A method for preparing cast-rolled 8021 alloy aluminum foil

Abstract

The present invention belongs to the technical field of aluminum alloy materials, and specifically discloses a method for preparing cast-rolled 8021 alloy aluminum foil. The method comprises the following steps: producing an 8021 alloy billet with a thickness of 6-8 mm by casting and rolling; directly homogenizing annealing the billet without cooling; rolling the billet through a cold rolling production process; and then rolling the billet through multiple passes such as trimming, secondary annealing, and foil rolling to obtain the finished product thickness. Compared with the traditional direct-chill ingot hot rolling process, the method omits multiple steps such as hot-rolled plate ingot casting, ingot sawing and milling, uniform annealing, and hot roughing mill opening and rolling with a large processing capacity, thereby saving energy and reducing carbon dioxide emissions. The finished product has performance equivalent to or even better than that of a hot-rolled product, thus meeting customer needs.

Description

Technical Field

[0001] The invention belongs to the technical field of aluminum alloy materials, and specifically discloses a preparation method of cast-rolled 8021 alloy aluminum foil. Background Art

[0002] Aluminum foil, thanks to its moisture-proof, airtight, light-blocking, abrasion-resistant, non-toxic and odorless properties, is widely used in the food, pharmaceutical, tobacco, and daily chemical industries. As usage scenarios become increasingly complex, the performance requirements of various industries for aluminum foil are increasing, and the requirements for its mechanical properties, such as elongation, are becoming increasingly stringent.

[0003] Against this backdrop, aluminum foil companies are continuously developing new technologies to improve foil quality and performance to meet the demands of the high-end market. However, overall, aluminum foil produced from hot-rolled billets is significantly superior to cast-rolled foil in terms of surface quality, mechanical properties, elongation, and pinhole index. Cast-rolled foil, however, suffers from a significant quality disadvantage compared to hot-rolled foil. This results in a narrow user base, limited application scenarios, and some high-end products failing to meet technical requirements.

[0004] The conventional hot-rolled 8021 alloy aluminum foil production process is: smelting → ingot casting → sawing and milling → homogenizing annealing → hot rolling → cold rolling → secondary annealing → cold rolling → trimming → foil rolling → slitting → finished product annealing → inspection and packaging. Hot-rolling lines require large heating furnaces, hot rolling mills, and finishing equipment. The purchase, installation, and maintenance costs of these equipment are very high, resulting in significant initial investment and, consequently, high equipment costs. The sawing and milling of hot-rolled ingots generates scrap, requiring numerous production passes and the associated tailing, leading to low yields and high production costs. Hot-rolled plate ingots typically require 21-23 rolling passes from 650mm to 6.0mm. The high number of rolling passes and high energy consumption in the entire process increase production costs. Overall, hot-rolling billet production is associated with high overall production costs due to high equipment investment, low billet yields, and numerous rolling passes.

[0005] Prior art CN111349825A discloses a preparation method for producing high-toughness battery aluminum foil using a short-process cast-rolling billet, which sequentially undergoes the steps of smelting, casting and rolling, cold rolling, homogenization and high-temperature treatment, intermediate rolling, longitudinal shearing, intermediate annealing, finishing rolling, foil rolling, coiling, finished product rolling, slitting, and furnace annealing. This method requires thirteen steps and at least ten rolling passes, resulting in a long production process and many rolling passes. In addition, during the smelting and casting process, this method requires the addition of 0.001-0.04% of a modifier Sr, which is melted at 770°C for 4-6 hours and then refined. Sr itself is expensive and has active properties. Adding the Sr element not only increases production costs, but also easily causes segregation, resulting in unstable quality of the finished product. Summary of the Invention

[0006] In order to solve the problems in the background technology, the present invention discloses a method for preparing cast-rolled 8021 alloy aluminum foil, in which 8021 alloy billets with a thickness of 6-8 mm are produced by casting and rolling. The billets are directly homogenized and annealed without cooling. After being rolled through a cold rolling production process, they are rolled into finished products through multiple passes such as trimming, secondary annealing and foil rolling. The performance of the finished products is equivalent to or even better than that of hot-rolled products, meeting customer needs.

