Preparation method of cast-rolled 8021 alloy aluminum foil

Abstract

The invention belongs to the technical field of aluminum alloy materials, and particularly discloses a preparation method of a cast-rolled 8021 alloy aluminum foil, an 8021 alloy blank with the thickness of 6-8 mm is produced through cast rolling, the blank is subjected to direct homogenizing annealing under the condition of not cooling, is rolled through a cold rolling production process, and then is subjected to edge cutting, secondary intermediate annealing and foil rolling to be subjected to multi-pass rolling to obtain the finished product with the thickness. Compared with a traditional direct-cooling cast ingot hot rolling process, multiple links such as hot-rolled plate ingot casting, ingot blank sawing and face milling, uniform annealing and large-machining-amount hot roughing mill cogging rolling are omitted, energy is saved, consumption is reduced, carbon dioxide emission is reduced, the performance of a finished product is equal to or even superior to that of a hot-rolled product, and the use requirements of customers are met.

Description

Technical Field

[0001] The present invention belongs to the technical field of aluminum alloy materials, and specifically discloses a preparation method for casting and rolling 8021 alloy aluminum foil. Background Art

[0002] Due to its moisture-proof, airtight, light-shielding, abrasion-resistant, non-toxic and odorless characteristics, aluminum foil is widely used in industries such as food, medicine, tobacco, and daily chemicals. As the usage scenarios become more and more complex, the performance requirements for aluminum foil in various industries are increasing day by day, and the requirements for its mechanical properties such as elongation index are becoming more and more stringent.

[0003] Under this background, each aluminum foil enterprise continuously researches and develops new technologies to improve the quality and performance of aluminum foil to meet the needs of the high-end market. Generally speaking, however, in terms of surface quality, mechanical property elongation, pinhole index, etc., the aluminum foil products produced from hot-rolled billets are significantly superior to the cast-rolled aluminum foil products. The cast-rolled aluminum foil products have great quality disadvantages in the face of hot-rolled products, resulting in a narrow user group, few usage scenarios, and the inability to meet technical requirements for some high-end products.

[0004] The production process flow of conventional hot-rolled 8021 alloy aluminum foil products is: melting → ingot casting → sawing and milling the head → homogenization annealing → hot rolling → cold rolling → secondary annealing → cold rolling → trimming → foil rolling → slitting → final annealing → inspection and packaging. The hot-rolling production line needs to be equipped with large-scale heating furnaces, hot-rolling mills, finishing equipment, etc. The purchase, installation, and maintenance costs of these equipment are very high, and the initial investment is huge, which in turn leads to high equipment costs; the hot-rolled ingots need to be sawed and milled at the head, which will generate waste, and there are many production passes and tailing at each pass, resulting in a low yield rate and high production costs; the hot-rolled slab ingots are rolled from 650 mm to 6.0 mm, and generally need to go through 21 - 23 rolling passes. The whole production process has many rolling passes and high energy consumption, increasing the production costs. Generally speaking, the production of billets by the hot-rolling method leads to high overall production costs due to factors such as large equipment investment, low billet yield rate, and many rolling passes.

[0005] The prior art CN111349825A discloses a preparation method for producing high-toughness battery aluminum foil using a short-process cast-rolled billet, which successively goes through the processes of melting, casting and rolling, cold rolling, homogenization heat treatment, medium rolling, longitudinal shearing and trimming, intermediate annealing, finish rolling, foil rolling, coiling, rolling the finished product, slitting, charging furnace annealing. This method requires thirteen processes and at least ten rolling passes. The production process is long and the number of rolling passes is many. In addition, in the process of melting and casting and rolling, 0.001 - 0.04% of a modifier Sr needs to be added and melted at 770 °C for 4 - 6 hours and then refined. Sr itself is expensive and chemically active. Adding Sr element not only increases the production cost, but also easily causes segregation and results in unstable finished product quality. Summary of the Invention

[0006] To solve the problems in the background art, the present invention discloses a preparation method of cast-rolled 8021 alloy aluminum foil. A 6-8 mm thick blank of 8021 alloy is produced by casting and rolling. Without cooling, the blank is directly subjected to homogenization annealing. After being rolled through the cold rolling production process, it is further subjected to trimming, secondary intermediate annealing, and foil rolling to produce the finished product thickness in multiple passes. The performance of the finished product is equivalent to or even better than that of the hot-rolled product, meeting the usage requirements of customers.

