific range, the problem of uneven deformation and excessive defects caused by excessively high rolling oil viscosity, as well as poor lubrication and numerous surface defects caused by excessively low rolling oil viscosity, was successfully avoided. Furthermore, the generation of microcracks on the surface of foil was effectively suppressed during foil rolling (hereinafter referred to as foil rolling), thereby significantly reducing the number of oil pits and pinholes on the surface of the finished 8-series aluminum alloy foil due to microcracks. Ultimately, the prepared 8-series aluminum alloy foil exhibits excellent surface properties, thus better adapting to the application needs of various fields.

[0023] Specifically, in the rolling process of aluminum alloy foil, a certain tension, known as curling tension, needs to be applied to control the degree of curling of the metal foil in order to maintain its flatness and prevent deformation during rolling. The magnitude of this tension significantly affects the quality of the aluminum alloy foil, especially its surface morphology. Excessive tension can lead to cracks or deformation on the surface of the aluminum alloy foil; insufficient tension may cause curling during rolling, affecting surface flatness and subsequent processing quality. Rolling speed is also a crucial factor affecting the metallographic structure and surface morphology of the alloy during foil rolling. At lower rolling speeds, the aluminum alloy foil has more time for dynamic recrystallization during deformation, resulting in larger grains and making it more prone to surface defects such as cracks and folds. Conversely, excessively high rolling speeds can lead to uneven stress distribution within the aluminum alloy foil, causing uneven local plastic deformation and subsequently forming defects in the microstructure and surface morphology. Therefore, for the special aluminum alloy material of 8-series aluminum alloy, the inventors conducted extensive experiments and synergistically controlled the coiling tension and rolling speed during the foil rolling process to 30 N / mm. 2 ~45N / mm 2 The rolling speed ranges from 500m / min to 800m / min, thereby enabling precise control of defects such as microcracks that may occur on the surface of the foil during the foil rolling process from the perspective of rolling process parameters, thus reducing the pinhole defect problem caused by microcracks.

[0024] It is worth noting that microcracks (oil pits) and pinholes are formed by the connection between bright surface microcracks and deep recesses in dark surface wavy areas. Therefore, controlling the formation and distribution of microcracks is beneficial to reducing pinhole formation. Bright surface microcracks are related to factors such as the internal quality of the aluminum foil billet, rolling conditions, and rolling process. During cold rolling and foil rolling, the lubrication mechanism of the rolling oil is a mixed lubrication consisting of boundary lubrication and fluid lubrication. The rolling oil introduced into the roll bite-in mouth will form periodically arranged microcracks (oil pits) perpendicular to the rolling furrows through the deformation of the aluminum surface. As the amount of interfacial rolling oil increases, the coefficient of friction decreases, and the size of the microcracks (oil pits) (such as depth, width, individual volume, area, and volume ratio) will gradually increase. After the initial amount of rolling oil exceeds a certain level, it tends to be constant. The present invention reduces the amount of rolling oil flowing into the roll bite zone during rolling. That is, by synergistically controlling the viscosity of the rolling oil, the rolling speed and the coiling tension, the generation of microcracks is effectively controlled, thereby successfully reducing the number of oil pits and pinhole defects that are ultimately formed on the foil surface.

[0025] In particular, the preparation method provided by the present invention is universally applicable to aluminum alloys with various composition formulations, but the settings of the rolling oil viscosity, rolling speed and coiling tension are additionally adapted to 8-series aluminum foil, and finally obtain 8-series aluminum alloy foil with excellent surface morphology.

[0026] Unless otherwise specified, all viscosities mentioned in this invention refer to viscosities at room temperature. Furthermore, casting and rolling combines the traditional casting and rolling processes, enabling a continuous production process from liquid metal to finished product. For the 8-series aluminum foil prepared according to this invention, this forming process, compared to traditional hot-rolled slabs, achieves continuous coil production in the casting stage, eliminating the hot rolling process, which effectively improves production efficiency and reduces costs. Simultaneously, due to the high cooling rate of casting and rolling, the solid solubility of Fe and Si elements in the alloy can be effectively increased, which is beneficial for controlling the quantity and size of the second phase in the microstructure of the cast-rolled slab.

