High-strength and easy-to-form 5G50 aluminum alloy sheet and strip for anodizing and preparation method thereof

Abstract

The invention discloses a high-strength and easy-to-form 5G50 aluminum alloy plate and strip for anodizing and a preparation method thereof, comprising the following steps: melting and casting the alloy components to obtain an aluminum alloy flat ingot; the alloy components are as follows by mass percentage: Si is 0.01% to 0.08%; Fe is 0.04% to 0.12%; Mg is 3.0% to 4.6%; Cr is 0.1% to 0.4%; Cu is 0.03% to 0.05%, other impurity elements are ≤ 0.02%, and the balance is Al; the aluminum alloy flat ingot is subjected to 460°C to 520°C / 8h to 16 h homogenization treatment, and the aluminum alloy flat ingot after the homogenization treatment is subjected to 15-25 hot rolling passes and 3-6 cold rolling passes to obtain a plate, the single hot rolling rate of the last three hot rolling passes is not less than 40%, and after the cold rolling intermediate annealing, the secondary cold rolling rate is not less than 30%; the finished product annealing temperature is 140-180°C to obtain an aluminum alloy plate and strip with a fine grain size. The aluminum alloy obtained by the present invention has high tensile strength and yield strength, can be formed at room temperature, and has no cracks on the surface; at the same time, the surface color is uniform after anodizing treatment, and there is no heterochromatic streak defect.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloys, and in particular to a high-strength and easy-to-form 5G50 aluminum alloy plate and strip material for anodizing and a preparation method thereof. Background Art

[0002] Aluminum is a lightweight, high-strength, and thermally conductive metal material. It is increasingly used in the exterior structural parts of consumer electronics. It has the following advantages: 1) Aluminum alloy is lightweight, and the density of aluminum alloy is one-third of that of steel. Using aluminum alloy as the shell of portable consumer electronic products can effectively reduce the weight; 2) Aluminum alloy has good mechanical properties, high strength, good compression resistance and toughness, and is sturdy and resistant to falling, which can meet the requirements of highly integrated, lightweight, and miniaturized products; 3) Aluminum alloy has good heat dissipation performance and can quickly take away the heat generated by electronic products; 4) The surface treatment process is rich, beautiful, and easy to color. After anodizing, it has good heat resistance and wear resistance, which is more textured and improves the product grade.

[0003] Adding a high proportion of Mg and Cr elements to aluminum alloys can reduce the density of aluminum alloy materials to achieve a weight reduction effect; in addition, by reasonably adding a certain proportion of Si, Mn and Cu elements, the thermal conductivity of aluminum alloy materials can be improved. However, when the amount of Mg added is high (≥5wt%), due to the low melting point of Mg and the density of Mg being less than Al (651°C), when the Mg ingot is added to the aluminum liquid during the smelting process, it floats to the surface of the aluminum liquid, and a large amount of Mg is easily burned, releasing a large amount of heat, which can easily cause the melt to overheat and slag to form seriously. The high Na content in the melt, the high gas content, the macro segregation of the ingot, and the hot rolling, the high processing rate and many other factors will cause the high-strength and high-formability 5 series alloy ingots and strips to crack and cause the product to be scrapped, which has become a key factor restricting the promotion and application of such products; at the same time, the aluminum alloy sheet obtained by using a high proportion of Cr elements is difficult to form at room temperature, and cracks appear on the surface during the bending process. Summary of the invention

[0004] In order to solve the technical problem that aluminum alloy sheets obtained with high proportions of Mg and Cr elements in the prior art are difficult to form, the present invention provides a high-strength and easy-to-form 5000 series aluminum alloy sheet and strip and a preparation method thereof. The obtained aluminum alloy has high tensile strength and yield strength, and can be formed at room temperature without surface cracks.