[0007] To achieve the above invention object, the present invention adopts the following technical solutions: A preparation method of cast-rolled 8021 alloy aluminum foil includes the following steps: S1. Melting: In a melting furnace, successively add 20% - 30% of self-produced waste, 10% - 30% of remelted aluminum ingots, and 50% - 60% of electrolytic aluminum liquid by mass percentage. Heat and stir evenly. After the furnace charge is leveled, add metal additives. After the alloy composition ratio is qualified, using high-purity argon as a carrier, introduce the refining agent into the aluminum melt through a stainless steel pipe by a refining machine for refining. After refining, skim the floating slag on the surface of the melt. After slag skimming, let the melt stand for 30 minutes and then pour the melt into a holding furnace. After the furnace tilting is completed, the aluminum alloy melt is held and static in the holding furnace. The temperature of the melt in the holding furnace is 730 - 740 °C; S2. Casting: Let the qualified aluminum alloy melt in the holding furnace of step S1 flow out smoothly. The uniformly flowing aluminum alloy melt successively passes through on-line titanium wire addition, on-line degassing box for degassing and slag removal, and plate filter box for filtration. The melt after on-line treatment is injected into the casting area of the casting machine in equal amounts and at a uniform speed through a casting nozzle. The melt forms a cast-rolled coil of a blank with a thickness of 6 - 8 mm and different widths in the casting area; S3. Homogenization annealing: Perform homogenization annealing on the cast-rolled coil obtained in S2; S4. Cold rolling: After the cast-rolled coil after homogenization annealing is taken out of the furnace and air-cooled to below 45 °C, it is rolled through a cold rolling blooming mill in multiple passes to a cold-rolled coil with a thickness of 0.2 mm; S5. Longitudinal trimming: Trim the cold-rolled coil. After trimming, the width tolerance of the material is required to be less than ±1 mm, and there should be no aluminum powder accumulation at the edges; S6. Secondary intermediate annealing: Place the trimmed material on an annealing rack and put it into an annealing furnace, ensuring that the material is suspended throughout the processes of transportation, annealing, and cooling. The annealing process is as follows: Raise the furnace temperature to 480 °C in 4 h and hold for 10 - 20 h, then lower the furnace temperature to 430 °C and hold for 5 h, and finally open the side cooling to lower the furnace temperature to 170 °C and hold for 2 hours before taking out of the furnace; S7. Foil Rolling: Feed the coiled material after annealing in S6 into a foil rolling mill for rolling. When rolling aluminum foil, the specific rolling passes are 0.2 mm → 0.09 mm → 0.05 mm. Among them, the first pass is for rolling O-state materials, with a processing rate of 55%, a rolling speed of less than 500 m / min, and a rolling oil spraying volume of more than 980 L / min; the second pass is for double-rolling, that is, double-rolling and overlapping rolling, with a rolling speed of less than 600 m / min and a rolling oil spraying volume of more than 800 L / min. S8. Finished Product Slitting: Slit the aluminum foil rolled in S7 as required. S9. Finished Product Annealing: Put the slit finished products in S8 into an annealing furnace for annealing. Heat the furnace temperature to 200 °C in 4 h and hold for 8 h, then heat the furnace temperature to 260 °C in 4 h and hold for 50 h, and finally heat the furnace temperature to 170 °C in 2 h and hold for 2 h. Keep negative pressure operation throughout the annealing process. After the annealing process is completed, take out of the furnace, use a convection fan to blow air to cool the material. After the material is cooled to room temperature, and after passing the inspection, package it according to the packaging requirements. Furthermore, in the preparation method of the cast-rolled 8021 alloy aluminum foil, the mass percentages of the alloy melt components in step S1 are as follows: Si = 0.1% - 0.15%, Fe = 1.4% - 1.5%, Cu = 0.04% - 0.05%, Mn ≤ 0.02%, Mg ≤ 0.02%, Cr ≤ 0.01%, Zn ≤ 0.05%, Ti ≤ 0.025%, and the balance is Al.

[0008] Furthermore, in the preparation method of the cast-rolled 8021 alloy aluminum foil, during the furnace tilting operation in step S1, high-purity argon gas should be introduced at the inlet of the holding furnace for furnace tilting refining, and skim the floating slag on the surface of the melt after the furnace tilting is completed.

