Method for improving comprehensive performance of 6xxx aluminum alloy coiled material and aluminum alloy coiled material

Abstract

The invention discloses a method for improving the comprehensive performance of a 6xxx aluminum alloy coiled material and the aluminum alloy coiled material, and belongs to the technical field of aluminum alloy manufacturing. The method comprises the following procedures of fusion casting, homogenizing heat treatment, temperature control rolling, low-temperature rolling, annealing, solid solution quenching, pre-deformation and pre-aging treatment.The traditional technology is optimized, the production period is shortened, efficiency is improved, and the production cost is reduced. By implementing the scheme, the ratio gt of the long axis to the short axis of the grain structure can be obtained; 1.2, the average grain size is 16 to 22 microns, and Cube {001} lt; 100 gt; according to the aluminum alloy coiled material finished product, the plastic strain ratio r is larger than or equal to 0.5, the anisotropy # imgabs0 # is smaller than 0.1, the tensile strength is larger than or equal to 250 MPa, the yield strength is larger than or equal to 125 MPa, the ductility is larger than or equal to 24%, and the bake hardening peak value increment reaches 90-150 MPa.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloy manufacturing, and particularly relates to a method for improving the comprehensive performance of 6xxx aluminum alloy coils and aluminum alloy coils. Background Art

[0002] 6xxx aluminum alloy has become the preferred material for automotive outer panels due to its comprehensive performance. The new alloy performs outstandingly in pedestrian protection and recycling. Other body panels such as car doors, trunk lids, and fenders are also gradually being aluminized. Moreover, the aluminum alloy has a high recycling value, and the increase in the aluminum usage in the whole vehicle is beneficial to the recycling of scrap metal from disassembled vehicles.

[0003] The 6xxx series aluminum alloy for the body is in the T4 state before baking, with an excellent yield ratio, which is beneficial for stamping. The stamped parts are age-hardened during the electrophoretic baking process. High-alloyed 6xxx aluminum alloys such as 6111 alloy sheets have higher strength than 6014 / 6016 / 6022 etc. after baking, but their stamping ability is slightly weaker. The conventional production process for 6xxx - T4 aluminum alloy products is: melting and casting → homogenization heat treatment → trimming → milling → hot rolling → cold rolling → intermediate annealing → cold rolling → quenching → pre-aging. The process flow is complex, the production cycle is long, the efficiency is low, and the energy consumption is high. A preparation method for 6xxx aluminum alloy coils with separated homogenization and heating, with the application number CN202210878837.0, requires two cold rolling processes, has a relatively long production cycle, a high temperature in the annealing step, high energy consumption, and a relatively low final rolling temperature during hot rolling, which is 240 - 280 °C, and is not conducive to dynamic recrystallization and texture ratio adjustment.

[0004] Based on this, it is expected to explore a method for improving the comprehensive performance of 6xxx aluminum alloy coils, optimize the production process and production technology, shorten the production cycle, improve efficiency, reduce energy consumption, and reduce the anisotropy of the product, and improve the stamping forming ability and age response ability. Summary of the Invention

[0005] In view of the above deficiencies, the present invention provides a method for improving the comprehensive performance of 6xxx aluminum alloy coils, which is beneficial to improving the tensile strength, yield strength, and elongation performance of the aluminum alloy coils, shortening the production cycle, improving efficiency, and reducing energy consumption. Through the implementation of this solution, an aluminum alloy coil finished product with a major-to-minor axis ratio of the grain structure > 1.2, an average grain size of 16 - 22 μm, a Cube{001}<100> texture ratio of 12 - 18% can be obtained. The plastic strain ratio r of the aluminum alloy finished product ≥ 0.5, and the anisotropy < 0.1, and the baking hardening value increment reaches 90 - 150 MPa. The specific technical solution is as follows: A method for improving the comprehensive performance of 6xxx aluminum alloy coils, comprising the following steps: S1. Melting and casting: Melting and casting aluminum alloy raw materials to obtain an ingot; S2. Homogenization heat treatment: Cut the head and tail of the ingot obtained in step S1, mill the surface, and then perform homogenization heat treatment to obtain the homogenized heat-treated ingot; S3. Temperature-controlled rolling: Perform temperature-controlled rolling on the homogenized heat-treated ingot obtained in step S2. Control the metal temperature at 350 - 450 °C during the rolling process, and the total rolling reduction rate > 60% to obtain the temperature-controlled rolled coil; S4. Low-temperature rolling: Perform low-temperature rolling on the temperature-controlled rolled coil obtained in step S3 to obtain the low-temperature rolled coil; S5. Annealing: Anneal the low-temperature rolled coil obtained in step S4 at an annealing temperature of 320 - 360 °C and a holding time of 0.2 - 1 h to obtain the annealed coil; S6. Solution quenching: Perform solution quenching on the annealed coil obtained in step S5 to obtain the solution-quenched coil; S7. Pre-deformation: Perform pre-deformation on the solution-quenched coil obtained in step S6 with a pre-tensile rate of 0.2 - 1.0% to obtain the pre-deformed coil; S8. Pre-aging treatment: Perform pre-aging treatment on the pre-deformed coil obtained in step S7 to obtain the finished aluminum alloy coil.