[0027] Meanwhile, for 8-series aluminum foil blanks, excessively large second-phase particle sizes or a high proportion of second-phase particles larger than a certain size in the metallographic structure are a major cause of high pinhole rates in the finished aluminum foil. Specifically, larger second-phase particles in the aluminum foil blank easily cause discontinuities in the aluminum foil matrix structure, disrupting the coherent relationship between the second phase and the matrix structure. Furthermore, during subsequent rolling and annealing, invariably sized particles are formed, which typically exhibit a certain degree of distribution along the rolling direction. As the aluminum foil becomes thinner, the matrix surrounding the large-sized second phase is further fragmented and crushed, increasing the probability of pinholes. Therefore, through extensive experimentation, the inventors have found that, in several typical embodiments, the metallographic structure of the aluminum foil blank in step S2 preferably includes both a matrix phase and a second phase, wherein the area of ​​the second phase with a gauge diameter > 5 μm accounts for 2.0% to 4.0% of the metallographic structure, and the area of ​​the second phase with a gauge diameter > 3 μm accounts for 6.0% to 10.0% of the metallographic structure. This allows for reasonable control of the second phase size distribution in the aluminum foil blank, further protecting the continuity of the aluminum foil matrix structure and suppressing its fragmentation during subsequent deformation, thereby significantly improving the surface quality of 8-series aluminum alloy foil. In several more typical embodiments, the second phase is the AlFe phase and / or the AlFeSi phase.

[0028] To avoid ambiguity, the term "microcrack pinhole" in this invention refers to "surface pinhole defects caused by microcracks".

[0029] In several typical embodiments, the composition of the 8-series aluminum alloy foil includes Fe and Si elements, with Fe accounting for 1.0% to 1.6% and Si accounting for 0.15% to 0.9% by weight. In principle, the preparation method provided by this invention is applicable to aluminum alloys that meet the composition requirements of 8-series aluminum alloy foil. However, due to the need to optimize the proportion of the second phase in the foil blank, the inventors have optimized the content of Fe and Si through numerous experiments to form fewer AlFeSi second phases and various impurity second phases, thereby more effectively ensuring the surface morphology of the final 8-series aluminum alloy foil. Furthermore, when the Fe and Si content is excessive, the high strength of the alloy matrix makes it easier to increase the maximum width and depth of surface microcracks. Simultaneously, after the aluminum foil is thinned to a certain extent, the number of pinholes caused by microcracks (oil pits) increases, resulting in a deterioration in surface morphology.

[0030] Based on the above, the cold rolling further includes multi-pass cold rolling with at least three passes and a total cold rolling rate of 95.0% to 96.5%, which more effectively causes the second phase to break up, refines the grains, and reduces the proportion of large-sized grains, so as to further reduce microcracks in the subsequent foil rolling process and improve the surface morphology of the final 8-series aluminum alloy foil.

[0031] In several typical embodiments, to more precisely control the foil thickness and the number of surface defects, and to make the foil deformation more uniform in all directions, step S3 preferably includes the following sequential processes: first foil rolling to obtain a first aluminum foil; second foil rolling to obtain a second aluminum foil; and third foil rolling to obtain a third aluminum foil. To better refine the grains, optimize the texture, and reduce internal and surface defects, the inventors, through extensive experimentation, have optimized the reduction rates of the first, second, and third foil rolling processes to be independently 40%–55%.

[0032] In order to further improve the surface finish of 8-series aluminum foil and reduce the number of oil pits and pinhole defects on its surface, the inventors optimized the line roughness of the rolls used for rolling the first and second foils to be 0.15μm to 0.20μm, and the line roughness of the rolls used for rolling the third foil to be 0.10μm to 0.12μm, through a large number of experiments.

[0033] Furthermore, through extensive experiments, the inventors optimized the surfaces of the first, second, and third foils by controlling the foil rolling process parameters. The maximum value of the microcrack limit depth was 1.30 μm; the maximum value of the maximum width of the microcracks on the surfaces of the first, second, and third foils was 21.5 μm; and the maximum value of the microcrack area ratio on the surfaces of the first, second, and third foils was 13.0%, thereby obtaining aluminum alloy foils with better surface morphology.