[0009] Furthermore, in the preparation method of the cast-rolled 8021 alloy aluminum foil, the hydrogen content of the aluminum alloy melt after online treatment in step S2 is less than 0.12 ml / 100 g·Al. During casting production, the forehearth temperature is 667 - 673 °C, the casting speed is 0.65 - 0.7 m / min, the cooling water temperature is 25 - 30 °C, and the cooling water pressure is 0.4 - 0.5 mpa.

[0010] Furthermore, in the preparation method of the cast-rolled 8021 alloy aluminum foil, the annealing process in step S3 is as follows: Raise the furnace gas temperature to 600 °C in 4 h. After the furnace temperature reaches, maintain positive pressure in the furnace gas for 40 h. After the 600 °C insulation is completed, open the side cooling to lower the furnace temperature to 170 °C and hold for 2 hours, then take out of the furnace.

[0011] Furthermore, in the preparation method of the cast-rolled 8021 alloy aluminum foil, during rolling in step S4, it is required that the coiling tension of each pass is less than the total uncoiling tension of the previous pass to prevent tension scratches. In addition, tail flicking is required during rolling of each pass.

[0012] Furthermore, in the method for preparing the cast-rolled 8021 alloy aluminum foil, in step S4, when rolling on the cold rolling blooming mill, 100# rolling oil is used, the content of the rolling oil additive is 7%, the light transmittance is above 97%, the rolling oil temperature during the rolling process is 35 - 45°C, the roll crown is controlled at +0.04 mm, and the roughness is controlled at 0.5 μm. The rolling thickness of each pass is as follows: 7 mm → 4 mm → 2.2 mm → 1.2 mm → 0.7 mm → 0.37 mm → 0.2 mm.

[0013] Furthermore, in the method for preparing the cast-rolled 8021 alloy aluminum foil, in step S5, before longitudinal shearing and edging, check whether there are foreign objects on the guide roller path and whether the guide rollers rotate flexibly. Before threading, each guide roller in the guide path must be wiped with alcohol; during production, strictly inspect the surface quality of the material to ensure that there are no surface defects such as imprints, sticking aluminum, abrasions, and / or scratches on the aluminum coil surface, and there are no burrs, tower shapes, flanging, and / or small edge wrinkles at the end face.

[0014] Furthermore, in the method for preparing the cast-rolled 8021 alloy aluminum foil, when inspecting before S9 finished product packaging, inspect the material thickness, width, end face quality, surface quality, water brushing condition, pinhole condition, and unfolding quality index. The tensile strength of the finished product is 95 - 110 Mpa, the elongation rate is ≥25%, and the cupping is ≥7.5 mm. After passing the inspection, package it with EPE, plastic film, desiccant, plug, threading pipe, and wooden box according to the packaging requirements. After packaging, stick a material label on the outside of the wooden box, and the label shall include information such as box number, alloy status, specification, net weight, gross weight, and packaging date.

[0015] Compared with the prior art, the beneficial effects of the present invention are: (1) In the method for preparing the cast-rolled 8021 alloy aluminum foil of the present invention, during melting, 20% - 30% of self-produced waste, 10% - 30% of remelted aluminum ingots, and 50% - 60% of electrolytic aluminum liquid are sequentially added to the melting furnace by mass percentage. The high-temperature electrolytic aluminum liquid conducts heat to the added self-produced waste through soaking. This feeding method can avoid the contact of self-produced waste with air during melting, reduce the oxidation loss ratio, lower the production cost, and also reduce the consumption of aluminum ingot and aluminum liquid raw materials, thereby realizing low-cost production and achieving green, low-carbon, and environmentally friendly production; (2) The preparation method of the cast-rolled 8021 alloy aluminum foil of the present invention has only nine production processes and eight rolling passes, while the method of CN111349825A requires thirteen processes and at least ten rolling passes. In addition, the blank in CN111349825A needs to be rolled during smelting and casting, and the blank is rolled into a blank with a thickness of 2.0 to 6.5 mm through 1-3 passes, and then the aluminum alloy coil is lubricated and cooled with rolling oil to obtain an aluminum alloy coil, and then the aluminum alloy coil is intermediate rolled, homogenized annealed, and the temperature of the blank after being cooled out of the furnace is less than 70°C, and then rolled into a blank with a thickness of 0.35 to 0.8 mm through 3 to 5 passes. The method of the present invention adopts direct homogenization annealing of the cast-rolled coil, and the heat of the blank off the machine is used during the homogenization annealing. Compared with CN111349825A, the present invention greatly shortens the production process, reduces production costs, and reduces the labor intensity of employees; The present invention adopts casting and rolling to directly produce 6-8mm thick billets. Compared with the traditional direct-cooling ingot hot rolling process, it omits multiple steps such as hot-rolled plate ingot casting, ingot sawing and milling, uniform annealing and hot rough rolling mill with large processing volume, thus saving energy and reducing consumption and carbon dioxide emissions. The saved production cost has obvious economic and social benefits. (3) The finished aluminum foil prepared by the method for preparing the cast-rolled 8021 alloy aluminum foil of the present invention has a tensile strength of 95 to 110 MPa, an elongation of ≥25%, and a cupping of ≥7.5 mm. The performance of the finished product is equivalent to or even better than that of the hot-rolled product, which fully meets the use requirements of customers. DETAILED DESCRIPTION

