Method for manufacturing 6000-series aluminum alloy sheet having improved formability and aluminum alloy sheet

Abstract

The application discloses a manufacturing method of 6000 series aluminum alloy plate with improved formability, which comprises the following steps: (1) homogenizing treatment is performed on a cast ingot, and the homogenizing treatment temperature is 530-580 DEG C; (2) directly performing hot rough rolling on the cast ingot, and the total deformation of the hot rough rolling is greater than 70%; (3) performing hot finish rolling on the hot rough rolled plate, the opening rolling temperature of the hot finish rolling is 450-550 DEG C, the final rolling temperature is 320-420 DEG C, and the total deformation of the hot finish rolling is greater than 80%; (4) performing coiling annealing on the hot finish rolled plate, the coiling annealing temperature is controlled to be 320-420 DEG C, the holding time is 0.5-3 h, and then the coiling annealing is cooled to room temperature in the furnace; the surface density of Mg2Si precipitated phase with an average equivalent diameter of 0.29-1.71 mu m in the grain of the coiling annealing plate is greater than or equal to 50000 / mm2 2 ; (5) performing cold rolling on the coiling annealing plate, and the total deformation of the cold rolling is 60-90%; (6) solid solution treatment; (7) performing pre-aging treatment, and then air cooling to obtain the 6000 series aluminum alloy plate. In addition, the application further discloses a 6000 series aluminum alloy plate prepared by the above manufacturing method.

Description

Technical Field

[0001] This invention relates to an aluminum alloy sheet and its manufacturing method, and more particularly to a 6000 series aluminum alloy sheet and its manufacturing method. Background Technology

[0002] In recent years, with the rapid development of the automotive industry, while automobile production and ownership have been increasing, energy consumption and environmental degradation have also increased to some extent. Therefore, in order to improve fuel efficiency and reduce environmental pollution, lightweighting of automobiles, which aims to improve fuel efficiency and reduce exhaust emissions, has become a key technology in the development plans of automakers.

[0003] As is well known, 6000 series aluminum alloys have the characteristics of high strength and good corrosion resistance. 6000 series aluminum alloys still have good surface quality after baking and their performance is improved after baking. They are currently a key material for lightweighting automobiles.

[0004] However, compared with traditional automotive steel, 6000 series aluminum alloy sheets have poorer formability, especially in terms of plastic strain ratio (r), which is much lower than that of traditional automotive steel. This disadvantage limits the application of 6000 series aluminum alloy sheets in automobiles. The plastic strain ratio (r), as an important indicator of sheet metal formability, is mainly affected by the texture of the alloy. Texture is influenced by the alloy preparation and processing procedures and heat treatment conditions. Studies have shown that weakening the texture and introducing γ-oriented lines can both improve the plastic strain ratio (r) value.

[0005] Since automotive sheet metal is supplied in T4P state (a state of heat treatment of aluminum alloy) before stamping, and T4P state aluminum alloy sheet metal is mainly composed of cube recrystallization texture, and cube texture usually leads to a lower r value, weakening the cube recrystallization texture of T4P state aluminum alloy sheet metal is beneficial to improving the forming performance of 6000 series aluminum alloy sheet metal.

[0006] In order to improve the formability of 6000 series aluminum alloy sheets, some researchers have conducted relevant research on aluminum alloy sheets and achieved certain results.

[0007] For example, Chinese patent document CN108048702A, published on May 18, 2018, entitled "A Preparation Method of Automotive Aluminum Alloy Sheet with Both High Strength and High Formability," discloses a method for preparing automotive aluminum alloy sheet with both high strength and high formability. This method employs a process flow of casting → two-stage homogenization heat treatment → hot rolling → cold rolling → intermediate annealing → secondary cold rolling → solution quenching heat treatment → pre-aging heat treatment, resulting in sheet material with excellent stamping formability. However, the disadvantage of this technical solution is the addition of an intermediate annealing process, which leads to high production costs and a long production cycle.

[0008] For example, Chinese patent document CN105074028B, published on June 6, 2017, entitled "Aluminum Alloy Sheet with Excellent Properties After Room Temperature Aging," discloses an aluminum alloy sheet with excellent properties after room temperature aging. It employs a process of casting → homogenization heat treatment → hot rolling → intermediate annealing → cold rolling → solution pre-aging. By adding an appropriate amount of Sn element to the chemical composition, the prepared material exhibits excellent formability. However, the drawback of this technical solution is the addition of the alloying element Sn, which increases the production cost of the aluminum alloy sheet.