[0007] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions:

[0008] A method for preparing cast-rolled 8021 alloy aluminum foil comprises the following steps:

[0009] S1. Melting: 20% to 30% of self-produced scrap, 10% to 30% of aluminum ingots for remelting, and 50% to 60% of electrolytic aluminum liquid are added to the melting furnace in sequence by mass percentage, heated and stirred evenly, and metal additives are added thereto after the charge is leveled. After the alloy composition ratio is qualified, high-purity argon is used as a carrier, and the refining agent is introduced into the aluminum melt through a stainless steel pipe through a refiner for refining. After the refining is completed, the slag on the surface of the melt is scraped off. After the slag is scraped off, the melt is allowed to stand for 30 minutes and then poured into a holding furnace. After the pouring is completed, the aluminum alloy melt is kept warm and stood in the holding furnace. The melt temperature in the holding furnace is 730-740℃.

[0010] S2. Casting: The qualified aluminum alloy melt in the holding furnace of step S1 is smoothly discharged. The aluminum alloy melt flowing out at a uniform rate is sequentially fed with an online titanium wire, degassed and deslagging in an online degassing box, and filtered in a plate filter box. The melt after online treatment is uniformly injected into the casting zone of the casting machine through a casting nozzle. The melt is formed into a billet cast-rolled coil with a thickness and width of 6-8 mm in the casting zone.

[0011] S3, homogenization annealing: homogenization annealing is performed on the cast-rolled coil obtained in S2;

[0012] S4, cold rolling: after homogenization annealing, the cast rolled coil is cooled to below 45°C after being taken out of the furnace, and then rolled in a cold rolling mill for multiple passes to a 0.2 mm thick cold rolled coil;

[0013] S5. Longitudinal shearing: trim the cold rolled coil. The width tolerance of the material after trimming is required to be less than ±1mm, and there should be no aluminum powder accumulation on the edge.

[0014] S6, secondary annealing: Place the trimmed material on the annealing rack and put it into the annealing furnace, ensuring that the material is suspended during the entire process of transportation, annealing and cooling. The annealing process is as follows: raise the furnace temperature to 480℃ over 4 hours and keep it warm for 10-20 hours, then reduce the furnace temperature to 430℃ and keep it warm for 5 hours, and finally turn on the side cooling to reduce the furnace temperature to 170℃ and keep it warm for 2 hours before taking it out of the furnace;

[0015] S7, foil rolling: the coil after S6 annealing is put into the foil rolling mill for rolling. When rolling aluminum foil, the specific rolling passes are 0.2mm→0.09mm→0.05mm. Among them, the first pass is the rolling of O-state material, the processing rate is 55%, the rolling speed is less than 500m / min, and the rolling oil spraying volume is greater than 980L / min; the second pass is double-combined rolling, that is, double-combined bundling, the rolling speed is less than 600m / min, and the rolling oil spraying volume is greater than 800L / min;

[0016] S8, finished product cutting: the aluminum foil rolled in S7 is cut into finished products as required;

[0017] S9, finished product annealing: Place the finished product cut in S8 into the annealing furnace for annealing. After 4 hours, raise the furnace temperature to 200℃ and keep it warm for 8 hours. Then, raise the furnace temperature to 260℃ and keep it warm for 50 hours. Finally, raise the furnace temperature to 170℃ and keep it warm for 2 hours. Maintain negative pressure throughout the annealing process. After the annealing process is completed, take the product out of the furnace and use a convection fan to blow air to cool the material. After the material cools to room temperature, it is packaged according to the packaging requirements after passing the inspection.

[0018] Furthermore, in the method for preparing 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.

[0019] Furthermore, in the method for preparing the cast-rolled 8021 alloy aluminum foil, during the pouring operation in step S1, high-purity argon gas is introduced into the inlet of the holding furnace for pouring refining, and the slag on the surface of the melt is scraped off after the pouring is completed.

[0020] Furthermore, in the method for preparing the cast-rolled 8021 alloy aluminum foil, the hydrogen content of the aluminum alloy melt subjected to online treatment in step S2 is less than 0.12 ml / 100 g·Al, and 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.

[0021] Furthermore, in the preparation method of the cast-rolled 8021 alloy aluminum foil, the annealing execution process of step S3 is as follows: the furnace gas temperature is raised to 600°C over 4 hours, and after the furnace temperature reaches the positive pressure of the furnace gas, it is kept warm for 40 hours. After the insulation at 600°C is completed, the side cooling is turned on to cool the furnace temperature down to 170°C and keep it warm for 2 hours before taking it out of the furnace.

