Aluminum alloy sheet with excellent deep drawability and preparation method thereof

Abstract

The invention discloses an aluminum alloy sheet with excellent deep drawability and a preparation method of the aluminum alloy sheet. The aluminum alloy sheet is prepared from the following components in percentage by mass: 1.0-1.5% of Mn, 0.8-1.3% of Mg, 0.1-0.2% of Si, 0.1-0.2% of Fe and the balance of Al and inevitable impurity elements. The preparation method sequentially comprises the steps of smelting and preparing aluminum alloy liquid, blowing and refining in a furnace, online degassing and filtering outside the furnace, ultrasonic-assisted cast rolling, slab high-temperature homogenizing treatment, large-deformation cold rolling, high-temperature annealing, medium-deformation cold rolling, recrystallization annealing, small-deformation cold rolling, finishing and trimming and finished product annealing. The mechanical property and the structure property uniformity of the aluminum alloy sheet are improved, the tensile strength is not lower than 200 MPa, the percentage elongation after fracture is not lower than 20%, the deep drawing cracking tendency and the earing rate are effectively reduced, and the deep drawing forming requirements of aluminum products such as ring-pull cans, new energy power battery shells, mobile phone and digital product shells and electric cooker liners are met.

Description

Technical Field

[0001] The invention belongs to the technical field of aluminum alloy plate preparation, and specifically relates to an aluminum alloy thin plate with excellent deep drawing performance and a preparation method thereof. Background Art

[0002] Aluminum-manganese aluminum alloy sheets have excellent corrosion resistance and are widely used in beverages, kitchenware, ships, automobiles, construction, electronic appliances and other fields, such as stamping cans, new energy power battery shells, mobile phone and digital product shells, rice cooker liner, etc. This type of aluminum alloy sheet is traditionally produced mainly by hot rolling process, and the process flow is as follows: melting aluminum ingots → preparing aluminum alloy liquid → refining degassing filtration → ingot casting → sawing → homogenization → washing → hot rolling → annealing → cold rolling → annealing → cold rolling → packaging, which has problems such as long process flow, multiple processes, low yield, large investment, and high cost. Casting and rolling is to pour the aluminum alloy liquid directly into the roll gap of the casting and rolling machine and roll it into aluminum plate. It is a short-process forming process that can greatly shorten the process flow, reduce production processes, and help reduce production costs.

[0003] The Chinese patent document with publication number CN101318198A discloses a method for manufacturing a cast 3004 alloy deep-drawn material, which includes casting and rolling a 3004 aluminum alloy billet, cold rolling the billet, high temperature annealing, multiple cold rolling, and finished product annealing to obtain a final product. Although the elongation of the 3004 alloy deep-drawn material is relatively high, the tensile strength is still relatively low.

[0004] The Chinese patent document with publication number CN115254953A discloses a method for manufacturing a cast-rolled 3004 patterned plate, including cast-rolled 3004 aluminum alloy billet, cold rolling, incomplete annealing, cold rolling embossing, spraying and brushing, vacuum liquid absorption, water cleaning, purging, drying, and incomplete annealing. The method overcomes the technical difficulties such as poor plasticity of the cast-rolled 3004 aluminum alloy billet, and the distorted and offset patterns and incomplete patterns that are easy to appear during embossing.

[0005] The Chinese patent document with publication number CN101664792A discloses an engineering process for producing low-iron and low-silicon 3004 alloy by direct casting and rolling of electrolytic aluminum liquid, including melting aluminum liquid, composition adjustment, three online refining, static, degassing, grain refinement, filtration, inclined casting and rolling, homogenization, cold rolling, intermediate annealing, cold rolling, complete annealing, coiling and packaging. This method simplifies the production process and is conducive to energy conservation and emission reduction.

[0006] The Chinese patent document with publication number CN116219210A discloses a process for producing deep-drawn aluminum strips for kitchenware from recycled aluminum, including smelting, standing, furnace tilting, casting, cast plate transmission cooling, three-continuous rolling, billet homogenization annealing, rough rolling, intermediate annealing, finishing rolling, and longitudinal shearing. The method uses recycled aluminum as raw material, reduces production costs, improves the stability of product performance, and reduces defects such as cracking and streaks.

[0007] Based on the results of literature retrieval and production practice experience, the aluminum alloy sheets produced by the existing casting and rolling technology still have the following problems: (1) The strength of aluminum alloy sheets is generally low, the plasticity is poor, and they are prone to cracking during deep drawing, resulting in a low pass rate for stamped aluminum products. (2) Due to the uneven organizational composition of the cast-rolled aluminum slab, the performance of the aluminum alloy sheets is anisotropic, and the stamping ear rate is high, which reduces the quality and yield of the products. (3) The preparation process is still relatively long and the number of steps is still too large. In order to obtain highly clean products, multiple spray refining is required, which increases the oxidation and burning loss of the aluminum liquid and the production cost. Therefore, the existing aluminum alloy sheets and their preparation methods still need to be improved and developed. Summary of the invention

[0008] In view of the problems and shortcomings mentioned in the background technology, the present invention provides an aluminum alloy thin plate with excellent deep drawing performance and a preparation method thereof. By scientifically designing the composition of the aluminum alloy, optimizing the degassing and slag removal process of the aluminum alloy liquid and adopting high-energy ultrasonic assisted casting and rolling, the cleanliness and uniformity of the structure of the cast and rolled aluminum slab are improved, the production process is shortened, the strength, plasticity and uniformity of the structure and performance of the aluminum alloy thin plate are improved, cracking during deep drawing is avoided, and the earing rate is reduced, thereby solving the problems and shortcomings mentioned in the background technology.

[0009] The technical solution adopted by the present invention to achieve the above-mentioned purpose is as follows:

[0010] The first aspect of the present invention provides an aluminum alloy sheet with excellent deep drawing performance, characterized in that the aluminum alloy sheet is composed of the following components in mass percentage: Mn 1.0-1.5%, Mg 0.8-1.3%, Si 0.1-0.2%, Fe 0.1-0.2%, and the remainder is Al and unavoidable impurity elements, the individual content of the impurity elements is ≤0.05%, and the total amount of the impurity elements is ≤0.15%.