[0009] Therefore, the existing improvement schemes still have some shortcomings. To address this, the inventors sought a new method for manufacturing 6000 series aluminum alloy sheets with improved formability. Through extensive research, the inventors discovered that second-phase particles significantly influence the recrystallization texture of 6000 series aluminum alloys. When coarse second-phase particles precipitate in the alloy, these particles stimulate particle-stimulated nucleation (PSN), thus promoting recrystallization. Generally, the PSN effect results in a predominantly random texture composition after recrystallization, reducing texture strength.

[0010] Based on this, in order to overcome the technical problem of insufficient formability of existing 6000 series aluminum alloy sheets, and under the premise of ensuring process rationality, this invention aims to obtain a new manufacturing method for 6000 series aluminum alloy sheets that improves formability. This manufacturing method promotes the precipitation of a large number of coarse Mg2Si particles and their size in the hot-rolled sheet by controlling the homogenization, hot rolling, and coiling process parameters during processing; and promotes particle-induced recrystallization nucleation (PSN) during the solution treatment process by controlling the cold rolling deformation amount and solution treatment process parameters, thereby weakening the recrystallization cube texture content and thus improving the formability of the aluminum alloy sheet. Summary of the Invention

[0011] One of the objectives of this invention is to provide a novel method for manufacturing 6000 series aluminum alloy sheets with improved formability. This method employs a rational process design, which involves coiling the sheet after hot rolling and adjusting appropriate process parameters to promote the precipitation of coarse Mg2Si particles within the hot-rolled sheet. This, in turn, stimulates the recrystallization nucleation (PSN) effect during subsequent solution pre-aging treatment, weakens the cube recrystallization texture content, and thus significantly improves the formability of the final aluminum alloy sheet.

[0012] To achieve the above objectives, this invention proposes a method for manufacturing 6000 series aluminum alloy sheets with improved formability, comprising the following steps:

[0013] (1) The ingot is homogenized at a temperature of 530-580℃.

[0014] (2) The ingot after homogenization treatment is directly subjected to hot rough rolling, and the total deformation of hot rough rolling is greater than 70%.

[0015] (3) Hot finishing rolling is performed on the hot rough rolled plate. The initial rolling temperature of hot finishing rolling is controlled at 450-550℃, the final rolling temperature is controlled at 320-420℃, and the total deformation of hot finishing rolling is greater than 80%.

[0016] (4) The hot-rolled sheet is subjected to coiling annealing, with the coiling annealing temperature controlled at 320-420℃ and the holding time at 0.5-3h, followed by furnace cooling to room temperature; the areal density of Mg2Si precipitates with an average equivalent diameter of 0.29-1.71μm in the grains of the coiled annealed sheet is ≥50,000 precipitates / mm. 2 ;

[0017] (5) Cold rolling is performed on the coiled annealed sheet, and the total deformation during cold rolling is 60-90%;

[0018] (6) Solution treatment of cold-rolled sheet material;

[0019] (7) Perform pre-aging treatment, followed by air cooling, to obtain 6000 series aluminum alloy sheet.

[0020] In this invention, the inventors discovered through extensive research that second-phase particles have a significant impact on the recrystallization texture of 6000 series aluminum alloy sheets. When coarse second-phase particles precipitate in the aluminum alloy sheet, these particles can stimulate recrystallization nucleation (PSN), thereby promoting recrystallization. Generally, the PSN effect will result in the recrystallized texture components being dominated by random texture, thus reducing the texture strength.

[0021] Non-equilibrium eutectic phases in as-cast 6000 series aluminum alloys can easily lead to compositional or microstructural inhomogeneity, resulting in poor hot deformation plasticity and thus limiting the forming and processing performance of 6000 series aluminum alloys to some extent. Further research indicates that dissolving most of the Mg2Si during homogenization is necessary above 530°C. To improve the hot working properties of 6000 series aluminum alloys and eliminate the influence of non-equilibrium eutectic phases, homogenization heat treatment at temperatures exceeding 530°C is required. Therefore, in this invention, the homogenization treatment temperature is controlled between 530 and 580°C.