[0016] In order to better understand the present invention, the content of the present invention is further clearly described below in conjunction with the embodiments, but the protection content of the present invention is not limited to the following embodiments. In the following description, a large number of specific details are given in order to provide a more thorough understanding of the present invention. However, it is obvious to those skilled in the art that the present invention can be implemented without one or more of these details. It should be noted that the self-produced waste in the present invention is the trimming and tailing waste generated in the process of producing aluminum alloy products with alloy grades of 1060, 1070, 1235 and / or 8021 in the applicant's company, and the mass percentages of the specific alloy components are as follows: Example 1

[0017] A method for preparing a cast-rolled 8021 alloy aluminum foil comprises the following steps: S1. Melting: The melting is carried out using a 30t round furnace. In the melting furnace, 25.33% of self-produced waste, 18.50% of remelted aluminum ingots, and 56.17% of electrolytic aluminum liquid are added in sequence by mass percentage. When adding materials for melting, the self-produced waste is added first, and then the remelted aluminum ingots are added and pressed on top of the waste to prevent the waste from floating and directly contacting the burner flame and burning out after the electrolytic aluminum water is added. After the solid materials are added completely, the electrolytic aluminum water is poured through the aluminum inlet. Through the combustion of two natural gas burners in the furnace, heating and stirring are carried out. After the melt in the furnace is melted evenly, metal additives such as iron agent, instant silicon, and copper agent are added. The composition of the aluminum alloy melt is as follows: Si 0.12%, Fe 1.45%, Cu 0.043%, Mn 0.01%, Mg 0.01%, Cr 0.005%, Zn 0.01%, Ti 0.022%, and the balance is Al. After the alloy composition ratio is qualified, with high-purity argon as the carrier, the refining agent is introduced into the aluminum melt through a stainless steel pipe by a refining machine for refining. The fixed-point refining method should be used during refining to ensure that every position in the furnace can be fully refined. At the same time, it is required that each fixed-point position needs to be refined for more than 20s. After refining, the dross on the surface of the melt is skimmed off to ensure that the surface of the melt presents a mirror-like state of aluminum liquid and no dross residue is allowed to prevent secondary pollution of the melt after hydrogen absorption. After skimming the dross, the melt is allowed to stand for 30min and then poured into the holding furnace. When pouring the furnace, high-purity argon is introduced at the inlet of the holding furnace for pouring furnace refining. After pouring the furnace, the dross on the surface of the melt is skimmed off, which is the same as the dross skimming requirement of the aforementioned melting furnace. When the aluminum alloy melt stands in the holding furnace, it is heated by the electric heating tubes on the furnace top to keep the melt temperature constant. It is required that the melt metal temperature is controlled at 730 - 740°C; S2. Casting: By controlling the gap size between the flow control brazing and the runner brick, the qualified aluminum alloy melt in the holding furnace in step S1 is smoothly discharged. The liquid level height fluctuation at the aluminum outlet of the holding furnace shall not exceed 5mm. After the aluminum alloy melt flowing out at a constant speed passes through the online double-stage titanium wire addition, high-purity argon is introduced into the degassing box through a silicon carbide rotor to degas and deslag the aluminum melt. The rotor speed of the degassing box is 460r / min, and the argon pressure is 0.8mpa. During the degassing process, it is necessary to ensure that the hydrogen flash is normal and uniform. In addition, nitrogen is introduced into the degassing box as a protective gas to relieve the oxidation and slag formation of the melt on the surface of the aluminum liquid. The degassed aluminum alloy melt enters the plate filter box for filtration. Two 50ppm ceramic filter plates connected in series are placed in the filter box. The hydrogen content of the aluminum alloy melt after online treatment is less than 0.12ml / 100g·Al; The melt after online treatment is injected into the casting area composed of upper and lower rollers through a casting nozzle in equal amounts and at a uniform speed. Cooling water is passed through the roller cores of the rollers, which can take away the heat of the melt. The melt forms billets with a thickness of 6.1 mm and varying widths in the casting area. During casting production, the temperature of the front box should be 667 - 673 °C, the casting speed should be 0.65 - 0.7 m / min, the cooling water temperature should be 25 - 30 °C, and the cooling water pressure should be 0.4 - 0.5 mpa. By adjusting the above process parameters, stable production of the cast billets can be achieved; S3. Homogenization annealing: The cast-rolled coil obtained in S2 is subjected to homogenization annealing. Since the cast-rolled coil is in a sleeve-free state, during homogenization annealing, floor annealing needs to be arranged. To avoid scratching the coil, buffer materials such as asbestos should be placed on the cargo pallet. To control the annealing production cost, full-furnace loading annealing should be ensured. Since the cast-rolled coil has no sleeve, the loading capacity of a single furnace can be increased to six coils, approximately 80 t, for annealing. The annealing process is as follows: The furnace gas temperature is raised to 600 °C in 4 h, and after the furnace temperature reaches, the furnace gas is kept at a positive pressure and insulated for 40 h. After the insulation at 600 °C ends, the furnace temperature is lowered to 170 °C by opening the side cooling and insulated for 2 hours before discharging; S4. Cold rolling: After the cast-rolled coil after homogenization annealing is cooled in air to below 45 °C, it is rolled into a cold-rolled coil with a thickness of 0.2 mm through a cold rolling blooming mill in multiple passes. During rolling, it is required that the coiling tension of each pass is less than the total uncoiling tension of the previous pass to prevent tension scratches. In addition, tail flicking is required during each pass of rolling. 