5G50 aluminum alloy plate strip for anodic oxidation and preparation method of 5G50 aluminum alloy plate strip

Abstract

The invention provides a 5G50 aluminum alloy plate strip for anodic oxidation and a preparation method of the 5G50 aluminum alloy plate strip. The 5G50 aluminum alloy plate strip for anodic oxidation comprises the following elements in percentage by mass: 0.01%-0.10% of Si element, 0.04%-0.15% of Fe element, 3.0%-4.0% of Mg element, 0.2%-1.2% of Mn element, less than or equal to 0.02% of inevitable impurity element in total content, less than 0.05 wt% of single impurity element and the balance of Al. Wherein after the aluminum alloy plate strip is subjected to anodic oxidation treatment, the surface of the aluminum material has no heterochromatic stripe defect, and the chromatic aberration E is less than 0.15. The 5G50 aluminum alloy plate strip for anodic oxidation can give consideration to both high surface quality and excellent mechanical performance, is widely applied to 3C consumer electronics, and can achieve the practical effects of falling resistance, light weight and attractive appearance of the product.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloys, and more particularly, to a 5G50 aluminum alloy sheet and strip for anodic oxidation and a preparation method thereof. Background Art

[0002] Aluminum and aluminum alloy sheet and strip have been widely used in the fields of transportation, packaging, construction, electronics, light industry, aviation, military, etc., especially high-performance aluminum alloy sheet and strip. At present, the preparation of aluminum alloy sheet and strip generally adopts the steps of melting and casting, hot rolling, cold rolling and annealing. Among them, the melting and casting process of aluminum and aluminum alloy includes the steps of batching, melting, casting and homogenization treatment. In the melting and casting steps, the composition of the aluminum alloy liquid is not much different from the chemical composition, and the composition of the ingot can be homogenized; in the hot rolling step, the aluminum alloy sheet and strip are extended and deformed by extrusion under high temperature conditions, and the properties such as the thickness, grain size, tensile strength, yield strength and elongation of the aluminum alloy sheet and strip can be improved; in the cold rolling step, the aluminum alloy sheet and strip are extended and deformed by extrusion under low temperature conditions, and the properties such as the thickness, grain size, tensile strength, yield strength and elongation of the aluminum alloy sheet and strip can be improved; in the annealing step, the aluminum alloy sheet and strip are recrystallized at high temperature, and the properties such as the grain size, tensile strength, yield strength and elongation of the aluminum alloy sheet and strip can be improved.

[0003] With the rapid development of the consumer electronics industry, especially the popularization of portable devices such as laptops, mobile phones and tablet computers, the demand for lightweight, high-strength and beautiful metal materials is increasing day by day. Aluminum alloy is widely used in the outer shell, middle frame and internal structural parts of electronic products due to its good processing performance, low density and rich colors that can be obtained through surface treatment. Especially the 5000 series aluminum alloy sheets, due to their good corrosion resistance and formability, have become the preferred materials for many high-end 3C brand products. However, the mainstream 5252 aluminum alloy sheets used for 3C product appearance parts are difficult to meet the technical requirements of high strength, lightweight and thinning. The existing 5000 series aluminum alloy sheets with high Mg content (such as 5G50 aluminum alloy) are difficult to balance high surface quality and excellent mechanical properties, especially in maintaining uniform color and no obvious defects after anodic oxidation treatment. Therefore, it is particularly important to develop a new type of 5000 series aluminum alloy sheet and strip containing Mn element (such as 5G50 aluminum alloy) and its preparation process. Summary of the Invention

[0004] The main object of the present invention is to provide a 5G50 aluminum alloy sheet and strip for anodic oxidation and a preparation method thereof, so as to solve the problem that it is difficult to balance high surface quality and excellent mechanical properties of the 5G50 aluminum alloy sheet and strip for anodic oxidation in the prior art.

[0005] To achieve the above object, according to one aspect of the present invention, there is provided a 5G50 aluminum alloy sheet and strip for anodic oxidation. By mass percentage, the 5G50 aluminum alloy sheet and strip for anodic oxidation comprises the following elements: the content of Si element is 0.01% - 0.10%, the content of Fe element is 0.04% - 0.15%, the content of Mg element is 3.0% - 4.0%, the content of Mn element is 0.2% - 1.2%, the total content of inevitable impurity elements ≤ 0.02%, the content of a single impurity element is less than 0.05wt%, and the balance is Al; wherein, after the aluminum alloy sheet and strip is subjected to anodic oxidation treatment, there are no discolored stripe defects on the surface of the aluminum material, and the color difference △E < 0.15.

[0006] Further, by mass percentage, the 5G50 aluminum alloy sheet and strip for anodic oxidation comprises the following elements: the content of Si element is 0.01% - 0.06%, the content of Fe element is 0.04% - 0.10%, the content of Mg element is 3.3% - 4.0%, the content of Mn element is 0.2% - 0.4%, the total content of inevitable impurity elements ≤ 0.02%, the content of a single impurity element is less than 0.05wt%, and the balance is Al.

[0007] Further, the mass ratio of the above Mg element to Mn element is 5 - 15:1.

[0008] Further, in the above 5G50 aluminum alloy sheet and strip for anodic oxidation, the number of second phases with a size > 5μm ≤ 30 pieces / mm 2 .

[0009] Further, the thickness of the above 5G50 aluminum alloy sheet and strip for anodic oxidation is 0.3mm - 3.0mm, the average grain size ≤ 30μm, the maximum grain size ≤ 60μm, the tensile strength is 300 - 335MPa, the yield strength is 230 - 280MPa, and the elongation ≥ 10%.

[0010] According to another aspect of the present invention, there is provided a preparation method of the above 5G50 aluminum alloy sheet and strip for anodic oxidation. The preparation method comprises: sequentially performing a batching step, a semi - continuous casting step, a soaking step, a hot rolling step, a cold rolling step, an intermediate annealing step, a secondary cold rolling step and a finished product annealing step on alloy raw materials to obtain a 5G50 aluminum alloy sheet and strip for anodic oxidation; wherein, the temperature of the intermediate annealing step is 280 - 380°C, and the holding time is 2 - 5h; the temperature of the finished product annealing step is 100 - 220°C, and the holding time is 2 - 5h.