[0022] Hot roughing rolling is an intermediate step between homogenization heat treatment and hot finishing rolling. Its function is to process the heated slab into an intermediate slab that meets the conditions for finishing rolling by rolling it through a roughing mill. Secondly, the hot roughing rolling process can also reduce or eliminate casting defects.

[0023] Because the precipitation temperature range for the Mg2Si phase is passed very slowly during conventional hot finishing rolling, coarse Mg2Si particles are formed after hot finishing. Literature indicates that the precipitation temperature range for the Mg2Si phase is 330℃~390℃. Therefore, to promote the precipitation of a large number of coarse Mg2Si particles in the hot-finished sheet, the final rolling temperature of the hot finishing process should be within the range of 320~420℃, and the hot-finished sheet should be coiled and annealed at the final rolling temperature.

[0024] Therefore, in the above-mentioned technical solution of the present invention, the manufacturing method of 6000 series aluminum alloy sheet of the present invention adopts a reasonable process design. It performs homogenization heat treatment on the ingot at a reasonable temperature and for a reasonable time to dissolve the non-equilibrium eutectic phase in the ingot. Then, the homogenized ingot is directly subjected to hot rough rolling to eliminate or reduce casting defects and process into an intermediate billet that meets the conditions for hot fine rolling. Then, the starting rolling temperature and the finishing rolling temperature of the hot fine rolling process, as well as the subsequent coiling annealing temperature, are controlled to obtain a coiled annealed sheet with a large number of coarse Mg2Si particles. Thus, before subsequent delivery, the amount of cold rolling deformation and the solution treatment process parameters are controlled to promote the particle-induced recrystallization nucleation effect in the solution process, weaken the Cube recrystallization texture content, and thus significantly improve the forming performance of the finally obtained T4P state aluminum alloy sheet.

[0025] In summary, the manufacturing method designed in this invention effectively controls the quantity and distribution of coarse second phases inside the aluminum alloy, thereby controlling the texture of the final T4P state 6000 series aluminum alloy sheet and significantly improving the forming performance of the 6000 series aluminum alloy sheet.

[0026] Furthermore, in the manufacturing method of 6000 series aluminum alloy sheet of the present invention, in step (1), the heat preservation time of the homogenization treatment is 6 to 24 hours.

[0027] Furthermore, in the manufacturing method of 6000 series aluminum alloy sheet of the present invention, in step (1), the heat preservation time of the homogenization treatment is 8 to 12 hours.

[0028] Furthermore, in the manufacturing method of 6000 series aluminum alloy sheet of the present invention, in step (1), the homogenization treatment temperature is 540-570°C.

[0029] Furthermore, in the manufacturing method of 6000 series aluminum alloy sheet described in this invention, in step (3), the initial rolling temperature of hot finishing rolling is 450-520°C, and the final rolling temperature is 330-390°C.

[0030] Furthermore, in the method for manufacturing 6000 series aluminum alloy sheets according to the present invention, in step (4), the temperature of the coiling annealing is 330 to 390°C.

[0031] Furthermore, in the manufacturing method of 6000 series aluminum alloy sheet described in this invention, in step (5), the total cold rolling deformation is controlled to be 70-80%.

[0032] Furthermore, in the manufacturing method of 6000 series aluminum alloy sheet described in this invention, in step (6), the solution treatment temperature is 540-570°C, the solution treatment time is 1-5 min, and the quenching method is water cooling.

[0033] Furthermore, in the manufacturing method of 6000 series aluminum alloy sheet described in this invention, in step (7), the pre-aging treatment is to slowly reduce the temperature from 100 to 120°C to room temperature at a rate of 1 to 4°C / h.

[0034] Furthermore, in the method for manufacturing 6000 series aluminum alloy sheet according to the present invention, the thickness of the hot-rolled sheet is 25-60 mm.

[0035] Furthermore, in the method for manufacturing 6000 series aluminum alloy sheet according to the present invention, the thickness of the hot-rolled sheet is 30-45 mm.

[0036] Accordingly, another objective of the present invention is to provide a 6000 series aluminum alloy sheet that is easy to produce and has low production costs. It has high formability and can be effectively applied in the vehicle manufacturing industry to meet the requirements of vehicle lightweighting, and has a very broad application prospect.

