6000 series aluminum alloy sheet material manufacturing method and aluminum alloy sheet material

Abstract

The present invention discloses a 6000 series aluminum alloy sheet having high formability, high flanging performance, and low roping mark defects, the sheet having an average grain size of 20 to 32 μm, a recrystallization texture density of 6.5 to 10.0, a cube texture component content of ≦8%, and a Goss texture component content of ≦7%, and a method for producing the same, the method comprising the following steps: (1) homogenizing the ingot, and the homogenizing temperature is 530-580°C; (2) The homogenized ingot is directly subjected to rough hot rolling, finish hot rolling, and coiling at the end of hot rolling, with the start temperature of finish hot rolling controlled at 400-480°C and the coiling temperature at the end of hot rolling controlled at 250°C or above; (3) Cold rolling: The total deformation amount of cold rolling is controlled to 50-85%; (4) Solution treatment; (5) Pre-aging is performed, followed by air cooling to obtain a 6000 series aluminum alloy sheet material.

Description

[Technical Field]

[0001] The present invention relates to an aluminum alloy sheet material and a manufacturing method thereof, and more particularly to a 6000 series aluminum alloy sheet material and a manufacturing method thereof. [Background technology]

[0002] 6000 series aluminum alloys have advantages such as high strength, good corrosion resistance, good surface quality after firing, and improved strength after firing, so alloys of this series are increasingly used in the production of automobile body exterior cover panels.

[0003] As an automobile body covering panel, the surface quality of 6000 series aluminum alloy automotive plates is as important as its mechanical performance, and it affects whether the appearance of the automobile after painting is ideal. Roping marks are one of the factors that affect the surface quality of aluminum alloy automotive plates.

[0004] Furthermore, during the flanging process of aluminum alloy sheets, serious stress concentration is often caused at the interface between the coarse intermetallic compounds and the aluminum sheet matrix, which induces the generation of microcracks and reduces the flanging performance of the alloy sheet. Therefore, it is also important to improve the flanging performance of aluminum alloy sheets.

[0005] A Chinese patent document with publication number CN101935785B and title "Highly Formable Aluminum Alloy for Automotive Body Sheets" discloses a 6000 series aluminum alloy for automotive body sheets with excellent formability, which is obtained by adjusting the contents and proportions of the main elements Si, Mg, and Cu. The excellent formability described in this patent focuses only on yield strength, plasticity, and work hardening rate, and does not address the r-value, flanging performance, and roping mark performance, which are closely related to the forming of automotive body cover panels.

[0006] A Chinese patent document with publication number CN105074028B, published on June 6, 2017, and titled "Aluminum alloy sheet with excellent properties after room temperature aging" discloses an aluminum alloy and a method for manufacturing the sheet, which, by adding an appropriate amount of Sn element to the chemical composition, provides excellent performance even after room temperature aging of the sheet, and the material manufactured thereby has excellent forming performance. Although the patent achieves a good technical effect by adding the alloy element Sn, it does not focus on how to improve the flanging performance of the sheet.

[0007] Therefore, in the prior art, all 6000 series aluminum alloy sheets have problems such as poor flanging performance and obvious roping mark defects on the surface after pressing, which affect the large-scale generalization and practical application of 6000 series automotive sheets.

[0008] Based on these facts, a manufacturing method is desired that can provide 6000 series aluminum alloy sheet with high formability, high flanging performance, and low roping mark defects. Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to provide a method for producing a 6000 series aluminum alloy sheet having high formability, high flanging performance, and low roping mark defects. The method for producing a 6000 series aluminum alloy sheet employs a rational process design, and through soaking, hot rolling, coiling, optional intermediate annealing, and cold rolling processes, can obtain an alloy sheet having a predetermined number and ratio of second phases and grain size. This stimulates the recrystallization nucleation (PSN) effect during the subsequent solution pre-aging treatment, and weakens the content of recrystallization texture, especially the content of cube texture and Goss texture components, thereby significantly improving the formability and flanging performance of the final aluminum alloy sheet and reducing the roping mark defects of the aluminum alloy sheet. [Means for solving the problem]

[0010] In order to achieve the above object, the present invention provides a method for producing a 6000 series aluminum alloy sheet material having high forming performance, high flanging performance, and low roping mark defects, which includes the following steps: (1) homogenizing the ingot, and the homogenizing temperature is 530-580°C; (2) The homogenized ingot is directly subjected to rough hot rolling, finish hot rolling, and coiling at the end of hot rolling, with the start temperature of finish hot rolling controlled at 400-480°C and the coiling temperature at the end of hot rolling controlled at 250°C or above; (3) Cold rolling: The total deformation amount of cold rolling is controlled to 50-85%, and the average size of the Mg2Si precipitates in the obtained cold-rolled sheet is 1.3-1.7 μm, and the areal density of the Mg2Si precipitates is ≧55,000 pieces / mm 2 is; (4) Solution treatment; (5) Pre-aging is performed, followed by air cooling to obtain a 6000 series aluminum alloy sheet material.

