Method for evaluating orange peel degree of aluminum alloy

Abstract

The invention provides an aluminum alloy orange peel degree evaluation method. The evaluation method comprises the following steps: performing 90-degree stamping bending on an aluminum alloy sample to obtain a bent aluminum alloy with a bent inner fillet of 0 mm; carrying out 3D surface contour scanning by adopting a magnification factor of 70X-90X to obtain a scanning graph; the curved surface of the bent inner fillet in the scanning image is spread into a plane, and then the surface roughness Sa and the surface maximum depth Sz are obtained through integration; n aluminum alloy test articles are tested according to the steps, the Sa average value A and the Sz average value B are obtained, A ranges from 1.0 micrometer to 2.2 micrometers, B ranges from 10 micrometers to 22 micrometers, and n is larger than or equal to 3; establishing an evaluation standard that the orange peel degree of the aluminum alloy sample meets the requirement: Sa < = A and Sz < = B; carrying out the above steps on an aluminum alloy product to be tested to obtain an Sa test value and an Sz test value; and judging the orange peel degree of the aluminum alloy to-be-detected product according to the evaluation standard. The evaluation method can quantitatively characterize the orange peel degree of the aluminum alloy.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloys, and in particular to a method for evaluating the orange peel degree of aluminum alloys. Background Art

[0002] Computers, communications, and consumer electronics (hereinafter referred to as "3C consumer electronics") are manufactured using aluminum alloys. Aluminum alloys not only provide the required strength, rigidity, and thermal conductivity for these products, but also, after anodizing and coloring, they can form an anodic oxide film that is both wear-resistant and corrosion-resistant, as well as aesthetically pleasing, thereby enhancing the artistic and technological appeal of these 3C products. 3C consumer electronics products are rapidly evolving, and the performance requirements for aluminum alloys in these newer products are increasing year by year. Specifically, these requirements include: 1) aesthetically pleasing appearance, uniform color, and high brightness; defects such as streaks and pits on the anodized surface, as well as batch-to-batch color variations, are not permitted; 2) lightweighting: aluminum alloy thickness is reduced from 2mm to 0.6mm, requiring high rigidity and pressure resistance, with tensile strength increased from 150MPa to over 300MPa; 3) ease of formability: structural design requires an internal corner radius reduced from 0.5mm to 0mm, requiring an elongation of at least 8%, and a surface free of orange peel.

[0003] At present, the degree of orange peel of the aluminum alloy bending fillet used in 3C consumer electronic products is mainly determined by human observation and subjective judgment, and there is still a lack of quantitative evaluation and control methods for the degree of orange peel of aluminum alloy. Summary of the Invention

[0004] The main purpose of the present invention is to provide a method for evaluating the orange peel degree of aluminum alloy, so as to solve the problem in the prior art that the orange peel degree of aluminum alloy bending fillet cannot be quantitatively evaluated.

[0005] In order to achieve the above-mentioned purpose, according to one aspect of the present invention, a method for evaluating the degree of orange peel of aluminum alloy is provided, which comprises: step S1, performing a 90° stamping and bending of the aluminum alloy sample to obtain a bent aluminum alloy with a bending inner fillet of 0 mm; step S2, performing a 3D surface profile scan of the bent aluminum alloy with a magnification of 70X to 90X to obtain a scanned image; spreading the curved surface of the bending inner fillet in the scanned image into a plane state and performing integration processing to obtain a surface roughness Sa and a surface maximum depth Sz; step S3, when the aluminum alloy sample is n different aluminum alloy test pieces with known orange peel degrees that meet the requirements, the aluminum alloy test pieces are sequentially subjected to steps S1 to S2 to obtain the surface roughness Sa test values ​​and surface maximum depth Sz test values ​​corresponding to the n aluminum alloy test pieces, and the surface roughness Sa test values ​​of the n aluminum alloy test pieces are calculated respectively. The average value of the surface roughness Sa and the average value of the surface maximum depth Sz test value are obtained, the average value of the surface roughness Sa and the average value of the surface maximum depth Sz are recorded as A, the average value of the surface maximum depth Sz is recorded as B, the condition for the orange peel degree to meet the requirements is that the surface of the aluminum alloy sample has no obvious unevenness, wherein A is 1.0-2.2 μm, B is 10-22 μm, and n ≥ 3; step S4, establishing an evaluation standard for whether the orange peel degree of the aluminum alloy sample meets the requirements: the surface roughness Sa of the aluminum alloy sample ≤ A, and the maximum depth Sz of the surface ≤ B; step S5, when the aluminum alloy sample is an aluminum alloy to be tested with an unknown orange peel degree, the aluminum alloy to be tested sequentially undergoes steps S1 to S2 to obtain the surface roughness Sa test value and the surface maximum depth Sz test value of the aluminum alloy to be tested; according to the evaluation standard in step S4, judge whether the orange peel degree of the aluminum alloy to be tested meets the requirements.

[0006] Furthermore, A is 1.2 to 2.0 μm, and B is 12 to 20 μm.

[0007] Furthermore, surface shape correction is used to flatten the curved surface with the inner fillet in the scanned image into a flat state.

[0008] Furthermore, when the aluminum alloy sample is an aluminum alloy formed product, the evaluation method also includes: lubricating the aluminum alloy sample and then stamping and bending it to obtain a bent aluminum alloy; the aluminum alloy on both sides of the fold line away from the inner fillet of the bend is respectively cut to obtain a bent sample, wherein the vertical distance between the cut-off position on the bent sample and the fold line is 10 to 15 mm; placing the bent sample in the center on the workbench of the 3D profile scanner and performing a 3D surface profile scan after automatic focusing, and obtaining a scanned image after the scanning is completed; after the curved surface of the inner fillet of the bend in the scanned image is spread into a plane state, the plane area containing the inner fillet of the bend in the scanned image is selected for integration processing to obtain the surface roughness Sa and the maximum depth of the surface Sz; wherein the plane area containing the inner fillet of the bend is a rectangle, the length of the rectangle is 3 to 5 mm, and the width of the rectangle is 0.5 to 1.0 mm.

[0009] Furthermore, A is 1.0 to 1.4 μm, and B is 10 to 14 μm.