100# rolling oil is used during the rolling of the cold rolling blooming mill, the additive content of the rolling oil is 7%, the light transmittance is above 97%, the rolling oil temperature during the rolling process is 35 - 45 °C, the roll convexity is controlled at +0.04 mm, and the roughness is controlled at 0.5 μm. The thickness of each pass of rolling is as follows: 7 mm → 4 mm → 2.2 mm → 1.2 mm → 0.7 mm → 0.37 mm → 0.2 mm; S5. Longitudinal shearing and trimming: Before longitudinal shearing and trimming, check whether there are foreign objects on the guide roller path and whether the guide rollers rotate flexibly. Before threading the strip, each guide roller in the guide path must be wiped with alcohol; during the production process, strictly check the surface quality of the material to ensure that there are no surface defects such as imprints, sticking aluminum, abrasions, and / or scratches on the surface of the aluminum coil, and there are no burrs, tower shapes, flanging, and / or small edge waves at the end faces. After trimming, the width tolerance of the material is required to be less than ±1 mm, and there should be no aluminum powder accumulation at the edges; S6. Secondary intermediate annealing: Place the trimmed material on the annealing rack and put it into the annealing furnace, ensuring that the material is suspended throughout the transportation, annealing, and cooling processes to avoid scratching and pressing of the material. In this annealing, four coils of the same width are arranged in a single furnace. The annealing process is as follows: The furnace temperature is raised to 480 °C in 4 h and insulated for 10 - 20 h, then the furnace temperature is lowered to 430 °C and insulated for 5 h, and finally the furnace temperature is lowered to 170 °C by opening the side cooling and insulated for 2 hours before discharging; S7. Foil Rolling: Feed the coiled material after annealing in S6 into the foil rolling mill for rolling. Before rolling the aluminum foil, it is necessary to inspect the surface quality of the rolls. There should be no defects such as roll marks, bright lines, width and thickness variations, and grinding wheel marks. Before threading the material, the outermost layer of waste should be removed to prevent foreign objects in the outer layer of the material from entering the roll gap and scratching the rolls to form roll marks. When rolling aluminum foil, the specific rolling passes are 0.2 mm → 0.09 mm → 0.05 mm. Among them, the first pass is for rolling O-state material with a processing rate of 55%, a rolling speed of less than 500 m / min, and a rolling oil spraying volume of more than 980 L / min. By adjusting the rolling speed and the rolling oil spraying volume, the problem of side turning during coiling can be prevented. Before the second pass of rolling the finished product, the thickness gauge should be calibrated to ensure that the thickness of the rolled finished product is normal. At the same time, adjust the splash guard to block the aluminum foil, and adjust the blowing angle and air volume of the air nozzles to ensure that there are no oil spots on the rolled material. The second pass is for double-roll rolling with a rolling speed of less than 600 m / min and a rolling oil spraying volume of more than 800 L / min; S8. Finished Product Slitting: Slit the aluminum foil rolled in S7 as required. Before slitting the finished product, clean each guide roll in the guide path and clean the aluminum chips in the tool slots of the tool slot roll with a brush to ensure that there are no imprints, sticky aluminum, scratches, or abrasions on the surface of the finished product material, and there are no burrs, tower shapes, flanging, or small edge waves on the end faces. Mark the batch number and specifications on the surface of the slit small coils with a marker pen. Materials of the same specification are threaded onto a spindle with a threading rod and placed in a suspended frame of the material rack, and are not allowed to be directly placed on the ground; S9. Finished Product Annealing: Put the slit finished product in S8 into the annealing furnace for annealing. Before entering the furnace, check the furnace condition of the annealing furnace, whether the deflector is deformed, whether there is aluminum foil adhered to the circulating fan cover on the furnace top, check whether the thermocouple on the furnace top is deformed, and check whether there is water dripping or bottom oil on the furnace top of the annealing furnace. After checking that there are no abnormalities, it can enter the furnace for annealing. After the material enters the furnace, close the furnace door. After checking that the furnace door is closed and sealed without air leakage, perform annealing production. The specific finished product annealing process is to heat the furnace temperature to 200 °C in 4 h and hold for 8 h, then heat the furnace temperature to 260 °C in 4 h and hold for 50 h, and finally heat the furnace temperature to 170 °C in 2 h and hold for 2 h. Keep negative pressure operation throughout the annealing process. After the annealing process is completed, take out of the furnace and use a convection fan to blow and cool the material until the material cools to room temperature; Inspection and Packaging: Before packaging the finished product, inspect the material thickness, width, end face quality, surface quality, water brushing condition, pinhole condition, and unfolding quality indicators, and take samples to detect the mechanical properties of the small materials. The tensile strength of the finished product is 95 - 110 Mpa, the elongation is 28%, and the Erichsen value is 8.2 mm. After passing the inspection, package it according to the packaging requirements using EPE, plastic film, desiccant, plug, threading tube, and wooden box. After packaging, stick a material label on the outside of the wooden box. The label should include information such as box number, alloy state, specification, net weight, gross weight, and packaging date. Example 2