[0005] In order to achieve the above object, the specific scheme adopted by the present invention is: a method for preparing a high-strength and easy-to-form 5G50 aluminum alloy plate and strip for anodizing, comprising the following steps:

[0006] The alloy components are melted and cast to obtain an aluminum alloy ingot; the alloy components are as follows by mass percentage: Si is 0.01% to 0.08%; Fe is 0.04% to 0.12%; Mg is 3.0% to 4.6%; Cr is 0.1% to 0.4%; Cu is 0.03% to 0.05%, other impurity elements are ≤ 0.02%, and the balance is Al;

[0007] The aluminum alloy slab is homogenized, and the homogenized aluminum alloy slab is hot rolled for 15 to 25 times and cold rolled for 3 to 6 times to obtain a plate, the hot rolling rate of the last three hot rolling passes is not less than 40%, after cold rolling intermediate annealing, the secondary cold rolling rate is not less than 30%, the finished product annealing temperature is 140-180°C, and the aluminum alloy plate and strip are obtained.

[0008] As an optimized scheme for the preparation method of the above-mentioned high-strength and easy-to-form 5G50 aluminum alloy plate and strip for anodizing: the alloy components by mass percentage are: Si is 0.01%~0.08%; Fe is 0.04%~0.10%; Mg is 3.6%~4.6%; Cr is 0.36%~0.4%; Cu is 0.03%~0.05%, other impurity elements are ≤0.02%, and the balance is Al.

[0009] As another optimized scheme for the preparation method of the above-mentioned high-strength and easy-to-form 5G50 aluminum alloy plate and strip for anodizing: the alloy components by mass percentage are: Si is 0.04%; Fe is 0.03%; Mg is 3.6%; Cr is 0.36%; Cu is 0.04%, other impurity elements are ≤0.02%, and the balance is Al.

[0010] As another optimized solution for the above-mentioned method for preparing the high-strength and easy-to-form 5G50 aluminum alloy plate and strip for anodizing: the temperature for homogenizing the aluminum alloy slab is 460-520°C / 8h-16h.

[0011] As another optimized solution for the preparation method of the above-mentioned high-strength and easy-to-form 5G50 aluminum alloy plate and strip for anodizing: the starting temperature of the hot rolling is 420-480°C, and the finishing temperature is 280-320°C.

[0012] As another optimization scheme for the preparation method of the above-mentioned high-strength and easy-to-form 5G50 aluminum alloy plate and strip for anodizing: the initial thickness of cold rolling is 7 mm, the ending thickness is 0.7 mm, and the intermediate annealing plate thickness is 1.0 mm.

[0013] As another optimization scheme for the preparation method of the above-mentioned high-strength and easy-to-form 5G50 aluminum alloy plate and strip for anodizing: the annealing temperature is 140-160°C.

[0014] A high-strength and easy-to-form 5G50 aluminum alloy plate and strip for anodizing is prepared by the above-mentioned preparation method.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1. The present invention provides a method for preparing a high-strength and easy-to-form 5G50 aluminum alloy sheet and strip for anodizing. The annealing temperature is determined according to the total cold rolling rate of cold rolling, and the annealing temperature is 140-180°C, which plays a role in controlling the fineness and uniform distribution of the grain size, so that the obtained aluminum alloy sheet and strip can be stamped and formed at room temperature.

[0017] 2. In the alloy composition of the present invention, Mg is 3.0% to 4.6% and Cr is 0.1% to 0.4%, that is, the contents of Mg and Cr in the aluminum alloy sheet and strip are increased. When the Mg content exceeds 3.5%, when the aluminum alloy sheet and strip are prepared by the existing preparation method, Mg has a high surface segregation, and its surface Mg content is increased from 3-5% in the interior to more than 80%. The enrichment of the surface Mg element seriously affects its anodic oxidation corrosion uniformity, resulting in heterochromatic stripe defects; in the present application, the annealing temperature is determined by the total cold rolling rate of the secondary cold rolling, and the annealing temperature is relatively low (140-180°C), which reduces the segregation degree of the Mg element, improves the surface quality of the anodic oxidation, and reduces the heterochromatic stripe defects; at the same time, the Cr content is increased. Under the preparation method of the present invention, the Cr element combines with Fe and Si elements to form a large amount of AlFeCrSi phase, which reduces the precipitation of Mg2Si phase in the alloy, further ensures that the aluminum alloy sheet and strip can be formed at room temperature, and at the same time, improves the surface quality of the aluminum alloy sheet and strip. DETAILED DESCRIPTION

[0018] The technical solution of the present invention is further elaborated in detail below in conjunction with specific embodiments. The parts of the present invention that are not described and disclosed in detail in the following embodiments should be understood as the prior art known or should be known to those skilled in the art.