[0010] Furthermore, when the aluminum alloy sample is an unformed aluminum alloy sample, the evaluation method also includes: cutting a rectangular sheet with a length of 13 to 15 mm and a width of 20 to 25 mm along the rolling direction of the aluminum alloy sample, placing the dry sheet on a 90° bending tester, and using a bending press to perform stamping and bending to obtain a bent aluminum alloy; wherein the fillet radius of the bending press is 0 mm; placing the bent aluminum alloy in the center on the workbench of the 3D profile scanner and performing a 3D surface profile scan after automatic focusing, and obtaining a scanned image after the scanning is completed; after the curved surface of the inner fillet of the bend in the scanned image is spread into a plane state, the plane area containing the inner fillet of the bend in the scanned image is selected for integration processing to obtain the surface roughness Sa and the maximum surface depth Sz; wherein, the plane area containing the inner fillet of the bend is a rectangle, the length of the rectangle is 3 to 5 mm, and the width of the rectangle is 0.5 to 1.0 mm.

[0011] Furthermore, A is 1.8 to 2.2 μm, and B is 18 to 22 μm.

[0012] Furthermore, the punching speed of the 90° punch bending is 10 to 50 mm / s, and the holding time of the 90° punch bending is 0.5 to 1.0 s.

[0013] Furthermore, the average grain size of the aluminum alloy is ≤22 μm.

[0014] Furthermore, the aluminum alloy sample is a 5 series aluminum alloy, and the grade of the aluminum alloy sample is selected from any one or more of 5052, 5252, 5005, 5083, 5086, 5154, 5454, 5754 and 5182; and / or the thickness of the aluminum alloy sample is 0.4 to 1.5 mm.

[0015] Applying the technical solution of the present invention, aiming at the degree of orange peel at the bend of aluminum alloy materials for 3C products, this application proposes a method for evaluating the degree of orange peel of aluminum alloy, which can quantitatively characterize the degree of orange peel of the bend fillet of aluminum alloy for 3C products, break through the subjectivity of traditional visual rating, and improve the detection rate of defective products. Specifically, the aluminum alloy sample is subjected to 90° stamping and bending, so that the bending angle of the aluminum alloy after bending is 90°, and the inner fillet of the bend is 0mm (that is, the inner fillet of the aluminum alloy after bending is a right angle, without a transition fillet). Through the aluminum alloy test product with known orange peel degree, the correlation between the degree of orange peel and the roughness is established, and it is concluded that the orange peel degree of the above aluminum alloy sample meets the required evaluation criteria. The surface roughness Sa test value and the surface maximum depth Sz test value of the aluminum alloy to be tested are obtained by the above steps S1 to S2, and it can be judged whether its orange peel degree meets the above requirements according to the above evaluation criteria. The evaluation method of the present application is simple to operate and the results are highly accurate. In summary, the application of the evaluation method of the present application has achieved a 40-50% increase in the test accuracy of the surface roughness of aluminum alloy bent parts (especially aluminum alloys for 3C products), and a 40-50% increase in the accuracy of judging the degree of orange peel, thereby meeting the stringent requirements of the anodizing process on the surface of the aluminum alloy substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0017] Figure 1 The 3D surface profile scanning diagram of the aluminum alloy to be tested at 80X magnification in Example 1 of the present application is shown;

[0018] Figure 2 The figure shows a microscope observation image of the aluminum alloy to be tested in Comparative Example 1 of the present application;

[0019] Figure 3 The 3D surface profile scanning diagram of the aluminum alloy to be tested in Comparative Example 2 of the present application at a magnification of 40X is shown;

[0020] Figure 4 The 3D surface profile scanning diagram of the aluminum alloy to be tested in Comparative Example 3 of the present application at a magnification of 120X is shown;

[0021] Figure 5 The microstructure diagram of the aluminum alloy to be tested in Example 2 of the present application is shown;

[0022] Figure 6 The 3D surface profile scanning diagram of the aluminum alloy to be tested at 80X magnification in Example 2 of the present application is shown;

[0023] Figure 7The figure shows a microscope observation image of the aluminum alloy to be tested in Comparative Example 4 of the present application;

[0024] Figure 8 The 3D surface profile scanning diagram of the aluminum alloy to be tested at 80X magnification in Example 5 of the present application is shown;

[0025] Figure 9 The 3D surface profile scanning diagram of the aluminum alloy to be tested at 80X magnification in Example 6 of the present application is shown;

[0026] Figure 10 The microstructure diagram of the aluminum alloy to be tested in Example 7 of the present application is shown;

[0027] Figure 11 The 3D surface profile scanning diagram of the aluminum alloy to be tested at 80X magnification in Example 7 of the present application is shown;

[0028] Figure 12 shows a grain size diagram of the aluminum alloy to be tested in Example 8 of the present application;

[0029] Figure 13 The 3D surface profile scanning diagram of the aluminum alloy to be tested at 80X magnification in Example 8 of the present application is shown. DETAILED DESCRIPTION

[0030] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0031] As analyzed in the background technology of this application, there is a problem in the prior art that the degree of orange peel at the bent corners of aluminum alloys cannot be quantified and evaluated. In order to solve the above problem, this application provides a method for evaluating the degree of orange peel of aluminum alloys.

[0032] In a typical embodiment of the present application, a method for evaluating the degree of orange peel of an aluminum alloy is provided, and the evaluation method includes: step S1, performing a 90° stamping and bending of an aluminum alloy sample to obtain a bent aluminum alloy with a bending inner fillet of 0 mm; step S2, performing a 3D surface profile scan of the bent aluminum alloy with a magnification of 70X to 90X to obtain a scanned image; spreading the curved surface of the bending inner fillet in the scanned image into a flat state, and detecting the surface roughness Sa and the maximum surface depth Sz; step S3, when the aluminum alloy sample is n different aluminum alloy test pieces with known orange peel degrees that meet the requirements, the aluminum alloy test pieces are sequentially subjected to steps S1 to S2 to obtain the surface roughness Sa test values ​​and the surface maximum depth Sz test values ​​corresponding to the n aluminum alloy test pieces, and respectively calculating the average and average values ​​of the surface roughness Sa test values ​​of the n aluminum alloy test pieces. The average value of the surface maximum depth Sz test value is obtained to obtain the average value of the surface roughness Sa and the average value of the surface maximum depth Sz, the average value of the surface roughness Sa is recorded as A, and the average value of the surface maximum depth Sz is recorded as B. The condition for the orange peel degree to meet the requirements is that the surface of the aluminum alloy sample has no obvious unevenness, wherein n≥3; step S4, establishing an evaluation standard for whether the orange peel degree of the aluminum alloy sample meets the requirements: the surface roughness Sa≤A and the maximum depth Sz≤B in the aluminum alloy sample, A is 1.0~2.2μm, and B is 10~22μm; step S5, when the aluminum alloy sample is an aluminum alloy to be tested with unknown orange peel degree, the aluminum alloy to be tested sequentially undergoes steps S1 to S2 to obtain the surface roughness Sa test value and the surface maximum depth Sz test value of the aluminum alloy to be tested; according to the evaluation standard in step S4, judge whether the orange peel degree of the aluminum alloy to be tested meets the requirements.