[0022] Furthermore, in the method for preparing the cast-rolled 8021 alloy aluminum foil, during rolling in step S4, the winding tension of each pass is required to be less than the total unwinding tension of the previous pass to prevent tension scratches, and tail swinging is required during each rolling pass.

[0023] Furthermore, in the preparation method of the cast-rolled 8021 alloy aluminum foil, in step S4, 100# rolling oil is used during the cold rolling mill, the rolling oil additive content is 7%, the transmittance is above 97%, the rolling oil temperature during the rolling process is 35-45°C, the roller crown is controlled at +0.04mm, the roughness is controlled at 0.5um, and the rolling thickness of each pass is as follows: 7mm→4mm→2.2mm→1.2mm→0.7 mm→0.37mm→0.2mm.

[0024] Furthermore, in the preparation method of the cast-rolled 8021 alloy aluminum foil, in step S5, before longitudinal shearing, the guide roller road is checked for foreign matter, and the guide rollers are checked for flexible rotation. Before threading, each guide roller in the guide road must be cleaned with alcohol; during the production process, the surface quality of the material is strictly checked to ensure that the surface of the aluminum coil has no marks, aluminum sticking, abrasions and / or scratches, and the end face has no burrs, towers, ruffles and / or small waves on the edges.

[0025] Furthermore, in the preparation method of the cast-rolled 8021 alloy aluminum foil, during the S9 finished product inspection before packaging, the material thickness, width, end face quality, surface quality, water brushing condition, pinhole condition and unfolding quality indicators are inspected. The finished product has a tensile strength of 95-110 MPa, an elongation ≥25%, and a cup protrusion ≥7.5 mm. After passing the inspection, it is packaged using pearl cotton, plastic film, desiccant, plug, feed tube and wooden box in accordance with the packaging requirements. After packaging is completed, a material label is affixed to the outside of the wooden box. The label must include the box number, alloy state, specifications, net weight, gross weight and packaging date information.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The preparation method of the cast-rolled 8021 alloy aluminum foil of the present invention comprises the following steps: during smelting, 20% to 30% of self-produced waste, 10% to 30% of aluminum ingots for remelting, and 50% to 60% of electrolytic aluminum liquid are sequentially added to the smelting furnace in terms of mass percentage; the high temperature of the high-temperature electrolytic aluminum liquid is used to immerse the added self-produced waste and conduct heat; this feeding method can avoid contact between the self-produced waste and air during melting, thereby reducing the proportion of oxidation and burning loss and lowering production costs; and can also reduce the amount of aluminum ingots and aluminum liquid raw materials, thereby achieving low-cost production and realizing green, low-carbon, and environmentally friendly production;

[0028] (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 the smelting and casting process. The blank is rolled into a blank with a thickness of 2.0 to 6.5 mm through 1 to 3 passes. The aluminum alloy coil is lubricated and cooled using rolling oil to obtain an aluminum alloy coil. The aluminum alloy coil is then subjected to intermediate rolling and homogenization annealing. The temperature of the blank after cooling out of the furnace is less than 70°C. The blank is 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 utilizes the heat of the blank off the machine during homogenization annealing. Compared with CN111349825A, the present invention greatly shortens the production process, reduces production costs, and reduces employee labor intensity.

[0029] The present invention uses casting and rolling to directly produce billets with a thickness of 6-8 mm. Compared with the traditional direct-chill ingot hot rolling process, it eliminates multiple steps such as hot-rolled plate ingot casting, ingot sawing and milling, uniform annealing, and hot roughing mill opening and rolling with large processing capacity, thereby saving energy and reducing carbon dioxide emissions. The saved production cost has obvious economic and social benefits.