[0037] To achieve the above objectives, the present invention proposes a 6000 series aluminum alloy sheet, which is manufactured using the 6000 series aluminum alloy sheet manufacturing method described above.

[0038] Furthermore, in the 6000 series aluminum alloy sheet described in this invention, its performance meets the following requirements:

[0039] Tensile strength ≥275MPa, yield strength ≥173MPa, elongation ≥21.7%;

[0040] The plastic strain ratios r0, r45, and r90 in the three directions with angles of 0°, 45°, and 90° to the rolling direction of the sheet metal respectively satisfy r0 ≥ 0.61, r 45 ≥0.38, r90 ≥0.62.

[0041] Compared with the prior art, the method for manufacturing 6000 series aluminum alloy sheets with improved formability described in this invention has the following advantages and beneficial effects:

[0042] (1) The 6000 series aluminum alloy sheet manufacturing method of the present invention can obtain a low cube recrystallization texture through homogenization, hot rough rolling and hot fine rolling processes, thereby reducing the density of cube recrystallization texture in subsequent processes and improving the formability of the sheet.

[0043] (2) The method for manufacturing 6000 series aluminum alloy sheet described in this invention promotes the precipitation of coarse Mg2Si particles in the sheet after coiling annealing by adjusting the homogenization, hot rolling and coiling process parameters during the processing; by adjusting the cold rolling deformation amount and solution treatment process parameters, the PSN mechanism recrystallization nucleation is fully utilized, thereby reducing the Cube recrystallization texture density in the final 6000 series aluminum alloy sheet, and thus significantly improving the formability of the aluminum alloy sheet.

[0044] (3) The manufacturing method of 6000 series aluminum alloy sheet described in this invention is simple and can be optimized by adjusting the parameters on the basis of existing aluminum alloy heat treatment production line. It has a wide range of applications and can meet the needs of industrial production.

[0045] (4) The manufacturing method of 6000 series aluminum alloy sheet described in this invention can quantify the microstructure of 6000 series aluminum alloy sheet. The resulting 6000 series aluminum alloy sheet has high formability and can be effectively applied in the vehicle manufacturing industry to meet the requirements of vehicle lightweighting. It has a very broad application prospect. Attached Figure Description

[0046] Figure 1 The diagram schematically illustrates the process flow of the manufacturing method for 6000 series aluminum alloy sheets according to the present invention.

[0047] Figure 2 The image shows the SEM microstructure of the 6000 series aluminum alloy sheet in the coiled annealed state in Example 2.

[0048] Figure 3 The SEM microstructure of the aluminum alloy sheet in the coiled annealed state is shown in Comparative Example 1.

[0049] Figure 4 The image shows the ODF (Orientation Distribution Function) of the T4P state texture of the finished 6000 series aluminum alloy sheet from Example 2.

[0050] Figure 5The ODF (Orientation Distribution Function) diagram of the T4P state texture of the finished aluminum alloy sheet used in Comparative Example 1 is shown. Detailed Implementation

[0051] The following will further explain and illustrate the method for manufacturing 6000 series aluminum alloy sheets with improved formability according to the present invention, in conjunction with specific embodiments and accompanying drawings. However, this explanation and illustration do not constitute an undue limitation on the technical solution of the present invention.

[0052] Examples 1-6 and Comparative Example 1

[0053] In this invention, the chemical composition of the 6000 series aluminum alloy sheets of Examples 1-6 and the comparative aluminum alloy of Comparative Example 1 is shown in Table 1 below.

[0054] Table 1 lists the chemical compositions of the 6000 series aluminum alloy sheets of Examples 1-6 and the comparative aluminum alloy of Comparative Example 1.

