Preparation method of high-strength 5000 series aluminum alloy sheet for anodic oxidation

Abstract

The invention discloses a preparation method of a high-strength 5000 series aluminum alloy sheet for anodic oxidation. An aluminum ingot, an aluminum intermediate alloy ingot and electrolytic aluminum water are used as raw materials, and the high-strength 5000 series aluminum alloy sheet for anodic oxidation is prepared through the steps of smelting, casting, homogenization treatment, hot rolling, cogging cold rolling, intermediate annealing, finished product low-temperature cold rolling, stress relief annealing, cleaning, straightening and trimming and finished product shaft splitting. The tensile strength of the aluminum alloy material with the thickness of 0.5-2.0 mm is larger than or equal to 280 MPa, the yield is larger than or equal to 240 MPa, and the ductility is larger than or equal to 8%. The grain size of any position of the surface of the obtained final product is smaller than or equal to 30 microns, the grain aspect ratio is 1.0-1.6%, it can be guaranteed that no material lines and different color lines appear on a 150 # zircon sand blasting anode, and the requirements for high-strength punch forming and anodic oxidation of the product are met.

Description

Technical Field

[0001] The invention belongs to the field of preparation of aluminum alloy strips, and in particular relates to a method for preparing a high-strength 5000 series aluminum alloy thin plate for anodizing. Background Art

[0002] Al-Mg aluminum alloy is a widely used alloy system. It is a non-heat-treatable strengthening alloy with the characteristics of low specific gravity, high specific strength, good corrosion resistance, weldability and easy processing and forming. Its plate and strip series products are light in weight, medium in strength, good in corrosion resistance, easy to process and form, and excellent in welding performance. It is widely used in various fields such as aerospace, transportation, construction, decoration, packaging and 3C electronics.

[0003] As 5G electronic products develop towards being thin, portable, efficient in heat dissipation and beautiful, the selection of new materials has become one of the important ways to reduce the weight of electronic product casings. Compared with materials such as magnesium alloys, plastics and carbon fibers, aluminum alloys have significant advantages in formability, corrosion resistance and cost performance. However, aluminum alloys face challenges in terms of insufficient strength and cannot be further thinned. High-performance aluminum materials suitable for electronic casings need to have excellent strong plasticity, and the characteristics of no cracking during stamping and hole drawing. At the same time, after sandblasting and anodizing, they should show the characteristics of no "material grain", uniform color, wear resistance and corrosion resistance.

[0004] The industry generally believes that adding high levels of Mg, Cu, Cr and other elements to 5 series aluminum alloys can improve strength. However, after anodizing, problems such as dark color, discoloration of anode material patterns and easy cracking during stamping are prone to occur, which has become a technical challenge faced by domestic and foreign counterparts.

[0005] Patent application No. 201610081536.x and 201610081538.9 proposed two high-strength anodized aluminum alloys and their preparation methods. By rationally controlling the alloy composition (Si≤0.08, Mg2.0-3.5, etc.) and specific cold rolling and annealing processes, the aluminum produced has a yield strength of ≥230MPa and a surface roughness of Ra≤0.30μm. However, this method also faces the problem of limited strength and plasticity.

[0006] Patent application No. 201710548317.2 discloses a mirror anodized aluminum strip and its preparation method. By adjusting the alloy composition (Si≤0.03, Mg4.05.0, etc.) and three-stage homogenization and double annealing processes, a material with a yield strength of 205235MPa is obtained. Although this process improves optical properties, the production cost is high and the strength is still limited.

[0007] Patent application No. 201811260701.3 provides a 5-series aluminum alloy sheet and strip with good gloss after anodizing and a preparation method thereof. By strictly controlling the alloy composition (Si≤0.04, Fe≤0.05, Cu≤0.05, etc.), as well as two-stage homogenization treatment and specific hot and cold rolling processes, the produced material has a tensile strength of ≥280MPa, a yield strength of ≥240MPa, an elongation of ≥6%, and a glossiness Gu value of ≥120 after anodizing. Although this method achieves performance improvement, due to the use of high-purity design and limited Mg content, the production cost is high and the strength improvement is limited.