[0030] (3) The finished aluminum foil prepared by the method for preparing 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, fully meeting the needs of customers. DETAILED DESCRIPTION

[0031] In order to better understand the present invention, the content of the present invention is further clearly described below in conjunction with the examples, but the protection content of the present invention is not limited to the following examples. 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 during the production of aluminum alloy products with alloy grades of 1060, 1070, 1235 and / or 8021 by the applicant's company. The mass percentages of the specific alloy components are as follows:

[0032] Example 1

[0033] A method for preparing cast-rolled 8021 alloy aluminum foil comprises the following steps:

[0034] S1. Melting: Melting is carried out in a 30t round furnace. 25.33% of self-produced scrap, 18.50% of remelting aluminum ingots and 56.17% of electrolytic aluminum liquid are added to the melting furnace in turn. When adding materials for smelting, self-produced scrap is added first, and then remelting aluminum ingots are added to press on the scrap to prevent the scrap from floating and directly contacting the burner flame after the electrolytic aluminum liquid is added, causing burning. After the solid material is added, electrolytic aluminum liquid is poured into the aluminum inlet, and heated and stirred by the combustion of two natural gas burners in the furnace. After the melt in the furnace is evenly melted, metal additives such as iron agent, quick-dissolving silicon and copper agent are added thereto. 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%, the balance is Al. After the alloy composition ratio is qualified, high-purity argon is used as a carrier, and the refining agent is introduced into the aluminum melt through a stainless steel pipe through 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, each fixed position is required to be refined for more than 20 seconds. After the refining is completed, the slag on the surface of the melt is scraped off to ensure that the surface of the melt presents a mirror-like shape of aluminum liquid. No slag residue is allowed to prevent secondary contamination of the melt after hydrogen absorption. After the slag is completed, the melt is allowed to stand for 30 minutes and then poured into the holding furnace. When pouring the furnace, high-purity argon should be introduced at the inlet of the holding furnace for pouring refining. After the pouring is completed, the slag on the surface of the melt is scraped off. The same as the slag removal requirements of the aforementioned smelting furnace, when the aluminum alloy melt is standing in the holding furnace, the top electric heating tube is used to heat the melt to keep the melt temperature constant. The molten metal temperature is required to be controlled at 730-740℃.

[0035] S2, casting: by controlling the gap size between the flow control rod and the flow eye brick, the qualified aluminum alloy melt in the holding furnace of step S1 is smoothly discharged, and the liquid level fluctuation at the aluminum outlet of the holding furnace shall not exceed 5mm. After the aluminum alloy melt flowing out at a uniform speed is added through the online two-stage titanium wire, high-purity argon gas is introduced into the degassing box through the silicon carbide rotor to degas and deslag the aluminum melt. The degassing box rotor speed 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 gas is introduced into the degassing box as a protective gas to alleviate the oxidation and slagging 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 in series are placed in the filter box. The hydrogen content of the aluminum alloy melt treated online is less than 0.12ml / 100g·Al;

[0036] The melt after online processing is injected into the casting area composed of two upper and lower rollers in equal amounts and at a uniform speed through the casting nozzle. Cooling water is passed into the roller core to remove the heat of the melt. The melt forms billets with a thickness of 6.1mm and varying widths in the casting area. During casting production, the front box temperature needs to be 667-673℃, the casting speed needs to be 0.65-0.7m / min, the cooling water temperature needs to be 25-30℃, and the cooling water pressure needs to be 0.4-0.5mpa. By adjusting the above process parameters, stable production of cast billets can be achieved.

[0037] S3, homogenization annealing: homogenization annealing is performed on the cast-rolled coil obtained in S2. Since the cast-rolled coil is in a sleeveless state, it is necessary to arrange floor annealing during homogenization annealing. To avoid the coil being damaged, asbestos and other cushioning materials need to be placed on the pallet. To control the annealing production cost, it is necessary to ensure that the furnace is fully loaded for annealing. Since the cast-rolled coil has no sleeve, the single-furnace annealing can increase the furnace load to six coils, about 80t. The annealing process is as follows: the furnace temperature is raised to 600℃ over 4 hours. After the furnace temperature reaches 600℃, the furnace is kept at positive pressure for 40 hours. After the 600℃ holding period is completed, the side cooling is turned on to reduce the furnace temperature to 170℃ and keep it at this temperature for 2 hours before unloading;