[0011] Further, the residual stress in the aluminum alloy sheet and strip obtained in the above finished product annealing step is controlled to be 0 - 20MPa; and / or the surface roughness of the aluminum alloy sheet and strip obtained in the finished product annealing step is 0.2 - 0.4μm.

[0012] Furthermore, the temperature of the soaking step described above is 440 - 480 °C, and the soaking time is 4 - 8 h.

[0013] Furthermore, the final rolling temperature of the hot rolling step described above is 300 °C - 340 °C, the thickness of the aluminum alloy sheet and strip obtained by the hot rolling step is 4 mm - 8 mm, and / or, in the last 3 - 5 rolling passes of the hot rolling step, the deformation rate is 30% - 50%, the average grain size of the aluminum alloy sheet and strip obtained by the hot rolling step is ≤ 80 μm, and in the aluminum alloy sheet and strip obtained by the hot rolling step, the number of second phases with a size > 5 μm is ≤ 20 per mm 2 。

[0014] Furthermore, the thickness of the aluminum alloy sheet and strip obtained by the cold rolling step described above is 0.3 mm - 3.0 mm, and / or, the deformation rate of the secondary cold rolling step is 20% - 40%, the average grain size of the aluminum alloy sheet and strip obtained by the cold rolling step is ≤ 30 μm, and in the aluminum alloy sheet and strip obtained by the cold rolling step, the number of second phases with a size > 5 μm is ≤ 30 per mm 2 。

[0015] Applying the technical solution of the present invention, by precisely controlling the alloy element content, compared with the mainstream 5252 anodized aluminum materials, the addition amounts of Mn and Mg elements in the aluminum materials of the present invention are increased, so that after anodization of the aluminum alloy sheet and strip, not only the color is uniform, but also the color difference is extremely small, and the surface quality of anodization is excellent. The color difference △E of the 5G50 aluminum alloy sheet and strip for anodization is < 0.15, and there are no abnormal color stripe-like defects on the surface detected visually. On the one hand, this technology ensures the aesthetics and consistency of the material surface after treatment, meets the strict requirements of high-end products for surface color, and makes it show excellent aesthetics and application potential in fields with high requirements for color consistency such as building decoration and electronic product casings. On the other hand, it solves the problem that it is difficult for the 5G50 aluminum alloy sheet and strip for anodization to balance high surface quality and excellent mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The specification drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0017] Figure 1 Shows the grain structure diagram inside a 5G50 aluminum alloy sheet and strip for anodization according to Embodiment 1 of the present invention;

[0018] Figure 2 Shows the second phase structure diagram inside a 5G50 aluminum alloy sheet and strip for anodization according to Embodiment 1 of the present invention;

[0019] Figure 3Shows the grain structure diagram inside a 5G50 aluminum alloy sheet for anodizing according to Comparative Example 1 of the present invention;

[0020] Figure 4 Shows the secondary phase structure diagram inside a 5G50 aluminum alloy sheet for anodizing according to Comparative Example 1 of the present invention. Detailed implementation manners

[0021] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the embodiments.

[0022] As analyzed in the background art of the present application, in the prior art, it is difficult to balance high surface quality and excellent mechanical properties for 5G50 aluminum alloy sheets for anodizing. To solve the above problems, the present application provides a 5G50 aluminum alloy sheet for anodizing and a preparation method thereof.

[0023] In a typical implementation manner of the present application, a 5G50 aluminum alloy sheet for anodizing is provided. In terms of mass percentage, the 5G50 aluminum alloy sheet for anodizing includes the following elements: the content of Si element is 0.01% - 0.10%, the content of Fe element is 0.04% - 0.15%, the content of Mg element is 3.0% - 4.0%, the content of Mn element is 0.2% - 1.2%, the total content of inevitable impurity elements ≤ 0.02%, the content of a single impurity element is less than 0.05wt%, and the balance is Al; wherein, after the aluminum alloy sheet is anodized, there are no discolored stripe defects on the surface of the aluminum material, and the color difference △E < 0.15.

[0024] By precisely controlling the content of alloying elements, compared with the mainstream 5252 anodized aluminum materials, the addition amounts of Mn and Mg elements in the aluminum materials of the present invention are increased, so that after the aluminum alloy sheet is anodized, not only the color is uniform, but also the color difference is extremely small, and the surface quality of the anodizing is excellent. The color difference △E of the 5G50 aluminum alloy sheet for anodizing < 0.15, and there are no discolored stripe-like defects on the surface detected by visual inspection. On the one hand, this technology ensures the aesthetics and consistency of the material surface after treatment, meets the strict requirements of high-end products for surface color, and makes it show excellent aesthetics and application potential in fields with high requirements for color consistency such as building decoration and electronic product casings. On the other hand, it solves the problem that it is difficult to balance high surface quality and excellent mechanical properties for 5G50 aluminum alloy sheets for anodizing.

[0025] In addition, after the above-mentioned 5G50 aluminum alloy sheet and strip for anodic oxidation are stamping formed, there are no cracks and orange peel defects on the surface of the deformed area, ensuring the surface integrity of the material during the processing, and improving the aesthetics and quality of the final product. The stamping forming methods include, but are not limited to, any one or more of single-point stamping, continuous stamping, and multi-station stamping.

[0026] Furthermore, preferably, the electrolyte for anodic oxidation treatment is one or more of sulfuric acid, oxalic acid, chromic acid, phosphoric acid, and mixed acid electrolytes. The temperature range of the electrolyte for anodic oxidation treatment is 15-25°C, and the current density is 0.5-2.5 A / dm 2 .

[0027] In an embodiment of the present application, by mass percentage, the above-mentioned 5G50 aluminum alloy sheet and strip for anodic oxidation include the following elements: the content of Si element is 0.01%-0.06%, the content of Fe element is 0.04%-0.10%, the content of Mg element is 3.3%-4.0%, the content of Mn element is 0.2%-0.4%, the total content of inevitable impurity elements ≤0.02%, the content of a single impurity element is less than 0.05 wt%, and the balance is Al.