[0008] Patent application No. 202010570708.6 provides a high-strength, high-elongation Al-Mg alloy sheet for automobiles and its preparation method. Through two annealing and fine cold rolling processes, the yield strength is greater than 130MPa, the tensile strength is greater than 300MPa, and the elongation A50 is greater than 30%. However, its yield strength is still relatively low and cannot meet the needs of some high-strength applications.

[0009] Patent application No. 202210362752.7 provides a method for preparing Al-Mg aluminum sheets and strips for high-strength anodizing. Through composition adjustment (adding more than 5.7% Mg), specific annealing and cold and hot rolling processes, the produced material has a tensile strength of ≥340MPa, a yield strength of ≥270MPa, an elongation of ≥10%, an average grain size of <15μm, a grain aspect ratio of 0.8-1.2, a maximum size of intermetallic compounds of <5um, and a compound ratio per unit area of ​​<10%. However, the high Mg content and the need to be fired in an air cushion furnace result in high production costs. At the same time, the finished product is in H16 state. After being placed at room temperature for a long time, Mg5Al8 may precipitate, resulting in weakened solid solution strengthening and thus a decrease in performance. In addition, due to composition restrictions, the high mesh sandblasting anode of 150# or above cannot be met, and the high anode surface requirements cannot be met. Summary of the invention

[0010] The purpose of the present invention is to provide a method for preparing a high-strength 5000 series anodized aluminum alloy sheet in view of the shortcomings of the prior art. The method has a reasonable process flow and low cost, and can meet the high-strength and high-surface requirements of customers.

[0011] To achieve the purpose of the present invention, the following technical scheme is adopted: A high-strength 5000 series aluminum alloy sheet for anodizing. The chemical composition of the aluminum alloy sheet and strip is as follows by mass fraction: Si 0.03-0.08%, Fe 0.05-0.20%, Cu 0.02-0.04%, Mn ≤ 0.3%, Mg 3.0-3.5%, Cr ≤ 0.01%, Ti ≤ 0.02%, and the balance is aluminum.

[0012] The method for preparing a high-strength 5000 series aluminum alloy thin plate for anodizing is as follows: aluminum ingots, intermediate alloy ingots and electrolytic aluminum water raw materials are smelted, cast, homogenized, hot rolled, cold rolled, intermediate annealed, finished product cold rolled, low-temperature stress relief annealing, cleaned and straightened, and slit to obtain high-strength Al-Mg aluminum strip for anodizing.

[0013] The specific preparation method comprises the following steps: (1) According to the alloy composition ratio, the aluminum ingot, the master alloy ingot and the electrolytic aluminum liquid raw materials are melted, refined, deslagging and degassing, and then semi-continuously cast into aluminum alloy flat ingots; (2) After milling, the aluminum alloy ingot is subjected to homogenization heat treatment at a homogenization temperature of 450-530°C and a homogenization time of 2-6 hours; (3) After being taken out of the furnace, the ingot is rolled into a hot-rolled coil with a thickness of 5.0-8.0 mm using a 1+3 hot rolling mill, and the final rolling temperature is 300-330°C; (4) The hot-rolled coil obtained in step (3) is cold-rolled to an intermediate thickness, subjected to intermediate annealing, and then cold-rolled to a finished thickness, subjected to low-temperature stress relief annealing, cleaned and straightened, and slit into finished Al-Mg aluminum sheets and strips.

[0014] Furthermore, the total cold rolling processing rate before intermediate annealing is 50-80%, and the intermediate annealing is performed at 330-380°C for 4-6 hours; Furthermore, the total processing rate from intermediate annealing to finished cold rolling is 10-20%, the single-pass rolling speed is controlled at 200-300 m / min, the coil temperature after rolling is ≤90°C, and the surface roughness of the finished product is Ra≤0.25μm.

[0015] Furthermore, the cold-rolled finished product is subjected to low-temperature stress relief annealing, with the annealing temperature being 80-160° C. and the time being 1 h-5 h.