[0055] Table 1. (wt.%, balance is Al and other unavoidable impurities)

[0056]

[0057] In this invention, the 6000 series aluminum alloy sheets of Examples 1-6 and the comparative aluminum alloy of Comparative Example 1 all require smelting and casting operations. The aluminum alloys of Examples 1-6 and Comparative Example 1 are smelted and cast according to the chemical element composition of steel grade A in Table 1. After smelting and casting, aluminum alloy ingots of Examples 1-6 and Comparative Example 1 are obtained. After trimming the ends and milling the surfaces, the aluminum alloy ingots undergo homogenization treatment. Immediately after homogenization, they are hot-rolled into rough blanks, then directly cooled to room temperature by spray water quenching. The hot-rolled sheets are then hot-finished. After hot-finishing, they are directly transferred to a holding furnace for coiling annealing, then the power is turned off and the furnace is cooled to room temperature. After coiling, they are cold-rolled to a final finished sheet thickness of 1 mm. The resulting cold-rolled sheet is solution-quenched and then pre-aged to obtain the finished T4P state aluminum alloy sheets of each example and comparative example.

[0058] The 6000 series aluminum alloy sheets in Examples 1-6 and the comparative aluminum alloy in Comparative Example 1 were all prepared using the following steps:

[0059] (1) Prepare aluminum alloy ingots by mixing the ingredients according to the chemical composition shown in Table 1, melting them in a smelting furnace and casting them.

[0060] (2) Homogenization treatment: The 180mm thick aluminum alloy ingot is heated in a homogenization heat treatment furnace and heated to 530-580℃ at a heating rate of 20-50℃ / h, preferably controlled to 540-570℃ for homogenization heat treatment; and the holding time for homogenization treatment is controlled to be 6-24h, preferably controlled to be 8-12h; after the sample is heated, it is directly subjected to hot rough rolling.

[0061] (3) Hot rough rolling: The ingot after homogenization treatment is directly subjected to hot rough rolling. The total deformation of hot rough rolling is controlled to be greater than 70%. The thickness of the plate after hot rough rolling is 40mm.

[0062] (4) Hot finishing rolling: Hot finishing rolling is performed on the hot rough rolled plate. The initial rolling temperature of hot finishing rolling is controlled at 450-550℃, preferably between 450-520℃; the final rolling temperature of hot finishing rolling is controlled at 320-420℃, preferably between 330-390℃; the total deformation of hot finishing rolling is controlled to be greater than 80%, and the plate thickness is 5mm after rolling.

[0063] (5) The hot-rolled sheet is coiled and annealed, and the coiling and annealing temperature is controlled at 320-420℃, preferably 330-390℃, and the holding time is 0.5-3h. Then it is cooled to room temperature in the furnace.

[0064] (6) Cold rolling: The coiled annealed sheet is cold rolled, and the total deformation of cold rolling is controlled to be 60-90%, preferably 70-80%, and a 1mm thick cold-rolled sheet is obtained after cold rolling.

[0065] (7) Solution quenching treatment: The cold-rolled sheet is subjected to solution treatment, the solution treatment temperature is controlled at 540-570℃, the solution treatment time is controlled at 1-5min, and then water cooling is used.

[0066] (8) Pre-aging treatment: Pre-aging treatment is carried out by slowly cooling from 100 to 120°C to room temperature at a rate of 1 to 4°C / h.

[0067] It should be noted that in the above technical solutions, the thickness of the aluminum alloy sheets in Examples 1-6 and Comparative Example 1 after hot rough rolling is controlled to be 40 mm. Of course, in some other embodiments, the thickness of the hot rough rolled sheet can be controlled between 25 and 60 mm, and preferably between 30 and 45 mm.

[0068] In this invention, the manufacturing processes of the 6000 series aluminum alloy sheets in Examples 1-6 all meet the design specifications of this invention. However, the preparation scheme of the comparative aluminum alloy in Comparative Example 1 does not conform to the design specifications of this invention.

[0069] Accordingly, unlike the preparation processes used in Examples 1-6 above, the hot finishing rolling start temperature, hot finishing rolling finish temperature, and coiling annealing temperature of the comparative aluminum alloy in Comparative Example 1 described in this invention are not within the design specifications of this invention.

[0070] Tables 2-1 and 2-2 list the specific process parameters of the 6-series aluminum alloy plates for semiconductor devices in Examples 1-6 and the comparative aluminum alloy plates in Comparative Examples 1-2 in the above process steps.

[0071] Table 2-1.

[0072]

[0073] Table 2-2.

[0074]

[0075] It should be noted that, in order to observe the size and distribution of the second phase (Mg2Si precipitate) in the longitudinal section of the aluminum alloy plates of each embodiment and comparative example, samples can be taken from the coiled annealed plates of Examples 1-6 and Comparative Example 1, and then the coiled annealed plates can be analyzed.