[0011] Among them, Mn and Mg are the main strengthening elements of aluminum alloy sheets. Mn and Mg can enhance the strength of aluminum alloy sheets through solid solution strengthening, and Mn can also form MnAl6 particles to enhance the strength of aluminum alloy sheets through dispersion strengthening. A Mn content lower than 1.0% or a Mg content lower than 0.8% will result in insufficient strength of the aluminum alloy sheet. The higher the Mn and Mg content, the higher the strength of the aluminum alloy sheet. However, if the Mn and Mg content is too high, the plasticity of the aluminum alloy sheet will also be reduced. Therefore, as a preferred embodiment, the Mn content is 1.0-1.5%, and the Mg content is 0.8-1.3%.

[0012] Si and Fe are inevitable impurity elements in aluminum alloy sheets, mainly from aluminum ingots and smelting tools. Aluminum alloy sheets contain less Si and Fe, which can enhance the strength of aluminum alloy sheets. However, Si and Fe are easy to form coarse intermetallic compounds in aluminum alloy sheets, which will not only reduce the strength, plasticity and corrosion resistance of aluminum alloy sheets, but also cause cracking of aluminum alloy sheets during deep drawing. Therefore, the content of Si and Fe in aluminum alloy sheets should be strictly limited. Preferably, the content of Si is 0.1-0.2% and the content of Fe is 0.1-0.2%.

[0013] A second aspect of the present invention provides a method for preparing an aluminum alloy sheet with excellent deep drawing performance, which is characterized by comprising the following steps in sequence:

[0014] Step 1: Melting and preparing aluminum alloy liquid according to the composition and mass percentage of the aluminum alloy sheet;

[0015] Step 2: Use argon gas and powder refining agent to spray and refine the aluminum alloy liquid in the furnace to remove gases and impurities;

[0016] Step 3: The aluminum alloy liquid flows through the degassing box and the filter box arranged on the flow trough in sequence for online degassing and filtering treatment;

[0017] Step 4: Continuously casting and rolling the aluminum alloy liquid into an aluminum alloy slab roll I under the action of ultrasonic waves;

[0018] Step 5: subjecting the aluminum alloy slab coil I to high temperature homogenization treatment and large deformation cold rolling to obtain the aluminum alloy slab coil II;

[0019] Step 6: performing high temperature annealing treatment and medium deformation cold rolling on the aluminum alloy slab coil II to obtain the aluminum alloy slab coil III;

[0020] Step 7: performing recrystallization annealing and multiple passes of small deformation cold rolling on the aluminum alloy slab coil III to obtain an aluminum alloy thin plate coil;

[0021] Step eight: finishing trimming and annealing the aluminum alloy sheet coil to obtain the aluminum alloy sheet with excellent deep drawing performance.

[0022] Furthermore, the aluminum melting furnace used for smelting and preparing the aluminum alloy liquid in step one is a regenerative gas-fired aluminum melting furnace, and the heating and melting temperature is 720-740°C. In addition to the regenerative gas-fired aluminum melting furnace, the aluminum melting furnace can also be a resistance-type aluminum melting furnace or an electromagnetic induction aluminum melting furnace. Since the regenerative gas-fired aluminum melting furnace has the advantages of high efficiency and energy saving, it is beneficial to reduce production costs. Therefore, the regenerative gas-fired aluminum melting furnace is preferred for smelting and preparing the aluminum alloy liquid. The heating and melting temperature should not be lower than 720°C, otherwise it will cause the aluminum ingot to melt slowly, affecting production efficiency. The heating and melting temperature should not be higher than 740°C, otherwise it will aggravate the oxidation and burning of the aluminum ingot and the aluminum alloy liquid, and will also increase production costs.

[0023] Furthermore, the purity of the argon gas in step 2 is ≥99.99%, the amount of the powder refining agent used is 0.1-0.2% of the weight of the aluminum alloy liquid, and the spray refining time is 10-20 minutes.

[0024] When smelting and preparing aluminum alloy liquid, it is inevitable to bring in water vapor and inclusions such as alumina, which will cause the aluminum alloy liquid to absorb hydrogen and inclusions. If the hydrogen and inclusions in the aluminum alloy liquid are not removed, the hydrogen and inclusions will eventually remain in the aluminum alloy sheet to form defects such as pores and looseness, which will not only seriously reduce the strength and plasticity of the aluminum alloy sheet, but also cause bubbling on the surface of the aluminum product and cracking during stamping. Therefore, in order to improve the strength and plasticity of the aluminum alloy sheet and eliminate defects such as cracking, the aluminum alloy liquid must be degassed and deslag purified.

[0025] The spray refining adopts a powder spraying tank and a metal tube, uses argon as a carrier, sprays the powder refining agent into the aluminum alloy liquid, makes the refining agent fully contact and react with the aluminum alloy liquid, and then takes out the inclusions and hydrogen in the aluminum alloy liquid. The degassing and slag removal effect of the spray refining is related to the purity of the argon gas, the amount of the refining agent and the spray refining time. The higher the purity of the argon gas, the higher the spray refining effect, but the production cost will increase accordingly. The spray refining time cannot be too short, and the amount of the refining agent cannot be too little, otherwise the degassing and slag removal effect cannot be achieved. The spray refining time cannot be too long, otherwise the oxidation and burning of the aluminum alloy liquid will increase. The amount of the refining agent cannot be too much, otherwise the alkali metal content in the aluminum alloy liquid will exceed the standard. After the spray refining is completed and the scum on the surface of the aluminum alloy liquid is removed, a covering agent should be sprinkled on the surface of the aluminum alloy liquid in time to avoid oxidation and burning of the aluminum alloy liquid and re-inhalation.

[0026] Furthermore, the powder refining agent in step 2 is composed of the following components in mass percentage: NaCl 35.12%, NaF 19.84%, TiCl 3 16.51%, SrSO 4 10.06%, KPO 3 11.45%, Na 2 B 4 O 7 7.02%, and the preparation method of the powder refining agent comprises the following steps in sequence:

[0027] (1) According to the composition and mass percentage of the refining agent, NaCl, NaF, TiCl3, SrSO4, KPO3, and Na2B4O7 with a purity of ≥99.8% are selected as raw materials for batching; (2) the ingredients are added into water at a temperature of 70° C. and stirred to dissolve into an aqueous solution, wherein the mass ratio of water to the ingredients is 1.2, and then the aqueous solution is heated to 100° C. to evaporate and obtain solid crystals; (3) the solid crystals are crushed into powders with a particle size of less than 2 mm, and the powders are dried and dehydrated at 160° C. for 4 hours to obtain the refining agent.