[0006] The mass percentages of the chemical components of the aluminum alloy are as follows: Si = 0.9 - 1.8%, Fe = 0.2 - 0.8%, Cu = 0.2 - 0.5%, Mn = 0.1 - 0.5%, Mg = 0.6 - 1.2%, Cr ≤ 0.25%, Zn ≤ 0.3%, Ti ≤ 0.1%, and the balance is Al and inevitable impurity elements.

[0007] Furthermore, the holding temperature of the homogenization heat treatment is 530 - 560 °C, and the holding time is 6 - 12 h.

[0008] Furthermore, the low-temperature rolling temperature is 10 - 60 °C, and the total rolling reduction rate > 60%.

[0009] Furthermore, the holding temperature of the solution quenching is 540 - 570 °C, and the holding time is 0.2 - 1 h.

[0010] Furthermore, the pre-aging treatment temperature is 70 - 150 °C, and the holding time is 3 - 25 h.

[0011] Furthermore, in the solution quenching step, the cooling rate > 45 °C / s.

[0012] The present invention also provides a finished 6xxx aluminum alloy coil prepared by the above preparation method.

[0013] Furthermore, for the 6xxx aluminum alloy coil described in the present invention, the aspect ratio of the grain structure is > 1.2, the average grain size is 16 - 22 μm, and the proportion of Cube{001}<100> texture is 12 - 18%.

[0014] Furthermore, the properties of the finished product of the 6xxx aluminum alloy coil described in the present invention meet the following requirements: Tensile strength ≥ 250 MPa, yield strength ≥ 125 MPa, elongation ≥ 24%, and the peak increment of bake hardening reaches 90 - 150 MPa; Plastic strain ratio r ≥ 0.5, anisotropy index Δr < 0.1.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. A method for improving the comprehensive properties of 6xxx aluminum alloy coil provided by the present invention includes the following processes: melting and casting, homogenization heat treatment, temperature-controlled rolling, cold rolling, annealing, solution quenching, pre-deformation, and pre-aging treatment. The solution of the present invention optimizes the production processes and production technology, shortens the production cycle, improves efficiency, and reduces energy consumption.

[0016] 2. In the method of the present invention, the temperature-controlled rolling process is beneficial to dynamic recrystallization and texture ratio adjustment. Combining with cold rolling can increase the energy storage and lattice distortion. During the short-time annealing process at 320 - 360 °C for 0.2 - 1 h, static recrystallization occurs rapidly, and then quenching is immediately carried out to obtain a quenched structure with elliptical grains having an aspect ratio > 1.2, and the average grain size is reduced, so that the grains of the aluminum alloy coil are fine, thereby improving the mechanical properties of the aluminum alloy; after 0.2 - 1.0% pre-tensile deformation, pre-aging treatment is carried out, and a more uniform and dispersed GP zone can be obtained, which is beneficial to improving the tensile strength, yield strength, and elongation properties.