[0076] In this invention, a 12mm (rolling direction) × 10mm (transverse direction) cube can be cut from the 5mm thick rolled annealed sheet sample corresponding to each embodiment and comparative example. The longitudinal section of the sheet is ground by coarse grinding with 320-grit, 800-grit, and 1500-grit wet sandpaper in sequence; then fine grinding is performed with 800-grit metallographic sandpaper; finally, the longitudinal section of the sheet is polished with a polishing cloth. Afterwards, the size and distribution of the second phase (Mg2Si precipitate) in the longitudinal section of the aluminum alloy sheet are observed using a Sirion 200 field emission scanning electron microscope. The relevant observation and analysis results are listed in Table 3 below.

[0077] Table 3 lists the average equivalent diameter and areal density of the Mg2Si precipitates in the coiled annealed plates of Examples 1-6 and the coiled annealed plate of Comparative Example 1.

[0078] Table 3.

[0079]

[0080] As shown in Table 3, the areal density of the Mg2Si precipitates in the coiled annealed plates of Examples 1-6 ranges from 52610 to 67195 precipitates / mm². 2 Between these, the areal density of the Mg2Si precipitate in the coiled annealed sheet of Examples 1-6 is much greater than the areal density of the Mg2Si precipitate in the coiled annealed sheet of Comparative Example 1.

[0081] In the above embodiments of the present invention, the analysis focuses on the size and distribution of the second phase (Mg2Si precipitate) in the coiled annealed sheet of each embodiment and comparative example, rather than the final finished sheet. This is because the recrystallization process occurs during the solution treatment of the cold-rolled sheet, so observing the influence of the second phase on the recrystallization process and its microstructure requires observing the second phase of the cold-rolled sheet. Since the second phase of the coiled annealed sheet does not change significantly during cold rolling, analyzing the second phase of the coiled annealed sheet can be used to explain the influence of the second phase on the recrystallization process and its microstructure.

[0082] Accordingly, samples were taken from the finished 6000 series aluminum alloy sheets of Examples 1-6 and the finished comparative aluminum alloy sheet of Comparative Example 1, and the macroscopic texture of the finished aluminum alloy sheets of each example and comparative example was tested.

[0083] The preparation and detection methods for XRD macrotexture analysis samples are described below:

[0084] 15mm (rolling direction) × 10mm (transverse direction) cubes were cut from 1mm thick finished T4P state aluminum alloy sheet samples corresponding to the embodiments and comparative examples, with the test surface being the flat surface of the sheet. The samples needed to be polished with wet sandpaper and metallographic sandpaper until the test surface was close to the center of the sheet thickness. Afterwards, they were immersed in a 30% NaOH aqueous solution for 8–15 minutes, then immersed in a 10% HNO3 aqueous solution for 5 seconds. The samples were then rinsed with water and dried. Macroscopic texture testing was performed on a Bruker D8 Discover X-ray diffractometer under the following conditions: tube voltage of 40kV, tube current of 40mA, CuKα radiation, and Ni filtering. The three incomplete pole figures {111}, {200}, and {220} of pure aluminum powder and each sample were determined by the Shulz reflection method, with the corresponding background values ​​for peak center deviations of Δθ = ±1.4°. Background correction and defocus correction were performed using Mtex-4.1.4, and the orientation distribution function (ODF) was calculated.

[0085] The above process details the sample preparation procedure, testing conditions, and analysis software and methods for T4P state XRD macrotexture testing. This process was used to observe the macrotexture of the finished sheets from Examples 1-6 and Comparative Example 1, and to analyze the impact of texture on performance. The results are as follows. Figure 4 and Figure 5 As shown.

[0086] In addition, to further illustrate the mechanical properties of the 6000 series aluminum alloy sheet described in this invention, the finished 6000 series aluminum alloy sheets of Examples 1-6 and the finished comparative aluminum alloy sheet of Comparative Example 1 were sampled again, and the mechanical properties of the finished aluminum alloy sheets of each example and comparative example were tested. The relevant mechanical property test results are listed in Table 4 below.