[0011] Extensive research by the present inventors has shown that second-phase particles have a significant effect on the recrystallization texture of 6000 series aluminum alloys. When coarse second-phase particles precipitate in the alloy, they stimulate particle-stimulated nucleation (PSN), thereby promoting recrystallization. This promotes random texture dominating the recrystallized texture, reducing the texture intensity. Furthermore, by reducing the contents of the cube and Goss texture components in the typical recrystallization texture, the degree of aggregation of these two components is reduced, resulting in a reduction in the occurrence of roping marks. Furthermore, research by the present inventors has shown that grain size decreases as the cold rolling reduction increases.

[0012] Based on these findings, in order to overcome the technical problems of conventional 6000 series aluminum alloy sheets, such as insufficient formability, poor flanging performance, and susceptibility to roping mark defects, the manufacturing method of the present invention, on the premise of ensuring process rationality, adjusts the process parameters of soaking, hot rolling, coiling, and optional intermediate annealing in the processing steps to adjust the size and number of coarse Mg2Si phases in the 6000 series aluminum alloy sheet, and fully utilizes the particle-stimulated nucleation (PSN) effect of the coarse Mg2Si phases in the subsequent solution treatment step to adjust the texture; and further adjusts the texture and grain size by adjusting the cold rolling reduction in the subsequent cold rolling step to weaken and adjust the type, proportion, and spatial distribution of the recrystallization texture, thereby obtaining a 6000 series aluminum alloy sheet for automobile bodies with high formability, high flanging performance, and low roping mark defects.

[0013] Specifically, the non-equilibrium eutectic phase in the cast 6000 series aluminum alloy is likely to lead to non-uniform composition or structure, causing problems such as poor plasticity in subsequent hot deformation, and to some extent limiting the forming processability of the 6000 series aluminum alloy. Therefore, this technical solution controls the soaking temperature in the homogenization process to above 530°C, thereby ensuring that most of the excessively coarse Mg2Si is dissolved, improving the hot processing of the 6000 series aluminum alloy and eliminating the effects of the non-equilibrium eutectic phase in the alloy.

[0014] Furthermore, according to the research of the present inventors, in this technical solution, when the hot finish rolling start temperature is controlled to 400-480°C, the size of the second phase (i.e., Mg2Si precipitate phase) in the cold rolled sheet material can be controlled to 1.3-1.7 μm, and the areal density of the second phase can be controlled to 55,000 pieces / mm 2 If the starting temperature of hot finish rolling is too high, the size of the precipitated second phases will be too large and the number will be too small, but if the starting temperature of hot finish rolling is too low, the size of the precipitated second phases will be too small.

[0015] Furthermore, according to the inventors' research, in this technical solution, if the cold rolling reduction is less than 50%, it will lead to coarsening of the crystal grains in the finished sheet material, which on the one hand will cause defects such as microcracks and continuous necking on the outer surface of the alloy sheet after flanging, thereby reducing flanging performance, and on the other hand will cause orange peel-like roughness on the sheet material after punching, reducing surface quality; if the cold rolling reduction is more than 85%, the local deformation area around the coarse second phase particles will become too large, which will become the initiation area for microcracks during forming, thereby deteriorating forming performance. Therefore, in the present invention, the cold rolling reduction is controlled to 50% to 85%.

[0016] Therefore, in the above technical solution of the present invention, the ingot is soaked at a reasonable temperature and time to dissolve the non-equilibrium eutectic phase in the ingot, and the homogenized ingot is then directly hot-rough rolled to eliminate or reduce casting defects and process into an intermediate billet that meets the conditions for hot-finish rolling. Subsequently, the hot-finish rolling, intermediate annealing and cold-rolling processes are controlled to obtain a cold-rolled plate having a large amount of coarse second phase and fine grains. In the subsequent solution pre-aging process before delivery, on the one hand, the PSN mechanism excited by the coarse second phase is utilized to weaken the content of recrystallization texture, and on the other hand, the cold-rolling reduction is adjusted to obtain a finished plate having fine grains, thereby providing a 6000 series aluminum alloy plate with high formability, high flanging performance and low roping mark defects.

[0017] In other words, the production method according to the present invention can effectively adjust the number and distribution of coarse second phases and the crystal grain size inside the aluminum alloy by combining specific processes, and as a result, can adjust the texture and structure of the 6000 series aluminum alloy sheet material in a T4P state, which is the final finished product, and can significantly improve the formability, flanging performance and roping mark defects of the 6000 series aluminum alloy sheet material.

[0018] Furthermore, in step (2) of the method for producing a 6000 series aluminum alloy sheet material according to the present invention, the coiling temperature at the end of hot rolling is controlled to 250 to 350° C. Furthermore, when the coiling temperature at the end of hot rolling is 250 to 340° C., intermediate annealing is performed before cold rolling in step (3), the intermediate annealing temperature is controlled to 350 to 430° C., the temperature retention time is controlled to 1 to 4 hours, and then cooling is performed together with the furnace to room temperature; when the coiling temperature at the end of hot rolling exceeds 340° C., step (3) is performed without intermediate annealing.