[0034] In several typical embodiments, the microcrack limit depth on the surface of the first foil is 0.95 μm to 1.30 μm, the maximum microcrack width is 15.5 μm to 21.5 μm, and the microcrack area percentage is 7.0% to 13.0%; and / or, the microcrack limit depth on the surface of the second foil is 0.85 μm to 1.25 μm, the maximum microcrack width is 14.0 μm to 18.5 μm, and the microcrack area percentage is 5.5% to 11.0%; and / or, the microcrack limit depth on the surface of the third foil is 0.75 μm to 1.00 μm, the maximum microcrack width is 11.5 μm to 16.5 μm, and the microcrack area percentage is 4.0% to 9.0%.

[0035] Currently, for metal foils, pinhole defects can only be detected online when the aluminum foil is thinned to near-finished product thickness. Because this is close to the final product stage, if the defect exceeds technical quality requirements, it can lead to product downgrading, reduced yield during slitting, or even scrapping of the entire roll. Microcracks account for a high proportion of pinhole defects in aluminum foil, especially for aluminum foil products with high alloy element content and single-zero, double-zero, and ultra-thin aluminum foil products. Microcracks, as mentioned earlier, are the main direct cause of oil pit pinholes. Therefore, in the above embodiments of the present invention, it is preferable to adjust the foil rolling process parameters to more precisely control the limit depth, maximum width, and area ratio of surface microcracks in each pass. This allows for more effective prediction and control of the size and number of microcracks in earlier passes, thereby significantly suppressing the number of oil pit pinhole defects on the surface of the final 8-series aluminum alloy foil and improving its surface quality.

[0036] Furthermore, the rolling oil includes base oil, acid compounds, ester compounds, and alcohol compounds. The acid compounds in the rolling oil act as lubricants and rust inhibitors, reacting with the alumina layer on the aluminum foil surface to form a protective film, preventing oxidation during rolling. The ester compounds form a lubricating film on the surface, reducing friction and wear during rolling and improving the surface properties of the aluminum foil, making it smoother and flatter. The alcohols improve the internal structure of the aluminum foil, making it more uniform and dense. Through extensive experimentation, the inventors have optimized the content of acid compounds to 0.08%–0.12%, ester compounds to 3.00%–5.00%, and alcohol compounds to 0.50%–12.00%. This better leverages the respective optimization effects of each compound, more effectively suppressing dark streaks caused by excessive acid reaction, black spots caused by excessive esters, and especially roll marks caused by excessive alcohol decomposition, further optimizing the surface properties of the resulting 8-series aluminum alloy foil.

[0037] The present invention does not impose any restrictions on the specific formulation of the rolling oil or the specific types of its components, as long as the content requirements mentioned above are met. For example, the base oil used in the rolling oil may be selected from one or more of mineral oil (such as kerosene), synthetic oil (such as polyalphaolefin, ester oil, and polyether oil), vegetable oil, silicone oil, and paraffin oil; the acids may be selected from one or more of boric acid, fatty acids, organic phosphoric acid, and sulfonic acid (such as lauric acid, stearic acid, etc.); the esters may be selected from one or more of phosphate esters, sulfonate esters, fatty acid esters, and polyol esters (such as methyl dodecanoate, methyl tetradecanoate, and methyl hexadecanoate); and the alcohols may be selected from one or more of glycerol, ethylene glycol, polyethylene glycol, and long-chain fatty alcohols. Furthermore, other types of additives, such as antioxidants, anti-wear agents, and extreme pressure agents, may be added according to the specific rolling process and the quality requirements of the aluminum foil to achieve better surface properties.