[0017] 3. Through the method of the present invention, a finished product of aluminum alloy coil with an aspect ratio of the grain structure > 1.2, an average grain size of 16 - 22 μm, and a proportion of Cube{001}<100> texture of 12 - 18% can be obtained. The plastic strain ratio r of the finished product of the aluminum alloy coil ≥ 0.5, and the anisotropy <0.1, tensile strength ≥ 250 MPa, yield strength ≥ 125 MPa, elongation ≥ 24%, and the peak increment of bake hardening reaches 90 - 150 MPa. Description of the Drawings

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0019] Figure 1 Schematic diagram of the process flow of the present invention; Figure 2 EBSD test diagram of the grain structure of the finished aluminum alloy coil in Example 1 of the present invention; Figure 3 EBSD test diagram of the texture ratio of the finished aluminum alloy coil in Example 1 of the present invention. Specific embodiments

[0020] The following is a detailed description of the specific embodiments of the present invention, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments. Unless otherwise defined, all professional terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention. Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the present invention can be obtained through the market or can be prepared by existing methods.

[0021] Refer to Figure 1 , the process flow of the embodiment of the present invention includes the following steps: Smelting and casting: Smelt and cast the aluminum alloy raw materials to obtain an ingot; Homogenization heat treatment: Cut the head and tail and mill the surface of the obtained ingot, and then perform homogenization heat treatment. The holding temperature is 530 - 560 °C, and the holding time is 6 - 12 h to obtain an ingot after homogenization heat treatment; Temperature-controlled rolling: Perform temperature-controlled rolling on the obtained ingot after homogenization heat treatment. Control the metal temperature at 350 - 450 °C during the rolling process, and the total rolling reduction rate > 60% to obtain a temperature-controlled rolling coil; Low-temperature rolling: Perform low-temperature rolling on the obtained temperature-controlled rolling coil. Control the metal temperature at 10 - 60 °C during the rolling process, and the total rolling reduction rate > 60% to obtain a low-temperature rolling coil; Annealing: Anneal the obtained low-temperature rolling coil. The holding temperature is 320 - 360 °C, and the holding time is 0.2 - 1 h to obtain an annealed coil; Solution quenching: Perform solution quenching on the obtained annealed coil. The holding temperature is 540 - 570 °C, and the holding time is 0.2 - 1 h, and the cooling rate > 45 °C / s to obtain a solution-quenched coil; Pre-deformation: Perform pre-deformation on the obtained solution-quenched coil. The pre-tensile rate is 0.2 - 1.0% to obtain a pre-deformed coil; Pre-aging treatment: Perform pre-aging treatment on the obtained pre-deformed coil. The holding temperature is 70 - 150 °C, and the holding time is 3 - 25 h, and then cool to obtain the finished aluminum alloy coil.

[0022] Example 1 The mass percentages of the chemical components of the aluminum alloy in this embodiment are as follows: Si = 1.3%, Fe = 0.6%, Cu = 0.3%, Mn = 0.3%, Mg = 0.8%, Cr = 0.20%, Zn = 0.2%, Ti = 0.03%, and the balance is Al and unavoidable impurity elements.

[0023] Referring to Figure 1 , a method for improving the comprehensive properties of 6xxx aluminum alloy coils in this embodiment includes the following steps: S1. Melting and casting: Melting and casting the aluminum alloy raw materials to obtain an ingot; S2. Homogenization heat treatment: Cutting the head and tail and milling the surface of the ingot obtained in step S1, and then performing homogenization heat treatment at a holding temperature of 545 °C for a holding time of 9 h to obtain a homogenized heat-treated ingot; S3. Temperature-controlled rolling: Performing temperature-controlled rolling on the homogenized heat-treated ingot obtained in step S2, with the starting rolling temperature of 400 °C, controlling the metal temperature at 350 - 450 °C during the rolling process, and the total rolling reduction rate of 70% to obtain temperature-controlled rolled coils; S4. Low-temperature rolling: Performing low-temperature rolling on the temperature-controlled rolled coils obtained in step S3, controlling the metal temperature at 30 - 40 °C during the rolling process, and the total rolling reduction rate of 70% to obtain low-temperature rolled coils; S5. Annealing: Annealing the low-temperature rolled coils obtained in step S4 at an annealing temperature of 340 °C for a holding time of 0.6 h to obtain annealed coils; S6. Solution quenching: Performing solution quenching on the annealed coils obtained in step S5 at a holding temperature of 555 °C for a holding time of 0.6 h and a cooling rate of 55 °C / s to obtain solution-quenched coils; S7. Pre-deformation: Performing pre-deformation on the solution-quenched coils obtained in step S6 with a pre-stretching rate of 0.6% to obtain pre-deformed coils; S8. Pre-aging treatment: Performing pre-aging treatment on the pre-deformed coils obtained in step S7 at a temperature of 110 °C for a holding time of 15 h, and obtaining the finished aluminum alloy coils after cooling.