[0033] In view of the degree of orange peel at the bend of aluminum alloy materials used in 3C products, this application proposes a method for evaluating the degree of orange peel of aluminum alloy, which can quantitatively characterize the degree of orange peel of the bend fillet of aluminum alloy used in 3C products, break through the subjectivity of traditional visual rating, and improve the detection rate of defective products. Specifically, the aluminum alloy sample is subjected to 90° stamping and bending, so that the bending angle of the aluminum alloy after bending is 90°, and the inner fillet of the bend is 0mm (that is, the inner fillet of the aluminum alloy after bending is a right angle, without a transition fillet). Through the aluminum alloy test product with known orange peel degree, the correlation between the degree of orange peel and the roughness is established, and it is concluded that the orange peel degree of the above aluminum alloy sample meets the required evaluation criteria. The surface roughness Sa test value and the surface maximum depth Sz test value of the aluminum alloy to be tested are obtained by the above steps S1 to S2, and it can be judged whether its orange peel degree meets the above requirements according to the above evaluation criteria. The evaluation method of the present application is simple to operate and the results are highly accurate. In summary, the application of the evaluation method of the present application has achieved a 40-50% increase in the test accuracy of the surface roughness of aluminum alloy bent parts (especially aluminum alloys for 3C products), and a 40-50% increase in the accuracy of judging the degree of orange peel, thereby meeting the stringent requirements of the anodizing process on the surface of the aluminum alloy substrate.

[0034] Surface roughness Sa (average surface roughness height) and surface maximum depth Sz (maximum surface roughness depth) are three-dimensional surface topography parameters (measured based on area). Surface roughness Sa is the three-dimensional arithmetic mean roughness, representing the average of the absolute values ​​of the height deviations from the reference surface for all points within the entire measurement area.

[0035] The maximum depth of the surface Sz is the maximum three-dimensional height difference, which represents the vertical distance between the highest point and the lowest point in the measurement area (i.e., the maximum value from the peak to the valley bottom).

[0036] Roughness is calculated as follows:

[0037] 1) The formula for surface roughness Sa is: C is the area of ​​the measured plane region, and Z(x, y) is the Z coordinate value of the surface peaks and troughs (i.e., the height of any point on the surface).

[0038] 2) The maximum depth of the surface Sz is calculated as the Z-direction distance between the highest peak and the lowest trough in the measured plane area.

[0039] The integration software is used to perform integration processing (i.e. the above calculation method) on the plane area containing the inner fillet of the bend in the scan image to obtain the roughness data.

[0040] The orange peel degree of aluminum alloy refers to the unevenness of its surface, similar to the peel of an orange. The condition for the aluminum alloy sample to meet the orange peel degree requirement is that the surface has no obvious unevenness and can proceed to the post-processing without polishing. It is mainly judged by visual or microscopic observation.

[0041] In order to further improve the accuracy of the orange peel degree of aluminum alloy, in one embodiment of the present application, A is 1.2-2.0 μm, and B is 12-20 μm.

[0042] In one embodiment of the present application, surface shape correction is performed to flatten the curved surface with rounded corners in the scan image into a flat state.

[0043] Surface shape correction uses 3D topography processing software to eliminate the geometric tolerances of the rounded corners when unfolded into a flat surface. This helps to improve the accuracy and consistency of subsequent roughness measurement data, reduces the errors caused by curved surface measurement, and thus improves the reliability of the evaluation results.

[0044] In one embodiment of the present application, when the aluminum alloy sample is an aluminum alloy formed product, the evaluation method further includes: lubricating the aluminum alloy sample and then stamping and bending it to obtain a bent aluminum alloy; the aluminum alloy on both sides of the fold line away from the inner fillet of the bending is respectively intercepted to obtain a bent sample, wherein the vertical distance between the intercepted position on the bent sample and the fold line is 10 to 15 mm; the bent sample is centered on the workbench of the 3D profile scanner and automatically focused before performing a 3D surface profile scan, and a scanned image is obtained after the scanning is completed; after the curved surface of the inner fillet of the bending in the scanned image is spread into a plane state, the plane area containing the inner fillet of the bending in the scanned image is selected for integration processing to obtain the surface roughness Sa and the maximum surface depth Sz; wherein the plane area containing the inner fillet of the bending is a rectangle, the length of the rectangle is 3 to 5 mm, and the width of the rectangle is 0.5 to 1.0 mm.

[0045] For pre-formed aluminum alloy products (formed aluminum alloy products), lubricating the aluminum alloy sample with lubricant before stamping and bending the material sample helps reduce friction and surface damage during the bending process, while also helping to improve bending accuracy and stability. The aluminum alloy after bending is cut into pieces as described above, which facilitates better 3D surface profile scanning. The preferred inspection area size helps match the magnification of the 3D surface profile scan, thereby improving the accuracy of the roughness test results.

[0046] In one embodiment of the present application, A is 1.0-1.4 μm, and B is 10-14 μm.

[0047] When the aluminum alloy sample is a formed aluminum alloy product, A and B are preferably within the above ranges, which helps further improve the accuracy and stability of determining whether the aluminum alloy's orange peel level meets the requirements. Furthermore, when the formed aluminum alloy product is preferably an aluminum alloy stamping part, the above evaluation method is suitable for testing aluminum alloy finished products, thereby quickly determining the degree of orange peel in the aluminum alloy.