[0019] To facilitate subsequent cold working, intermediate annealing may be added between hot rolling and cold rolling. In this technical solution, intermediate annealing reduces deformation resistance and facilitates deformation. Research by the inventors has shown that when the coiling temperature at the end of hot rolling is 250-340°C, the average size of the Mg2Si precipitates is 1.3-1.7 μm, and their areal density is ≧55,000 / mm 2 Intermediate annealing is required to control the second phase so that it becomes larger. However, if the intermediate annealing temperature is above 350°C, the precipitation rate of the second phase becomes faster and the size of the second phase becomes larger. However, if the intermediate annealing temperature is below 350°C, the precipitation rate of the second phase becomes slower and the size of the second phase particles becomes smaller, which is unfavorable for the formation of the PSN mechanism. However, if the intermediate annealing temperature is above 430°C, the size of the precipitated second phase particles becomes too large, which can become the initiation point for microcracks during processing, which is unfavorable for the subsequent sheet forming. At high temperatures, the number of second phase particles often decreases, which is unfavorable for the subsequent formation of the PSN texture.

[0020] Furthermore, in another embodiment, when the coiling temperature at the end of hot rolling exceeds 340°C, the areal density of MgSi precipitate phases having an average size of 1.3 to 1.7 μm is ≧55000 pieces / mm 2 A second phase of

[0021] Furthermore, in step (2), the steel sheet is subjected to rough hot rolling at a temperature of 530 to 570°C, preferably at a temperature of 540 to 560°C.

[0022] Furthermore, in the step (2), when intermediate annealing is performed, the temperature increase rate in the intermediate annealing is 13 to 17°C / h, and the temperature decrease rate in the intermediate annealing is 12 to 15°C / h.

[0023] Furthermore, in step (1) of the method for producing a 6000 series aluminum alloy sheet material according to the present invention, the temperature retention time for the homogenization treatment is 6 to 16 hours, and preferably 8 to 12 hours.

[0024] Furthermore, in step (1) of the method for producing a 6000 series aluminum alloy sheet material according to the present invention, the temperature increase rate in the homogenization treatment is 20 to 50°C / h.

[0025] Furthermore, in the step (1) of the method for producing a 6000 series aluminum alloy sheet material according to the present invention, the temperature of the homogenization treatment is 550 to 570°C.

[0026] Furthermore, in step (2) of the method for producing a 6000 series aluminum alloy sheet material according to the present invention, the total deformation amount in rough hot rolling is controlled to more than 70%, for example, 70 to 95%; and / or the total deformation amount in finish hot rolling is controlled to more than 80%, for example, 85 to 90%.

[0027] Furthermore, in the step (2) of the method for producing a 6000 series aluminum alloy sheet material according to the present invention, the rolling start temperature of the hot finish rolling is 440 to 480°C.

[0028] Furthermore, in the step (3) of the method for producing a 6000 series aluminum alloy sheet material according to the present invention, the total deformation amount in cold rolling is controlled to 60 to 85%.

[0029] Furthermore, in step (4) of the method for producing a 6000 series aluminum alloy sheet material according to the present invention, the solution treatment temperature is 550 to 570°C, the solution treatment temperature rise rate is 15 to 30°C / s, the solution treatment temperature retention time is 1 to 5 minutes, and the quenching method is water cooling.

[0030] Furthermore, in step (5) of the method for producing a 6000 series aluminum alloy sheet material according to the present invention, a preliminary aging treatment is carried out within 3 minutes after the end of step (4).

[0031] Furthermore, in step (5) of the method for producing a 6000 series aluminum alloy sheet material according to the present invention, the pre-aging treatment is performed by raising the temperature to 80 to 100°C and then slowly lowering the temperature from 80 to 100°C to room temperature at a temperature lowering rate of 1 to 4°C / h.

[0032] Accordingly, another object of the present invention is to provide a 6000 series aluminum alloy sheet having high formability, high flanging performance and low roping mark defects, which is easy to produce, has low production costs, and has fairly high formability, high flanging performance and low roping mark defects, so that it can be effectively used in the automobile manufacturing industry to meet the requirements of vehicle weight reduction.

[0033] In order to achieve the above object, the present invention provides a 6000 series aluminum alloy sheet material having high formability, high flanging performance, and low roping mark defects, which is produced by using the method for producing a 6000 series aluminum alloy sheet material according to the present invention.

[0034] Furthermore, the 6000 series aluminum alloy sheet according to the present invention has an average grain size of 20 to 32 μm, a recrystallization texture density of 6.5 to 10.0, a cube texture component content of ≦8%, and a Goss texture component content of ≦7%.

[0035] Furthermore, the 6000 series aluminum alloy sheet material according to the present invention satisfies the following performance requirements: tensile strength is ≧210 MPa, preferably ≧215 MPa; yield strength is ≧104 MPa, preferably ≧110 MPa; and elongation is ≧24%, preferably ≧24.5%.

[0036] Furthermore, the 6000 series aluminum alloy sheet material according to the present invention further satisfies the following performances: a plastic strain ratio r of ≧0.68, preferably r≧0.70, more preferably r≧0.72, and even more preferably ≧0.74; a planar anisotropy index Δr of ≦0.10, preferably ≦0.08, more preferably ≦0.06, and even more preferably ≦0.04; a flanging level (flanging factor of 0.6) evaluated as 1; and a roping mark level evaluated as 1.