[0028] By further optimizing the ratio of alloying elements, the obtained 5G50 aluminum alloy sheet and strip for anodic oxidation not only has good formability, but also can maintain high hardness and corrosion resistance after anodic oxidation, and is suitable for applications such as automotive parts and electronic device frames that require high strength and durability.

[0029] In an embodiment of the present application, the mass ratio of the above-mentioned Mg element to the Mn element is 5-15:1.

[0030] This specific element ratio can promote the formation of uniformly distributed strengthening phases, thereby significantly improving the mechanical strength of the material without sacrificing ductility, and enabling the 5G50 aluminum alloy sheet and strip for anodic oxidation to have excellent forming performance and surface performance.

[0031] In an embodiment of the present application, in the above-mentioned 5G50 aluminum alloy sheet and strip for anodic oxidation, the number of second phases with a size >5μm ≤30 / mm 2 .

[0032] Controlling the number of second phases with a size >5μm ≤30 / mm 2 , effectively reduces the negative impact of large-size particles on the performance of the 5G50 aluminum alloy sheet and strip for anodic oxidation, provides the uniformity and aesthetics of the surface color of the aluminum alloy sheet and strip after anodic oxidation, and at the same time enhances the forming performance and mechanical strength of the material, meeting the stringent requirements of high-end electronic product casings for materials.

[0033] In an embodiment of the present application, the thickness of the 5G50 aluminum alloy sheet strip for anodic oxidation is 0.3 mm to 3.0 mm, the average grain size is ≤30 μm, the maximum grain size is ≤60 μm, the tensile strength is 300 - 335 MPa, the yield strength is 230 - 280 MPa, and the elongation is ≥10%.

[0034] This range of grain size (the measurement methods of grain size include but are not limited to optical microscopy and electron microscopy) provides good formability and surface quality for the 5G50 aluminum alloy sheet strip for anodic oxidation, and reduces the surface cracks and grain coarsening phenomena that occur during the processing. The strength range indicates that the aluminum alloy sheet strip has excellent mechanical properties and can meet the requirements of high-end 3C products for strength and stability. The high elongation provides excellent plasticity for the aluminum alloy sheet strip during stamping and bending, reducing the possibility of cracks and surface damage. These physical property parameters above show that the aluminum alloy sheet strip of the present invention has excellent mechanical properties and good processing properties, and is suitable for manufacturing components that require high precision and strength, such as mobile phone back panels, laptop computer casings, etc.

[0035] In another typical embodiment of the present application, a preparation method of the aforementioned 5G50 aluminum alloy sheet strip for anodic oxidation is provided. The preparation method includes: sequentially performing a batching step, a semi-continuous casting step, a soaking step, a hot rolling step, a cold rolling step, an intermediate annealing step, a secondary cold rolling step, and a final annealing step on alloy raw materials to obtain the 5G50 aluminum alloy sheet strip for anodic oxidation; wherein, the temperature of the intermediate annealing step is 280 - 380 °C, and the holding time is 2 - 5 h; the temperature of the final annealing step is 100 - 220 °C, and the holding time is 2 - 5 h.

[0036] The control of the above element contents in the present application, especially the increase in the addition amounts of Mn and Mg elements, combined with stepwise annealing, makes the strength, ductility, and surface quality of the 5G50 aluminum alloy sheet strip for anodic oxidation more suitable for use as an appearance decoration part of high-end electronic products. The stepwise annealing step therein involves heat preservation treatments at different temperatures to eliminate the residual stress inside the material, optimize the material formability and surface quality. The first-stage annealing is carried out in a relatively high temperature range, and the second-stage annealing is carried out in a lower temperature range, so that the residual stress of the finished sheet is relatively low, and thus the finished sheet is easy to achieve stamping forming, and the surface quality of the deformation zone is excellent. This method is generally applicable to deformed aluminum materials. On the one hand, it improves the stability and consistency of the material, making it perform better in high-demand fields such as aerospace and precision instrument manufacturing. On the other hand, it solves the problem that it is difficult for the 5G50 aluminum alloy sheet strip for anodic oxidation to balance high surface quality and excellent mechanical properties.

[0037] In addition, it is preferred to use a semi - continuous casting method to make the flat ingot, and the casting temperature of the flat ingot is controlled at 700 - 750 °C, which helps to control the microstructure of the material and the uniformity of chemical composition. Further, it is preferred that the flux used in the semi - continuous casting process is selected from one or more of chlorides, fluorides, chlorides and fluorides.

[0038] In an embodiment of the present application, the residual stress in the aluminum alloy sheet and strip obtained in the above - mentioned finished product annealing step is controlled to be 0 - 20 MPa; and / or the surface roughness of the aluminum alloy sheet and strip obtained in the finished product annealing step is 0.2 - 0.4 μm.

[0039] Low - level residual stress ensures the dimensional stability of the aluminum alloy sheet and strip and the surface quality during the forming process. Preferred methods for measuring residual stress include, but are not limited to, X - ray diffraction method and measurement by a residual stress analyzer. By controlling the residual stress within the above range, it helps the aluminum alloy sheet and strip to maintain good dimensional stability during subsequent processing and use, avoid deformation and cracking, and is suitable for the manufacture of precision mechanical parts, such as watch movements, high - end camera components, etc.

[0040] Controlling the surface roughness of the aluminum alloy sheet and strip obtained in the above - mentioned finished product annealing step helps to better contact with the mold or tool in the subsequent process, reduce friction and wear, improve processing accuracy and dimensional stability, reduce processing difficulty and cost, and extend the service life of the mold and tool; and the oxide film layer after anodic oxidation is more uniform and smooth, improving the decorative and durable properties of the product.

[0041] In an embodiment of the present application, the temperature of the above - mentioned soaking step is 440 - 480 °C, and the holding time is 4 - 8 h.

[0042] The control of the above temperature and time has an important impact on the material properties during the subsequent hot rolling process.