[0048] In one embodiment of the present application, when the aluminum alloy sample is an unformed aluminum alloy sample, the evaluation method further includes: cutting a rectangular sheet with a length of 13 to 15 mm and a width of 20 to 25 mm along the rolling direction of the aluminum alloy sample, placing the dry sheet on a 90° bending tester and using a bending press to perform stamping and bending to obtain a bent aluminum alloy; wherein the fillet radius of the bending press is 0 mm; placing the bent aluminum alloy in the center on the workbench of a 3D profile scanner and performing a 3D surface profile scan after automatic focusing, and obtaining a scanned image after the scanning is completed; after the curved surface of the inner fillet of the bend in the scanned image is spread into a plane state, the plane area containing the inner fillet of the bend in the scanned image is selected for integration processing to obtain the surface roughness Sa and the maximum surface depth Sz; wherein the plane area containing the inner fillet of the bend is a rectangle, the length of the rectangle is 3 to 5 mm, and the width of the rectangle is 0.5 to 1.0 mm.

[0049] For unformed aluminum alloy samples, under experimental conditions, the aforementioned evaluation method helps improve the accuracy of roughness test results, thereby increasing the accuracy and stability of orange peel determination results. It also helps improve the yield rate of aluminum alloys. The degree of orange peel can be quickly determined at the experimental stage before entering production, thereby preventing potential processing issues, improving yield, and reducing production costs. It is preferred that the bending head be aligned with the middle of the sheet's length during the stamping and bending process.

[0050] In one embodiment of the present application, A is 1.8 to 2.2 μm, and B is 18 to 22 μm.

[0051] When the aluminum alloy sample is an unformed aluminum alloy sample, A and B are preferably within the above ranges, which helps further improve the accuracy and stability of determining whether the aluminum alloy's orange peel level meets the requirements. The above evaluation method is suitable for testing unformed aluminum alloy samples during the experimental stage, allowing for quick determination of the aluminum alloy's orange peel level and prompt adjustment of the aluminum alloy process. The unformed aluminum alloy sample is preferably an aluminum alloy sheet sample.

[0052] In one embodiment of the present application, the punching speed of the 90° punching bend is 10-50 mm / s, and the holding time of the 90° punching bend is 0.5-1.0 s.

[0053] It is preferred that the stamping speed and holding time of the 90° stamping bend are within the above range, which helps to make the bending angle of the aluminum alloy after bending 90° and the inner fillet of the bending 0mm, thereby facilitating the subsequent roughness detection and further improving the accuracy of the judgment of the orange peel degree of the aluminum alloy.

[0054] In one embodiment of the present application, the average grain size of the aluminum alloy is ≤22 μm.

[0055] This application establishes a correlation between the grain size of aluminum alloys and the quality of the bending surface. It is preferred to control the average grain size of aluminum alloys for 3C products with defect-free bending surfaces within the above range. This helps to optimize the aluminum alloy processing technology in advance, thereby improving the yield rate of the aluminum alloy. The above grain size helps to improve the uniformity of the aluminum alloy and reduce internal stress, thereby reducing surface orange peel defects during the bending process. It also helps to improve the tensile strength and fatigue resistance of the aluminum alloy.

[0056] In one embodiment of the present application, the aluminum alloy sample is a 5 series aluminum alloy, and the grade of the aluminum alloy sample is selected from any one or more of 5052, 5252, 5005, 5083, 5086, 5154, 5454, 5754 and 5182.

[0057] The preferred aluminum alloy sample is a 5 series aluminum alloy, which not only helps to meet the performance requirements of 3C products for aluminum alloy bent parts, such as good bending formability, high surface quality, lightness, high strength and high corrosion resistance, but also can improve production efficiency and reduce production costs by optimizing the processing technology. The grades of aluminum alloy samples include but are not limited to the above grades. The evaluation method of this application has better accuracy and stability for the above aluminum alloys. The thickness of the preferred aluminum alloy sample is 0.4 to 1.5 mm, which is conducive to stamping and bending.

[0058] This application addresses the lack of quantitative evaluation for the orange peel defect in aluminum alloy bend fillets used in 3C consumer electronics products. By constructing a three-level evaluation system (part level (molded product) - laboratory level (unmolded samples) - material level) and combining it with microstructure control, this approach achieves quantitative characterization of the orange peel defect and optimizes aluminum alloy processing technology.

[0059] The beneficial effects of the present application will be further illustrated below with reference to embodiments.

[0060] Example 1

[0061] In step S1, three aluminum alloy test pieces (5052 aluminum alloy stamping parts) with a thickness of 0.8 mm and known to meet the orange peel requirement (no surface irregularities) are lubricated with lubricating oil and then subjected to 90° stamping and bending. Each bent aluminum alloy has a 0 mm inner bend radius. The stamping speed for the 90° stamping and bending is 20 mm / s, and the holding time for the 90° stamping and bending is 0.5 s. The aluminum alloy on both sides of the fold line away from the inner bend radius is cut to obtain bent samples. The vertical distance between the cut position and the fold line on the bent sample is 10 mm. Three bent samples are obtained, namely, Test 1, Test 2, and Test 3.

[0062] In step S2, the bent samples were centered on the workbench of a 3D profile scanner. After autofocusing, a 3D surface profile scan of the bent aluminum alloy was performed at an 80X magnification. After the scan, the curved surface of the inner fillet of the bend was flattened using 3D topography processing software. The geometric tolerances of the flat surface of the inner fillet of the bend were eliminated. A 0.5mm*3mm rectangular area was selected in the plane containing the inner fillet of the bend. Integration software was used to perform integration processing to obtain the surface roughness Sa and maximum surface depth Sz. The surface roughness Sa of Sample 1 was 1.199μm, and the maximum surface depth Sz was 11.996μm. The surface roughness Sa of Sample 2 was 1.197μm, and the maximum surface depth Sz was 11.998μm. The surface roughness Sa of Sample 3 was 1.205μm, and the maximum surface depth Sz was 12.004μm. The average value A of the surface roughness Sa test values ​​of the test pieces 1 to 3 was calculated to be 1.2 μm, and the average value B of the surface maximum depth Sz test values ​​was calculated to be 12 μm.