[0028] The degassing and deslagging effect of spray refining is closely related to the composition and preparation method of the refining agent. Existing refining agents are mainly fluoride salts and chloride salts, which are directly mixed after crushing. The components of the refining agent exist independently of each other, resulting in a high melting point of the refining agent and low degassing and impurity removal efficiency. In order to obtain highly clean aluminum alloy liquid, it is necessary to spray the refining agent on the aluminum alloy liquid multiple times, which not only increases the production process, but also increases the oxidation and burning of the aluminum alloy liquid, resulting in excessive alkali metals in the aluminum alloy liquid, reducing the surface gloss, mechanical properties and corrosion resistance of the aluminum alloy sheet. In addition, the existing refining agent has a single function and does not have the function of refining and modifying. The refiner and modifier must be added separately, thereby increasing the production process and cost of the aluminum alloy sheet.

[0029] In view of the problems and shortcomings of existing refining agents, the present invention has developed a high-efficiency multifunctional powder refining agent, which is prepared by solution evaporation method, so that the components re-solidify and recrystallize to form a eutectic with a lower melting point. For example, the melting point of NaCl is usually 801°C, and the melting point of NaF is usually 993°C. When the two form NaCl·NaF eutectic, the melting point drops to 698°C, thereby greatly reducing the melting point of the refining agent, making the refining agent easier to dissolve in the aluminum alloy liquid, and enhancing the degassing and slag removal effect of the refining agent. Among them, NaCl reacts with the aluminum alloy liquid to generate AlCl3 with a boiling point of only 180°C. During the floating process, AlCl3 bubbles absorb and capture inclusions and hydrogen to escape from the aluminum alloy liquid, which plays a role in degassing and slag removal. NaF molten salt can destroy the aluminum oxide film, dissolve inclusions such as aluminum oxide into the molten salt, increase the surface tension between the inclusions and the aluminum alloy liquid, promote the separation of inclusions such as aluminum oxide from the aluminum alloy liquid, and enhance the deslag removal function of the refining agent. The Ti element generated by the reaction of TiCl3 with the aluminum alloy liquid directly enters the aluminum alloy liquid, which can refine the grains of the cast aluminum slab, improve the plasticity and uniformity of the organizational composition of the cast aluminum slab, and avoid the additional addition of refiners to increase production costs. The generated AlCl3 bubbles can also absorb and capture inclusions and hydrogen in the aluminum alloy liquid during the floating process, enhancing the degassing and slag removal effect of the refining agent. The Sr and P elements generated by the reaction of SrSO4 and KPO3 with the aluminum alloy liquid enter the aluminum alloy liquid, which can refine the modified Si phase, eliminate the damage to the relative strength and plasticity of coarse Si, and improve the strength and plasticity of the aluminum alloy sheet. The SO2 bubbles obtained by the reaction can also absorb and capture inclusions and hydrogen in the aluminum alloy liquid during the floating process, enhancing the degassing and slag removal ability of the refining agent. Na2B4O7 reacts with the aluminum alloy liquid to generate B elements and enter the aluminum alloy liquid, which can refine the modified Fe-rich phase, eliminate the damage to the relative strength and plasticity of coarse Fe-rich phase, and improve the strength and plasticity of the aluminum alloy sheet.

[0030] Furthermore, the degassing medium introduced into the degassing box in step three is a mixed gas consisting of argon with a purity of ≥99.99%, sulfur hexafluoride and carbon monoxide, wherein the volume percentage of sulfur hexafluoride in the mixed gas is 9-11%, and the volume percentage of carbon monoxide is 3-5%.

[0031] After the refining agent spray refining in the furnace, the gas and slag content of the aluminum alloy liquid has been greatly reduced, but the aluminum alloy liquid still contains gas and slag, because the refining agent spray refining brings in inclusions such as chloride salts and fluoride salts again. In addition, although the refining agent spray refining also has a dehydrogenation effect, the dehydrogenation effect is limited, because the refining agent inevitably contains water, which will be brought in during the spray refining, causing the aluminum alloy liquid to absorb hydrogen again, so that the dehydrogenation of the refining agent spray refining is always in a dynamic equilibrium process. Usually, it is difficult to reduce the hydrogen content of the aluminum alloy liquid to below 0.1ml / 100gAl by refining agent spray refining. Therefore, in order to obtain highly clean aluminum alloy liquid, it is also necessary to carry out online degassing and filtration outside the furnace.

[0032] In the existing degassing box degassing technology, the degassing medium introduced into the degassing box is usually inert gas nitrogen or argon, or a mixture of inert gas and chlorine. Since the relative molecular mass of nitrogen, argon and chlorine is small, the gas density is small. Among them, the relative molecular mass of nitrogen is 28.01 and the density is 1.25kg / m 3 The relative molecular mass of argon is 39.94 and the density is 1.78 kg / m 3 The relative molecular mass of chlorine is 70.91 and the density is 3.21kg / m 3 This causes the bubbles to float faster in the aluminum alloy liquid, and the contact time between the bubbles and the aluminum alloy liquid is shorter, which greatly affects the degassing effect of the degassing box. In addition, although the relative density of chlorine is relatively large, chlorine is a toxic gas with a strong pungent odor, which will not only seriously corrode the equipment, but also cause environmental pollution.

[0033] In view of the problems and shortcomings of the existing degassing technology of the degassing box, in order to improve the degassing effect of the degassing box, the present invention creatively introduces a degassing medium into the degassing box, which is a mixed gas composed of argon with a purity of ≥99.99%, sulfur hexafluoride and carbon monoxide, wherein sulfur hexafluoride is a high-density, high-stability gas, and sulfur hexafluoride is non-toxic, non-combustible and non-corrosive. The relative molecular mass of sulfur hexafluoride is 146.05 and the density is 6.5kg / m 3 , adding 9-11% by volume of sulfur hexafluoride to the mixed gas can significantly slow down the floating speed of bubbles in the aluminum alloy liquid, increase the contact time between the bubbles and the aluminum alloy liquid, and enable the bubbles to capture and absorb more hydrogen and inclusions, thereby improving the degassing effect of the degassing box. Adding 3-5% by volume of carbon monoxide to the mixed gas is to allow carbon monoxide to capture oxygen in the aluminum alloy liquid to form carbon dioxide, prevent oxygen from forming an aluminum oxide film on the bubble surface again with aluminum, enhance the ability of the bubbles to capture and absorb hydrogen and inclusions, and improve the degassing effect. Through mixed gas refining, the hydrogen content of the aluminum alloy liquid can be reduced to below 0.1ml / 100gAl, greatly improving the cleanliness of the aluminum alloy liquid.