[0037] In this specification, the 6000 series aluminum alloy refers to a series of aluminum alloys containing elements such as silicon and magnesium, and their compositions comply with the GB / T 33227-2016 standard. Common 6000 series aluminum alloy designations include 6A16, 6111, 6013, 6014, 6016, 6022, 6061, 6063, 6181, and 6082. In this specification, the 6000 series aluminum alloy may contain, by mass percentage, 0.3-1.5% Si, 0.05-0.5% Fe, 0.02-1.1% Cu, 0.35-1.2% Mg, ≦0.8% Zn, ≦0.8% Mn, ≦0.35% Cr, ≦0.15% Ti, and ≦0.20% V, with the balance being Al and unavoidable impurities such as P, S, and O.

[0038] In some embodiments, the aluminum alloy plate according to the present invention has an elemental composition of Mg: 0.4-0.7%, Si: 0.5-0.8%, Fe: 0.1-0.3%, Mn: 0.05-0.15%, Cu: 0.05-0.3%, Zn: ≦0.05%, V: ≦0.05%, Cr: ≦0.05%, and the balance being Al and unavoidable impurities.

[0039] In some embodiments, the present invention provides a 6000 series aluminum alloy sheet, wherein the 6000 series aluminum alloy sheet has an average grain size of 20 to 32 μm, a recrystallization texture density of 6.5 to 10.0, a cube texture component content of ≦8%, and a Goss texture component content of ≦7%. Preferably, the 6000 series aluminum alloy sheet has a tensile strength of ≧210 MPa, a yield strength of ≧104 MPa, and an elongation of ≧24%. More preferably, the 6000 series aluminum alloy sheet has a plastic strain ratio r of ≧0.68, preferably r≧0.70, more preferably r≧0.72, and even more preferably ≧0.74. More preferably, the 6000 series aluminum alloy sheet has a planar anisotropy index Δr of ≦0.10, preferably Δr≦0.08, more preferably ≦0.06, and even more preferably ≦0.04. More preferably, the 6000 series aluminum alloy sheet material is evaluated as having a flanging level of 1 and a roping mark level of 1. Preferably, the 6000 series aluminum alloy may contain, in mass percentage, Si: 0.3 to 1.5%, Fe: 0.05 to 0.5%, Cu: 0.02 to 1.1%, Mg: 0.35 to 1.2%, Zn: ≦0.8%, Mn: ≦0.8%, Cr: ≦0.35%, Ti: ≦0.15%, V: ≦0.20%, with the balance being Al and unavoidable impurities; more preferably, the elemental composition of the aluminum alloy plate is Mg: 0.4 to 0.7%, Si: 0.5 to 0.8%, Fe: 0.1 to 0.3%, Mn: 0.05 to 0.15%, Cu: 0.05 to 0.3%, Zn: ≦0.05%, V: ≦0.05%, Cr: ≦0.05%, with the balance being Al and unavoidable impurities. [Effects of the Invention]

[0040] The method for producing a 6000 series aluminum alloy sheet material according to the present invention has the following advantages and beneficial effects compared to the prior art: (1) The method for producing 6000 series aluminum alloy sheet according to the present invention can produce a large amount of large second phases through homogenization, hot rolling, coiling, optional intermediate annealing, and cold rolling processes. This induces recrystallization nucleation via the PSN mechanism during the subsequent solution treatment and pre-aging processes, thereby reducing the density of recrystallization texture, especially the content of the soft cube texture and the hard Goss texture, thereby improving the formability of the sheet (provided that the plastic strain ratio r is ≥ 0.68 and the planar anisotropy index Δr is ≤ 0.10) and reducing roping mark defects in the sheet.

[0041] (2) In the method for producing a 6000 series aluminum alloy sheet according to the present invention, the crystal grains of the aluminum sheet are refined by adjusting the cold rolling process in the working process, thereby improving the flanging performance of the aluminum alloy sheet.

[0042] (3) The method for producing 6000 series aluminum alloy sheet material according to the present invention has a simple process. By simply adjusting the parameters based on the conventional aluminum alloy heat treatment production line, the process can be optimized. The method has a wide applicability and can meet the demands of industrialized production.

[0043] (4) By adopting the manufacturing method of the present invention, the structure and texture of 6000 series aluminum alloy sheet can be quantified, and the manufactured 6000 series aluminum alloy sheet has high forming performance, high flanging performance and low roping mark defects, and can be effectively used in the automobile manufacturing industry to meet the requirements of vehicle weight reduction, with good application prospects. [Brief explanation of the drawings]

[0044] [Figure 1] FIG. 1 conceptually shows a process flow chart of the method for producing a 6000 series aluminum alloy sheet material according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0045] Specific Embodiments Hereinafter, the 6000 series aluminum alloy sheet material and the manufacturing method thereof according to the present invention will be further explained with reference to specific examples and drawings, but the explanations and interpretations are not intended to unduly limit the technical solutions of the present invention.

[0046] Examples 1 to 8 and Comparative Examples 1 to 4 The chemical compositions of the 6000 series aluminum alloy sheets according to Examples 1 to 8 and the aluminum alloy sheets according to Comparative Examples 1 to 4 are shown in Table 1.