[0063] The evaluation criteria for the orange peel degree of the aluminum alloy sample to meet the requirements are as follows: the surface roughness Sa of the aluminum alloy sample is ≤ 1.2 μm, and the maximum surface depth Sz is ≤ 12 μm.

[0064] An aluminum alloy product to be tested with an unknown degree of orange peel, a thickness of 0.8 mm, and an average grain size of 22 μm is sequentially subjected to steps S1 to S2, and a surface roughness Sa test value of the aluminum alloy product to be tested is obtained to be 1.045 μm, and a surface maximum depth Sz test value is obtained to be 11.315 μm; according to the above evaluation criteria, the surface roughness Sa test value and the surface maximum depth Sz test value are compared, and the surface roughness Sa test value is <1.2 μm, and the surface maximum depth Sz test value is <12 μm, indicating that the orange peel degree of the aluminum alloy product to be tested meets the requirements.

[0065] Example 2

[0066] Step S1, cut 13mm*20mm rectangular sheets of 0.8mm thickness from three aluminum alloy test pieces (5052 aluminum alloy plates) with known orange peel degree meeting the requirements (no unevenness on the surface), roll them in the 13mm direction, place them on a 90° bending tester in a dry state, and use a bending press to perform stamping and bending. The bending press is aligned with the middle position of the 20mm length direction of the sheet to obtain bent aluminum alloys with 0mm inner fillet, which are respectively Test piece 1, Test piece 2 and Test piece 3. Among them, the stamping speed of the 90° stamping bending is 20mm / s, and the holding time of the 90° stamping bending is 0.5s.

[0067] In step S2, the bent aluminum alloys were centered on the workbench of a 3D profile scanner and automatically focused. A 3D surface profile scan was performed at 80X magnification. After the scan, the curved surface of the inner fillet of the bend was flattened using 3D topography processing software. The geometric tolerances of the flat surface of the inner fillet of the bend were eliminated. A 0.5mm*3mm rectangular area was selected within the plane containing the inner fillet of the bend. Integration software was used to perform integration processing to obtain the surface roughness Sa and maximum surface depth Sz. The surface roughness Sa of Test 1 was 2.025μm, and the maximum surface depth Sz was 20.8μm. The surface roughness Sa of Test 2 was 1.988μm, and the maximum surface depth Sz was 19.8μm. The surface roughness Sa of Test 3 was 1.991μm, and the maximum surface depth Sz was 19.28μm. The average value A of the surface roughness Sa test values ​​of the test pieces 1 to 3 was calculated to be 2.0 μm, and the average value B of the surface maximum depth Sz test values ​​was calculated to be 20 μm.

[0068] The evaluation conditions for the orange peel degree of the aluminum alloy sample to meet the requirements are: the surface roughness Sa of the aluminum alloy sample is ≤ 2.0 μm, and the maximum surface depth Sz is ≤ 20 μm.

[0069] An aluminum alloy product to be tested with an unknown degree of orange peel, a thickness of 0.8 mm, and an average grain size of 22 μm is sequentially subjected to steps S1 to S2, and a surface roughness Sa test value of the aluminum alloy product to be tested is obtained to be 1.955 μm, and a surface maximum depth Sz test value is obtained to be 17.783 μm; based on the above evaluation conditions, the surface roughness Sa test value and the surface maximum depth Sz test value are compared, and the surface roughness Sa test value is <2.0 μm, and the surface maximum depth Sz test value is <20 μm, indicating that the orange peel degree of the aluminum alloy product to be tested meets the requirements.

[0070] Example 3

[0071] The difference from Example 1 is that in step S1, three aluminum alloy test pieces (5052 aluminum alloy stamping parts) with a thickness of 0.8 mm and known to meet the orange peel requirement (no surface irregularities) are lubricated with lubricating oil and then stamped and bent at 90°, resulting in bent aluminum alloys with a 0 mm inner bend radius. The aluminum alloy on both sides of the fold line away from the inner bend radius is cut to obtain bent samples, where the vertical distance between the cut point and the fold line is 10 mm. Three bent samples are obtained, namely, Test 1, Test 2, and Test 3.

[0072] In step S2, the bent samples were centered on the workbench of a 3D profile scanner. After autofocusing, a 3D surface profile scan of the bent aluminum alloy was performed at a magnification of 70X. After the scan, the curved surface of the inner fillet of the bend was flattened using 3D topography processing software. The geometric tolerances of the flat surface of the inner fillet of the bend were eliminated. A 0.5mm*3mm rectangular area was selected in the plane containing the inner fillet of the bend. Integration software was used to perform integration processing to obtain the surface roughness Sa and maximum surface depth Sz. The surface roughness Sa of Sample 1 was 1.397μm, and the maximum surface depth Sz was 13.998μm. The surface roughness Sa of Sample 2 was 1.396μm, and the maximum surface depth Sz was 13.996μm. The surface roughness Sa of Sample 3 was 1.402μm, and the maximum surface depth Sz was 14.003μm. The average value A of the surface roughness Sa test values ​​of the test pieces 1 to 3 was calculated to be 1.4 μm, and the average value B of the surface maximum depth Sz test values ​​was calculated to be 14 μm.

[0073] The evaluation standard for the orange peel degree of aluminum alloy samples to meet the requirements is established as follows: the surface roughness Sa of the aluminum alloy sample is ≤ 1.4 μm, and the maximum surface depth Sz is ≤ 14 μm.

[0074] An aluminum alloy product to be tested with an unknown degree of orange peel, a thickness of 0.8 mm, and an average grain size of 22 μm is sequentially subjected to steps S1 to S2, and a surface roughness Sa test value of the aluminum alloy product to be tested is obtained to be 1.197 μm, and a surface maximum depth Sz test value is obtained to be 11.998 μm; according to the above evaluation criteria, the surface roughness Sa test value and the surface maximum depth Sz test value are compared, and the surface roughness Sa test value is <1.4 μm, and the surface maximum depth Sz test value is <14 μm, indicating that the orange peel degree of the aluminum alloy product to be tested meets the requirements.