[0034] Furthermore, in step 3, the rotation speed of the graphite rotor in the degassing box is 400-500 rpm, the flow rate of the mixed gas is 4-5 cubic meters per hour, and the pressure of the mixed gas is 0.2-0.3 MPa.

[0035] The degassing box is to make the aluminum alloy liquid flow through the degassing box, and use the high-speed rotating graphite rotor in the degassing box to shear and break the mixed gas into small and uniform bubbles. The hydrogen atoms in the aluminum alloy liquid are continuously diffused into the bubbles by using the partial pressure difference between the aluminum alloy liquid and the bubbles, and then the bubbles float out of the aluminum alloy liquid along a spiral trajectory. The degassing effect of the degassing box is also related to the speed of the graphite rotor, the flow rate and pressure of the mixed gas. The speed of the graphite rotor cannot be too low, otherwise it cannot shear and break the bubbles, but the speed cannot be too high, otherwise it is easy to cause aluminum splashing. The flow rate of the mixed gas cannot be too low, and the pressure cannot be too small, otherwise the number of bubbles will be too small, but the flow rate does not need to be too much, and the pressure does not need to be too high, otherwise it will increase the production cost and cause the aluminum alloy liquid to splash too seriously.

[0036] Furthermore, the filter box described in step three is a tubular filter box. The filter medium of the tubular filter box is a ceramic filter tube, which is made of fine silicon nitride ceramic particles and a binder sintered at high temperature. There are a large number of tortuous pores inside. When the aluminum alloy liquid flows through the ceramic filter tube, inclusions are adsorbed or blocked on the surface of the ceramic filter tube and the inner wall of the pores, thereby achieving the effect of filtering and removing impurities. The ceramic filter tube has high thermal strength, strong resistance to thermal shock and thermal erosion, large filtration capacity, and high filtration efficiency. The structure and use of the tubular filter box are available in public literature and will not be repeated here. Tubular filtration is a high-precision filtration. After tubular filtration, the removal rate of inclusions larger than 5μm in the aluminum alloy liquid can reach more than 98%, and the slag content in the aluminum alloy liquid can be reduced to 0.05mm 2 / kg, thereby greatly improving the cleanliness of the aluminum alloy liquid, eliminating the damage of inclusions to the strength and plasticity of the aluminum alloy sheet, and improving the strength and plasticity of the aluminum alloy sheet.

[0037] Furthermore, in step 4, the frequency of the ultrasound is 40-50kHz, the power of the ultrasound is 15-20kW, the temperature of the aluminum alloy liquid is 700-710°C, the casting speed is 700-800 mm / min, and the thickness of the aluminum alloy slab coil I is 5.5-6.5 mm.

[0038] The production of aluminum alloy sheets requires high uniformity of the microstructure and composition of cast-rolled aluminum slabs. Casting and rolling is to inject aluminum alloy liquid directly into the gap between the two casting rolls of the casting and rolling machine through the front box casting nozzle, and cool and solidify into aluminum slabs under the cooling and pressure of the casting rolls. Under conventional casting and rolling conditions, due to the non-equilibrium solidification of aluminum alloy liquid, the grains of cast-rolled aluminum slabs will be coarse, and the components on the cross section of the aluminum slab will be segregated, resulting in uneven microstructure and composition. Coarse grains and uneven composition will reduce the strength and plasticity of aluminum alloy sheets, and cause serious anisotropy of the performance of aluminum alloy sheets.

[0039] In view of the problems and shortcomings of the existing casting and rolling technology, the present invention adopts casting and rolling under the action of ultrasound, and the ultrasonic probe is set in the aluminum alloy liquid in the front box of the casting and rolling machine. Through the vibration and acoustic cavitation effect of the ultrasonic wave, the temperature uniformity of the aluminum alloy liquid in the casting and rolling zone is improved, the number of heterogeneous nucleation of grains is increased, and the segregation of the components of the aluminum alloy liquid is avoided, thereby effectively refining the grains of the cast-rolled aluminum alloy slab and improving the component uniformity of the cast-rolled aluminum alloy slab. In order to effectively play the role of ultrasound and meet the requirements of aluminum alloy thin plates for cast-rolled aluminum slabs, the frequency of ultrasound cannot be lower than 40kHz, and the power of ultrasound cannot be lower than 15kW, otherwise it is impossible to obtain a cast-rolled aluminum alloy slab with sufficiently fine grains and sufficiently uniform components. In addition, the thickness of the aluminum alloy slab cannot be lower than 5.5 mm, otherwise it is impossible to obtain sufficient deformation in the subsequent aluminum alloy thin plate rolling process. But the thickness of the aluminum alloy slab cannot be too thick, otherwise it will increase the number of cold rolling and annealing of the subsequent aluminum alloy slab.

[0040] Furthermore, the temperature of the high temperature homogenization in step five is 560-570° C., the time of the high temperature homogenization is 12-14 hours, the deformation of the large deformation cold rolling is 54.5-76.9%, and the thickness of the aluminum alloy coil II is 1.5-2.5 mm.

[0041] Furthermore, the temperature of the high temperature annealing in step six is ​​500-510° C., the time of the high temperature annealing is 10-12 hours, the deformation of the medium deformation cold rolling is 40-50%, and the thickness of the aluminum alloy slab coil III is 0.75-1.5 mm.

[0042] Furthermore, the temperature of the recrystallization annealing in step seven is 220-230° C., the time of the recrystallization annealing is 5-6 hours, the deformation of each small deformation cold rolling does not exceed 20%, and the thickness of the aluminum alloy sheet coil is 0.1-1 mm.

[0043] Furthermore, in step eight, the temperature for annealing the aluminum alloy sheet coil is 180-190° C., and the annealing time is 3-4 hours.