[0043] In an embodiment of the present application, the final rolling temperature of the above - mentioned hot rolling step is 300 °C - 340 °C, the thickness of the aluminum alloy sheet and strip obtained in the hot rolling step is 4 mm - 8 mm, and / or in the last 3 - 5 rolling passes of the hot rolling step, the deformation rate is 30% - 50%, the average grain size of the aluminum alloy sheet and strip obtained in the hot rolling step is ≤80 μm, and in the aluminum alloy sheet and strip obtained in the hot rolling step, the number of second phases with a size > 5 μm is ≤20 per mm 2 。

[0044] Controlling the finish rolling temperature range of the hot rolling step is beneficial to the dynamic recrystallization of metallic materials, which helps to refine the grains, enabling the average grain size of the aluminum alloy sheet and strip obtained in the hot rolling step to be controlled within ≤80 μm. The refined grain structure can improve the mechanical properties of the material, especially the tensile strength and yield strength, while maintaining good ductility. The second-phase particles have an important influence on the strength and formability of aluminum alloys, and their size and distribution need to be strictly controlled to obtain uniform material properties. Controlling the number of second-phase particles with a size >5 μm in the aluminum alloy sheet and strip obtained in the hot rolling step to be ≤20 particles / mm 2 can effectively avoid the risk of material property degradation and surface quality defects caused by over-sized second-phase particles. In the last 3 - 5 rolling passes of the hot rolling step, controlling the deformation rate at 30% - 50% helps to improve the surface quality of the aluminum alloy strip and reduce surface defects such as cracks and orange peel phenomenon. Due to grain refinement and optimized second-phase distribution, a more uniform oxide film can be formed, thereby reducing the color difference △E, enabling the surface of the aluminum alloy to be free of striped color difference defects and meeting the stringent requirements for surface quality of high-end decorative parts. In summary, by precisely controlling the finish rolling temperature, deformation rate, and second-phase particle distribution in the hot rolling process, the comprehensive performance of 5G50 aluminum alloy sheet and strip, including surface quality, mechanical strength, and processability, can be significantly improved, making it an ideal choice for high-end electronic product casings.

[0045] In addition, the thickness of the aluminum alloy sheet and strip obtained in the hot rolling step includes but is not limited to 4 mm, 4.5 mm, 5 mm, 5.5 mm, 6.0 mm, 6.5 mm, 7.0 mm, 7.5 mm, or 8.0 mm. In addition, it is preferred to use water or oil as a lubricant during the hot rolling process, and the preferred lubricant is selected from one or more of vegetable oils, mineral oils, and synthetic lubricants.

[0046] In one embodiment of the present application, the thickness of the aluminum alloy sheet and strip obtained in the above cold rolling step is 0.3 mm - 3.0 mm, and / or the deformation rate of the secondary cold rolling step is 20% - 40%. The average grain size of the aluminum alloy sheet and strip obtained in the cold rolling step is ≤30 μm, and in the aluminum alloy sheet and strip obtained in the cold rolling step, the number of second-phase particles with a size >5 μm is ≤30 particles / mm 2 。

[0047] The thickness within the above range helps the material to have good mechanical properties and processability during the forming process, while meeting the lightweight requirements.

[0048] Fine grains contribute to improving the strength of aluminum alloy strips while maintaining good plasticity and workability, which is crucial for the surface quality and overall performance of the products after anodizing treatment. Controlling the deformation rate within the above range during cold rolling helps to further refine the grains, making the average grain size of the aluminum alloy strips obtained in the cold rolling step ≤ 30 μm. The reasonable distribution of the second-phase particles helps to improve the strength and wear resistance of the aluminum alloy strips, while reducing surface defects caused by over-sized particles, such as the risk of color difference and stripes that appear after anodizing, and limiting the number of second-phase particles larger than 5 μm to ≤ 30 pieces / mm 2 This is conducive to reducing the adverse effects of the second phase on the material properties. Controlling the deformation rate and the average grain size of the aluminum alloy sheet strips obtained in the cold rolling step is conducive to further optimizing the microstructure of the material and improving the surface quality and mechanical properties of the material. The combined effect of the refined grain structure and the optimized second-phase distribution can significantly improve the surface finish and flatness of the aluminum alloy strips, reduce surface scratches and non-uniformity. And make the aluminum alloy sheet strips after cold rolling exhibit higher tensile strength, yield strength, and good elongation.

[0049] In addition, preferably, the thickness range of the aluminum alloy sheet strips obtained in the above cold rolling step not only meets the requirements of lightweight design but also enables the aluminum alloy strips to have sufficient strength and rigidity. The thickness of the aluminum alloy sheet strips obtained in the cold rolling step includes but is not limited to 0.3 mm, 0.5 mm, 0.6 mm, 0.8 mm, 1.2 mm, 1.5 mm, 1.8 mm, 2.0 mm, 2.2 mm, 2.4 mm, 2.5 mm or 3.0 mm, which will not be elaborated here.

[0050] In addition, the above-mentioned second phase includes Al-Fe phase, Al6-Mn phase, Mg2-Si phase, Al2-Mg3 phase.

[0051] The beneficial effects of the present application will be further described below in conjunction with embodiments.

[0052] Example 1

[0053] Ingredient ratio: By mass percentage, Si = 0.05%, Fe = 0.07%, Mg = 3.5%, Mn = 0.3%, Al and other trace elements.

[0054] First, the alloy raw materials are accurately proportioned to ensure that the content of each element meets the above range. Subsequently, the raw materials are fed into a melting furnace for melting, and the melting temperature is controlled at 750 °C to ensure uniform alloy composition. After melting is completed, casting is carried out, and the obtained aluminum alloy ingot is heated to 440 °C with a holding time of 4 h. After heating is completed, a hot rolling step is carried out, the final rolling temperature is 300 °C, the thickness of the obtained aluminum alloy sheet and strip is 4 mm, and the deformation rate of the hot rolling step is 75%. Subsequently, the hot-rolled aluminum alloy sheet and strip are cold-rolled, and the thickness of the obtained aluminum alloy sheet and strip is 0.5 mm, and the deformation rate of the cold rolling step is 88%. Finally, the aluminum alloy sheet and strip are subjected to stepped annealing treatment. The temperature of the first-stage annealing step is 300 °C with a holding time of 2 h; the temperature of the second-stage annealing step is 100 °C with a holding time of 2 h, and a 5G50 aluminum alloy sheet and strip for anodic oxidation is obtained, and its internal grain structure diagram is as shown in Figure 1 shown, in which, the average grain size of the 5G50 aluminum alloy sheet and strip for anodic oxidation is about 14 μm. The second-phase structure diagram inside the 5G50 aluminum alloy sheet and strip for anodic oxidation is as shown in Figure 2 shown, in which, the number of the second phase with a size > 5 μm is about 20 per mm 2 .