[0075] Example 4

[0076] The difference from Example 2 is that, in step S1, three aluminum alloy test pieces (5052 aluminum alloy plates) with a thickness of 0.8 mm and known to meet the requirements of orange peel degree (no unevenness on the surface) are cut into 13mm*20mm rectangular sheets, rolled in the 13mm direction, placed on a 90° bending tester in a dry state, and punched and bent using a bending press. The bending press is aligned with the middle position of the 20mm length direction of the sheet, and bent aluminum alloys with a bending inner fillet of 0mm are obtained, namely Test 1, Test 2 and Test 3.

[0077] In step S2, the bent aluminum alloys were centered on the workbench of a 3D profile scanner. After autofocusing, the bent aluminum alloys were scanned in 3D profile at a magnification of 90X. After the scan, the curved surface of the inner fillet of the bend was flattened using 3D profile processing software. The geometric tolerances of the flat surface of the inner fillet of the bend were eliminated. A 0.5mm*3mm rectangular area was selected in the plane containing the inner fillet of the bend. Integration software was used to perform integration processing to obtain the surface roughness Sa and maximum surface depth Sz. The surface roughness Sa of Test 1 was 2.215μm, and the maximum surface depth Sz was 22.778μm. The surface roughness Sa of Test 2 was 2.196μm, and the maximum surface depth Sz was 21.984μm. The surface roughness Sa of Test 3 was 2.189μm, and the maximum surface depth Sz was 21.997μm. The average value A of the surface roughness Sa test values ​​of the test pieces 1 to 3 was calculated to be 2.2 μm, and the average value B of the surface maximum depth Sz test values ​​was calculated to be 22 μm.

[0078] The evaluation criteria for the orange peel degree of the aluminum alloy sample to meet the requirements are as follows: the surface roughness Sa of the aluminum alloy sample is ≤ 2.2 μm, and the maximum surface depth Sz is ≤ 22 μm.

[0079] An aluminum alloy product to be tested, with an unknown degree of orange peel, a thickness of 0.8 mm and an average grain size of 22 μm, is sequentially subjected to steps S1 to S2, and a surface roughness Sa test value of the aluminum alloy product to be tested is obtained to be 1.998 μm, and a surface maximum depth Sz test value is obtained to be 19.995 μm; according to the above evaluation criteria, the surface roughness Sa test value and the surface maximum depth Sz test value are compared, and the surface roughness Sa test value is <2.2 μm, and the surface maximum depth Sz test value is <22 μm, indicating that the orange peel degree of the aluminum alloy product to be tested meets the requirements.

[0080] Example 5

[0081] The difference from Example 1 is that the aluminum alloy product to be tested with unknown orange peel degree is subjected to steps S1 to S2 in sequence, and the surface roughness Sa test value of the aluminum alloy product to be tested is 1.444 μm, and the surface maximum depth Sz test value is 14.325 μm; according to the above evaluation criteria, the surface roughness Sa test value and the surface maximum depth Sz test value are compared, and the surface roughness Sa test value is greater than 1.2 μm, and the surface maximum depth Sz test value is greater than 12 μm. The orange peel degree of the aluminum alloy product to be tested does not meet the requirements.

[0082] Example 6

[0083] The difference from Example 2 is that the aluminum alloy product to be tested with unknown orange peel degree is sequentially subjected to steps S1 to S2, and the surface roughness Sa test value of the aluminum alloy product to be tested is 2.153 μm, and the surface maximum depth Sz test value is 21.727 μm; according to the above evaluation criteria, the surface roughness Sa test value and the surface maximum depth Sz test value are compared, and the surface roughness Sa test value is greater than 2.0 μm, and the surface maximum depth Sz test value is greater than 20 μm. The orange peel degree of the aluminum alloy product to be tested does not meet the requirements.

[0084] Example 7

[0085] The difference from Example 2 is that the grain size of the aluminum alloy product to be tested is 17 μm, and the aluminum alloy product to be tested with unknown orange peel degree is sequentially subjected to steps S1 to S2, and the surface roughness Sa test value of the aluminum alloy product to be tested is 1.458 μm, and the surface maximum depth Sz test value is 14.417 μm; according to the above evaluation conditions, the surface roughness Sa test value and the surface maximum depth Sz test value are compared, and the surface roughness Sa test value is <2.0 μm, and the surface maximum depth Sz test value is <20 μm. The orange peel degree of the aluminum alloy product to be tested meets the requirements.

[0086] Example 8

[0087] The difference from Example 2 is that the grain size of the aluminum alloy product to be tested is 55 μm, and the aluminum alloy product to be tested with unknown orange peel degree is sequentially subjected to steps S1 to S2, and the surface roughness Sa test value of the aluminum alloy product to be tested is 2.153 μm, and the surface maximum depth Sz test value is 20.727 μm; according to the above evaluation conditions, the surface roughness Sa test value and the surface maximum depth Sz test value are compared, the surface roughness Sa test value is greater than 2.0 μm, and the surface maximum depth Sz test value is greater than 20 μm, and the orange peel degree of the aluminum alloy product to be tested does not meet the requirements.

[0088] Comparative Example 1

[0089] The difference from Example 1 is that the surface of the rounded corner of the aluminum alloy to be tested is directly observed under a microscope after bending and has no obvious unevenness, and it is judged that the orange peel degree of the aluminum alloy to be tested meets the requirements.

[0090] Comparative Example 2

[0091] The difference from Example 1 is that after the bent aluminum alloy is scanned in 3D at a magnification of 40X, the curved surface of the bent inner corner is spread into a flat state, and a rectangular area of ​​0.5mm*3mm is selected to detect the surface roughness Sa and the maximum depth Sz of the surface.

[0092] Comparative Example 3

[0093] The difference from Example 1 is that after the bent aluminum alloy is scanned in 3D at a magnification of 120X, the curved surface of the bent inner corner is spread into a flat state, and a rectangular area of ​​0.5mm*3mm is selected to detect the surface roughness Sa and the maximum depth Sz of the surface.

[0094] Comparative Example 4

[0095] The difference from Example 2 is that the surface of the rounded corner of the aluminum alloy to be tested is directly observed under a microscope after bending and has no obvious unevenness, and it is judged that the orange peel degree of the aluminum alloy to be tested meets the requirements.