[0024] Figure 2 is the EBSD test diagram of the grain structure of the finished aluminum alloy coils in Example 1. The grain structure of the finished aluminum alloy coils shows recrystallization characteristics, and the grains are elliptical. For this diagram, the average major axis and minor axis dimensions of the grains can be measured using ImageJ software, and the calculated aspect ratio > 1.2, and the calculated average grain size reaches 21 μm. The fine grains can further improve the mechanical properties of the finished aluminum alloy coils; Figure 3 is the EBSD test diagram of the texture ratio of the finished aluminum alloy coils in Example 1, which shows the grain orientation distribution and texture ratio. Figure 3The Cube{001}<100> texture ratio shown on the right is 15%, indicating that Example 1 successfully adjusted the texture ratio required for the finished aluminum alloy coil.

[0025] Example 2 The mass percentages of the chemical components of the aluminum alloy in this example are as follows: Si = 1.2%, Fe = 0.3%, Cu = 0.3%, Mn = 0.2%, Mg = 0.8%, Cr = 0.13%, Zn = 0.1%, Ti = 0.06%, and the balance is Al and inevitable impurity elements.

[0026] Refer to Figure 1 , a method for improving the comprehensive properties of 6xxx aluminum alloy coils in this example includes the following steps: S1. Melting and casting: Melting and casting the aluminum alloy raw materials to obtain an ingot; S2. Homogenization heat treatment: Cutting the head and tail of the ingot obtained in step S1, milling the surface, and then performing homogenization heat treatment at a holding temperature of 530 °C for 12 h to obtain a homogenized heat-treated ingot; S3. Temperature-controlled rolling: Performing temperature-controlled rolling on the homogenized heat-treated ingot obtained in step S2, with the starting rolling temperature of 370 °C, controlling the metal temperature at 350 - 450 °C during the rolling process, and the total rolling reduction rate of 65% to obtain a temperature-controlled rolled coil; S4. Low-temperature rolling: Performing low-temperature rolling on the temperature-controlled rolled coil obtained in step S3, controlling the metal temperature at 15 - 25 °C during the rolling process, and the total rolling reduction rate of 65% to obtain a low-temperature rolled coil; S5. Annealing: Annealing the low-temperature rolled coil obtained in step S4 at an annealing temperature of 320 °C for 1 h to obtain an annealed coil; S6. Solution quenching: Performing solution quenching on the annealed coil obtained in step S5 at a holding temperature of 540 °C for 1 h and a cooling rate of 50 °C / s to obtain a solution-quenched coil; S7. Pre-deformation: Performing pre-deformation on the solution-quenched coil obtained in step S6 with a pre-stretching rate of 0.2% to obtain a pre-deformed coil; S8. Pre-aging treatment: Performing pre-aging treatment on the pre-deformed coil obtained in step S7 at a temperature of 70 °C for 25 h, and obtaining the finished aluminum alloy coil after cooling.

[0027] Example 3 The mass percentages of the chemical components of the aluminum alloy in this example are as follows: Si = 1.6%, Fe = 0.7%, Cu = 0.2%, Mn = 0.4%, Mg = 1.1%, Cr = 0.23%, Zn = 0.3%, Ti = 0.1%, and the balance is Al and inevitable impurity elements.

[0028] Reference Figure 1 A method for improving the comprehensive properties of 6xxx aluminum alloy coils in this embodiment includes the following steps: S1. Melting and casting: Melting and casting aluminum alloy raw materials to obtain ingots; S2. Homogenization heat treatment: Cutting the heads and tails of the ingots obtained in step S1, milling the surfaces, and then performing homogenization heat treatment at a holding temperature of 560°C for 6 hours to obtain homogenized heat-treated ingots; S3. Temperature-controlled rolling: Performing temperature-controlled rolling on the homogenized heat-treated ingots obtained in step S2, with the starting rolling temperature of 450°C, controlling the metal temperature at 350 - 450°C during the rolling process, and the total rolling reduction of 72% to obtain temperature-controlled rolled coils; S4. Low-temperature rolling: Performing low-temperature rolling on the temperature-controlled rolled coils obtained in step S3, controlling the metal temperature at 50 - 60°C during the rolling process, and the total rolling reduction of 72% to obtain low-temperature rolled coils; S5. Annealing: Annealing the low-temperature rolled coils obtained in step S4 at an annealing temperature of 360°C for 0.2 hours to obtain annealed coils; S6. Solution quenching: Performing solution quenching on the annealed coils obtained in step S5 at a holding temperature of 570°C for 0.2 hours and a cooling rate of 60°C / s to obtain solution-quenched coils; S7. Pre-deformation: Performing pre-deformation on the solution-quenched coils obtained in step S6 with a pre-stretching rate of 0.9% to obtain pre-deformed coils; S8. Pre-aging treatment: Performing pre-aging treatment on the pre-deformed coils obtained in step S7 at a temperature of 150°C for 3 hours, and obtaining the finished aluminum alloy coils after cooling.