[0047] [Table 1]

[0048] It is necessary to explain that the composition of the aluminum alloy sheet material is not limited in the present invention, and therefore the functions of Table 1 above are only for the purpose of fully disclosing the manufacturing method according to the present invention, and are not intended to limit the manufacturing method and aluminum alloy sheet material according to the present invention.

[0049] FIG. 1 conceptually shows a process flow chart of the method for producing a 6000 series aluminum alloy sheet material according to the present invention.

[0050] As shown in FIG. 1, the 6000 series aluminum alloy sheets according to Examples 1 to 8 of the present invention were produced by the following steps: (1) Melting and casting: The aluminum alloys were mixed according to the chemical compositions shown in Table 1, melted in a melting furnace, and then cast into aluminum alloy ingots; (2) Homogenization treatment: The aluminum alloy ingot was heated together with the furnace in the homogenization heat treatment furnace, and the temperature was increased to 530-580°C at a temperature increase rate of 20-50°C / h; preferably, the temperature retention time of the homogenization treatment was controlled to 6-16 hours; (3) Hot rough rolling: The ingot was hot rough rolled at 530-570°C, and the total deformation amount of the hot rough rolling was controlled to more than 70%; (4) Hot finish rolling: The plate material in the hot rough rolling state was hot finish rolled, and the hot finish rolling start temperature was controlled to 400-480°C; the hot rolling end coiling temperature was controlled to 250°C or more, and the hot finish rolling total deformation amount was controlled to more than 80%; (5) Intermediate annealing: When the coiling temperature at the end of hot rolling was 250 to 340°C, intermediate annealing was performed. The temperature during intermediate annealing was controlled to 350 to 430°C, the temperature retention time was controlled to 1 to 4 hours, the temperature increase rate during intermediate annealing was controlled to 13 to 17°C / h, and the temperature decrease rate during intermediate annealing was controlled to 12 to 15°C / h; when the coiling temperature at the end of hot rolling was higher than 340°C, cold rolling was performed without intermediate annealing; (6) Cold rolling: The total deformation amount of cold rolling was controlled to 50-85%; (7) Solution treatment: The solution treatment temperature was controlled to 550-570°C, the solution treatment temperature increase rate was controlled to 15-30°C / s, and the solution treatment time was controlled to 1-5 min, followed by water cooling.

[0051] (8) Pre-aging treatment: After the completion of step (7), a pre-aging treatment was immediately carried out within 3 minutes, which consisted of heating to 80-100°C and then slowly cooling from 80-100°C to room temperature at a rate of 1-4°C / h, thereby obtaining an aluminum alloy sheet in a T4P state.

[0052] It should be mentioned that although the manufacturing process flows of Comparative Examples 1 to 4 were similar to those of the Examples of the present application, their process parameters did not meet the ranges designed by the present invention.

[0053] Specific process parameters in the above-mentioned process steps for the 6000 series aluminum alloy sheet materials according to Examples 1 to 8 and the aluminum alloy sheet materials according to Comparative Examples 1 to 4 are shown in Tables 2-1 and 2-2.

[0054] [Table 2-1]

[0055] [Table 2-2]

[0056] It should be noted that in the present invention, the observation of the size and distribution of the second phase (MgSi precipitate phase) in the longitudinal cross section of the aluminum alloy sheet according to each Example and Comparative Example was performed on samples sampled from the cold-rolled sheet, not on samples sampled from the final finished sheet. This is because the recrystallization process occurs during the solution treatment of the cold-rolled sheet, and therefore it is necessary to observe the second phase in the cold-rolled sheet in order to observe the recrystallization process and the effect of the second phase on the texture of the structure.

[0057] In the present invention, square pieces of 12 mm (rolling direction) × 10 mm (transverse direction) were cut out from the corresponding cold-rolled plate samples of each Example and Comparative Example, and the longitudinal cross sections of the plates were polished, followed by rough polishing using 320 mesh, 800 mesh, and 1500 mesh water-polished sandpapers in sequence, and then finish polishing using 800 mesh metallographic sandpaper. Finally, the longitudinal cross sections of the plates were hub-polished with a hub-polished polishing cloth, and then the size and distribution of the second phase (i.e., MgSi precipitate phase) in the longitudinal cross sections of the aluminum alloy plates were observed and analyzed using a Sirion 200 field emission scanning electron microscope, and the relevant observation and analysis results are shown in Table 3 below.

[0058] Table 3 shows the average size and areal density of the Mg2Si precipitate phase in the cold-rolled sheet materials according to Examples 1 to 8 and Comparative Examples 1 to 4.

[0059] [Table 3]

[0060] Furthermore, the present invention measured the grain size of the finished aluminum alloy sheet material in the T4P state according to each example and comparative example. The specific method was as follows.

[0061] A 15 mm (rolling direction) x 10 mm (transverse direction) square sample was cut from the corresponding finished T4P aluminum alloy sheet for each example and comparative example, and the longitudinal section was used as the statistical surface. The sample was polished once using a water polishing machine with 320, 800, 1000, and 1500 grit water-polished sandpaper and 800 and 1000 grit metallographic sandpaper, and then mechanically hub-polished using a woolen cloth coated with 0.5 μm grit diamond abrasive paste. An anodic coating was then applied to the hub-polished sample using a DC power source. Metallographic photographs were then taken using a metallographic microscope at 100x magnification, and the grain size of the aluminum alloy sheet was measured using the intercept method with ImageJ software. The measurement results are shown in Table 4.