[0038] S4. Cold rolling: After homogenization annealing, the cast coil is cooled to below 45℃ after being taken out of the furnace, and then rolled into 0.2mm thick cold rolled coil in multiple passes on the cold rolling blank mill. During rolling, the coiling tension of each pass is required to be less than the total tension of the previous pass to prevent tension scratches. In addition, tail swinging is required during each rolling pass. 100# rolling oil is used when rolling on the cold rolling blank mill. The rolling oil additive content is 7%, and the transmittance is more than 97%. The rolling oil temperature during the rolling process is 35-45℃, the roller crown is controlled at +0.04mm, and the roughness is controlled at 0.5um. The rolling thickness of each pass is as follows: 7mm→4mm→2.2mm→1.2mm

[0039] →0.7 mm→0.37 mm→0.2 mm;

[0040] S5. Longitudinal shearing: Before longitudinal shearing, check whether there are foreign objects on the guide roller road and whether the guide rollers are flexible. Before threading, use alcohol to clean each guide roller in the guide road. During the production process, strictly check the surface quality of the material to ensure that there are no marks, aluminum sticking, abrasions and / or scratches on the surface of the aluminum coil, and no burrs, pyramids, ruffles and / or small waves on the edge of the end face. After trimming, the material width tolerance must be less than ±1mm, and there must be no aluminum powder accumulation on the edge.

[0041] S6, Secondary annealing: Place the trimmed material on the annealing rack and put it into the annealing furnace, ensuring that the material is suspended during the entire process of transportation, annealing and cooling to avoid bruising or crushing of the material. Four rolls of the same width are arranged in one furnace for this annealing. The annealing process is as follows: raise the furnace temperature to 480℃ over 4 hours and keep it warm for 10-20 hours, then reduce the furnace temperature to 430℃ and keep it warm for 5 hours, finally turn on the side cooling to reduce the furnace temperature to 170℃ and keep it warm for 2 hours before taking it out of the furnace;

[0042] S7, foil rolling: the S6 annealed coil is put into the foil rolling mill for rolling. The surface quality of the rollers needs to be inspected before rolling the aluminum foil. There should be no defects such as roller marks, bright lines, width marks, grinding wheel marks, etc. The material needs to be scrapped from the outermost ring before being threaded. The outer ring material is placed in the roller gap to prevent foreign objects from scratching the rollers and forming roller marks. When rolling aluminum foil, the specific rolling passes are 0.2mm→0.09mm→0.05mm. Among them, the first pass is for rolling the material in O state, with a processing rate of 55% and a rolling speed of less than 50 0m / min, the rolling oil spray volume is greater than 980L / min. By adjusting the rolling speed and the rolling oil spray volume, the problem of coiling side flanging should be prevented. The thickness gauge should be calibrated before the second rolling to ensure that the thickness of the rolled product is normal. At the same time, the splash plate should be adjusted to block the aluminum foil, and the nozzle blowing angle and air volume should be adjusted to ensure that there are no oil spots on the rolled material. The second pass is double-joint rolling, the rolling speed is less than 600m / min, and the rolling oil spray volume is greater than 800L / min.

[0043] S8, finished product slitting: The aluminum foil rolled in S7 is slitting into finished products as required. Before slitting, clean the guide rollers in the guide path and use a brush to clean the aluminum chips in the grooves of the knife rollers to ensure that there are no marks, aluminum sticking, abrasions, or scratches on the surface of the finished product. The end surface is not allowed to have burrs, tower shapes, ruffles, small waves on the edges, etc. The batch number and specifications of the slit small rolls are marked on the surface with a marker. Materials of the same specifications are threaded into one axis using a threading rod and placed in a frame suspended material rack. They are not allowed to fall directly on the ground.

[0044] S9, finished product annealing: put the finished product cut in S8 into the annealing furnace for annealing. Check the annealing furnace condition before entering the furnace, whether the guide plate is deformed, whether there is aluminum foil stuck on the circulation fan cover on the furnace top, check whether the thermocouple on the furnace top is deformed, check whether there is dripping or bottom oil on the annealing furnace top, and only enter the furnace for annealing after checking that there are no abnormalities. After the material enters the furnace, close the furnace door. After checking that the furnace door is closed and sealed without air leakage, annealing production is carried out. The finished product annealing process is specifically to raise the furnace temperature to 200℃ after 4h and keep it warm for 8h, then raise the furnace temperature to 260℃ after 4h and keep it warm for 50h, and finally raise the furnace temperature to 170℃ after 2h and keep it warm for 2h. Maintain negative pressure throughout the annealing process. After the annealing process is completed, take the material out of the furnace and use a convection fan to blow air to cool the material until it cools to room temperature.