[0019] A method for preparing a high-strength and easy-to-form 5G50 aluminum alloy plate and strip for anodizing, comprising the following steps:

[0020] The alloy components are melted and cast to obtain an aluminum alloy ingot; the alloy components are as follows by mass percentage: Si is 0.01% to 0.08%; Fe is 0.04% to 0.12%; Mg is 3.0% to 4.6%; Cr is 0.1% to 0.4%; Cu is 0.03% to 0.05%, other impurity elements are ≤ 0.02%, and the balance is Al;

[0021] The aluminum alloy flat ingot is homogenized, and the aluminum alloy flat ingot after the homogenization treatment is hot rolled for 15 to 25 times and cold rolled for 3 to 6 times to obtain a plate. The single hot rolling rate of the last three hot rolling passes is not less than 40%. After the cold rolling intermediate annealing, the secondary cold rolling rate is not less than 30%. The finished product annealing temperature is 140-180°C to obtain an aluminum alloy plate and strip. The annealing temperature is 140-180°C, which plays a role in controlling the fineness and uniform distribution of grain size, so that the obtained aluminum alloy plate and strip can be stamped at room temperature.

[0022] The alloy composition includes Mg of 3.0% to 4.6% and Cr of 0.1% to 0.4%, that is, the content of Mg and Cr in the aluminum alloy sheet and strip is increased. When the Mg content exceeds 3.5%, when the aluminum alloy sheet and strip is prepared by the existing preparation method, Mg has a high surface segregation, and its surface Mg content is increased from 3-5% in the interior to more than 80%. The enrichment of the surface Mg element seriously affects its anodic oxidation corrosion uniformity, resulting in heterochromatic stripe defects; in the present application, the annealing temperature is determined by the total cold rolling rate of the secondary cold rolling, and the annealing temperature is relatively low (140-180°C), which reduces the segregation degree of the Mg element, improves the surface quality of the anodic oxidation, and reduces the heterochromatic stripe defects; at the same time, the Cr content is increased. Under the preparation method of the present invention, the Cr element combines with Fe and Si elements to form a large amount of AlFeCrSi phase, which reduces the precipitation of the Mg2Si phase in the alloy, further ensures that the aluminum alloy sheet and strip can be formed at room temperature, and at the same time, improves the surface quality of the aluminum alloy sheet and strip.

[0023] Example 1

[0024] A method for preparing a high-strength and easy-to-form 5G50 aluminum alloy plate and strip for anodizing, comprising the following steps:

[0025] The alloy components are melted and cast to obtain an aluminum alloy ingot; the alloy components are calculated by mass percentage as follows: Si is 0.01%; Fe is 0.08%; Mg is 3.6%; Cr is 0.1%; Cu is 0.03%, other impurity elements are ≤0.02%, and the balance is Al; melting and casting are existing technologies and will not be described in detail here.

[0026] The aluminum alloy slabs were kept at 500°C for 5 hours for homogenization treatment, and the homogenized aluminum alloy slabs were subjected to 21 hot rolling passes and 5 cold rolling passes to obtain plates. The hot rolling rates of the last three hot rolling passes were 40%, 45%, and 50%, respectively, and the total cold rolling rate of the secondary cold rolling was 30%.

[0027] The annealing temperature of the plate is determined based on the total cold rolling rate of the cold rolling, and the plate is annealed at 140°C for 2 hours to obtain an aluminum alloy plate. The aluminum alloy plate prepared by the method has a tensile strength of 305-310MPa, a yield strength of 239-240MPa, an elongation of 11.0-11.5%, and a hardness of 91.7HV. When bent 180° at room temperature, there is no crack on the surface.