[0096] Comparative Example 5

[0097] The difference from Example 5 is that the degree of orange peel of the rounded corners of the aluminum alloy to be tested after bending is directly observed under a microscope. There is no obvious unevenness on the surface visually. After the subsequent anodizing process is magnified, orange peel defects appear on the surface, and the degree of orange peel does not meet the requirements.

[0098] Comparative Example 6

[0099] The difference from Example 1 is that, in step S1, the aluminum alloy sample is stamped and bent at 60° to obtain a bent aluminum alloy with a bending inner fillet of 2 mm. The bending deformation of the material is insufficient, the grain deformation is small, and the test results cannot represent the actual results.

[0100] Test method:

[0101] Roughness is calculated as follows:

[0102] 1) The formula for surface roughness Sa is: C is the area of ​​the measured plane region, and Z(x, y) is the Z coordinate value of the surface peaks and troughs (i.e., the height of any point on the surface).

[0103] 2) The maximum depth of the surface Sz is calculated as the Z-direction distance between the highest peak and the lowest trough in the measured plane area.

[0104] In addition, due to the limitations of the 3D surface profile scanning instrument, the image shows a plane that actually contains the Z coordinate. Technical personnel in this field can use integration software to integrate the plane area containing the inner fillet of the bend in the scan image based on the 3D surface profile scanning results to obtain roughness data.

[0105] in, Figure 1 This is a 3D surface profile scan of the aluminum alloy to be tested in Example 1 at 80X magnification. Figure 1 It can be seen that the subtle orange peel structure of the curved corners can be fully presented.

[0106] Figure 2 This is a microscope observation picture of the aluminum alloy to be tested in Comparative Example 1. Figure 2 It can be seen that the aluminum alloy product to be tested can only observe the roughness of the bend fillet of the aluminum alloy product to be tested, while the method of Example 1 can effectively measure the surface roughness Sa and the maximum surface depth Sz of the bend fillet, thereby achieving quantitative characterization of the degree of orange peel of the aluminum alloy bend.

[0107] Figure 3 This is a 3D surface profile scan of the aluminum alloy to be tested in Example 2 at 40X magnification. Figure 4 It can be seen that the subtle orange peel structure of the bend fillet is covered, and the orange peel depth displacement of the bend fillet cannot be scanned.

[0108] Figure 4 This is a 3D surface profile scan of the aluminum alloy to be tested in Example 3 at 120X magnification. Figure 5 It can be seen that when the measurement range is 0.5*2mm, the scanning range is small, which makes it impossible to accurately represent the entire bend radius.

[0109] and Figure 3 and Figure 4 In comparison, Example 1 can more effectively characterize the roughness value of the aluminum alloy bending fillet at a magnification of 80X.

[0110] Figure 5 is the microstructure diagram of the aluminum alloy to be tested in Example 2, Figure 2 It can be seen from the figure that the grains of the aluminum alloy to be tested in Example 2 are evenly distributed, and the average grain size obtained through measurement and calculation is 22 μm.

[0111] Figure 6 This is a 3D surface profile scan of the aluminum alloy to be tested in Example 2 at 80X magnification. Figure 6 It can be seen that the subtle orange peel structure of the curved corners can be fully presented.

[0112] Figure 7 This is a microscope observation diagram of the aluminum alloy to be tested in Comparative Example 4. Figure 7 It can be seen that the aluminum alloy product to be tested can only observe the roughness of the bend fillet of the aluminum alloy product to be tested, while the method of Example 2 can effectively measure the surface roughness Sa and the maximum surface depth Sz of the bend fillet, thereby achieving quantitative characterization of the degree of orange peel of the aluminum alloy bend.

[0113] Figure 8 This is a 3D surface profile scan of the aluminum alloy to be tested in Example 5 at 80X magnification. Figure 8 It can be seen that the subtle orange peel structure of the curved corners can be fully presented.

[0114] Figure 9 This is a 3D surface profile scan of the aluminum alloy to be tested in Example 6 at 80X magnification. Figure 9 It can be seen that the subtle orange peel structure of the curved corners can be fully presented.

[0115] Figure 10 is the microstructure diagram of the aluminum alloy to be tested in Example 7. Figure 10 It can be seen from the figure that the grains of the aluminum alloy to be tested in Example 7 are evenly distributed, and the average grain size obtained through measurement and calculation is 17 μm.

[0116] Figure 11 This is a 3D surface profile scan of the aluminum alloy to be tested in Example 7 at 80X magnification. Figure 11 It can be seen that the subtle orange peel structure of the curved corners can be fully presented.

[0117] Figure 12 is the microstructure diagram of the aluminum alloy to be tested in Example 8, Figure 12 It can be seen from the figure that the grains of the aluminum alloy to be tested in Example 8 are evenly distributed, and the average grain size obtained through measurement and calculation is 55 μm.

[0118] Figure 13 This is a 3D surface profile scan of the aluminum alloy to be tested in Example 8 at 80X magnification. Figure 13 It can be seen that the subtle orange peel structure of the curved corners can be fully presented.

[0119] As can be seen from the above, in Comparative Example 1, the presence of unevenness on the rounded corners of the aluminum alloy sample after bending was observed using a microscope. This was highly subjective and did not allow for a quantitative evaluation standard. Using the evaluation method of Example 5, the orange peel level of the aluminum alloy sample did not meet the requirements. However, in Comparative Example 5, the orange peel level met the requirements only through microscopic observation, but orange peel defects appeared on the surface after actual anodized magnification. This demonstrates that the evaluation method of the present application is more accurate and reliable than the microscopic observation method. Therefore, compared to the comparative example, the evaluation method of the present application for the orange peel level of aluminum alloys has higher accuracy and stability.