[0029] Comparative Example 1 The temperature-controlled rolling process in this comparative example is that the starting hot rolling temperature is 400°C, the final hot rolling temperature is 250°C, and the total rolling reduction is 70%. The other processes are the same as those in Example 1.

[0030] Comparative Example 2 In this comparative example, after low-temperature rolling, the annealing process is not carried out, and it directly enters the solution quenching process.

[0031] The mass percentages of the chemical components of the aluminum alloy in this comparative example are: Si = 1.3%, Fe = 0.6%, Cu = 0.3%, Mn = 0.3%, Mg = 0.8%, Cr = 0.20%, Zn = 0.2%, Ti = 0.03%, and the balance is Al and unavoidable impurity elements.

[0032] A method for improving the comprehensive properties of 6xxx aluminum alloy coils in this comparative example includes the following steps: S1. Casting: The aluminum alloy raw materials are cast to obtain ingots. S2. Homogenization heat treatment: The ingots obtained in step S1 are trimmed at both ends and milled on the surface, and then subjected to homogenization heat treatment at a holding temperature of 545 °C for 9 h to obtain homogenized heat-treated ingots. S3. Temperature-controlled rolling: The homogenized heat-treated ingots obtained in step S2 are subjected to temperature-controlled rolling. The starting rolling temperature is 400 °C, the metal temperature is controlled at 350 - 450 °C during the rolling process, and the total rolling reduction is 70% to obtain temperature-controlled rolled coils. S4. Low-temperature rolling: The temperature-controlled rolled coils obtained in step S3 are subjected to low-temperature rolling. The metal temperature is controlled at 30 - 40 °C during the rolling process, and the total rolling reduction is 70% to obtain low-temperature rolled coils. S5. Solution quenching: The annealed coils obtained in step S4 are subjected to solution quenching at a holding temperature of 555 °C for 0.6 h and a cooling rate of 55 °C / s to obtain solution-quenched coils. S6. Pre-deformation: The solution-quenched coils obtained in step S5 are pre-deformed with a pre-stretching rate of 0.6% to obtain pre-deformed coils. S7. Pre-aging treatment: The pre-deformed coils obtained in step S6 are subjected to pre-aging treatment at a temperature of 110 °C for 15 h, and after cooling, the finished aluminum alloy coils are obtained.

[0033] Comparative Example 3 The mass percentages of the chemical components of the aluminum alloy in this comparative example are as follows: Si = 1.2%, Fe = 0.6%, Cu = 0.3%, Mn = 0.4%, Mg = 0.9%, Cr = 0.21%, Zn = 0.2%, Ti = 0.08%, and the balance is Al and inevitable impurity elements.

[0034] A method for improving the comprehensive properties of 6xxx aluminum alloy coils in this comparative example includes the following steps: S1. Casting: The aluminum alloy raw materials are cast to obtain ingots. S2. Homogenization heat treatment: The ingots obtained in step S1 are trimmed at both ends and milled on the surface, and then subjected to homogenization heat treatment at a holding temperature of 545 °C for 9 h. After the treatment, the top and bottom are sawed and the surface is milled to obtain homogenized heat-treated ingots. S3. Temperature-controlled rolling: The homogenized heat-treated ingots obtained in step S2 are subjected to temperature-controlled rolling. The starting rolling temperature is 400 °C, the total rolling reduction is 70%, and the metal temperature is controlled at 350 - 450 °C during the rolling process to obtain temperature-controlled rolled coils. S4. Annealing: The temperature-controlled rolled coils obtained in step S3 are annealed at an annealing temperature of 340 °C for 0.6 h to obtain annealed coils. S5. Cold rolling: Cold roll the annealed coil obtained in step S4 at a rolling temperature of 30 - 40°C and a total rolling reduction rate of 70% to obtain a cold-rolled coil. S6. Solution quenching: Solution quench the cold-rolled coil obtained in step S5 at a holding temperature of 555°C for 0.6 h with a cooling rate of 55°C / s to obtain a solution-quenched coil. S7. Pre-deformation: Pre-deform the solution-quenched coil obtained in step S6 with a pre-tensile rate of 0.6% to obtain a pre-deformed coil. S8. Pre-aging treatment: Perform pre-aging treatment on the pre-deformed coil obtained in step S7 at a temperature of 110°C for 15 h, and after cooling, obtain the finished aluminum alloy coil.