[0062] Furthermore, in order to explain the relationship between the structure and texture and the performance, the present invention further measured the macroscopic texture by sampling from the finished 6000 series aluminum alloy sheets according to Examples 1 to 8 and the aluminum alloy sheets according to Comparative Examples 1 to 4. The preparation of the samples for XRD macroscopic texture measurement and the measurement procedures were as follows.

[0063] A 15 mm (rolling direction) x 10 mm (transverse direction) square was cut from a 1 mm-thick, finished T4P aluminum alloy sheet sample corresponding to each of Examples 1-8 and Comparative Examples 1-4, and the sheet plane was used as the measurement surface. The sample was polished with water-polished sandpaper and metallographic sandpaper, and the measurement surface was polished to near the center of the sheet thickness. It was then immersed in a 30% NaOH aqueous solution for 8-15 minutes, removed, and immersed in a 10% HNO3 aqueous solution for 5 seconds. The sample was then removed, washed with water, and spray-dried. Macroscopic texture measurements were performed using a Bruker D8 Discover X-ray diffractometer under the following measurement conditions: tube voltage 40 kV, tube current 40 mA, CuKα radiation, and Ni filter. Using the Schulz reflection method, the three incomplete pole figures (α = 0° to 75°; β = 0° to 360°) of {111}, {200}, and {220} for the pure aluminum powder and each sample were measured, along with the corresponding background at Δθ = ±1.4° from the peak center. The orientation distribution function (ODF) was calculated using Mtex-4.1.4 after background and defocus corrections. The measurement results are shown in Table 4.

[0064] Furthermore, in the present invention, in order to further explain the mechanical properties, flanging performance and surface quality of the finished 6000 series aluminum alloy sheet materials according to the present invention, samples were again taken from the obtained finished 6000 series aluminum alloy sheet materials according to Examples 1 to 8 and the finished comparative aluminum alloy sheet materials according to Comparative Examples 1 to 4, and the mechanical properties, flanging performance and roping mark defects of the finished aluminum alloy sheet materials according to each of the Examples and Comparative Examples were measured and evaluated.

[0065] Relevant mechanical performance measures were: The corresponding finished T4P aluminum alloy sheet samples of each example and comparative example were subjected to natural aging treatment at room temperature for 7 days, and then the tensile properties were measured at room temperature. The room temperature tensile test was performed in accordance with the requirements of ASTM E8 / E8M-16a. The room temperature tensile samples were each cut from the finished T4P aluminum alloy sheet samples at an angle of 0°C to the sheet rolling direction. o , 45o and 90 o The specimens were cut in three directions: 1. The room temperature tensile tests were carried out using an MTS810 tensile testing machine, and the tensile speed was controlled at 2 mm / min. Correspondingly, the plastic strain ratio r value and the planar anisotropy index Δr value were measured according to the GB / T 5027-2007 standard.

[0066] The relevant flanging performance assessment measures were: For each example and comparative example, a 250 mm (rolling direction) x 30 mm (transverse direction) square sample was cut from the corresponding finished T4P aluminum alloy sheet, and flanging performance was evaluated. The flanging performance evaluation was performed in accordance with the requirements of GMW 15421-2018. The sample was pre-tensioned 10% along the rolling direction, and then a 50 mm (rolling direction) x 30 mm (transverse direction) square sample was cut. A 180° bending test was then performed using an indenter with a 0.6 mm radius. The spacing between the support rollers was maintained at 3.0-3.1 mm during the test. After bending, the outer surface was evaluated according to the following criteria: Level 1: smooth surface; Level 2: discontinuous localized shrinkage; Level 3: microcracks; Level 4: obvious cracks; Levels 1 and 2 were acceptable, while Levels 3 and 4 were unacceptable.

[0067] The relevant roping mark defect assessment measures were as follows: A square sample of 250 mm (rolling direction) x 35 mm (transverse direction) was cut out from the corresponding finished T4P aluminum alloy plate material of each of Examples 1 to 8 and Comparative Examples 1 to 4, and roping mark defects were evaluated. The roping mark defect evaluation sample needed to be polished on a flat workbench. First, to facilitate cleanup after measurement, oil paper was placed under the sample, and black ink was evenly applied to the surface of the sample, and the ink was allowed to evaporate for 10 to 15 seconds. The sample surface was then polished using a sponge pad with sandpaper attached to the surface. Light pressure was applied to the sample surface during polishing. Generally, polishing was performed 2-3 times along a single direction in the rolling direction, and then the level of roping mark defects was manually evaluated: Level 1: The surface must be free of vertical stripes parallel to the rolling direction; Level 2: It is acceptable for the surface to have 1-5 vertical stripes parallel to the rolling direction; Level 3: The surface has more than 5 vertical stripes parallel to the rolling direction; Level 4: The surface has more than 5 vertical stripes parallel to the rolling direction, and the spacing between the vertical stripes is less than 3 mm; however, levels 1 and 2 are acceptable, while levels 3 and 4 are not.

[0068] Table 4 shows the results of measuring the structure, texture and performance of the finished 6000 series aluminum alloy sheets according to Examples 1 to 8 and the finished aluminum alloy sheets according to Comparative Examples 1 to 4.