[0044] Cast aluminum alloy slabs must undergo high-temperature homogenization, multiple passes of cold rolling deformation and annealing to obtain the final aluminum alloy sheet. The control of homogenization, cold rolling and annealing processes is crucial to obtaining aluminum alloy sheets with excellent deep drawing performance. It is necessary to reasonably distribute the deformation amount of each cold rolling pass, and strictly control the temperature of high-temperature homogenization, high-temperature annealing, recrystallization annealing and finished product annealing. If the deformation amount and temperature of each cold rolling pass are unreasonable, it will not only cause cracking of the aluminum alloy slab and sheet, but also fail to obtain aluminum alloy sheets with excellent deep drawing performance.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] (1) The present invention scientifically designs the composition and mass percentage of the aluminum alloy sheet, and adopts a highly efficient and multifunctional recrystallization type powder refining agent for in-furnace spray refining, online degassing in a mixed gas degassing box, and ceramic tube filtration, thereby significantly reducing the gas slag content of the aluminum alloy liquid, reducing the hydrogen content of the aluminum alloy liquid to less than 0.1 ml / 100 gAl, and reducing the inclusion content to 0.05 mm 2 / kgAl or less, by greatly improving the cleanliness of aluminum alloy liquid, eliminating the damage of pores and inclusions to the strength and plasticity of aluminum alloy thin plates, improving the strength and plasticity of aluminum alloy thin plates, avoiding cracking of aluminum alloy thin plates during deep drawing, and improving the qualified rate of stamped aluminum products.

[0047] (2) The present invention refines the grains of the cast-rolled aluminum alloy slab through ultrasonic-assisted casting and rolling, improves the uniformity of the organizational composition of the cast-rolled aluminum alloy slab, and is beneficial to reducing the performance anisotropy of the aluminum alloy sheet and the stamping earing rate of the aluminum alloy sheet.

[0048] (3) The present invention significantly shortens the process flow of aluminum alloy thin plates, reduces the processes of in-furnace refining and online degassing and filtration outside the furnace as well as cold rolling and deformation, improves the production efficiency of aluminum alloy thin plates, and helps reduce the production cost of aluminum alloy thin plates.

[0049] (4) The tensile strength of the aluminum alloy sheet prepared by the technical solution of the present invention is higher than 200 MPa, and the elongation after fracture is greater than 20%. Compared with the similar aluminum alloy sheet produced by the prior art, the tensile strength of the aluminum alloy sheet prepared by the present invention is increased by more than 5%, and the plasticity is increased by more than 25%. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 The present invention is a process flow chart for preparing the aluminum alloy thin plate. DETAILED DESCRIPTION

[0051] The technical solution of the present invention is described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] Embodiment 1:

[0053] The aluminum alloy sheet is composed of the following components in mass percentage: Mn 1.26%, Mg 1.19%, Si 0.16%, Fe0.18%, and the balance is Al and unavoidable impurity elements, the individual content of the impurity elements is ≤0.05%, and the total amount of the impurity elements is ≤0.15%. The preparation method comprises the following steps in sequence: step 1: according to the composition and mass percentage of the aluminum alloy sheet, a regenerative gas-fired aluminum melting furnace is used to melt and prepare aluminum alloy liquid at 730°C; step 2: argon gas with a purity of 99.99% and a powder refining agent with a weight of 0.15% of the aluminum alloy liquid are used to spray and refine the aluminum alloy liquid in the furnace for 15 minutes to degas and remove impurities; step 3: the aluminum alloy liquid is sequentially passed through a degassing box and a filter box arranged on a flow trough for online degassing and filtering treatment, a mixed gas composed of argon gas with a purity of 99.99%, sulfur hexafluoride and carbon monoxide is introduced into the degassing box, the volume percentage of sulfur hexafluoride in the mixed gas is 10%, the volume percentage of carbon monoxide is 4%, the speed of the graphite rotor in the degassing box is 450 rpm, the flow rate of the mixed gas is 4.5 cubic meters per hour, the pressure of the mixed gas is 0.25 MPa, and the filter box is a tubular filter box; step 4 : Under the action of ultrasonic waves with a frequency of 42kHz and a power of 18kW, the aluminum alloy liquid at 705°C is continuously cast and rolled into an aluminum alloy slab coil I with a thickness of 6 mm, and the casting and rolling speed is 750 mm / min; Step 5: The aluminum alloy slab coil I is subjected to high-temperature homogenization treatment at 565°C for 13 hours, and then cold-rolled into an aluminum alloy slab coil II with a thickness of 2 mm, and the cold rolling deformation is 66.7%; Step 6: The aluminum alloy slab coil II is subjected to high-temperature annealing at 505°C for 11 hours, and then cold-rolled into an aluminum alloy slab coil III with a thickness of 1 mm, and the cold rolling deformation is 50%; Step 7: The aluminum alloy slab coil III is subjected to recrystallization annealing at 225°C for 5.5 hours, and then cold-rolled into an aluminum alloy sheet coil with a thickness of 0.5 mm through multiple passes, and the cold rolling deformation of each pass does not exceed 20%; Step 8: The aluminum alloy sheet coil is subjected to finishing trimming and finished product annealing at 185°C for 3.5 hours to obtain the aluminum alloy sheet.

[0054] Embodiment 2:

[0055] The aluminum alloy sheet is composed of the following components in mass percentage: Mn 1.48%, Mg 0.86%, Si 0.12%, Fe0.15%, and the balance is Al and unavoidable impurity elements, the individual content of the impurity elements is ≤0.05%, and the total amount of the impurity elements is ≤0.15%. The preparation method comprises the following steps in sequence: step 1: according to the composition and mass percentage of the aluminum alloy sheet, a regenerative gas-fired aluminum melting furnace is used to melt and prepare aluminum alloy liquid at 735°C; step 2: argon gas with a purity of 99.99% and a powder refining agent with a weight of 0.18% of the aluminum alloy liquid are used to spray and refine the aluminum alloy liquid in the furnace for 17 minutes to degas and remove impurities; step 3: the aluminum alloy liquid is sequentially passed through a degassing box and a filter box arranged on a flow trough for online degassing and filtering treatment, and a mixed gas composed of argon gas with a purity of 99.99%, sulfur hexafluoride and carbon monoxide is introduced into the degassing box, the volume percentage of sulfur hexafluoride in the mixed gas is 9.5%, the volume percentage of carbon monoxide is 4.2%, the speed of the graphite rotor in the degassing box is 480 rpm, the flow rate of the mixed gas is 4.2 cubic meters per hour, the pressure of the mixed gas is 0.28 MPa, and the filter box is a tubular filter box; step 4 : Under the action of ultrasonic waves with a frequency of 40kHz and a power of 20kW, the aluminum alloy liquid at 708°C is continuously cast and rolled into an aluminum alloy slab coil I with a thickness of 6.5 mm, and the casting and rolling speed is 720 mm / min; Step 5: The aluminum alloy slab coil I is subjected to high temperature homogenization treatment at 565°C for 13 hours, and then cold rolled into an aluminum alloy slab coil II with a thickness of 1.5 mm, and the cold rolling deformation is 76.9%; Step 6: The aluminum alloy slab coil II is subjected to high temperature annealing at 500°C for 12 hours, and then cold rolled into an aluminum alloy slab coil III with a thickness of 0.8 mm, and the cold rolling deformation is 46.7%; Step 7: The aluminum alloy slab coil III is subjected to recrystallization annealing at 225°C for 5 hours, and then cold rolled into an aluminum alloy sheet coil with a thickness of 0.2 mm through multiple passes, and the cold rolling deformation of each pass does not exceed 20%; Step 8: The aluminum alloy sheet coil is subjected to finishing trimming and finished product annealing at 185°C for 4 hours to obtain the aluminum alloy sheet.