[0035] Comparative Example 4 The mass percentages of the chemical components of the aluminum alloy in this comparative example are as follows: Si = 1.0%, Fe = 0.2%, Cu = 0.1%, Mn = 0.1%, Mg = 0.5%, Cr = 0.1%, Zn = 0.05%, Ti = 0.08%, and the balance is Al and unavoidable impurity elements.

[0036] A method for improving the comprehensive properties of 6xxx aluminum alloy coil in this comparative example includes the following steps: S1. Melting and casting: Melt and cast the aluminum alloy raw materials to obtain an ingot. S2. Homogenization heat treatment: Cut the head and tail and mill the surface of the ingot obtained in step S1, and then perform homogenization heat treatment at a holding temperature of 565°C for 15 h to obtain a homogenized ingot. S3. Hot rolling: Hot roll the homogenized ingot obtained in step S2 at an initial rolling temperature of 500°C with a total rolling reduction rate of 70% and a final rolling temperature of 300°C to obtain a hot-rolled coil. S4. Cold rolling: Cold roll the hot-rolled coil obtained in step S3 at a metal temperature of 30 - 40°C during the rolling process with a total rolling reduction rate of 70% to obtain a cold-rolled coil. S5. Solution quenching: Solution quench the cold-rolled coil obtained in step S4 at a holding temperature of 555°C for 0.6 h to obtain a solution-quenched coil. S6. Pre-aging treatment: Perform pre-aging treatment on the solution-quenched coil obtained in step S5 at a temperature of 110°C for 15 h, and after cooling, obtain the finished aluminum alloy coil.

[0037] Perform microstructure testing and performance testing on the finished aluminum alloy coils of the examples and comparative examples.

[0038] The grain size of the finished aluminum alloy coil was detected by the intercept method using ImageJ software; the Cube{001}<100> texture ratio was detected by electron backscatter diffraction (EBSD) technology; the room-temperature tensile properties of the finished aluminum alloy coil were tested after natural aging at room temperature for 7 days, and the room-temperature tensile test was carried out according to the requirements of GB / T 228.1-2021; the plastic strain ratio r value and the planar anisotropy index were determined according to the standard of GB / T 5027-2007.

[0039] The results are shown in Table 1 below.

[0040] Table 1 Microstructure test and property test results of the finished aluminum alloy coils in the examples and comparative examples In summary, a method for improving the comprehensive properties of 6xxx aluminum alloy coils provided by the present invention includes the following processes: melting and casting, homogenization heat treatment, temperature-controlled rolling, cold rolling, annealing, solution quenching, pre-deformation, pre-aging treatment. The temperature-controlled hot rolling process of the present invention's solution is beneficial to dynamic recrystallization and texture ratio adjustment. Combining cold rolling can increase energy storage and lattice distortion. During the short-time annealing process at 320~360°C / 0.2~1h, static recrystallization occurs rapidly, and then quenching is immediately carried out to obtain a quenched structure with elliptical grains having a major-to-minor axis ratio > 1.2 and reduce the average grain size, thereby making the grains of the finished aluminum alloy coil fine, and further improving the mechanical properties of the finished aluminum alloy coil. After 0.2~1.0% pre-tensile deformation, pre-aging treatment is carried out to obtain a more uniform and dispersed GP zone, which is beneficial to improving the tensile strength, yield strength, and elongation properties. Through the implementation of this solution, a finished aluminum alloy coil with a major-to-minor axis ratio of the grain structure > 1.2, an average grain size of 16~22μm, and a Cube{001}<100> texture ratio of 12~18% can be obtained. The plastic strain ratio r of the finished aluminum alloy coil is ≥0.5, and the anisotropy <0.1, the tensile strength is ≥250MPa, the yield strength is ≥125MPa, the elongation is ≥24%, and the peak increment of bake hardening reaches 90~150MPa.