[0038] To better suit the raw materials and cold rolling process of 8-series aluminum alloy foil, step S2 preferably includes annealing the cold-rolled sheet to obtain an aluminum foil blank, thereby more effectively reducing the proportion of the second phase in its microstructure. Through extensive experimentation, the inventors further optimized the annealing temperature to be 200℃~270℃, the heating rate to be 30℃ / h~65℃ / h, and the holding time to be 1.5h~6h. Under these conditions, an 8-series aluminum alloy foil with a lower proportion of the second phase and better surface properties was obtained. A more preferable method is furnace heating for the annealing process, which further enhances the overall performance of the 8-series aluminum alloy foil.

[0039] A second aspect of the present invention provides an 8-series aluminum alloy foil, which is prepared by the above-described method for preparing 8-series aluminum alloy foil, and the thickness of the 8-series aluminum alloy foil is 35 μm to 45 μm. The 8-series aluminum alloy foil prepared by the above-described method has a more suitable thickness and superior surface properties.

[0040] Furthermore, the number of pinholes on the surface of the 8-series aluminum alloy foil is 0 per 10,000 m². 2 ~4 per 10,000 m 2 The diameter of the pinhole is ≤0.05mm, which means fewer surface defects. At the same time, compared with traditional 8021 and 8079 aluminum foils, the 8-series aluminum alloy foil prepared by this invention has high strength and excellent formability.

[0041] A third aspect of this invention provides an application of the aforementioned 8-series aluminum alloy foil as a packaging aluminum foil material in the fields of new energy, industrial and consumer electrical equipment, food, and pharmaceuticals. The 8-series aluminum alloy foil obtained by this invention has excellent surface morphology and can better meet the application needs of the aforementioned fields.

[0042] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0043] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0044] Example 1

[0045] A method for preparing 8-series aluminum alloy foil:

[0046] Step S1: Using Fe with a content of 1.6% and Si with a content of 0.15%, and the balance being Al as raw material, the alloy raw material is smelted and cast to obtain a plate with a thickness of 7 mm.

[0047] Step S2: The obtained sheet is then cold-rolled to obtain a cold-rolled sheet with a thickness of 0.34 mm (i.e., a total cold rolling rate of 95.1%). Afterwards, intermediate annealing is performed at 240℃ with a furnace heating rate of 45℃ / h. The billet is held at the annealing temperature for 4 hours after reaching the set temperature, resulting in the aluminum foil billet. The microstructure of the aluminum foil billet is equiaxed, and the area ratio of the second phase with a size greater than 3 μm is 6.2%, and the area ratio of the second phase with a size greater than 5 μm is 2.8%.

[0048] Step S3: Before foil rolling, the viscosity of the rolling oil used for foil rolling is 2.1 mm. 2 / s, which uses kerosene as the base oil and adds 0.09% lauric acid, 3.8% methyl palmitate and 10.0% dodecyl alcohol by weight of the total rolling oil.

[0049] The obtained aluminum foil blank was subjected to three foil rolling passes, with the thickness changing from 0.34 mm to 0.16 mm to 0.070 mm to 0.035 mm (i.e., the reduction rates of the three foil rolling passes were 52.9%, 56.3%, and 50.0%, respectively). The coiling tension of the foil in all three passes was controlled at 35 N / mm. 2 The rolling speed is controlled at 650 m / min. The surface roughness of the rolls used in the first two foil rolling passes is 0.19 μm, while the surface roughness of the rolls used in the final pass, the third foil rolling pass, is 0.12 μm. Simultaneously:

[0050] The microcrack limit depth on the surface of the foil after the first foil rolling is 0.96 μm, the maximum width of the microcrack is 15.8 μm, and the area ratio of the microcrack is 7.9%.

[0051] The microcrack limit depth on the surface of the foil after the second foil rolling is 0.89 μm, the maximum microcrack width is 14.2 μm, and the microcrack area accounts for 5.9%.

[0052] The microcrack limit depth on the surface of the foil after the third foil rolling is 0.77 μm, the maximum width of the microcrack is 11.8 μm, and the area ratio of the microcrack is 4.3%.

[0053] Step S4: After slitting, the obtained aluminum foil undergoes degreasing and annealing to finally obtain 8-series aluminum alloy foil with a thickness of 35 μm and a surface oil pit / 10,000 m² count. 2 .