[0018] The difference between Example 2 and Example 1 is that in step S1, the raw materials are 20.19% of self-produced waste, 29.50% of remelted aluminum ingots, and 50.31% of electrolytic aluminum liquid. The composition of the aluminum alloy melt is as follows: Si 0.14%, Fe 1.48%, Cu 0.046%, Mn 0.01%, Mg 0.01%, Cr 0.004%, Zn 0.02%, Ti 0.018%, and the balance is Al. In step S2, the melt forms billets with a thickness of 8 mm and different widths in the casting area. Other steps are the same as those in Example 1. The tensile strength of the finished product is 95 - 110 Mpa, the elongation is 28%, and the Erichsen value is 8.2 mm. Example 3

[0019] The difference between Example 3 and Example 1 is that in step S1, the raw materials are 30.10% of self-produced waste, 10.03% of remelted aluminum ingots, and 59.87% of electrolytic aluminum liquid. The composition of the aluminum alloy melt is as follows: Si 0.11%, Fe 1.41%, Cu 0.042%, Mn 0.01%, Mg 0.01%, Cr 0.007%, Zn 0.03%, Ti 0.022%, and the balance is Al. In step S2, the melt forms billets with a thickness of 7 mm and different widths in the casting area. Other steps are the same as those in Example 1. The tensile strength of the finished product is 95 - 110 Mpa, the elongation is 28%, and the Erichsen value is 8.2 mm.