[0055] Test results: The thickness of the obtained 5G50 aluminum alloy sheet and strip for anodic oxidation is 1.2 mm, the number of the second phase with a size > 5 μm is about 20 per mm 2 , the average grain diameter is about 14 μm; the tensile strength is 320 MPa, the yield strength is 260 MPa, and the elongation is 12%; no cracks and orange peel defects are found in the 180° bending test; the surface is smooth and delicate and the color is consistent (ΔE = 0.03) after anodic oxidation, and no visible defects are found; the residual stress in the aluminum alloy sheet and strip obtained in the finished product annealing step is 6 MPa; the average grain size of the aluminum alloy sheet and strip obtained in the hot rolling step is about 50 μm, and in the aluminum alloy sheet and strip obtained in the hot rolling step, the number of the second phase with a size > 5 μm is about 15 per mm 2 ; the average grain size of the aluminum alloy sheet and strip obtained in the cold rolling step is about 24 μm, and in the aluminum alloy sheet and strip obtained in the cold rolling step, the number of the second phase with a size > 5 μm is about 20 per mm 2 .

[0056] Example 2

[0057] The difference from Example 1 is that Si = 0.05%, Fe = 0.10%, Mg = 3.9%, Mn = 0.7%, Al and other trace elements, and finally a 5G50 aluminum alloy sheet and strip for anodic oxidation is obtained.

[0058] Test results: The thickness of the obtained product is 0.6 mm, and the number of the second phase with a size > 5 μm is about 25 per mm2 , the average grain diameter is about 22 μm; the tensile strength is 330 MPa, the yield strength is 270 MPa, the elongation is 10%, and no cracks and orange peel defects are found after the 180° bending test; the surface is smooth and delicate after anodizing, the color is consistent (ΔE = 0.04), and no visible defects are found; the residual stress in the aluminum alloy sheet obtained in the finished product annealing step is 15 MPa; the average grain size of the aluminum alloy sheet obtained in the hot rolling step is about 60 μm, and in the aluminum alloy sheet obtained in the hot rolling step, the number of second phases with a size > 5 μm is about 14 per mm 2 ; the average grain size of the aluminum alloy sheet obtained in the cold rolling step is about 25 μm, and in the aluminum alloy sheet obtained in the cold rolling step, the number of second phases with a size > 5 μm is about 23 per mm 2 .

[0059] Example 3

[0060] The difference from Example 1 is that the mass ratio of Mg element to Mn element is 16, and finally an aluminum alloy sheet for anodizing containing 5G50 is obtained.

[0061] Test results: The thickness of the obtained product is 1.0 mm, and the number of second phases with a size > 5 μm is about 18 per mm 2 , the average grain diameter is about 20 μm; the tensile strength is 310 MPa, the yield strength is 240 MPa, the elongation is 11%, and no cracks and orange peel defects are found after the 180° bending test; the surface is smooth and delicate after anodizing, the color is consistent (ΔE = 0.03), and no visible defects are found; the residual stress in the aluminum alloy sheet obtained in the finished product annealing step is 18 MPa; the average grain size of the aluminum alloy sheet obtained in the hot rolling step is about 65 μm, and in the aluminum alloy sheet obtained in the hot rolling step, the number of second phases with a size > 5 μm is about 16 per mm 2 ; the average grain size of the aluminum alloy sheet obtained in the cold rolling step is about 20 μm, and in the aluminum alloy sheet obtained in the cold rolling step, the number of second phases with a size > 5 μm is about 20 per mm 2 .

[0062] Example 4

[0063] The difference from Example 1 is the ingredient ratio: by mass percentage, Si = 0.08%, Fe = 0.12%, Mg = 3.8%, Mn = 0.4%, Al and other trace elements, and finally an aluminum alloy sheet for anodizing containing 5G50 is obtained.

[0064] Test results: The thickness of the obtained product is 1.0 mm, and the number of second phases with a size > 5 μm is about 26 per mm 2, the average grain diameter is about 15 μm; the tensile strength is 335 MPa, the yield strength is 265 MPa, and the elongation is 10%. No cracks and orange peel defects are found after the 180° bending test; the surface is smooth and delicate after anodization, and the color is consistent (△E = 0.12), and no visible defects are found; the residual stress in the aluminum alloy strip obtained by the finished product annealing step is 8 MPa; the average grain size of the aluminum alloy strip obtained by the hot rolling step is about 60 μm. In the aluminum alloy strip obtained by the hot rolling step, the number of second phases with a size > 5 μm is about 15 / mm 2 ; the average grain size of the aluminum alloy strip obtained by the cold rolling step is about 23 μm. In the aluminum alloy strip obtained by the cold rolling step, the number of second phases with a size > 5 μm is about 22 / mm 2 .

[0065] Example 5

[0066] The difference from Example 1 lies in the ingredient ratio: by mass percentage, Si = 0.08%, Fe = 0.13%, Mg = 3.8%, Mn = 0.4%, Al and other trace elements, and finally an aluminum alloy strip for anodization containing 5G50 is obtained.

[0067] Test results: the thickness of the obtained product is 1.2 mm, and the number of second phases with a size > 5 μm is about 16 / mm 2 , the average grain diameter is about 20 μm; the tensile strength is 312 MPa, the yield strength is 242 MPa, and the elongation is 10%; no cracks and orange peel defects are found after the 180° bending test; the surface is smooth and delicate after anodization, and the color is consistent (△E = 0.06), and no visible defects are found; the residual stress in the aluminum alloy strip obtained by the finished product annealing step is 12 MPa; the average grain size of the aluminum alloy strip obtained by the hot rolling step is about 60 μm. In the aluminum alloy strip obtained by the hot rolling step, the number of second phases with a size > 5 μm is about 16 / mm 2 ; the average grain size of the aluminum alloy strip obtained by the cold rolling step is about 24 μm. In the aluminum alloy strip obtained by the cold rolling step, the number of second phases with a size > 5 μm is about 25 / mm 2 .