[0087] The relevant mechanical property testing methods are as follows:

[0088] The 1mm thick finished T4P state aluminum alloy sheet samples corresponding to each embodiment and comparative example were subjected to room temperature tensile property tests after natural aging at room temperature for 7 days. The room temperature tensile tests were conducted according to ASTM E8 / E8M-16a requirements. The room temperature tensile specimens were cut from the finished T4P state aluminum alloy sheet samples at angles of 0°, 45°, and 90° to the rolling direction of the sheet, respectively, to obtain the plastic strain ratios r0 and r in these three directions. 45 r 90 The room temperature tensile test was conducted on an MTS810 tensile testing machine, with the tensile rate controlled at 2 mm / min. Accordingly, the plastic strain ratio r value was determined according to GB / T 5027-2007 standard.

[0089] Table 4 lists the mechanical property test results of the finished 6000 series aluminum alloy sheets of Examples 1-6 and the finished comparative aluminum alloy sheet of Comparative Example 1.

[0090] Table 4.

[0091]

[0092] As shown in Table 4, the formability of the 6000 series aluminum alloy sheets of Examples 1-6 and the comparative aluminum alloy sheet of Comparative Example 1 was evaluated by the r-value and elongation of the aluminum alloy sheets of Examples 1-6 and Comparative Example 1.

[0093] Referring to Table 4, it can be seen that the tensile strength of the finished 6000 series aluminum alloy sheets in Examples 1-6 is between 275-283 MPa, the yield strength is between 173-182 MPa, and the elongation is between 21.7-23.6%; r0≥0.61, r 45 ≥0.38, r 90 ≥0.62.

[0094] As can be seen from the mechanical property data in Table 4, compared with the comparative aluminum alloy sheet of Comparative Example 1, the 6000 series aluminum alloy sheets of Examples 1-6 of the present invention have significantly larger r values ​​and improved elongation. The forming performance of the aluminum alloy sheets can be significantly improved, which can meet the basic performance requirements of automobile body panels.

[0095] Figure 1 The diagram schematically illustrates the process flow of the manufacturing method for 6000 series aluminum alloy sheets according to the present invention.

[0096] like Figure 1 As shown, in this invention, after the aluminum alloy sheet is melted and cast according to the designed chemical element composition, a corresponding aluminum alloy ingot can be obtained. After the ingot is trimmed and milled, it undergoes homogenization treatment. Immediately after homogenization, it is hot-rolled into a rough blank, then directly cooled to room temperature by spray water quenching, and then hot-finished. After hot-finishing, the sheet is directly transferred to a holding furnace for coiling annealing, and then the power can be turned off and the furnace cooled to room temperature. After coiling annealing, it can be further cold-rolled to the final finished sheet thickness. The resulting cold-rolled sheet is solution-quenched and then pre-aged to obtain the finished aluminum alloy sheet.

[0097] Figure 2 The image shows the SEM microstructure of the 6000 series aluminum alloy sheet in the coiled annealed state in Example 2.

[0098] Figure 3 The SEM microstructure of the aluminum alloy sheet in the coiled annealed state is shown in Comparative Example 1.

[0099] Combination Figure 2 and Figure 3 It can be seen that after coiling annealing, a large number of coarse Mg2Si particles (black spherical particles) precipitate in the coiled annealed aluminum alloy sheet of Example 2 of the present invention, wherein the areal density of the coarse Mg2Si particles is approximately 58862 particles / mm². 2 The average equivalent diameter is 0.50 μm.

[0100] In Comparative Example 1, only trace amounts of coarse Mg2Si particles (black spherical particles) precipitated in the coiled annealed aluminum alloy sheet, with an areal density of approximately 2605 particles / mm². 2 The average equivalent diameter is 0.39 μm. Therefore, compared to Comparative Example 1, Example 2, by appropriately increasing the initial and final rolling temperatures during hot finishing, and by appropriately increasing the coiling temperature during coiling annealing, can effectively promote the precipitation of coarse Mg2Si particles.

[0101] Figure 4 The image shows the ODF (Orientation Distribution Function) of the T4P state texture of the finished 6000 series aluminum alloy sheet from Example 2.

[0102] Figure 5 The ODF (Orientation Distribution Function) diagram of the T4P state texture of the finished aluminum alloy sheet used in Comparative Example 1 is shown.