[0020] The 0.05 mm finished aluminum foil prepared by using the preparation method of the cast-rolled 8021 alloy aluminum foil of the present invention has a tensile strength of 95 - 110 Mpa, an elongation of 28%, and an Erichsen value of 8.2 mm. In the prior art CN111349825A, the 0.09 mm double-layer aluminum foil roll, i.e., a single-layer aluminum foil coil with a thickness of 0.045 mm, has an elongation of 23% and a cup convexity value of 7.0 mm; the 0.13 mm double-layer aluminum foil roll, i.e., a single-layer aluminum foil coil with a thickness of 0.065 mm, has an elongation of 32% and a cup convexity value of 7.5 mm. For aluminum foils in the same state and with the same thickness, the larger the elongation and the cup convexity value, the better. The thickness of the 0.05 mm aluminum foil of the present invention is different from that of the aluminum foil in the prior art CN111349825A, so the elongation cannot be effectively compared. However, the cup convexity value of the 0.05 mm aluminum foil of the present invention is 0.7 mm higher than the detected value of 7.5 mm of the 0.065 mm aluminum foil in the solution of the prior art CN111349825A, which fully shows that the quality of the aluminum foil produced by the production method of the present invention is more superior. The performance of the finished product of the present invention is equivalent to or even better than that of the hot-rolled product, fully meeting the usage requirements of customers.

[0021] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Any other modifications or equivalent replacements made by those of ordinary skill in the art to the technical solutions of the present invention should be covered within the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solutions of the present invention.

Claims

1. A preparation method of cast-rolled 8021 alloy aluminum foil, characterized in that, It includes the following steps: S1. Melting: Add successively into the melting furnace 20% - 30% of self-produced waste, 10% - 30% of remelting aluminum ingots, and 50% - 60% of electrolytic aluminum liquid by mass percentage, heat and stir evenly. After the furnace charge is leveled, add metal additives into it. After the alloy component ratio is qualified, using high-purity argon as the carrier, introduce the refining agent into the aluminum melt through a stainless steel pipe by a refining machine for refining. After refining is completed, skim the dross on the surface of the melt. After skimming the dross, let the melt stand for 30 min and then pour the melt into the holding furnace. After pouring the furnace, keep the aluminum alloy melt in the holding furnace for heat preservation and standing. The temperature of the melt in the holding furnace is 730 - 740 °C; S2. Casting: Let the qualified aluminum alloy melt in the holding furnace in step S1 flow out smoothly and at a constant speed. The aluminum alloy melt flowing out at a constant speed successively passes through online titanium wire addition, online degassing and slag removal in a degassing box, and filtration in a plate filter box. The melt after online treatment is injected into the casting area of the casting machine in equal amounts and at a constant speed through a casting nozzle. The melt forms a billet casting and rolling coil with a thickness of 6 - 8 mm and unequal widths in the casting area; S3. Homogenization annealing: Perform homogenization annealing on the casting and rolling coil obtained in S2; S4. Cold rolling: After the casting and rolling coil after homogenization annealing is taken out of the furnace and air-cooled to below 45 °C, it is rolled through a cold rolling blooming mill in multiple passes to a cold rolling coil with a thickness of 0.2 mm; S5. Longitudinal shearing and edging: Trim the cold rolling coil. After trimming, the width tolerance of the material is required to be less than ±1 mm, and there should be no aluminum powder accumulation at the edges; S6. Secondary intermediate annealing: Place the trimmed material on an annealing rack and put it into an annealing furnace, ensuring that the material is suspended throughout the processes of transportation, annealing, and cooling. The annealing process is as follows: Raise the furnace temperature to 480 °C in 4 h and keep it warm for 10 - 20 h, then lower the furnace temperature to 430 °C and keep it warm for 5 h, and finally open the side cooling to lower the furnace temperature to 170 °C and keep it warm for 2 h and then take it out of the furnace; S7. Foil rolling: Feed the coil after annealing in S6 into a foil rolling mill for rolling. When rolling aluminum foil, the specific rolling passes are 0.2 mm → 0.09 mm → 0.05 mm. Among them, the first pass is for rolling O-state material, with a processing rate of 55%, a rolling speed of less than 500 m / min, and a rolling oil spraying amount of more than 980 L / min; the second pass is for double-sheet rolling, with a rolling speed of less than 600 m / min and a rolling oil spraying amount of more than 800 L / min; S8. Finished product slitting: Slit the aluminum foil rolled in S7 as required; S9. Finished product annealing: Put the slit finished product in S8 into an annealing furnace for annealing. Raise the furnace temperature to 200 °C in 4 h and keep it warm for 8 h, then raise the furnace temperature to 260 °C in 4 h and keep it warm for 50 h, and finally raise the furnace temperature to 170 °C in 2 h and keep it warm for 2 h. Keep a negative pressure throughout the annealing process. After the annealing process is completed, take it out of the furnace, use a convection fan to blow air to cool the material. After the material is cooled to room temperature, after passing the inspection, package it according to the packaging requirements.