[0120] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0121] In view of the degree of orange peel at the bend of aluminum alloy materials used in 3C products, this application proposes a method for evaluating the degree of orange peel of aluminum alloy, which can quantitatively characterize the degree of orange peel of the bend fillet of aluminum alloy used in 3C products, break through the subjectivity of traditional visual rating, and improve the detection rate of defective products. Specifically, the aluminum alloy sample is subjected to 90° stamping and bending, so that the bending angle of the aluminum alloy after bending is 90°, and the inner fillet of the bend is 0mm (that is, the inner fillet of the aluminum alloy after bending is a right angle, without a transition fillet). Through the aluminum alloy test product with known orange peel degree, the correlation between the degree of orange peel and the roughness is established, and it is concluded that the orange peel degree of the above aluminum alloy sample meets the required evaluation criteria. The surface roughness Sa test value and the surface maximum depth Sz test value of the aluminum alloy to be tested are obtained by the above steps S1 to S2, and it can be judged whether its orange peel degree meets the above requirements according to the above evaluation criteria. The evaluation method of the present application is simple to operate and the results are highly accurate. In summary, the application of the evaluation method of the present application has achieved a 40-50% increase in the test accuracy of the surface roughness of aluminum alloy bent parts (especially aluminum alloys for 3C products), and a 40-50% increase in the accuracy of judging the degree of orange peel, thereby meeting the stringent requirements of the anodizing process on the surface of the aluminum alloy substrate.

[0122] The above are merely embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for evaluating the orange peel degree of aluminum alloy, characterized in that: The evaluation method includes: Step S1, performing 90° stamping and bending of the aluminum alloy sample to obtain a bent aluminum alloy having a bending inner fillet of 0 mm; Step S2, performing a 3D surface profile scan of the bent aluminum alloy at a magnification of 70X to 90X to obtain a scanned image; flattening the curved surface of the inner fillet of the bend in the scanned image into a flat state and performing integration processing to obtain a surface roughness Sa and a surface maximum depth Sz; Step S3, when the aluminum alloy sample is n different aluminum alloy test products with known orange peel degrees that meet the requirements, the aluminum alloy test products are sequentially subjected to steps S1 to S2 to obtain the surface roughness Sa test values ​​and surface maximum depth Sz test values ​​corresponding to each of the n aluminum alloy test products, and the average values ​​of the surface roughness Sa test values ​​and the average values ​​of the surface maximum depth Sz test values ​​of the n aluminum alloy test products are calculated to obtain the average value of the surface roughness Sa and the average value of the surface maximum depth Sz, the average value of the surface roughness Sa is recorded as A, and the average value of the surface maximum depth Sz is recorded as B. The condition for the orange peel degree to meet the requirements is that the surface of the aluminum alloy sample has no obvious unevenness, wherein A is 1.0 to 2.2 μm, B is 10 to 22 μm, and n ≥ 3; Step S4, establishing an evaluation standard for whether the orange peel degree of the aluminum alloy sample meets the requirements: the surface roughness Sa of the aluminum alloy sample ≤ the A, and the maximum surface depth Sz ≤ the B; Step S5: When the aluminum alloy sample is an aluminum alloy product to be tested with an unknown degree of orange peel, the aluminum alloy product to be tested sequentially undergoes steps S1 to S2 to obtain a surface roughness Sa test value and a surface maximum depth Sz test value of the aluminum alloy product to be tested; and according to the evaluation criteria in step S4, it is determined whether the degree of orange peel of the aluminum alloy product to be tested meets the requirements.

2. The evaluation method according to claim 1, wherein The A is 1.2 to 2.0 μm, and the B is 12 to 20 μm.

3. The evaluation method according to claim 1 or 2, characterized in that The curved surface of the bent inner fillet in the scanned image is flattened into a flat state by using surface shape correction.

4. The evaluation method according to claim 1 or 2, characterized in that When the aluminum alloy sample is an aluminum alloy formed product, the evaluation method further includes: The aluminum alloy sample is lubricated and then subjected to the stamping and bending to obtain the bent aluminum alloy; the aluminum alloy on both sides of the fold line away from the inner fillet of the bend is respectively cut to obtain a bent sample, wherein the vertical distance between the cut position on the bent sample and the fold line is 10 to 15 mm, respectively; the bent sample is centered on the workbench of the 3D profile scanner and the 3D surface profile is scanned after automatic focusing, and the scanned image is obtained after the scanning is completed; after the curved surface of the inner fillet of the bend in the scanned image is spread into a plane state, the plane area containing the inner fillet of the bend in the scanned image is selected for integration processing to obtain the surface roughness Sa and the maximum surface depth Sz; wherein, the plane area containing the inner fillet of the bend is a rectangle, the length of the rectangle is 3 to 5 mm, and the width of the rectangle is 0.5 to 1.0 mm.

5. The evaluation method according to claim 4, wherein: The A is 1.0 to 1.4 μm, and the B is 10 to 14 μm.

6. The evaluation method according to claim 1 or 2, characterized in that When the aluminum alloy sample is an unformed aluminum alloy sample, the evaluation method further includes: Cutting a rectangular sheet with a length of 13 to 15 mm and a width of 20 to 25 mm along the rolling direction of the aluminum alloy sample, placing the dried sheet on a 90° bending tester and performing the punching and bending using a bending press to obtain the bent aluminum alloy; wherein the fillet radius of the bending press is 0 mm; The bent aluminum alloy is placed centrally on the workbench of a 3D profile scanner and automatically focused before performing the 3D surface profile scan, and the scanned image is obtained after the scanning is completed; after the curved surface of the inner fillet of the bend in the scanned image is spread into a plane state, the plane area containing the inner fillet of the bend in the scanned image is selected for integration processing to obtain the surface roughness Sa and the maximum depth Sz of the surface; wherein, the plane area containing the inner fillet of the bend is a rectangle, the length of the rectangle is 3 to 5 mm, and the width of the rectangle is 0.5 to 1.0 mm.

7. The evaluation method according to claim 6, wherein: The A is 1.8 to 2.2 μm, and the B is 18 to 22 μm.

8. The evaluation method according to claim 1 or 2, characterized in that The punching speed of the 90° punching and bending is 10-50 mm / s, and the holding time of the 90° punching and bending is 0.5-1.0 s.

9. The evaluation method according to claim 1 or 2, characterized in that The average grain size of the aluminum alloy is ≤22 μm.

10. The evaluation method according to claim 1 or 2, characterized in that: The aluminum alloy sample is a 5 series aluminum alloy, and the grade of the aluminum alloy sample is selected from any one or more of 5052, 5252, 5005, 5083, 5086, 5154, 5454, 5754 and 5182; and / or the thickness of the aluminum alloy sample is 0.4 to 1.5 mm.

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