[0041] The foregoing description of specific exemplary embodiments of the invention has been presented for purposes of illustration and exemplification. These descriptions are not intended to limit the invention to the precise forms disclosed, and it is apparent that many modifications and variations are possible in light of the above teaching. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the invention and its practical applications, so that those skilled in the art can implement and utilize various different exemplary embodiments of the invention, as well as various different selections and modifications. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for improving the comprehensive properties of 6xxx aluminum alloy coils, characterized in that, It includes the following steps: S1. Melting and casting: Melting and casting aluminum alloy raw materials to obtain ingots. S2. Homogenization heat treatment: Cutting the head and tail and milling the surface of the ingots obtained in step S1, and then performing homogenization heat treatment to obtain homogenized heat-treated ingots. S3. Temperature-controlled rolling: Performing temperature-controlled rolling on the homogenized heat-treated ingots obtained in step S2. During the rolling process, control the metal temperature at 350 - 450 °C, and the total rolling reduction rate > 60% to obtain temperature-controlled rolled coils. S4. Low-temperature rolling: Performing low-temperature rolling on the temperature-controlled rolled coils obtained in step S3 to obtain low-temperature rolled coils. S5. Annealing: Annealing the low-temperature rolled coils obtained in step S4 at an annealing temperature of 320 - 360 °C and a holding time of 0.2 - 1 h to obtain annealed coils. S6. Solution quenching: Performing solution quenching on the annealed coils obtained in step S5 to obtain solution-quenched coils. S7. Pre-deformation: Performing pre-deformation on the solution-quenched coils obtained in step S6 with a pre-stretching rate of 0.2 - 1.0% to obtain pre-deformed coils. S8. Pre-aging treatment: Performing pre-aging treatment on the pre-deformed coils obtained in step S7 to obtain finished aluminum alloy coils. The mass percentages of the chemical components of the aluminum alloy are as follows: Si = 0.9 - 1.8%, Fe = 0.2 - 0.8%, Cu = 0.2 - 0.5%, Mn = 0.1 - 0.5%, Mg = 0.6 - 1.2%, Cr ≤ 0.25%, Zn ≤ 0.3%, Ti ≤ 0.1%, and the balance is Al and unavoidable impurity elements.

2. A method for improving the comprehensive properties of 6xxx aluminum alloy coils according to claim 1, characterized in that, The holding temperature of the homogenization heat treatment is 530 - 560 °C, and the holding time is 6 - 12 h.

3. A method for improving the comprehensive properties of 6xxx aluminum alloy coils according to claim 1, characterized in that, The low-temperature rolling temperature is 10 - 60 °C, and the total rolling reduction rate > 60%.

4. A method for improving the comprehensive properties of 6xxx aluminum alloy coils according to claim 1, characterized in that, The holding temperature of the solution quenching is 540 - 570 °C, and the holding time is 0.2 - 1 h.

5. A method for improving the comprehensive properties of 6xxx aluminum alloy coils according to claim 1, characterized in that, The pre-aging treatment temperature is 70 - 150 °C, and the holding time is 3 - 25 h.

6. A method for improving the comprehensive properties of 6xxx aluminum alloy coils according to claim 5, characterized in that, In the solution quenching step, the cooling rate > 45 °C / s.

7. A 6xxx aluminum alloy coil prepared by the method according to any one of claims 1 - 6.

8. The 6xxx aluminum alloy coil according to claim 7, characterized in that, Its grain structure has an aspect ratio of the major and minor axes > 1.2, an average grain size of 16 - 22 μm, and a Cube{001}<100> texture ratio of 12 - 18%.

9. The 6xxx aluminum alloy coil according to claim 7, characterized in that, Its properties meet the following: Tensile strength ≥ 250 MPa, yield strength ≥ 125 MPa, elongation ≥ 24%, and the baking hardening peak increment reaches 90 - 150 MPa; Plastic strain ratio r ≥ 0.5, and the anisotropy index Δr < 0.1.

Images