[0068] Example 6

[0069] The difference from Example 1 lies in that the aluminum alloy strip is subjected to stepped annealing treatment. The temperature of the first-stage annealing step is 380 °C, and the holding time is 2 h; the temperature of the second-stage annealing step is 150 °C, and the holding time is 2 h, and finally an aluminum alloy strip for anodization containing 5G50 is obtained.

[0070] Test results: The thickness of the 5G50 aluminum alloy sheet strip for anodizing obtained is 1.2 mm, and the number of second phases with a size > 5 μm is approximately 22 per mm. 2 , the average grain diameter is approximately 16 μm; the tensile strength is 325 MPa, the yield strength is 265 MPa, and the elongation is 13%; no cracks and orange peel defects are found in the 180° bending test; the surface is smooth and delicate after anodizing, the color is consistent (ΔE = 0.03), and no visible defects are found; the residual stress in the aluminum alloy sheet strip obtained in the finished product annealing step is 7 MPa; the average grain size of the aluminum alloy sheet strip obtained in the hot rolling step is approximately 55 μm, and in the aluminum alloy sheet strip obtained in the hot rolling step, the number of second phases with a size > 5 μm is approximately 16 per mm. 2 ; the average grain size of the aluminum alloy sheet strip obtained in the cold rolling step is approximately 25 μm, and in the aluminum alloy sheet strip obtained in the cold rolling step, the number of second phases with a size > 5 μm is approximately 21 per mm. 2 .

[0071] Example 7

[0072] The difference from Example 1 is that after melting is completed, casting is carried out, and the obtained aluminum alloy ingot is heated to 480 °C and the holding time is 8 h, and finally a 5G50 aluminum alloy sheet strip for anodizing is obtained.

[0073] Test results: The thickness of the 5G50 aluminum alloy sheet strip for anodizing obtained is 1.2 mm, and the number of second phases with a size > 5 μm is approximately 23 per mm. 2 , the average grain diameter is approximately 16 μm; the tensile strength is 334 MPa, the yield strength is 270 MPa, and the elongation is 15%; no cracks and orange peel defects are found in the 180° bending test; the surface is smooth and delicate after anodizing, the color is consistent (ΔE = 0.03), and no visible defects are found; the residual stress in the aluminum alloy sheet strip obtained in the finished product annealing step is 7 MPa; the average grain size of the aluminum alloy sheet strip obtained in the hot rolling step is approximately 56 μm, and in the aluminum alloy sheet strip obtained in the hot rolling step, the number of second phases with a size > 5 μm is approximately 17 per mm. 2 ; the average grain size of the aluminum alloy sheet strip obtained in the cold rolling step is approximately 26 μm, and in the aluminum alloy sheet strip obtained in the cold rolling step, the number of second phases with a size > 5 μm is approximately 22 per mm. 2 .

[0074] Example 8

[0075] The difference from Example 1 is that after melting is completed, casting is carried out, and the obtained aluminum alloy ingot is heated to 420 °C and the holding time is 8 h, and finally a 5G50 aluminum alloy sheet strip for anodizing is obtained.

[0076] Test results: The thickness of the 5G50 aluminum alloy sheet and strip for anodic oxidation obtained is 1.2 mm, and the number of second phases with a size > 5 μm is approximately 23 per mm 2 , the average grain diameter is approximately 16 μm; the tensile strength is 314 MPa, the yield strength is 240 MPa, and the elongation is 10%; no cracks and orange peel defects are found in the 180° bending test; the surface is smooth and delicate after anodic oxidation, the color is consistent (ΔE = 0.06), and no visible defects are found; the residual stress in the aluminum alloy sheet and strip obtained in the finished product annealing step is 10 MPa; the average grain size of the aluminum alloy sheet and strip obtained in the hot rolling step is approximately 58 μm, and in the aluminum alloy sheet and strip obtained in the hot rolling step, the number of second phases with a size > 5 μm is approximately 20 per mm 2 ; the average grain size of the aluminum alloy sheet and strip obtained in the cold rolling step is approximately 30 μm, and in the aluminum alloy sheet and strip obtained in the cold rolling step, the number of second phases with a size > 5 μm is approximately 25 per mm 2 .

[0077] Example 9

[0078] The difference from Example 1 is that the final rolling temperature in the hot rolling step is 340 °C, and finally, an aluminum alloy sheet and strip containing 5G50 for anodic oxidation is obtained.

[0079] Test results: The thickness of the 5G50 aluminum alloy sheet and strip for anodic oxidation obtained is 1.2 mm, and the number of second phases with a size > 5 μm is approximately 21 per mm 2 , the average grain diameter is approximately 16 μm; the tensile strength is 330 MPa, the yield strength is 280 MPa, and the elongation is 15%; no cracks and orange peel defects are found in the 180° bending test; the surface is smooth and delicate after anodic oxidation, the color is consistent (ΔE = 0.03), and no visible defects are found; the residual stress in the aluminum alloy sheet and strip obtained in the finished product annealing step is 8 MPa; the average grain size of the aluminum alloy sheet and strip obtained in the hot rolling step is approximately 52 μm, and in the aluminum alloy sheet and strip obtained in the hot rolling step, the number of second phases with a size > 5 μm is approximately 16 per mm 2 ; the average grain size of the aluminum alloy sheet and strip obtained in the cold rolling step is approximately 26 μm, and in the aluminum alloy sheet and strip obtained in the cold rolling step, the number of second phases with a size > 5 μm is approximately 23 per mm 2 .

[0080] Example 10

[0081] The difference from Example 1 is that the final rolling temperature in the hot rolling step is 290 °C, and finally, an aluminum alloy sheet and strip containing 5G50 for anodic oxidation is obtained.