[0069] [Table 4]

[0070] As shown in Tables 3 and 4, the 6xxx plates manufactured according to the processes of Examples 1 to 8 meet the requirements of the present invention, and the areal density of Mg2Si precipitates with an average size of 1.3 to 1.7 μm in the cold-rolled plate is ≧55,000 pieces / mm 2the average grain size of the finished plate is 20-32 μm, the recrystallization texture density is 6.5-10.0, the content of cube texture component is ≦8%, and the content of Goss texture component is ≦7%; the performance of the finished plate satisfies the following: tensile strength is ≧210 MPa, yield strength is ≧104 MPa, elongation is ≧24%, plastic strain ratio r value is ≧0.68, Δr is ≦0.10, the flanging level (flanging factor is 0.6) is evaluated as 1, and the roping mark level is evaluated as 1. In contrast, in the comparative examples, the 6xxx plate materials manufactured according to the processes of Comparative Examples 1 to 4 did not satisfy the scope of the process of the present invention, and the following results were obtained: In Comparative Example 1, the coiling temperature at the end of hot finish rolling was below 340°C, but intermediate annealing was not performed. This resulted in excessive precipitation of fine second phases and a low number of coarse second phases, which suppressed the PSN effect induced by the coarse second phases during the subsequent solution treatment. This resulted in an excessively high recrystallization texture density, leading to poor formability of the finished sheet (low r-value and high Δr-value). In particular, the contents of the soft orientation component of the cube texture and the hard orientation component of the Goss texture were high, and both types of texture components aggregated and distributed alternately along the rolling direction. During 10% pre-tensioning perpendicular to the rolling direction, the hard orientation grains with the Goss texture were resistant to deformation and appeared as ridges, while the soft orientation grains with the cube texture were easily deformed and thinned and appeared as valleys, resulting in the appearance of roping marks with unevenness along the rolling direction.

[0071] In Comparative Example 2, the intermediate annealing temperature was too high, causing the secondary phase to grow excessively and the size of the coarse secondary phase to become too large, making it difficult to sufficiently melt back in the subsequent solution treatment process. As a result, the secondary phase remained in the final finished plate, which created many crack sources during the flanging process and led to poor flanging performance (flanging level 4).

[0072] In Comparative Example 3, the cold rolling reduction was too low, resulting in excessively large grain size in the finished sheet. The coarse grains promoted the generation and propagation of shear bands during the flanging process, resulting in poor flanging performance (flanging level 4).

[0073] In Comparative Example 4, the cold rolling reduction was too high, resulting in an excessively high deformation texture density in the cold-rolled sheet. Due to the inherited texture effect, the density of recrystallization texture in the finished sheet was also high, particularly in the contents of the soft orientation component of the cube texture and the hard orientation component of the Goss texture, leading to severe roping marks (roping mark defect level 3).

[0074] As can be seen from the above, the method for producing a 6000 series aluminum alloy sheet having high formability, high flanging performance and low roping mark defects according to the present invention, on the one hand, adjusts the size and number of coarse Mg2Si precipitate phases in the 6000 series aluminum alloy sheet by rationally adjusting the process parameters of soaking, hot rolling, coiling and intermediate annealing in the processing steps, so that the PSN effect of the coarse Mg2Si phases is fully exerted in the subsequent solution treatment step, thereby adjusting the texture; on the other hand, adjusts the cold rolling reduction rate to further adjust the texture and grain size of the finished sheet, ultimately achieving the goals of weakening the recrystallization texture density of the finished sheet and refining the grain size of the finished sheet, thereby achieving the results of obtaining a 6000 series aluminum alloy sheet for automobile bodies having high formability, high flanging performance and low roping mark defects.

[0075] Furthermore, the combinations of the technical features in this application are not limited to the combinations described in the claims of this application or the combinations described in the specific examples, and as long as there are no contradictions, all technical features described in this application can be freely combined or combined in any form.

[0076] Furthermore, it should be noted that the above-mentioned embodiments are merely specific embodiments of the present invention, and the present invention is not limited to the above-mentioned embodiments, and it is clear that any similar changes or modifications that can be directly derived or easily conceived by those skilled in the art from the disclosure of the present invention are included in the protection scope of the present invention.

Claims

1. 1. A 6000 series aluminum alloy sheet, comprising: an average crystal grain size of 20 to 32 μm; a recrystallization texture density of 6.5 to 10.0; a cube texture component content of ≦8%; and a Goss texture component content of ≦7%.

2. 2. The 6000 series aluminum alloy sheet according to claim 1, wherein the 6000 series aluminum alloy sheet has a tensile strength of ≥ 210 MPa, a yield strength of ≥ 104 MPa, and an elongation of ≥ 24%.

3. 3. The 6000 series aluminum alloy sheet according to claim 1, wherein the 6000 series aluminum alloy sheet has a plastic strain ratio r of ≥ 0.68, a planar anisotropy index Δr of ≤ 0.10, a flanging level evaluated as 1, and a roping mark level evaluated as 1.