[0056] Embodiment 3:

[0057] The aluminum alloy sheet is composed of the following components in mass percentage: Mn 1.5%, Mg 0.8%, Si 0.1%, Fe 0.2%, and the balance is Al and unavoidable impurity elements, the content of each impurity element is ≤0.05%, and the total amount of impurity elements is ≤0.15%. The preparation method comprises the following steps in sequence:

[0058] Step 1: According to the composition and mass percentage of the aluminum alloy sheet, a regenerative gas-fired aluminum melting furnace is used to melt and prepare the aluminum alloy liquid at 740°C; Step 2: Argon with a purity of 99.99% and a powder refining agent of 0.2% by weight of the aluminum alloy liquid are used to spray and refine the aluminum alloy liquid in the furnace for 20 minutes for degassing and impurity removal; Step 3: The aluminum alloy liquid is sequentially passed through a degassing box and a filter box arranged on the flow trough for online degassing and filtration treatment, and a mixed gas composed of argon with a purity of 99.99%, sulfur hexafluoride and carbon monoxide is introduced into the degassing box, the volume percentage of sulfur hexafluoride in the mixed gas is 9%, and the volume percentage of carbon monoxide is 5%, the speed of the graphite rotor in the degassing box is 500 rpm, the flow rate of the mixed gas is 4 cubic meters / hour, the pressure of the mixed gas is 0.3MPa, and the filter box is a tubular filter box; Step 4: At a frequency of 50kH z. Under the action of ultrasonic wave with power of 15kW, the aluminum alloy liquid at 710℃ is continuously cast and rolled into aluminum alloy slab coil I with thickness of 6.5mm, and the casting and rolling speed is 700mm / min; Step 5: The aluminum alloy slab coil I is subjected to high temperature homogenization treatment at 570℃ for 12 hours, and then cold rolled into aluminum alloy slab coil II with thickness of 2.5mm, and the cold rolling deformation is 61.5%; Step 6: The aluminum alloy slab coil II is subjected to high temperature annealing at 500℃ for 12 hours, and then cold rolled into aluminum alloy slab coil III with thickness of 1.5mm, and the cold rolling deformation is 40%; Step 7: The aluminum alloy slab coil III is subjected to recrystallization annealing at 220℃ for 6 hours, and then cold rolled into aluminum alloy thin plate coil with thickness of 1mm through multiple passes, and the cold rolling deformation of each pass does not exceed 20%; Step 8: The aluminum alloy thin plate coil is subjected to finishing trimming and finished product annealing at 190℃ for 3 hours to obtain the aluminum alloy thin plate.

[0059] Embodiment 4:

[0060] The aluminum alloy sheet is composed of the following components in mass percentage: Mn 1.0%, Mg 1.3%, Si 0.2%, Fe 0.1%, and the balance is Al and unavoidable impurity elements, the content of each impurity element is ≤0.05%, and the total amount of impurity elements is ≤0.15%. The preparation method comprises the following steps in sequence:

[0061] Step 1: According to the composition and mass percentage of the aluminum alloy sheet, a regenerative gas-fired aluminum melting furnace is used to melt and prepare aluminum alloy liquid at 720°C; Step 2: Argon with a purity of 99.99% and a powder refining agent of 0.1% by weight of the aluminum alloy liquid are used to spray and refine the aluminum alloy liquid in the furnace for 10 minutes for degassing and impurity removal; Step 3: The aluminum alloy liquid is sequentially passed through a degassing box and a filter box arranged on the flow trough for online degassing and filtration treatment, and a mixed gas composed of argon with a purity of 99.99%, sulfur hexafluoride and carbon monoxide is introduced into the degassing box, the volume percentage of sulfur hexafluoride in the mixed gas is 11%, and the volume percentage of carbon monoxide is 3%. The speed of the graphite rotor in the degassing box is 400 rpm, the flow rate of the mixed gas is 5 cubic meters / hour, the pressure of the mixed gas is 0.2MPa, and the filter box is a tubular filter box; Step 4: At a frequency of 48kH z. Under the action of ultrasonic wave with power of 16kW, the aluminum alloy liquid at 700℃ is continuously cast and rolled into aluminum alloy slab coil I with thickness of 5.5mm, and the casting and rolling speed is 800mm / min; Step 5: The aluminum alloy slab coil I is subjected to high temperature homogenization treatment at 560℃ for 14 hours, and then cold rolled into aluminum alloy slab coil II with thickness of 1.5mm, and the cold rolling deformation is 72.7%; Step 6: The aluminum alloy slab coil II is subjected to high temperature annealing at 510℃ for 10 hours, and then cold rolled into aluminum alloy slab coil III with thickness of 0.75mm, and the cold rolling deformation is 50%; Step 7: The aluminum alloy slab coil III is subjected to recrystallization annealing at 230℃ for 5 hours, and then cold rolled into aluminum alloy thin plate coil with thickness of 0.1mm through multiple passes, and the cold rolling deformation of each pass does not exceed 20%; Step 8: The aluminum alloy thin plate coil is subjected to finishing trimming and finished product annealing at 180℃ for 4 hours to obtain the aluminum alloy thin plate.