[0082] Test results: The thickness of the 5G50 aluminum alloy sheet and strip for anodic oxidation obtained is 1.2 mm, and the number of second phases with a size > 5 μm is approximately 22 per mm2 , the average grain diameter is about 18 μm; the tensile strength is 312 MPa, the yield strength is 250 MPa, and the elongation is 10%; no cracks and orange peel defects are found in the 180° bending test; the surface is smooth and delicate after anodizing, the color is uniform (ΔE = 0.03), and no visible defects are found; the residual stress in the aluminum alloy strip obtained in the finished product annealing step is 10 MPa; the average grain size of the aluminum alloy strip obtained in the hot rolling step is about 55 μm, and in the aluminum alloy strip obtained in the hot rolling step, the number of second phases with a size > 5 μm is about 12 per mm 2 ; the average grain size of the aluminum alloy strip obtained in the cold rolling step is about 28 μm, and in the aluminum alloy strip obtained in the cold rolling step, the number of second phases with a size > 5 μm is about 26 per mm 2 .

[0083] Example 11

[0084] The difference from Example 1 is that in the last 3 rolling passes of the hot rolling step, the deformation rates are 40%, 45%, and 50% respectively, and finally an aluminum alloy strip for anodizing containing 5G50 is obtained.

[0085] Test results: The thickness of the 5G50 aluminum alloy strip for anodizing obtained is 1.2 mm, and the number of second phases with a size > 5 μm is about 21 per mm 2 , the average grain diameter is about 16 μm; the tensile strength is 332 MPa, the yield strength is 278 MPa, and the elongation is 16%; no cracks and orange peel defects are found in the 180° bending test; the surface is smooth and delicate after anodizing, the color is uniform (ΔE = 0.03), and no visible defects are found; the residual stress in the aluminum alloy strip obtained in the finished product annealing step is 9 MPa; the average grain size of the aluminum alloy strip obtained in the hot rolling step is about 53 μm, and in the aluminum alloy strip obtained in the hot rolling step, the number of second phases with a size > 5 μm is about 18 per mm 2 ; the average grain size of the aluminum alloy strip obtained in the cold rolling step is about 27 μm, and in the aluminum alloy strip obtained in the cold rolling step, the number of second phases with a size > 5 μm is about 24 per mm 2 .

[0086] Example 12

[0087] The difference from Example 1 is that in the last 3 rolling passes of the hot rolling step, the deformation rates are 40%, 55%, and 60% respectively, and finally an aluminum alloy strip for anodizing containing 5G50 is obtained.

[0088] Test results: The thickness of the 5G50 aluminum alloy strip for anodizing obtained is 1.2 mm, and the number of second phases with a size > 5 μm is about 20 per mm 2, the average grain diameter is about 18 μm; the tensile strength is 315 MPa, the yield strength is 248 MPa, and the elongation is 10%; no cracks and orange peel defects are found in the 180° bending test; the surface is smooth and delicate after anodization, the color is consistent (△E = 0.03), and no visible defects are found; the residual stress in the aluminum alloy sheet and strip obtained by the finished product annealing step is 10 MPa; the average grain size of the aluminum alloy sheet and strip obtained by the hot rolling step is about 56 μm, and in the aluminum alloy sheet and strip obtained by the hot rolling step, the number of second phases with a size > 5 μm is about 14 per mm 2 ; the average grain size of the aluminum alloy sheet and strip obtained by the cold rolling step is about 28 μm, and in the aluminum alloy sheet and strip obtained by the cold rolling step, the number of second phases with a size > 5 μm is about 27 per mm 2 .

[0089] Comparative Example 1

[0090] The difference from Example 1 is that the aluminum alloy sheet and strip is subjected to step annealing treatment. The temperature of the first-stage annealing step is 270 °C and the holding time is 2 h; the temperature of the second-stage annealing step is 90 °C and the holding time is 2 h, obtaining the 5G50 aluminum alloy sheet and strip for anodization, and its internal grain structure diagram is as shown in Figure 3 . Among them, the average grain size of the 5G50 aluminum alloy sheet and strip for anodization is about 55 μm. The internal second-phase structure diagram of the 5G50 aluminum alloy sheet and strip for anodization is as shown in Figure 4 . Among them, the number of second phases with a size > 5 μm is about 50 per mm 2 .

[0091] Test results: The thickness of the obtained product is 3.0 mm, and the number of second phases with a size > 5 μm is about 50 per mm 2 , the average grain diameter is about 55 μm; the tensile strength is 330 MPa, the yield strength is 290 MPa, the elongation is 6%, cracks and orange peel defects are visible in the 180° bending test; there are stripe defects on the surface after anodization, the color difference △E = 0.35, unqualified; the residual stress in the aluminum alloy sheet and strip obtained by the finished product annealing step is 35 MPa; the average grain size of the aluminum alloy sheet and strip obtained by the hot rolling step is about 80 μm, and in the aluminum alloy sheet and strip obtained by the hot rolling step, the number of second phases with a size > 5 μm is about 15 per mm 2 ; the average grain size of the aluminum alloy sheet and strip obtained by the cold rolling step is about 30 μm, and in the aluminum alloy sheet and strip obtained by the cold rolling step, the number of second phases with a size > 5 μm is about 25 per mm 2 .

[0092] Comparative Example 2

[0093] Ratio of ingredients: By mass percentage, Si = 0.05%, Fe = 0.07%, Mg = 2.5%, Mn = 0.3%, and Al and other trace elements total 95.58%.

[0094] First, the alloy raw materials are accurately proportioned to ensure that the content of each element meets the above range. Subsequently, the raw materials are sent into a melting furnace for melting, and the melting temperature is controlled at 750 °C to ensure uniform alloy composition. After melting is completed, casting is carried out, and the obtained aluminum alloy ingot is heated to 440 °C with a holding time of 4 h. After heating is completed, a hot rolling step is carried out, the final rolling temperature is 300 °C, the thickness of the obtained aluminum alloy sheet and strip is 4 mm, and the deformation rate of the hot rolling step is 75%. Subsequently, the hot-rolled aluminum alloy sheet and strip are cold-rolled, the thickness of the obtained aluminum alloy sheet and strip is 0.5 mm, and the deformation rate of the cold rolling step is 88%. Finally, the aluminum alloy sheet and strip are subjected to finish annealing treatment, and the finish annealing process uses a temperature of 300 °C and a holding time of 2 h to obtain a 5G50 aluminum alloy sheet and strip for anodic oxidation.