[0016] Furthermore, the characteristics of the finished product are as follows: thickness 0.5-2.0mm, tensile strength ≥280MPa, yield strength ≥240MPa, elongation ≥8%, the grain size at any position on the surface of the final product is ≤30μm, and the grain aspect ratio is 1.0~1.6%, which can ensure that the 150# zircon sand sandblasting anode will not have material lines and discolored lines, meeting the product's high-strength stamping and anodizing requirements.

[0017] The beneficial effects of the present invention are: The present invention carries out matching design for each element, and adjusts the grain size, texture orientation, and precipitate distribution through intermediate annealing; the cold rolling pass after annealing is controlled at 10-20%, and a processing rate that is too high will lead to poor equiaxed grains and affect the finished anode effect, and high performance will lead to stamping cracking of the finished product, and a processing rate that is too low will lead to poor stamping of the finished product due to low performance; the single-pass rolling speed after annealing is controlled at 200-300m / min, and the coil temperature after rolling is ≤90°C. Too high a temperature will lead to uneven precipitation of β' phase, weakening the Mg concentration in the matrix, and aging precipitation will induce local stress concentration, affecting the ductility and strength of the material and leading to poor forming; the finished product is subjected to low-temperature stress relief annealing, and the annealing temperature is 8 0-160℃, time 1h-3h, under low temperature annealing conditions of 80-160℃, the precipitated phase (such as β' phase) is quickly formed and reaches a stable form, avoiding slow precipitation at room temperature and causing performance degradation. If the temperature is too high and the time is too long, the number or size of the precipitated phase will be too large or too large (such as coarsened β' phase), weakening the precipitation strengthening effect, inducing partial recrystallization, and significantly reducing the work hardening effect after cold rolling, resulting in a decrease in material strength. If the temperature is too low and the time is too short, the diffusion capacity of Mg atoms will be insufficient, the precipitation process will be very slow, and a uniformly dispersed precipitated phase (such as β' phase) cannot be formed, and the ductility is insufficient, affecting the quality of anodizing and subsequent stamping performance. This method has simple production passes and low manufacturing costs, and conforms to the development trend of high-strength thinning of anodized materials. At the same time, the thickness of the aluminum alloy strip produced is 0.5-2.0mm, the yield is ≥240MPa, the elongation is ≥8%, the grain size at any position on the surface of the final product is ≤30μm, and the grain aspect ratio is 1.0~1.6%, which can ensure that the 150# zircon sand blasting anode will not have material lines and discolored lines, meeting the product's high-strength stamping and anodizing requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The present invention is a flow chart of the preparation method.

[0019] Figure 2 It is a stamping comparison diagram (the left picture is comparative example 1, which has cracking during stamping; the right picture is example 1, which has good stamping).

[0020] Figure 3 Comparison pictures of 150# zirconium sand blasting anodes (the left picture is comparative example 1, anode material grain; the right picture is example 1, good surface).

[0021] Figure 4 It is a comparison diagram of finished product grains (the left one is comparative example 1, with an average grain size of 22.42 μm and a grain aspect ratio of 4.15; the right one is example 1: with an average grain size of 15.59 μm and a grain aspect ratio of 1.55). DETAILED DESCRIPTION

[0022] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings.

[0023] The present invention aims to provide a method for preparing a high-strength 5000 series aluminum alloy thin plate for anodizing, wherein the mass fractions of the components involved are: Si 0.03-0.08%, Fe 0.05-0.20%, Cu 0.02-0.04%, Mn ≤ 0.3%, Mg 3.0-3.5%, Cr ≤ 0.01%, Ti ≤ 0.02%, and the balance is aluminum.