[0028] Example 2

[0029] A method for preparing a high-strength and easy-to-form 5G50 aluminum alloy plate and strip for anodizing, comprising the following steps:

[0030] The alloy components are melted and cast to obtain an aluminum alloy ingot; the alloy components are calculated by mass percentage as follows: Si is 0.01%; Fe is 0.08%; Mg is 3.6%; Cr is 0.1%; Cu is 0.03%, other impurity elements are ≤0.02%, and the balance is Al; melting and casting are existing technologies and will not be described in detail here.

[0031] The aluminum alloy slabs were kept at 500°C for 5 hours for homogenization treatment, and the homogenized aluminum alloy slabs were subjected to 21 hot rolling passes and 5 cold rolling passes to obtain plates. The hot rolling rates of the last three hot rolling passes were 40%, 45%, and 50%, respectively, and the total cold rolling rate of the secondary cold rolling was 40%.

[0032] The annealing temperature of the plate is determined based on the total cold rolling rate of the cold rolling, and the plate is annealed at 150°C for 2 hours to obtain an aluminum alloy plate. The aluminum alloy plate prepared by the method has a tensile strength of 315-320MPa, a yield strength of 249-250MPa, an elongation of 10.0-10.5%, and a hardness of 93.8HV. When bent 180° at room temperature, there is no crack on the surface.

[0033] Example 3

[0034] A method for preparing a high-strength and easy-to-form 5G50 aluminum alloy plate and strip for anodizing, comprising the following steps:

[0035] The alloy components are melted and cast to obtain an aluminum alloy ingot; the alloy components are calculated by mass percentage as follows: Si is 0.01%; Fe is 0.08%; Mg is 3.6%; Cr is 0.1%; Cu is 0.03%, other impurity elements are ≤0.02%, and the balance is Al; melting and casting are existing technologies and will not be described in detail here.

[0036] The aluminum alloy slabs were kept at 500°C for 5 hours for homogenization treatment, and the homogenized aluminum alloy slabs were subjected to 21 hot rolling passes and 5 cold rolling passes to obtain plates. The hot rolling rates of the last three hot rolling passes were 40%, 45%, and 50%, respectively, and the total cold rolling rate of the secondary cold rolling was 50%.

[0037] The annealing temperature of the plate is determined based on the total cold rolling rate of the cold rolling, and the plate is annealed at 180°C for 2 hours to obtain an aluminum alloy plate. The aluminum alloy plate prepared by the method has a tensile strength of 330-335MPa, a yield strength of 255-260MPa, an elongation of 9.0-10.0%, and a hardness of 96.2HV. When bent 180° at room temperature, there is no crack on the surface.

[0038] Example 4

[0039] A method for preparing a high-strength and easy-to-form 5G50 aluminum alloy plate and strip for anodizing, comprising the following steps:

[0040] The alloy components are melted and cast to obtain an aluminum alloy ingot; the alloy components are calculated by mass percentage as follows: Si is 0.08%; Fe is 0.10%; Mg is 4.6%; Cr is 0.4%; Cu is 0.05%, other impurity elements are ≤0.02%, and the balance is Al; melting and casting are existing technologies and will not be described in detail here.

[0041] The aluminum alloy slabs were kept at 500°C for 5 hours for homogenization treatment, and the homogenized aluminum alloy slabs were subjected to 25 hot rolling passes and 4 cold rolling passes to obtain plates. The single hot rolling rates of the last three passes of each hot rolling were 40%, 42%, and 44%, respectively, and the total cold rolling rate of the secondary cold rolling was 40%.

[0042] The annealing temperature of the plate is determined based on the total cold rolling rate of the cold rolling, and the plate is annealed at 140°C for 2 hours to obtain an aluminum alloy plate. The aluminum alloy plate prepared by the method has a tensile strength of 350-370 MPa, a yield strength of 280-290 MPa, an elongation of 11.0-11.5%, and a hardness of 107.7 HV. When bent 180° at room temperature, there is no crack on the surface.