[0054] The surface morphology of the obtained 8-series aluminum alloy foil was analyzed by scanning electron microscopy, see [the results]. Figure 1 The figure shows the microscopic morphology of the pinholes, indicating that their diameter is approximately 0.05 mm. It also shows that the 8-series aluminum alloy foil obtained in this embodiment has high surface smoothness and few microcracks, pinholes, and oil pits.

[0055] Example 2

[0056] A method for preparing 8-series aluminum alloy foil:

[0057] Step S1: Using Fe with a content of 1.0%, Si with a content of 0.9%, and the balance being Al as raw material, the alloy raw material is smelted and cast to obtain a plate with a thickness of 7.2 mm.

[0058] Step S2: The obtained sheet is then cold-rolled to obtain a cold-rolled sheet with a thickness of 0.28 mm (i.e., a total cold rolling rate of 96.1%). Afterwards, intermediate annealing is performed at 250℃ with a furnace heating rate of 40℃ / h. The billet is held at the annealing temperature for 5 hours after reaching the set temperature, resulting in the aluminum foil billet. The microstructure of the aluminum foil billet is equiaxed, and the area ratio of the second phase with a size greater than 3 μm is 8.5%, and the area ratio of the second phase with a size greater than 5 μm is 3.2%.

[0059] Step S3: Before foil rolling, the viscosity of the rolling oil used for foil rolling is 2.0 mm. 2 / s, which uses kerosene as the base oil and adds 0.12% lauric acid, 5.0% methyl palmitate and 5.0% dodecyl alcohol by weight of the total rolling oil.

[0060] The obtained aluminum foil blank was subjected to three foil rolling passes, with the thickness changing from 0.28 mm to 0.17 mm, then to 0.080 mm, and finally to 0.045 mm (i.e., the reduction rates for the three foil rolling passes were 50.0%, 52.9%, and 43.8%, respectively). The coiling tension for all three foil rolling passes was controlled at 42 N / mm. 2 The rolling speed is controlled at 700 m / min. The surface roughness of the rolls used in the first two foil rolling passes is 0.16 μm, while the surface roughness of the rolls used in the final pass, the third foil rolling pass, is 0.12 μm. Simultaneously:

[0061] The microcrack limit depth on the surface of the foil after the first foil rolling is 0.98 μm, the maximum width of the microcrack is 16.1 μm, and the area ratio of the microcrack is 8.7%.

[0062] The microcrack limit depth on the surface of the foil after the second foil rolling is 0.88 μm, the maximum width of the microcrack is 14.5 μm, and the area ratio of the microcrack is 6.2%.

[0063] The microcrack limit depth on the surface of the foil after the third foil rolling is 0.78 μm, the maximum microcrack width is 12.0 μm, and the microcrack area accounts for 4.7%. The above structural characteristics are shown in Tables 1 and 2.

[0064] Step S4: After slitting, the obtained aluminum foil undergoes degreasing and annealing to finally obtain 8-series aluminum alloy foil with a thickness of 45 μm and a surface oil pit / pinhole count of 2 per 10,000 m. 2 .

[0065] Example 3

[0066] A method for preparing 8-series aluminum alloy foil:

[0067] The only difference between this embodiment and Embodiment 1 is the alloy raw materials. Specifically, the raw materials are Fe with a content of 0.8%, Si with a content of 1.0%, and the balance being Al.

[0068] Example 4

[0069] A method for preparing 8-series aluminum alloy foil:

[0070] The only difference between this embodiment and Embodiment 1 is the alloy raw materials. Specifically, the raw materials are Fe with a content of 1.8%, Si with a content of 0.12%, and the balance being Al.

[0071] Example 5

[0072] A method for preparing 8-series aluminum alloy foil:

[0073] The only difference between this embodiment and Embodiment 1 is that in step S1, the casting and rolling parameters are controlled to obtain a sheet with a thickness of 6.2 mm; and in step S2, the obtained sheet is then cold-rolled to obtain a cold-rolled sheet with a thickness of 0.34 mm (i.e., the total cold rolling rate is 94.5%), and then intermediate annealing is performed at an annealing temperature of 180°C and a furnace heating rate of 25°C / h. After the billet reaches the temperature, it is held at that temperature for 7 hours to obtain the aluminum foil billet.