[0024] The present invention also provides a method for preparing the high-strength 5000 series aluminum alloy sheet for anodizing as described above, wherein aluminum ingots, intermediate alloy ingots and electrolytic aluminum water raw materials are subjected to smelting, casting, homogenization treatment, hot rolling, cold rolling, intermediate annealing, finished product cold rolling, finished product annealing, cleaning and straightening, and slitting to obtain high-strength Al-Mg aluminum sheet for anodizing; Figure 1 As shown, the preparation method specifically comprises the following steps: (1) Aluminum ingots, master alloy ingots and electrolytic aluminum liquid raw materials are semi-continuously cast into aluminum alloy flat ingots after melting, refining, deslagging and degassing; (2) After milling, the aluminum alloy ingot is subjected to homogenization heat treatment at a homogenization temperature of 450-530°C and a homogenization time of 2-6 hours; (3) After being taken out of the furnace, hot rolling is performed to a thickness of 5-8 mm, and the final hot rolling temperature is 300-350°C; (4) The hot-rolled coil is cold-rolled to an intermediate thickness, intermediate annealing is performed, and then cold-rolled to a finished thickness, low-temperature short-time finished product annealing is performed, and then cleaned, straightened, and slit into finished Al-Mg aluminum sheets and strips.

[0025] The following is the specific implementation process of the present invention.

[0026] The film quality of the anodized film not only depends on the anodizing process, but is also closely related to several key characteristics of the aluminum material itself, such as material composition, surface hardness, surface quality and internal structure. Specifically, grain size and orientation, type and size of intermetallic compounds, and surface roughness will significantly affect the film quality. In addition, in order to achieve continuous stamping, it is necessary to strictly control the mold and stamping process at the same time, and coordinately optimize the material structure and performance, including grain size, equiaxed, orientation, distribution of coarse second phases and precipitates, and strong plasticity and other indicators.

[0027] The invention provides a method for preparing a high-strength 5000 series aluminum alloy thin plate for anodizing, wherein the chemical composition (mass fraction) is as follows: Si 0.03-0.08%, Fe 0.05-0.20%, Cu 0.02-0.04%, Mn ≤ 0.3%, Mg 3.0-3.5%, Cr ≤ 0.01%, Ti ≤ 0.02%, and the balance is aluminum. The high-strength 5000 series aluminum alloy thin plate strip for anodizing is prepared by smelting, casting, homogenizing, hot rolling, cold rolling, intermediate annealing, finished product cold rolling, finished product stress relief annealing, cleaning and straightening, and slitting.

[0028] Key process features: Appropriate cold rolling reduction rate: After intermediate annealing, a cold rolling process with a low reduction rate of less than 10-20% is adopted, which can maintain good plasticity and grain equiaxility, thereby improving the forming performance and anodizing quality. After annealing, the number of cold rolling passes is controlled at 10-20%. Too high a processing rate will lead to poor grain equiaxility and affect the effect of the finished anode. Too high performance will lead to cracking of the finished product during stamping. Too low a processing rate will lead to low performance of the finished product and poor stamping.

[0029] Low-temperature rolling control of cold-rolled finished products: After annealing, the single-pass rolling speed is controlled at 200-300m / min, and the coil temperature after rolling is ≤90℃. Too high temperature will cause the β' phase to precipitate and distribute unevenly, weaken the Mg concentration in the matrix, and induce local stress concentration due to aging precipitation, which affects the ductility and strength of the material and leads to poor forming. Ensure the forming performance and anode effect.

[0030] Stress relief annealing temperature control: The finished product is subjected to low-temperature stress relief annealing, the annealing temperature is 80-160℃, and the time is 1h-3h. Under the low-temperature annealing conditions of 80-160℃, the precipitated phase (such as β' phase) is quickly formed and reaches a stable form, avoiding slow precipitation at room temperature and causing performance degradation. If the temperature is too high and the time is too long, the number or size of the precipitated phase will be too large or too large (such as coarsened β' phase), weakening the precipitation strengthening effect, inducing partial recrystallization, and significantly reducing the work hardening effect after cold rolling, resulting in a decrease in material strength. If the temperature is too low and the time is too short, the diffusion capacity of Mg atoms will be insufficient, the precipitation process will be very slow, and a uniformly dispersed precipitated phase (such as β' phase) cannot be formed, and the ductility is insufficient, affecting the anodizing quality and subsequent stamping performance.

[0031] The process is described in detail below through specific examples to verify its effects and advantages.