[0043] Comparative Example 1

[0044] A method for preparing a high-strength and easy-to-form 5G50 aluminum alloy plate and strip for anodizing, comprising the following steps:

[0045] The alloy components are melted and cast to obtain an aluminum alloy ingot; the alloy components are calculated by mass percentage as follows: Si is 0.05%; Fe is 0.10%; Mg is 3.6%; Cr is 0.36%; Cu is 0.03%, other impurity elements are ≤0.02%, and the balance is Al; melting and casting are existing technologies and will not be described in detail here.

[0046] The aluminum alloy slabs were kept at 500°C for 5 hours for homogenization treatment, and the homogenized aluminum alloy slabs were subjected to 21 hot rolling passes and 5 cold rolling passes to obtain plates. The hot rolling rates of the last three hot rolling passes were 40%, 45%, and 50%, respectively, and the total cold rolling rate of the secondary cold rolling was 30%.

[0047] The annealing temperature of the plate is determined based on the total cold rolling rate of the cold rolling, and the plate is annealed at 100°C for 3 hours to obtain an aluminum alloy plate. The aluminum alloy plate prepared by the method has a tensile strength of 313-314MPa, a yield strength of 261-263MPa, an elongation of 8.0%, and a hardness of 94.8HV. The surface cracks when bent 180° at room temperature.

[0048] Comparative Example 2

[0049] A method for preparing a high-strength and easy-to-form 5G50 aluminum alloy plate and strip for anodizing, comprising the following steps:

[0050] The alloy components are melted and cast to obtain an aluminum alloy ingot; the alloy components are calculated by mass percentage as follows: Si is 0.05%; Fe is 0.10%; Mg is 3.6%; Cr is 0.36%; Cu is 0.03%, other impurity elements are ≤0.02%, and the balance is Al; melting and casting are existing technologies and will not be described in detail here.

[0051] The aluminum alloy slabs were kept at 500°C for 5 hours for homogenization treatment, and the homogenized aluminum alloy slabs were subjected to 21 hot rolling passes and 5 cold rolling passes to obtain plates. The hot rolling rates of the last three hot rolling passes were 40%, 45%, and 50%, respectively, and the total cold rolling rate of the secondary cold rolling was 30%.

[0052] The annealing temperature of the plate is determined based on the total cold rolling rate of the cold rolling, and the plate is annealed at 120°C for 3 hours to obtain an aluminum alloy plate. The aluminum alloy plate prepared by the method has a tensile strength of 313-314MPa, a yield strength of 261-263MPa, an elongation of 8.0%, and a hardness of 94.8HV. The surface cracks when bent 180° at room temperature.

[0053] Comparative Example 3

[0054] A method for preparing a high-strength and easy-to-form 5G50 aluminum alloy plate and strip for anodizing, comprising the following steps:

[0055] The alloy components are melted and cast to obtain an aluminum alloy ingot; the alloy components are calculated by mass percentage as follows: Si is 0.05%; Fe is 0.10%; Mg is 3.6%; Cr is 0.36%; Cu is 0.03%, other impurity elements are ≤0.02%, and the balance is Al; melting and casting are existing technologies and will not be described in detail here.

[0056] The aluminum alloy slabs were kept at 500°C for 5 hours for homogenization treatment, and the homogenized aluminum alloy slabs were subjected to 21 hot rolling passes and 5 cold rolling passes to obtain plates. The hot rolling rates of the last three hot rolling passes were 30%, 35%, and 40%, respectively, and the total cold rolling rate of the secondary cold rolling was 30%.

[0057] The annealing temperature of the sheet is determined based on the total cold rolling rate of the cold rolling, and the sheet is annealed at 190°C for 3 hours to obtain an aluminum alloy sheet. The aluminum alloy sheet prepared by the method has a tensile strength of 290-294MPa, a yield strength of 222-225MPa, an elongation of 12.5%, and a hardness of 88.3HV. There is no crack on the surface when bent 180° at room temperature, but the tensile strength is low and does not meet the standard.