[0062] The powder refining agent described in Examples 1-4 of the present invention is composed of the following components in mass percentage: NaCl 35.12%, NaF 19.84%, TiCl 3 16.51%, SrSO 4 10.06%, KPO 3 11.45%, and Na 2 B 4 O 7 7.02%. The preparation method of the refining agent comprises the following steps in sequence: (1) according to the composition and mass percentage of the refining agent, NaCl, NaF, TiCl 3, SrSO 4, KPO 3, and Na 2 B 4 O 7 with a purity of 99.8% are selected as raw materials for batching; (2) the ingredients are added into water at a temperature of 70° C. and stirred to dissolve into an aqueous solution, the mass ratio of water to the ingredients being 1.2, and then the aqueous solution is heated to 100° C. to evaporate to obtain a solid crystal; (3) the solid crystal is crushed into a powder with a particle size of less than 2 mm, and the powder is dried and dehydrated at 160° C. for 4 hours to obtain the powder refining agent.

[0063] Comparative Example 1:

[0064] The preparation method of the aluminum alloy thin plate in this comparative example is the same as that in Example 1, except that the aluminum alloy thin plate is composed of the following components in mass percentage: Mn 0.83%, Mg 1.19%, Si 0.16%, Fe 0.18%, and the remainder is Al and unavoidable impurity elements, the individual content of the impurity elements is ≤0.05%, and the total amount of impurity elements is ≤0.15%.

[0065] Comparative Example 2:

[0066] The preparation method of the aluminum alloy thin plate in this comparative example is the same as that in Example 1, except that the aluminum alloy thin plate is composed of the following components in mass percentage: Mn 1.26%, Mg 0.74%, Si 0.16%, Fe 0.18%, and the remainder is Al and unavoidable impurity elements, the individual content of the impurity elements is ≤0.05%, and the total amount of impurity elements is ≤0.15%.

[0067] Comparative Example 3:

[0068] The components, mass percentage and preparation method of the aluminum alloy thin plate in this comparative example are the same as those in Example 1, except that the powder refining agent used is a conventional powder refining agent available on the market, and the powder refining agent is composed of the following components in mass percentage: NaCl 36.13%, KCl 15.42%, CaF2 16.84%, NaF 19.24%, and C2Cl6 12.37%. The powder refining agent is obtained by directly crushing and mixing the raw materials.

[0069] Comparative Example 4:

[0070] The component composition, mass percentage and preparation method of the aluminum alloy thin plate in this comparative example are the same as those in Example 1, except that the degassing medium introduced into the degassing box in step three is argon with a purity of 99.99%, rather than a mixed gas composed of argon with a purity of 99.99%, sulfur hexafluoride and carbon monoxide.

[0071] Comparative Example 5:

[0072] The component composition, mass percentage and preparation method of the aluminum alloy thin plate in this comparative example are the same as those in Example 1, except that ultrasound is not applied in step 4, but the aluminum alloy liquid is continuously cast and rolled into an aluminum alloy slab coil under conventional conditions.

[0073] Comparative Example 6:

[0074] The components and mass percentages of the aluminum alloy thin plate in this comparative example are the same as those in Example 1, except that in step 2, a commercially available conventional powder refining agent is used, and in step 3, the degassing medium introduced into the degassing box is argon with a purity of 99.99%, rather than a mixed gas composed of argon with a purity of 99.99%, sulfur hexafluoride and carbon monoxide, and in step 4, ultrasound is not implemented, but the aluminum alloy liquid is continuously cast and rolled into an aluminum alloy slab coil under conventional conditions.

[0075] Verification Example 1:

[0076] The hydrogen content and slag content of the aluminum alloy liquid before casting in Examples 1-4 and Comparative Examples 3, 4, and 6 were tested on site using a HDA-V hydrogen meter and an Analyze PoDFA slag meter. The results are shown in Table 1. As can be seen from Table 1, the hydrogen content of the aluminum alloy liquid in Examples 1-4 is less than 0.1 ml / 100 gAl, and the slag content is less than 0.05 mm 2 / kgAl. Since the refining agent used in Comparative Example 3 is a conventional refining agent available on the market, the degassing medium introduced into the degassing box in Comparative Example 4 is only argon gas without mixed gas, and since the refining agent used in Comparative Example 6 is a conventional refining agent available on the market, and the degassing box does not introduce mixed gas for degassing, the hydrogen slag content of the aluminum alloy liquid before casting in Comparative Examples 3, 4, and 6 is relatively high. By comparison, it can be seen that the use of the technical solution of the present invention can significantly reduce the gas slag content of the aluminum alloy liquid before casting and improve the cleanliness of the aluminum alloy sheet.

[0077] Table 1 Hydrogen content and slag content of aluminum alloy liquid

[0078] Hydrogen content / (ml / 100gAl) <![CDATA[Sludge content / (mm 2 / kgAl)]]> Example 1 0.062 0.032 Example 2 0.045 0.027 Example 3 0.081 0.042 Example 4 0.073 0.035 Comparative Example 3 0.114 0.135 Comparative Example 4 0.162 0.062 Comparative Example 6 0.185 0.151

[0079] Verification Example 2:

[0080] Samples were taken from the aluminum alloy sheets prepared in Examples 1-4 and Comparative Examples 1-6 to test the tensile strength and elongation after fracture of the aluminum alloy sheets, and the results are shown in Table 2. As can be seen from Table 2, the tensile strength of the aluminum alloy sheets prepared in Examples 1-4 is greater than 200MPa, and the elongation after fracture is greater than 20%. Due to insufficient Mn content in Comparative Example 1 and insufficient Mg content in Comparative Example 2, the tensile strength of the aluminum alloy sheets is less than 200MPa. Comparative Example 3 uses a commercially available conventional powder refining agent for furnace spray refining, Comparative Example 4 does not use a mixed gas for online degassing in a degassing box, and Comparative Example 5 does not use continuous casting under the action of ultrasonic waves, resulting in the tensile strength of the aluminum alloy sheets prepared in Comparative Examples 3-5 being less than 200MPa and the elongation after fracture being less than 20%. Comparative Example 6 uses a commercially available conventional powder refining agent for furnace spray refining, does not use a mixed gas for online degassing in a degassing box, and does not use continuous casting and rolling under the action of ultrasonic waves. It belongs to a conventional casting and rolling process. The tensile strength of the aluminum alloy sheet is only 179.5MPa, and the elongation after fracture is only 15.8%. By comparison, it can be seen that the strength and plasticity of the aluminum alloy sheet can be significantly improved by adopting the technical solution of the present invention. The tensile strength of similar aluminum alloy sheets produced by conventional casting and rolling is usually lower than 190MPa, and the elongation after fracture is lower than 16%. Compared with similar aluminum alloy sheets produced by conventional casting, the tensile strength of the aluminum alloy sheet prepared by the technical solution of the present invention is increased by more than 5%, and the plasticity is increased by more than 25%. The substantial improvement in plasticity is conducive to solving the problem of cracking in deep drawing of aluminum alloy sheets and reducing the earing rate of stamping products.