[0032] Example 1 A high-strength 5000 series aluminum alloy sheet for anodizing: the chemical composition of the aluminum alloy sheet and strip is as follows by mass fraction: Si 0.046%, Fe 0.070%, Cu 0.026%, Mn 0.22%, Mg 3.49%, Cr 0.006%, Ti 0.011%, and the balance is aluminum and unavoidable impurities.

[0033] The method for producing high-strength 5000 series aluminum alloy thin plates for anodizing comprises the following steps: subjecting aluminum ingots, intermediate alloy ingots and electrolytic aluminum water raw materials to smelting, casting, homogenization treatment, hot rolling, cold rolling, intermediate annealing, finished product cold rolling, finished product annealing, cleaning and straightening, and slitting to obtain high-strength Al-Mg aluminum plates and strips for anodizing.

[0034] The specific preparation method comprises the following steps: (1) According to the alloy composition ratio, the aluminum ingot, the master alloy ingot and the electrolytic aluminum liquid raw materials are melted, refined, deslagging and degassing, and then semi-continuously cast into aluminum alloy flat ingots; (2) After milling, the aluminum alloy slab is subjected to homogenization heat treatment (450°C / 2h). After being taken out of the furnace, the hot rolling crown is set to 0.3%, and the hot rolled coil is rolled to a thickness of 5.1mm, and the final rolling temperature is 320°C; (3) The hot rolled coil is cold rolled to an intermediate thickness of 1.0 mm, and intermediate annealing is performed in a nitrogen furnace at 330°C for 5 h, and then cold rolled to a finished thickness of 0.80 mm, with a processing rate of 20%, a cold rolling speed of 250 m / min after annealing, and a coil temperature of 70°C after rolling; (4) The finished product is subjected to low temperature stress relief annealing at 80°C for 2h; (5) Clean, straighten and cut into finished products for delivery.

[0035] The tensile strength of the aluminum alloy strip is 291 MPa, the yield strength is 256 MPa, the elongation is 8.6%, the average grain size of the product is 15.59 μm, and the grain aspect ratio is 1.55%, which meets the requirements of high-strength stamping and anodizing of the product.

[0036] Example 2 A high-strength 5000 series aluminum alloy sheet for anodizing: the chemical composition of the aluminum alloy sheet and strip is as follows by mass fraction: Si 0.052%, Fe 0.073%, Cu 0.032%, Mn 0.22%, Mg 3.43%, Cr 0.006%, Ti 0.013%, and the balance is aluminum and unavoidable impurities.

[0037] The method for producing high-strength 5000 series aluminum alloy thin plates for anodizing comprises the following steps: subjecting aluminum ingots, intermediate alloy ingots and electrolytic aluminum water raw materials to smelting, casting, homogenization treatment, hot rolling, cold rolling, intermediate annealing, finished product cold rolling, finished product annealing, cleaning and straightening, and slitting to obtain high-strength Al-Mg aluminum plates and strips for anodizing.

[0038] The specific preparation method comprises the following steps: (1) According to the alloy composition ratio, the aluminum ingot, the master alloy ingot and the electrolytic aluminum liquid raw materials are melted, refined, deslagging and degassing, and then semi-continuously cast into aluminum alloy flat ingots; (2) After milling, the aluminum alloy ingot is subjected to homogenization heat treatment (450°C / 2h). After being taken out of the furnace, the hot rolling crown is set to 0.3%, and the hot rolled coil is rolled to a thickness of 5.1mm, and the final rolling temperature is 300°C; (3) The hot rolled coil is cold rolled to an intermediate thickness of 0.73 mm, and intermediate annealing is performed in a nitrogen furnace at 310°C for 6 hours, and then cold rolled to a finished thickness of 0.60 mm, with a processing rate of 17%, a cold rolling speed of 200 m / min after annealing, and a coil temperature of 64°C after rolling; (4) The finished product is subjected to low temperature stress relief annealing at 100°C for 2h; (5) Clean, straighten and cut into finished products for delivery.