[0058] The performance parameters of the aluminum alloy sheets and strips obtained in Examples 1-4 and Comparative Examples 1-3 are shown in Table 1.

[0059] Table 1 Annealing process tensile strength Yield Strength Elongation Bending surface Microhardness Remark Example 1 140℃ / 2h 305-310 239-240 11.0-11.5 No cracks 91.7 qualified Example 2 150℃ / 2h 315-320 249-250 10.0-10.5 No cracks 93.8 qualified Example 3 180℃ / 2h 330-335 255-260 9.0-10.0 No cracks 96.2 qualified Example 4 180℃ / 3h 350-370 280-290 11.0-11.5 No cracks 107.7 qualified Comparative Example 1 100℃ / 3h 313-314 261-263 8.0 Fine crack 94.8 Cracking Comparative Example 2 120℃ / 3h 309-311 250-251 8.0 Fine crack 92.3 Cracking Comparative Example 3 190℃ / 3h 290-294 222-225 12.5 No cracks 88.3 Low strength

[0060] Example 5

[0061] A high-strength and easy-to-form 5000 series aluminum alloy plate and strip for anodizing is prepared by the preparation method described in any one of Examples 1-4.

[0062] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing high-strength and easy-to-form 5G50 aluminum alloy sheet and strip for anodizing, characterized in that: The following steps are involved: The alloy components are melted and cast to obtain an aluminum alloy ingot; the alloy components are as follows by mass percentage: Si is 0.01% to 0.08%; Fe is 0.04% to 0.12%; Mg is 3.0% to 4.6%; Cr is 0.1% to 0.4%; Cu is 0.03% to 0.05%, other impurity elements are ≤ 0.02%, and the balance is Al; The aluminum alloy slab is homogenized, and the homogenized aluminum alloy slab is hot rolled for 15 to 25 times and cold rolled for 3 to 6 times to obtain a plate, the hot rolling rate of the last three hot rolling passes is not less than 40%, after cold rolling intermediate annealing, the secondary cold rolling rate is not less than 30%, the finished product annealing temperature is 140-180°C, and the aluminum alloy plate and strip are obtained.

2. The method for preparing a high-strength and easy-to-form 5G50 aluminum alloy sheet and strip for anodizing according to claim 1, characterized in that: The alloy components are calculated by mass percentage as follows: Si is 0.01% to 0.08%; Fe is 0.04% to 0.10%; Mg is 3.6% to 4.6%; Cr is 0.36% to 0.4%; Cu is 0.03% to 0.05%, other impurity elements are ≤0.02%, and the balance is Al.

3. The method for preparing a high-strength and easy-to-form 5G50 aluminum alloy sheet and strip for anodizing according to claim 1, characterized in that: The alloy components are calculated by mass percentage as follows: Si is 0.04%, Fe is 0.03%, Mg is 3.6%, Cr is 0.36%, Cu is 0.04%, other impurity elements are ≤0.02%, and the balance is Al.

4. The method for preparing a high-strength and easy-to-form 5G50 aluminum alloy sheet and strip for anodizing according to claim 1, characterized in that: The homogenization process of aluminum alloy slabs is 460℃~520℃ / 8h~16h.

5. The method for preparing a high-strength and easy-to-form 5G50 aluminum alloy sheet and strip for anodizing according to claim 1, characterized in that: The hot rolling starting temperature is 420-480°C, and the final rolling temperature is 280-320°C.

6. The method for preparing a high-strength and easy-to-form 5G50 aluminum alloy sheet and strip for anodizing according to claim 1, characterized in that: The initial thickness of the cold rolling is 7 mm, the final thickness is 0.7 mm, and the intermediate annealing thickness is 1.0 mm.

7. The method for preparing a high-strength and easy-to-form 5G50 aluminum alloy sheet and strip for anodizing according to claim 1, characterized in that: The annealing temperature is 140-180°C.

8. A high-strength and easy-to-form 5G50 aluminum alloy sheet and strip for anodizing, characterized in that: The preparation is carried out by the preparation method according to any one of claims 1 to 7.