[0074] Example 6

[0075] A method for preparing 8-series aluminum alloy foil:

[0076] The only difference between this embodiment and embodiment 2 is that in step S1, the casting and rolling parameters are controlled to obtain a plate with a thickness of 8.2 mm; and in step S2, the obtained plate is then cold-rolled to obtain a cold-rolled plate with a thickness of 0.28 mm (i.e., the total cold rolling rate is 96.6%), and then intermediate annealing is performed at an annealing temperature of 300°C and a furnace heating rate of 75°C / h. After the billet reaches the temperature, it is held at that temperature for 1 hour to obtain the aluminum foil billet.

[0077] Example 7

[0078] A method for preparing 8-series aluminum alloy foil:

[0079] The only difference between this embodiment and Embodiment 1 is that the intermediate annealing process in step S2 is not performed; instead, the cold-rolled sheet is directly used as foil blank for subsequent foil rolling.

[0080] Example 8

[0081] A method for preparing 8-series aluminum alloy foil:

[0082] The only difference between this embodiment and Embodiment 1 is the thickness variation of the foil rolling in step S3, i.e., the reduction rate of the three-pass foil rolling. Specifically, the obtained aluminum foil blank is subjected to three-pass foil rolling, and the thickness variation is 0.340mm→0.209mm→0.128mm→0.035mm (i.e., the reduction rates of the three-pass foil rolling are 38.5%, 38.5% and 72.7%, respectively).

[0083] Example 9

[0084] A method for preparing 8-series aluminum alloy foil:

[0085] The only difference between this embodiment and Embodiment 1 is the thickness variation of the foil rolling in step S3, i.e., the reduction rate of the three-pass foil rolling. Specifically, the obtained aluminum foil blank is subjected to three-pass foil rolling, with the thickness variation being 0.340mm→0.136mm→0.054mm→0.035mm (i.e., the reduction rates of the three-pass foil rolling are 60.0%, 60.0%, and 35.7%, respectively).

[0086] Example 10

[0087] A method for preparing 8-series aluminum alloy foil:

[0088] The only difference between this embodiment and embodiment 1 is the change in the thickness of the foil during rolling in step S3. Specifically, the obtained aluminum foil blank is subjected to two passes of foil rolling, with the thickness changing from 0.340mm to 0.106mm to 0.035mm (i.e., the reduction rate of both passes of foil rolling is 68.8%).

[0089] Example 11

[0090] A method for preparing 8-series aluminum alloy foil:

[0091] The only difference between this embodiment and Embodiment 1 is that in step S3, the roll roughness used in the three foil rolling passes is different. Specifically, the roll roughness used in the first and second foil rolling passes is 0.12 μm, while the roughness of the roll used in the third foil rolling pass is 0.15 μm. The surface structure characteristics of the foil obtained after each foil rolling pass are shown in Tables 1 and 2.

[0092] Example 12

[0093] A method for preparing 8-series aluminum alloy foil:

[0094] The only difference between this embodiment and Embodiment 1 is that in step S3, the roll surface roughness used in the three foil rolling passes is different. Specifically, the roll surface roughness used in the first and second foil rolling passes is 0.22 μm, while the roughness of the rolls used in the third foil rolling pass is 0.08 μm. The surface structure characteristics of the foil obtained after each foil rolling pass are shown in Tables 1 and 2.

[0095] Example 13

[0096] A method for preparing 8-series aluminum alloy foil:

[0097] The only difference between this embodiment and Example 1 is the rolling oil formulation used in step S3. Specifically, kerosene is used as the base oil, and 0.05% lauric acid, 2.5% methyl palmitate, and 13.0% dodecyl alcohol by weight of the total rolling oil are added, while the viscosity remains unchanged. The surface structure characteristics of the foil obtained after each foil rolling are shown in Tables 1 and 2.