[0039] The aluminum alloy strip has a tensile strength of 281 MPa, a yield strength of 264 MPa, an elongation of 8.9%, an average grain size of 18.54 μm, and a grain aspect ratio of 1.2%, meeting the requirements of high-strength stamping and anodizing of the product.

[0040] Example 3 A high-strength 5000 series aluminum alloy sheet for anodizing: the chemical composition of the aluminum alloy sheet and strip is as follows by mass fraction: Si 0.046%, Fe 0.070%, Cu 0.026%, Mn 0.22%, Mg 3.49%, Cr 0.006%, Ti 0.011%, and the balance is aluminum and unavoidable impurities.

[0041] The method for producing high-strength 5000 series aluminum alloy thin plates for anodizing comprises the following steps: subjecting aluminum ingots, intermediate alloy ingots and electrolytic aluminum water raw materials to smelting, casting, homogenization treatment, hot rolling, cold rolling, intermediate annealing, finished product cold rolling, finished product annealing, cleaning and straightening, and slitting to obtain high-strength Al-Mg aluminum plates and strips for anodizing.

[0042] The specific preparation method comprises the following steps: (1) According to the alloy composition ratio, the aluminum ingot, the master alloy ingot and the electrolytic aluminum liquid raw materials are melted, refined, deslagging and degassing, and then semi-continuously cast into aluminum alloy flat ingots; (2) After milling, the aluminum alloy slab is subjected to homogenization heat treatment (450°C / 2h). After being taken out of the furnace, the hot rolling crown is set to 0.3%, and the hot rolled coil is rolled to a thickness of 5.1mm. The final rolling temperature is 315°C. (3) The hot rolled coil is cold rolled to an intermediate thickness of 0.83 mm, and intermediate annealing is performed in a nitrogen furnace at 350°C for 4 hours, and then cold rolled to a finished thickness of 0.70 mm, with a processing rate of 15%, a cold rolling speed of 300 m / min after annealing, and a coil temperature of 78°C after rolling; (4) The finished product is subjected to low temperature stress relief annealing at 80°C / 1h; (5) Clean, straighten and cut into finished products for delivery.

[0043] The aluminum alloy strip has a tensile strength of 287 MPa, a yield strength of 263 MPa, an elongation of 8.1%, an average grain size of 18.12 μm, and a grain aspect ratio of 1.5%, meeting the requirements of high-strength stamping and anodizing of the product.

[0044] Comparative Example 1 (Total processing rate from intermediate annealing to finished product cold rolling is too large) A high-strength 5000 series aluminum alloy sheet for anodizing: the chemical composition of the aluminum alloy sheet and strip is as follows by mass fraction: Si 0.046%, Fe 0.070%, Cu 0.026%, Mn 0.22%, Mg 3.49%, Cr 0.006%, Ti 0.011%, and the balance is aluminum and unavoidable impurities.

[0045] The method for producing high-strength 5000 series aluminum alloy thin plates for anodizing comprises the following steps: subjecting aluminum ingots, intermediate alloy ingots and electrolytic aluminum water raw materials to smelting, casting, homogenization treatment, hot rolling, cold rolling, intermediate annealing, finished product cold rolling, finished product annealing, cleaning and straightening, and slitting to obtain high-strength Al-Mg aluminum plates and strips for anodizing.

[0046] The specific preparation method comprises the following steps: (1) According to the alloy composition ratio, the aluminum ingot, the master alloy ingot and the electrolytic aluminum liquid raw materials are melted, refined, deslagging and degassing, and then semi-continuously cast into aluminum alloy flat ingots; (2) After milling, the aluminum alloy slab is subjected to homogenization heat treatment (450°C / 2h). After being taken out of the furnace, the hot rolling crown is set to 0.3%, and the hot rolled coil is rolled to a thickness of 5.1mm, and the final rolling temperature is 320°C; (3) The hot rolled coil is cold rolled to an intermediate thickness of 1.23 mm, and intermediate annealing is performed in a nitrogen furnace at 350°C for 6 hours, and then cold rolled to a finished thickness of 0.80 mm, with a processing rate of 35%, a cold rolling speed of 300 m / min after annealing, and a coil temperature of 75°C after rolling; (4) The finished product is subjected to low temperature stress relief annealing at 80°C for 2h; (5) Clean, straighten and cut into finished products for delivery.