[0081] Table 2 Tensile strength and elongation after fracture of aluminum alloy sheets

[0082] Tensile strength / MPa Elongation after break / % Example 1 226.8 20.8 Example 2 219.5 22.4 Example 3 201.8 24.6 Example 4 217.4 23.1 Comparative Example 1 194.5 22.5 Comparative Example 2 188.2 23.7 Comparative Example 3 198.9 16.8 Comparative Example 4 191.7 18.4 Comparative Example 5 189.4 17.5 Comparative Example 6 179.5 15.8

Claims

1. An aluminum alloy sheet with excellent deep drawing performance, characterized in that: The aluminum alloy sheet is composed of the following components in mass percentage: Mn 1.0-1.5%, Mg 0.8-1.3%, Si 0.1-0.2%, Fe 0.1-0.2%, and the balance is Al and unavoidable impurity elements, the content of each impurity element is ≤0.05%, and the total amount of impurity elements is ≤0.15%.

2. A method for preparing an aluminum alloy sheet with excellent deep drawing performance, for preparing an aluminum alloy sheet with excellent deep drawing performance as claimed in claim 1, characterized in that: The following steps are included in sequence: Step 1: Melting and preparing aluminum alloy liquid according to the composition and mass percentage of the aluminum alloy sheet; Step 2: Use argon gas and powder refining agent to spray and refine the aluminum alloy liquid in the furnace to remove gases and impurities; Step 3: The aluminum alloy liquid flows through the degassing box and the filter box arranged on the flow trough in sequence for online degassing and filtering treatment; Step 4: Continuously casting and rolling the aluminum alloy liquid into an aluminum alloy slab roll I under the action of ultrasonic waves; Step 5: subjecting the aluminum alloy slab coil I to high temperature homogenization treatment and large deformation cold rolling to obtain the aluminum alloy slab coil II; Step 6: performing high temperature annealing treatment and medium deformation cold rolling on the aluminum alloy slab coil II to obtain the aluminum alloy slab coil III; Step 7: performing recrystallization annealing and multiple passes of small deformation cold rolling on the aluminum alloy slab coil III to obtain an aluminum alloy thin plate coil; Step eight: finishing trimming and annealing the aluminum alloy sheet coil to obtain the aluminum alloy sheet with excellent deep drawing performance.

3. The method for preparing the aluminum alloy sheet with excellent deep drawing performance according to claim 2, characterized in that: The aluminum melting furnace used for smelting and preparing the aluminum alloy liquid in step 1 is a regenerative gas-fired aluminum melting furnace, and the heating melting temperature is 720-740°C.

4. The method for preparing the aluminum alloy sheet with excellent deep drawing performance according to claim 2, characterized in that: The purity of the argon gas in step 2 is ≥99.99%, the amount of the powder refining agent is 0.1-0.2% of the weight of the aluminum alloy liquid, the blowing refining time is 10-20 minutes, and the powder refining agent is composed of the following components in mass percentage: NaCl 35.12%, NaF19.84%, TiCl3 16.51%, SrSO4 10.06%, KPO3 11.45%, Na2B4O7 7.02%. The preparation method of the powder refining agent comprises the following steps in sequence: (1) selecting NaCl, NaF, TiCl3, SrSO4, KPO3, and Na2B4O7 with a purity of ≥99.8% as raw materials for batching according to the composition and mass percentage of the refining agent; (2) adding the ingredients into water at a temperature of 70°C and stirring to dissolve them into an aqueous solution, wherein the mass ratio of water to the ingredients is 1.2, and then heating the aqueous solution to 100°C to evaporate the aqueous solution to obtain solid crystals; (3) crushing the solid crystals into powder with a particle size of less than 2 mm, and drying and dehydrating the powder at 160°C for 4 hours to obtain the refining agent.

5. The method for preparing the aluminum alloy sheet with excellent deep drawing performance according to claim 2, characterized in that: The degassing medium introduced into the degassing box in step 3 is a mixed gas composed of argon with a purity of ≥99.99%, sulfur hexafluoride and carbon monoxide, the volume percentage of sulfur hexafluoride in the mixed gas is 9-11%, the volume percentage of carbon monoxide is 3-5%, the speed of the graphite rotor in the degassing box is 400-500 rpm, the flow rate of the mixed gas is 4-5 cubic meters / hour, and the pressure of the mixed gas is 0.2-0.3MPa.

6. The method for preparing the aluminum alloy sheet with excellent deep drawing performance according to claim 2, characterized in that: The frequency of the ultrasound in step 4 is 40-50kHz, the power of the ultrasound is 15-20kW, the temperature of the aluminum alloy liquid is 700-710°C, the casting speed is 700-800 mm / min, and the thickness of the aluminum alloy slab roll I is 5.5-6.5 mm.

7. The method for preparing the aluminum alloy sheet with excellent deep drawing performance according to claim 2, characterized in that: The temperature of the high temperature homogenization in step five is 560-570° C., the time of the high temperature homogenization is 12-14 hours, the deformation of the large deformation cold rolling is 54.5-76.9%, and the thickness of the aluminum alloy coil II is 1.5-2.5 mm.

8. The method for preparing the aluminum alloy sheet with excellent deep drawing performance according to claim 2, characterized in that: The temperature of the high temperature annealing in step six is ​​500-510° C., the time of the high temperature annealing is 10-12 hours, the deformation of the medium deformation cold rolling is 40-50%, and the thickness of the aluminum alloy slab roll III is 0.75-1.5 mm.

9. The method for preparing the aluminum alloy sheet with excellent deep drawing performance according to claim 2, characterized in that: The temperature of the recrystallization annealing in step seven is 220-230° C., the time of the recrystallization annealing is 5-6 hours, the deformation of each small deformation cold rolling does not exceed 20%, and the thickness of the aluminum alloy sheet coil is 0.1-1 mm.

10. The method for preparing the aluminum alloy sheet with excellent deep drawing performance according to claim 2, characterized in that: The temperature for annealing the aluminum alloy sheet coil in step eight is 180-190° C., and the annealing time is 3-4 hours.

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