[0098] Example 14

[0099] A method for preparing 8-series aluminum alloy foil:

[0100] The only difference between this embodiment and Embodiment 1 is the rolling oil formulation used in step S3. Specifically, kerosene is used as the base oil, and 1.50% lauric acid, 8.0% methyl palmitate, and 0.3% dodecyl alcohol by weight of the total rolling oil are added, while the viscosity remains unchanged. The surface structure characteristics of the foil obtained after each foil rolling are shown in Tables 1 and 2.

[0101] Comparative Example 1

[0102] A method for preparing 8-series aluminum alloy foil:

[0103] The only difference between this comparative example and Example 1 is the conditions for the three-pass foil rolling in step S3. Specifically, the coiling tension for all three passes of foil rolling is controlled at 28 N / mm. 2The rolling speed is controlled at 850 m / min.

[0104] Comparative Example 2

[0105] A method for preparing 8-series aluminum alloy foil:

[0106] The only difference between this comparative example and Example 1 is the conditions for the three-pass foil rolling in step S3. Specifically, the coiling tension for all three passes of foil rolling is controlled at 50 N / mm. 2 The rolling speed is controlled at 450 m / min.

[0107] Comparative Example 3

[0108] A method for preparing 8-series aluminum alloy foil:

[0109] The only difference between this comparative example and Example 1 is that the rolling oil formulation used in step S3 is changed to a viscosity of 1.2 mm. 2 / s. The surface structure characteristics of the foil obtained after each foil rolling are shown in Tables 1 and 2.

[0110] Test methods

[0111] Second phase area ratio: Tested using an optical microscope, and its evaluation and calculation were carried out in accordance with GB / T 3246.1-2024 "Methods for testing the microstructure of wrought aluminum and aluminum alloy products - Part 1: Methods for testing the microstructure".

[0112] Microcracks: Microcracks were detected using a super depth-of-field microscope and an optical profilometer. The super depth-of-field microscope characterized the distribution of microcracks, calculated the area ratio, and measured the maximum width, while the optical profilometer measured and statistically analyzed the limiting depth data of microcracks on the aluminum foil surface in 2D and 3D morphology. To avoid errors, the foil materials in each embodiment and comparative example were sampled and tested 10 times during the preparation process, and the maximum value was taken as the test results of the limiting depth, maximum width, and area ratio of microcracks on its surface.

[0113] Pinhole count: After identifying pinholes using online pinhole detection equipment on the production line, their morphology and energy dispersive spectroscopy (EDS) were analyzed using scanning electron microscopy (SEM). The SEM results confirmed the pinhole type as microcrack pinholes. The quality requirements for pinhole defects were in accordance with the provisions of "3.5.1" and "3.5.2" in GB / T 3198-2020 Aluminum and Aluminum Alloy Foil. In the examples of this invention, the pinhole diameter on the foil surface was ≤0.05mm. The evaluation and calculation of pinholes were based on GB / T 22638.2-2016 "Aluminum Foil Test Methods Part 2: Detection of Pinholes".

[0114] The aluminum alloy foils obtained in each embodiment and comparative example were subjected to the above-mentioned performance tests, and the results are shown in Table 1 and Table 2, respectively.

[0115] Table 1

[0116]

[0117]

[0118] Table 2

[0119]

[0120] As can be seen from the above description, the above embodiments of the present invention achieve surface morphology optimization of 8-series aluminum alloy foil, and the number of microcracks and pinholes on the surface of the resulting 8-series aluminum alloy foil is significantly reduced, thus enabling it to be used as a packaging material to meet the application needs of various fields.

[0121] Specifically, when the number of foil rolling passes is reduced or the pass reduction rate is too high, uneven deformation during rolling can easily lead to defects such as surface microcracks and wrinkles on the aluminum foil surface, resulting in an increase in microcracks and pinholes in the finished aluminum foil. Excessive rolling speed can affect the lubrication state within the rolling deformation zone, causing poor lubrication and reduced oil film thickness, thus increasing the surface roughness and microcrack severity of the aluminum foil. During aluminum foil rolling, insufficient tension can lead to wrinkling, ridge formation, and delamination at the coil end. However, excessive winding tension accelerates grain changes, resulting in coarse grains and uneven deformation in some areas, significantly increasing the number of microcracks and pinholes on the aluminum foil surface, and in severe cases, even causing strip breakage. Furthermore, excessive tension can cause the foil roll to be loose inside and tight outside, resulting in a folding phenomenon, the so-called "bird's nest" defect.