[0047] The tensile strength of the aluminum alloy strip obtained is 302MPa, the yield strength is 276MPa, the elongation is 6.8%, the average grain size of the product is 22.42μm, the grain aspect ratio is 2.0%, and the customer stamping cracks.

[0048] Comparative Example 2 (Lack of finished product annealing process) A high-strength 5000 series aluminum alloy sheet for anodizing: the chemical composition of the aluminum alloy sheet and strip is as follows by mass fraction: Si 0.046%, Fe 0.070%, Cu 0.026%, Mn 0.22%, Mg 3.49%, Cr 0.006%, Ti 0.011%, and the balance is aluminum and unavoidable impurities.

[0049] The method for producing high-strength 5000 series aluminum alloy thin plates for anodizing comprises the following steps: subjecting aluminum ingots, intermediate alloy ingots and electrolytic aluminum water raw materials to smelting, casting, homogenization treatment, hot rolling, cold rolling, intermediate annealing, finished product cold rolling, cleaning and straightening, and slitting to obtain high-strength Al-Mg aluminum plates and strips for anodizing.

[0050] The specific preparation method comprises the following steps: (1) According to the alloy composition ratio, the aluminum ingot, the master alloy ingot and the electrolytic aluminum liquid raw materials are melted, refined, deslagging and degassing, and then semi-continuously cast into aluminum alloy flat ingots; (2) After milling, the aluminum alloy slab is subjected to homogenization heat treatment (450°C / 2h). After being taken out of the furnace, the hot rolling crown is set to 0.3%, and the hot rolled coil is rolled to a thickness of 5.1mm, and the final rolling temperature is 320°C; (3) The hot rolled coil is cold rolled to an intermediate thickness of 1.0 mm, and intermediate annealing is performed in a nitrogen furnace at 330°C for 5 h, and then cold rolled to a finished thickness of 0.80 mm, with a processing rate of 20%, a cold rolling speed of 200 m / min after annealing, and a coil temperature of 65°C after rolling; (4) Clean, straighten and cut into finished products for delivery.

[0051] The tensile strength of the aluminum alloy strip obtained is 302MPa, the yield strength is 276MPa, the elongation is 7.1%, the average grain size of the product is 16.32μm, the grain aspect ratio is 1.6%, and the quality of the finished 150# zircon sand anode is poor, with obvious material lines.

[0052] Comparative Example 3 (the cold rolling speed after medium heat is too high, and the coil temperature after rolling is too high) A high-strength 5000 series aluminum alloy sheet for anodizing: the chemical composition of the aluminum alloy sheet and strip is as follows by mass fraction: Si 0.051%, Fe 0.086%, Cu 0.022%, Mn 0.26%, Mg 3.15%, Cr 0.008%, Ti 0.015%, and the balance is aluminum and unavoidable impurities.

[0053] The method for producing high-strength 5000 series aluminum alloy thin plates for anodizing comprises the following steps: subjecting aluminum ingots, intermediate alloy ingots and electrolytic aluminum water raw materials to smelting, casting, homogenization treatment, hot rolling, cold rolling, intermediate annealing, finished product cold rolling, finished product annealing, cleaning and straightening, and slitting to obtain high-strength Al-Mg aluminum plates and strips for anodizing.

[0054] The specific preparation method comprises the following steps: (1) According to the alloy composition ratio, the aluminum ingot, the master alloy ingot and the electrolytic aluminum liquid raw materials are melted, refined, deslagging and degassing, and then semi-continuously cast into aluminum alloy flat ingots; (2) After milling, the aluminum alloy slab is subjected to homogenization heat treatment (450°C / 2h). After being taken out of the furnace, the hot rolling crown is set to 0.3%, and the hot rolled coil is rolled to a thickness of 5.1mm. The final rolling temperature is 330°C. (3) The hot rolled coil is cold rolled to an intermediate thickness of 1.0 mm, and intermediate annealing is performed in a nitrogen furnace at 330°C for 5 h, and then cold rolled to a finished thickness of 0.80 mm, with a processing rate of 20%, a cold rolling speed of 600 m / min after annealing, and a coil temperature of 110°C after rolling; (4) The finished product is subjected to low temperature stress relief annealing at 80°C / 1h; (5) Clean, straighten and cut into finished products for delivery.