[0045] Inspection and packaging: Before packaging the finished products, the material thickness, width, end face quality, surface quality, water brushing condition, pinhole condition and unfolding quality indicators are inspected, and samples are taken to test the mechanical properties of small materials. The finished product has a tensile strength of 95-110Mpa, an elongation of 28%, and a cup protrusion of 8.2mm. After passing the inspection, it is packaged in accordance with the packaging requirements using pearl cotton, plastic film, desiccant, plug, feed tube and wooden box. After packaging is completed, the material label is affixed to the outside of the wooden box. The label must include information such as the box number, alloy state, specifications, net weight, gross weight and packaging date. Example 2

[0046] The difference between Example 2 and Example 1 is that the raw materials in step S1 are 20.19% of self-produced scrap, 29.50% of aluminum ingots for remelting 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 of varying thickness and width of 8 mm in the casting area. The other steps are the same as in Example 1. The finished product has a tensile strength of 95 to 110 MPa, an elongation of 28%, and a cupping of 8.2 mm. Example 3

[0047] The difference between Example 3 and Example 1 is that the raw materials in step S1 are 30.10% of self-produced scrap, 10.03% of aluminum ingots for remelting 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 of varying thickness and width of 7 mm in the casting area. The other steps are the same as in Example 1. The finished product has a tensile strength of 95 to 110 MPa, an elongation of 28%, and a cupping of 8.2 mm.

[0048] The 0.05mm 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 95-110Mpa, an elongation of 28%, and a cupping value of 8.2mm. The 0.09mm double-layer aluminum foil roll in the prior art CN111349825A, that is, a single-layer aluminum foil coil with a thickness of 0.045mm, has an elongation of 23% and a cupping value of 7.0mm; the 0.13mm double-layer aluminum foil roll, that is, a single-layer aluminum foil coil with a thickness of 0.065mm, has an elongation of 32% and a cupping value of 7.5mm. For thicker aluminum foil, the greater the elongation, the better, and the greater the cupping value, the better. The 0.05mm aluminum foil of the present invention is different from the aluminum foil in the existing CN111349825A technology in thickness, and the elongation cannot be effectively compared. However, the cupping value of the 0.05mm aluminum foil of the present invention is 0.7mm higher than the detection value of 7.5mm of the 0.065mm aluminum foil in the existing technology CN111349825A, which fully demonstrates 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 hot-rolled products, fully meeting the use needs of customers.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention and are not limiting. Other modifications or equivalent substitutions made to the technical solution of the present invention by ordinary technicians in this field should be included in the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for preparing cast-rolled 8021 alloy aluminum foil, characterized in that: The steps include: S1. Melting: 20% to 30% of self-produced scrap, 10% to 30% of aluminum ingots for remelting, and 50% to 60% of electrolytic aluminum liquid are added to the melting furnace in sequence by mass percentage, heated and stirred evenly, and metal additives are added thereto after the charge is leveled. After the alloy composition ratio is qualified, high-purity argon is used as a carrier, and the refining agent is introduced into the aluminum melt through a stainless steel pipe through a refiner for refining. After the refining is completed, the slag on the surface of the melt is scraped off. After the slag is scraped off, the melt is allowed to stand for 30 minutes and then poured into a holding furnace. After the pouring is completed, the aluminum alloy melt is kept warm and stood in the holding furnace. The melt temperature in the holding furnace is 730-740℃. S2. Casting: The qualified aluminum alloy melt in the holding furnace of step S1 is smoothly discharged. The aluminum alloy melt flowing out at a uniform rate is sequentially fed with an online titanium wire, degassed and deslagging in an online degassing box, and filtered in a plate filter box. The melt after online treatment is uniformly injected into the casting zone of the casting machine through a casting nozzle. The melt is formed into a billet cast-rolled coil with a thickness and width of 6-8 mm in the casting zone. S3, homogenization annealing: homogenization annealing is performed on the cast-rolled coil obtained in S2; S4, cold rolling: after homogenization annealing, the cast rolled coil is cooled to below 45°C after being taken out of the furnace, and then rolled in a cold rolling mill for multiple passes to a 0.2 mm thick cold rolled coil; S5. Longitudinal shearing: trim the cold rolled coil. The width tolerance of the material after trimming is required to be less than ±1mm, and there should be no aluminum powder accumulation on the edge. S6, secondary annealing: Place the trimmed material on the annealing rack and put it into the annealing furnace, ensuring that the material is suspended during the entire process of transportation, annealing and cooling. The annealing process is as follows: raise the furnace temperature to 480℃ over 4 hours and keep it warm for 10-20 hours, then reduce the furnace temperature to 430℃ and keep it warm for 5 hours, and finally turn on the side cooling to reduce the furnace temperature to 170℃ and keep it warm for 2 hours before taking it out of the furnace; S7, foil rolling: the coil after S6 annealing is put into the foil rolling mill for rolling. When rolling aluminum foil, the specific rolling passes are 0.2mm→0.09mm→0.05mm. Among them, the first pass is the rolling of O-state material, the processing rate is 55%, the rolling speed is less than 500m / min, and the rolling oil spraying volume is greater than 980L / min; the second pass is double-combined rolling, the rolling speed is less than 600m / min, and the rolling oil spraying volume is greater than 800L / min; S8, finished product cutting: the aluminum foil rolled in S7 is cut into finished products as required; S9, finished product annealing: Place the S8 cut finished product into the annealing furnace for annealing. After 4 hours, raise the furnace temperature to 200℃ and keep it warm for 8 hours. Then, raise the furnace temperature to 260℃ and keep it warm for 50 hours. Finally, raise the furnace temperature to 170℃ and keep it warm for 2 hours. Maintain negative pressure throughout the annealing process. After the annealing process is completed, take the material out of the furnace and use a convection fan to blow air to cool the material. After the material cools to room temperature, it is packaged according to the packaging requirements after passing the inspection.