4. 4. The 6000 series aluminum alloy sheet according to claim 3, wherein the 6000 series aluminum alloy sheet has a plastic strain ratio r of ≥ 0.70, preferably r ≥ 0.72, and more preferably r ≥ 0.

74.

5. 5. The 6000 series aluminum alloy sheet according to claim 3, wherein the planar anisotropy index Δr of the 6000 series aluminum alloy sheet is ≦0.08, preferably ≦0.06, and more preferably ≦0.

04.

6. The 6000 series aluminum alloy may contain, in mass percentage, Si: 0.3 to 1.5%, Fe: 0.05 to 0.5%, Cu: 0.02 to 1.1%, Mg: 0.35 to 1.2%, Zn: ≦0.8%, Mn: ≦0.8%, Cr: ≦0.35%, Ti: ≦0.15%, V: ≦0.20%, and the balance being Al and unavoidable impurities; preferably, the aluminum 6. The 6000 series aluminum alloy sheet according to claim 1, wherein the alloy sheet has an elemental composition of Mg: 0.4 to 0.7%, Si: 0.5 to 0.8%, Fe: 0.1 to 0.3%, Mn: 0.05 to 0.15%, Cu: 0.05 to 0.3%, Zn: ≦0.05%, V: ≦0.05%, Cr: ≦0.05%, and the balance being Al and unavoidable impurities.

7. A method for producing a 6000 series aluminum alloy sheet material having high formability, high flanging performance, and low roping mark defects, comprising the steps of: (1) subjecting the ingot to homogenization treatment, the homogenization treatment temperature being 530 to 580°C, preferably 550 to 570°C; (2) The homogenized ingot is directly subjected to rough hot rolling, finish hot rolling, and coiling at the end of hot rolling, with the start temperature of the finish hot rolling being controlled to 400-480°C, preferably 440-480°C, and the coiling temperature at the end of hot rolling being controlled to 250°C or higher; (3) Cold rolling: The total deformation amount of cold rolling is controlled to 50 to 85%, and Mg in the obtained cold-rolled sheet is ２ The average size of the Si precipitate phase is 1.3 to 1.7 μm, and the Mg ２ The surface density of the Si precipitate phase is ≧55,000 pieces / mm ２ is; (4) solution treatment; (5) Pre-aging is performed, followed by air cooling to obtain a 6000 series aluminum alloy sheet material.

8. 8. The method for producing a 6000 series aluminum alloy sheet according to claim 7, wherein, in step (2), when the coiling temperature at the end of hot rolling is 250 to 340°C, intermediate annealing is performed before the cold rolling in step (3), the intermediate annealing temperature is controlled to 350 to 430°C, the temperature retention time is controlled to 1 to 4 hours, and then cooling to room temperature together with the furnace is performed; preferably, the temperature rise rate in the intermediate annealing is 13 to 17°C / h, and the temperature decrease rate in the intermediate annealing is 12 to 15°C / h; or, when the coiling temperature at the end of hot rolling exceeds 340°C, step (3) is carried out without performing intermediate annealing.

9. The method for producing a 6000 series aluminum alloy sheet material according to claim 7, wherein in the step (1), the temperature retention time for the homogenization treatment is 6 to 16 hours.

10. 8. The method for producing a 6000 series aluminum alloy sheet according to claim 7, wherein, in the step (2), the rough hot rolling temperature is controlled to 530 to 570°C; and / or the rough hot rolling total deformation amount is controlled to more than 70%; and / or the finish hot rolling total deformation amount is controlled to more than 80%.

11. The method for producing a 6000 series aluminum alloy sheet material according to claim 7, wherein in the step (3), a total cold rolling deformation amount is controlled to 60 to 85%.

12. The method for producing a 6000 series aluminum alloy sheet material according to claim 7, wherein in the step (4), the solution treatment temperature is 550 to 570°C, the solution treatment heating rate is 15 to 30°C / s, the solution treatment temperature retention time is 1 to 5 min, and the quenching method is water cooling.

13. The method for producing a 6000 series aluminum alloy sheet material according to claim 7, wherein in the step (5), pre-aging treatment is performed within 3 minutes after completion of the step (4); and / or the pre-aging treatment is performed by raising the temperature to 80 to 100°C and then slowly lowering the temperature from 80 to 100°C to room temperature at a temperature lowering rate of 1 to 4°C / h.

14. The method for producing a 6000 series aluminum alloy sheet material according to any one of claims 7 to 13, wherein the 6000 series aluminum alloy sheet material is the 6000 series aluminum alloy sheet material according to any one of claims 1 to 6.

15. A 6000 series aluminum alloy sheet produced by the production method according to any one of claims 8 to 13, wherein the 6000 series aluminum alloy sheet preferably has an average grain size of 20 to 32 μm, a recrystallization texture density of 6.5 to 10.0, a cube texture component content of ≦8%, and a Goss texture component content of ≦7%; more preferably, the performance of the 6000 series aluminum alloy sheet further satisfies the following: The tensile strength is ≥ 210 MPa, the yield strength is ≥ 104 MPa, and the elongation is ≥ 24%; A 6000 series aluminum alloy sheet material, wherein a plastic strain ratio r is ≧0.68, a planar anisotropy index Δr is ≦0.10, a flanging level is evaluated as 1, and a roping mark level is evaluated as 1.

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