[0122] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in a sequence other than those described herein.

[0123] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for producing an 8-series aluminum alloy foil, characterized by, The preparation method comprises the following steps: S1, melting and casting rolling of the raw material of the 8-series aluminum alloy foil to obtain a plate; S2, cold rolling of the plate to obtain an aluminum foil blank; the metallographic structure of the aluminum foil blank comprises a matrix phase and a second phase, wherein the area ratio of the second phase with a caliper diameter > 5 μm in the metallographic structure is 2.0% to 4.0%, and the area ratio of the second phase with a caliper diameter > 3 μm in the metallographic structure is 6.0% to 10.0%; the second phase is an AlFe phase and / or an AlFeSi phase; S2 further comprises annealing treatment of the plate after the cold rolling to obtain the aluminum foil blank; the annealing treatment is performed at a temperature of 200°C to 270°C, a heating rate of 30°C / h to 65°C / h, and a holding time of 1.5 h to 6 h; Step S3, foil rolling the aluminum foil blank at a curl tension of 30 N / mm 2 45 N / mm 2 , a rolling speed of 500 m / min to 800 m / min to obtain the 8-series aluminum alloy foil; The rolling oil viscosity used in the rolling of the foil is 1.5 mm 2 / s ~ 2.5 mm 2 / s.

2. The method of producing an 8-series aluminum alloy foil according to claim 1, wherein S3, the foil rolling comprises the following steps in sequence: first foil rolling to obtain a first aluminum foil; second foil rolling to obtain a second aluminum foil; third foil rolling to obtain a third aluminum foil.

3. The method of producing an 8-series aluminum alloy foil according to claim 2, wherein The reduction rate of the first foil rolling, the second foil rolling and the third foil rolling is independently 40% to 55%.

4. The method for preparing 8-series aluminum alloy foil according to claim 2, characterized in that, The linear roughness Ra of the rolling mill used for the first foil rolling and the second foil rolling is independently 0.15 μm to 0.20 μm, and the linear roughness of the rolling mill used for the third foil rolling is 0.10 μm to 0.12 μm.

5. The preparation method of the 8-series aluminum alloy foil according to claim 4, wherein the maximum value of the micro-crack limit depth of the surface of the first foil, the second foil and the third foil is 1.30 μm; the maximum value of the micro-crack maximum width of the surface of the first foil, the second foil and the third foil is 21.5 μm; the maximum value of the micro-crack area ratio of the surface of the first foil, the second foil and the third foil is 13.0%.

6. The method of producing an 8-series aluminum alloy foil according to any one of claims 1 to 5, characterized in that, The rolling oil comprises base oil, acid compound, ester compound and alcohol compound, and the content of the acid compound is 0.08% to 0.12%, the content of the ester compound is 3.00% to 5.00%, and the content of the alcohol compound is 0.50% to 12.00%.

7. The method of producing an 8-series aluminum alloy foil according to any one of claims 1 to 5, characterized in that, The heating mode of the annealing treatment is furnace heating.

8. An 8-series aluminum alloy foil, characterized by, The 8-series aluminum alloy foil is prepared by the preparation method of the 8-series aluminum alloy foil according to any one of claims 1 to 7, and the thickness of the 8-series aluminum alloy foil is 35 μm to 45 μm.

9. The 8000-series aluminum alloy foil according to claim 8, wherein The number of pinholes on the surface of the 8-series aluminum alloy foil is 2 per 10,000 m 2 4 per 10,000 m 2 , and the diameter of the pinholes is ≤0.05 mm.

10. Application of the 8-series aluminum alloy foil according to claim 8 or 9 as an aluminum foil material for packaging in the fields of new energy, industrial and household electrical appliances, food and medicine.

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