2. The method for preparing the cast-rolled 8021 alloy aluminum foil according to claim 1, wherein: 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.

3. The method for preparing the cast-rolled 8021 alloy aluminum foil according to claim 1, wherein: During the pouring operation in step S1, high-purity argon gas is introduced into the inlet of the holding furnace for pouring and refining. After pouring, the slag on the surface of the melt is scraped off.

4. The method for preparing the cast-rolled 8021 alloy aluminum foil according to claim 1, wherein: The hydrogen content of the aluminum alloy melt processed online in step S2 is less than 0.12 ml / 100 g·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 method for preparing the cast-rolled 8021 alloy aluminum foil according to claim 1, wherein: The annealing process in step S3 is as follows: the furnace gas temperature is raised to 600°C over 4 hours, and after the furnace temperature reaches 600°C, the furnace gas is kept at positive pressure for 40 hours. After the 600°C insulation is completed, the side cooling is turned on to reduce the furnace temperature to 170°C and keep it at this temperature for 2 hours before taking it out of the furnace.

6. The method for preparing the cast-rolled 8021 alloy aluminum foil according to claim 1, wherein: During rolling in step S4, the coiling tension of each pass is required to be less than the total uncoiling tension of the previous pass to prevent tension scratches. In addition, tail swinging is required during each rolling pass.

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

8. The method for preparing the cast-rolled 8021 alloy aluminum foil according to claim 1, wherein: In step S5, before longitudinal shearing, check whether there are foreign objects on the guide roller road and whether the guide rollers can rotate flexibly. Before threading the belt, use alcohol to clean each guide roller in the guide road. During the production process, strictly check the surface quality of the material to ensure that there are no marks, aluminum sticking, abrasions and / or scratches on the surface of the aluminum coil, and no burrs, pyramids, ruffles and / or small waves on the edge of the end face.

9. The method for preparing the cast-rolled 8021 alloy aluminum foil according to claim 1, wherein: During the inspection in step S9, the material thickness, width, end face quality, surface quality, water brushing condition, pinhole condition and expandability quality indicators are inspected. The finished product has a tensile strength of 95-110Mpa, an elongation ≥25%, and a cup protrusion ≥7.5mm. After passing the inspection, it is packaged in accordance with the packaging requirements using pearl cotton, plastic film, desiccant, plug, feed tube and wooden box. After packaging is completed, a material label is affixed to the outside of the wooden box. The label must include the box number, alloy state, specifications, net weight, gross weight and packaging date information.

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