2. The preparation method of the cast-rolled 8021 alloy aluminum foil according to claim 1, characterized in that, In step S1, the mass percentages of the alloy melt components are as follows: Si = 0.1% - 0.15%, Fe = 1.4% - 1.5%, Cu = 0.04% - 0.05%, Mn ≤ 0.02%, Mg ≤ 0.02%, Cr ≤ 0.01%, Zn ≤ 0.05%, Ti ≤ 0.025%, and the balance is Al.

3. The preparation method of the cast-rolled 8021 alloy aluminum foil according to claim 1, characterized in that, In step S1 during the tilting operation, high-purity argon gas shall be introduced at the inlet of the holding furnace for tilting refining, and the dross on the surface of the melt shall be skimmed off after the tilting is completed.

4. The preparation method of the cast-rolled 8021 alloy aluminum foil according to claim 1, characterized in that, In step S2, the hydrogen content of the aluminum alloy melt after on-line treatment is less than 0.12 ml / 100g·Al. During casting production, the front box temperature is 667 - 673 °C, the casting speed is 0.65 - 0.7 m / min, the cooling water temperature is 25 - 30 °C, and the cooling water pressure is 0.4 - 0.5 mpa.

5. The preparation method of the cast-rolled 8021 alloy aluminum foil according to claim 1, characterized in that, The annealing process in step S3 is as follows: the furnace gas temperature is raised to 600 °C in 4 h, the furnace gas is kept under positive pressure for 40 h after the furnace temperature reaches, after the insulation at 600 °C is completed, the side cooling is turned on to lower the furnace temperature to 170 °C and keep it for 2 hours and then the product is taken out of the furnace.

6. The preparation method of the cast-rolled 8021 alloy aluminum foil according to claim 1, characterized in that, In step S4 during rolling, it is required that the coiling tension of each pass is less than the total uncoiling tension of the previous pass to prevent tension scratches. In addition, tail flicking is required during rolling of each pass.

7. The preparation method of the cast-rolled 8021 alloy aluminum foil according to claim 1, characterized in that, In step S4, 100# rolling oil is used during rolling on the cold rolling blooming mill. The additive content of the rolling oil is 7%, the light transmittance is more than 97%. During the rolling process, the rolling oil temperature is 35 - 45 °C, the roll crown is controlled at +0.04 mm, and the roughness is controlled at 0.5 um. The rolling thickness of each pass is as follows: 7 mm → 4 mm → 2.2 mm → 1.2 mm → 0.7 mm → 0.37 mm → 0.2 mm.

8. The preparation method of the cast-rolled 8021 alloy aluminum foil according to claim 1, characterized in that, In step S5, before slitting and trimming longitudinally, check whether there are foreign objects on the guide roller path and whether the guide rollers rotate flexibly. Each guide roller in the guide path must be wiped with alcohol before threading; during production, strictly check the surface quality of the material to ensure that there are no surface defects such as imprints, sticking aluminum, abrasions and / or scratches on the surface of the aluminum coil, and there are no burrs, tower shapes, flanging and / or small edge wrinkles at the end face.

9. The method for preparing the cast-rolled 8021 alloy aluminum foil according to claim 1, characterized in that, In step S9 during inspection, inspect the material thickness, width, end face quality, surface quality, water brushing condition, pinhole condition and unfolding quality indicators. The tensile strength of the finished product is 95 - 110 Mpa, the elongation is ≥ 25%, and the Erichsen value is ≥ 7.5 mm. After passing the inspection, package it with EPE, plastic film, desiccant, plug, threading pipe and wooden box according to the packaging requirements. After packaging is completed, stick a material label on the outside of the wooden box, and the label shall contain information such as box number, alloy status, specification, net weight, gross weight and packaging date.

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