[0095] Test results: The thickness of the obtained product is 1.2 mm, the number of the second phase with a size > 5 μm is about 20 per mm 2 , the average grain diameter is about 55 μm; the tensile strength is 260 MPa, the yield strength is 160 MPa, the elongation is 11%, and no cracks and orange peel defects are found in the 180° bending test; there are stripe defects on the surface after anodic oxidation, the color difference △E = 0.20, and the mechanical properties are low and unqualified; the residual stress in the aluminum alloy sheet and strip obtained in the finish annealing step is 5 MPa; the average grain size of the aluminum alloy sheet and strip obtained in the hot rolling step is about 75 μm, and in the aluminum alloy sheet and strip obtained in the hot rolling step, the number of the second phase with a size > 5 μm is about 18 per mm 2 ; the average grain size of the aluminum alloy sheet and strip obtained in the cold rolling step is about 28 μm, and in the aluminum alloy sheet and strip obtained in the cold rolling step, the number of the second phase with a size > 5 μm is about 25 per mm 2 .

[0096] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0097] By precisely controlling the alloy element content, compared with the mainstream 5252 anodized aluminum materials, the addition amounts of Mn and Mg elements in the aluminum materials of the present invention are increased, so that after anodization of the aluminum alloy sheet and strip, not only the color is uniform, but also the color difference is extremely small, and the surface quality of anodization is excellent. The color difference △E of the 5G50 aluminum alloy sheet and strip for anodization is <0.15, and there are no abnormal color stripe defects on the surface detected visually. On the one hand, this technology ensures the aesthetics and consistency of the material after surface treatment, meets the strict requirements of high-end products for surface color, and makes it show excellent aesthetics and application potential in fields with high requirements for color consistency such as building decoration and electronic product casings. On the other hand, it solves the problem that it is difficult for the 5G50 aluminum alloy sheet and strip for anodization to balance high surface quality and excellent mechanical properties.

[0098] The above are only embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A 5G50 aluminum alloy sheet and strip for anodizing, characterized in that: The 5G50 aluminum alloy sheet and strip for anodizing comprises the following elements in percentage by mass: Si content is 0.01% to 0.10%, Fe content is 0.04% to 0.15%, Mg content is 3.0% to 4.0%, Mn content is 0.2% to 1.2%, the total content of unavoidable impurity elements is ≤0.02%, the content of a single impurity element is lower than 0.05wt%, and the balance is Al; wherein, after anodizing treatment, the aluminum alloy sheet and strip has no heterochromatic streak defects on the surface of the aluminum material, and the color difference △E is less than 0.

15.

2. The 5G50 aluminum alloy sheet and strip for anodizing according to claim 1, characterized in that: The 5G50 aluminum alloy plate and strip for anodizing comprises the following elements in percentage by mass: 0.01% to 0.06% Si, 0.04% to 0.10% Fe, 3.3% to 4.0% Mg, 0.2% to 0.4% Mn, the total content of unavoidable impurity elements is ≤0.02%, the content of a single impurity element is less than 0.05wt%, and the balance is Al.

3. The 5G50 aluminum alloy sheet and strip for anodizing according to claim 1 or 2, characterized in that: The mass ratio of the Mg element to the Mn element is 5 to 15:

1.

4. The 5G50 aluminum alloy sheet and strip for anodizing according to any one of claims 1 to 3, characterized in that: In the 5G50 aluminum alloy plate and strip for anodizing, the number of second phases with a size of more than 5 μm is ≤30 / mm 2 .

5. The 5G50 aluminum alloy sheet and strip for anodizing according to any one of claims 1 to 4, characterized in that: The 5G50 aluminum alloy plate and strip for anodizing has a thickness of 0.3 mm to 3.0 mm, an average grain size of ≤30 μm, a maximum grain size of ≤60 μm, a tensile strength of 300 to 335 MPa, a yield strength of 230 to 280 MPa, and an elongation of ≥10%.

6. A method for preparing the 5G50 aluminum alloy sheet and strip for anodizing according to any one of claims 1 to 5, characterized in that: The preparation method comprises: The alloy raw material is sequentially subjected to a batching step, a semi-continuous casting step, a soaking step, a hot rolling step, a cold rolling step, an intermediate annealing step, a secondary cold rolling step and a finished product annealing step to obtain a 5G50 aluminum alloy sheet and strip for anodizing; The temperature of the intermediate annealing step is 280-380° C., and the holding time is 2-5 hours; the temperature of the finished product annealing step is 100-220° C., and the holding time is 2-5 hours.

7. The method for preparing the 5G50 aluminum alloy sheet and strip for anodizing according to claim 6, characterized in that: The residual stress in the aluminum alloy plate and strip obtained in the finished product annealing step is controlled to be 0-20 MPa; and / or the surface roughness of the aluminum alloy plate and strip obtained in the finished product annealing step is 0.2-0.4 μm.

8. The method for preparing the 5G50 aluminum alloy sheet and strip for anodizing according to claim 6 or 7, characterized in that: The temperature of the soaking step is 440-480° C., and the soaking time is 4-8 hours.

9. The method for preparing the 5G50 aluminum alloy sheet and strip for anodizing according to any one of claims 6 to 8, characterized in that: The final rolling temperature of the hot rolling step is 300°C to 340°C, the thickness of the aluminum alloy sheet and strip obtained in the hot rolling step is 4mm to 8mm, and / or, the deformation rate of the last 3 to 5 rolling passes of the hot rolling step is 30% to 50%, the average grain size of the aluminum alloy sheet and strip obtained in the hot rolling step is ≤80μm, and the number of second phases with a size of >5μm in the aluminum alloy sheet and strip obtained in the hot rolling step is ≤20 / mm 2 .

10. The method for preparing the 5G50 aluminum alloy sheet and strip for anodizing according to any one of claims 6 to 9, characterized in that: The thickness of the aluminum alloy strip obtained in the cold rolling step is 0.3 mm to 3.0 mm, and / or the deformation rate of the secondary cold rolling step is 20% to 40%, the average grain size of the aluminum alloy strip obtained in the cold rolling step is ≤30 μm, and the number of second phases with a size of >5 μm in the aluminum alloy strip obtained in the cold rolling step is ≤30 / mm 2 .

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