[0055] The tensile strength of the aluminum alloy strip produced is 275MPa, the yield strength is 220MPa, the elongation is 8.1%, the average grain size of the product is 24.11μm, and the grain aspect ratio is 1.1%. The performance of the finished product is low and cannot meet the customer's forming requirements.

[0056] It can be seen from the above embodiments and comparative examples that the high-strength stamping anodized aluminum strip can be produced according to the scheme of the present invention, but the production process is not suitable, and stamping cracking or abnormal anodization is likely to occur.

[0057] Figure 2 It is a stamping comparison diagram; the left picture is comparative example 1, which has stamping cracking; the right picture is example 1, which has good stamping.

[0058] Figure 3 Comparison diagram of 150# zircon sand blasting anode; the left diagram is comparative example 1, anode material pattern; the right diagram is example 1, with good surface.

[0059] Figure 4 It is a comparison chart of finished product grains. The left one is comparative example 1, with an average grain size of 22.42 μm and a grain aspect ratio of 4.15; the right one is example 1: with an average grain size of 15.59 μm and a grain aspect ratio of 1.55.

[0060] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A method for preparing a high-strength 5000 series anodized aluminum alloy sheet, characterized in that: The raw materials of aluminum ingots, intermediate alloy ingots and electrolytic aluminum liquid are smelted, cast, homogenized, hot rolled, cold rolled, intermediate annealed, finished product cold rolled, low temperature stress relief annealed, cleaned and straightened, and cut to obtain high-strength 5000 series aluminum alloy sheets for anodizing.

2. The preparation method according to claim 1, characterized in that: The specific preparation method comprises the following steps: (1) According to the alloy composition ratio, the aluminum ingot, the master alloy ingot and the electrolytic aluminum liquid raw materials are melted, refined, deslagging and degassing, and then semi-continuously cast into aluminum alloy flat ingots; (2) After milling, the aluminum alloy ingot is subjected to homogenization heat treatment at a homogenization temperature of 450-530°C and a homogenization time of 2-6 hours; (3) After being taken out of the furnace, hot rolling is carried out to roll the ingot into a hot-rolled coil with a thickness of 5.0-8.0 mm, and the final rolling temperature is 300-330°C; (4) The hot rolled coil obtained in step (3) is cold rolled to an intermediate thickness, subjected to intermediate annealing, and then cold rolled to a finished thickness, subjected to low temperature stress relief annealing, and then cleaned, straightened, and slit to obtain a high-strength 5000 series aluminum alloy sheet for anodizing.

3. The preparation method according to claim 2, characterized in that: The conditions in step (4) are: the cold rolling processing rate before intermediate annealing is 50-80%, the intermediate annealing is performed at 330-380°C, and the temperature is kept for 4-6 hours.

4. The preparation method according to claim 2, characterized in that: The conditions in step (4) are: the processing rate of cold rolling from intermediate annealing to finished product is 10-20%, the single-pass rolling speed is controlled at 200-300 m / min, the coil temperature after rolling is ≤90°C, and the surface roughness of the finished product Ra is ≤0.25 μm.

5. The preparation method according to claim 2, characterized in that: In step (4), the low temperature stress relief annealing temperature is 80-160°C and the time is 1-5h.

6. The preparation method according to claim 2, characterized in that: Hot rolling adopts 1+3 hot rolling mill.

7. The preparation method according to claim 1, characterized in that: The chemical composition of the prepared aluminum alloy plate and strip is as follows by mass fraction: Si0.03-0.08%, Fe0.05-0.20%, Cu0.02-0.04%, Mn≤0.3%, Mg3.0-3.5%, Cr≤0.01%, Ti≤0.02%, and the balance is aluminum.

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