[0103] Combination Figure 4 and Figure 5 It can be seen that the finished T4P state aluminum alloy sheets of Example 2 and Comparative Example 1 of the present invention are mainly composed of Cube recrystallization texture. The Cube recrystallization texture density of the finished T4P state 6000 series aluminum alloy sheet of Example 2 is 7.7, and the Cube recrystallization texture density of the finished T4P state comparative aluminum alloy sheet of Comparative Example 1 is 14.

[0104] As can be seen, compared with Comparative Example 1, after the preceding hot rolling and coiling annealing processes, the coarse Mg2Si particles precipitated in the plate of Example 2 stimulate recrystallization nucleation (PSN) during the subsequent solid solution pre-aging process, thereby reducing the cube recrystallization texture density and improving the alloy's formability.

[0105] In summary, it can be seen that the method for manufacturing 6000 series aluminum alloy sheets with improved formability described in this invention, through reasonable hot rolling and coiling annealing process design, controls the texture composition of the finished 6000 series aluminum alloy sheets, and significantly improves the formability of 6000 series aluminum alloy sheets.

[0106] It should be noted that the combination of the technical features in this case is not limited to the combination methods described in the claims of this case or the combination methods described in the specific embodiments. All technical features described in this case can be freely combined or combined in any way, unless they contradict each other.

[0107] It should also be noted that the embodiments listed above are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and similar changes or modifications made thereto are those that can be directly derived or easily conceived by those skilled in the art from the content disclosed in the present invention, and should all fall within the protection scope of the present invention.

Claims

1. A method of manufacturing a 6000-series aluminum alloy sheet having improved formability, characterized by, The method comprises the steps of: (1) homogenizing the ingot at a temperature of 530-580℃; (2) directly hot rough rolling the homogenized ingot, with a total deformation of more than 70%; (3) hot finish rolling the hot rough rolled plate, with a starting rolling temperature of 450-550℃, a final rolling temperature of 320-420℃, and a total deformation of more than 80%; (4) coiling and annealing the hot-rolled plate, controlling the coiling and annealing temperature to be 320-420°C, the holding time to be 0.5-3h, and then cooling to room temperature in the furnace; the surface density of Mg2Si precipitated phase with an average equivalent diameter of 0.29-1.71μm in the grain of the coiling and annealed plate being ≥50000 / mm2 2 ; (5) cold rolling the coiling annealed plate, with a total deformation of 60-90%; (6) solid solution treating the cold rolled plate; (7) pre-aging, followed by air cooling, to obtain the 6000 series aluminum alloy plate.

2. The 6000-series aluminum alloy sheet manufacturing method according to claim 1, characterized in that, In step (1), the holding time of the homogenization treatment is 6-24h.

3. The 6000-series aluminum alloy sheet manufacturing method according to claim 2, characterized in that, In step (1), the holding time of the homogenization treatment is 8-12h.

4. The 6000-series aluminum alloy sheet manufacturing method according to claim 1, characterized in that, In step (1), the temperature of the homogenization treatment is 540-570℃.

5. The 6000-series aluminum alloy sheet manufacturing method according to claim 1, wherein In step (3), the starting rolling temperature of the hot finish rolling is 450-520℃, and the final rolling temperature is 330-390℃.

6. The 6000-series aluminum alloy sheet manufacturing method according to claim 1, wherein In step (4), the coiling annealing temperature is 330-390℃.

7. The 6000-series aluminum alloy sheet manufacturing method according to claim 1, wherein In step (5), the total deformation of the cold rolling is controlled to be 70-80%.

8. The 6000-series aluminum alloy sheet manufacturing method according to claim 1, wherein In step (6), the solid solution treatment temperature is 540-570℃, the solid solution treatment time is 1-5min, and the quenching mode is water cooling.

9. The 6000-series aluminum alloy sheet manufacturing method according to claim 1, wherein In step (7), the pre-aging treatment is slowly decreasing from 100-120℃ to room temperature, with a cooling rate of 1-4℃ / h.

10. The 6000-series aluminum alloy sheet manufacturing method according to claim 1, wherein The thickness of the hot rough rolled plate is 25-60mm.

11. The 6000-series aluminum alloy sheet manufacturing method according to claim 10, wherein The thickness of the hot rough rolled plate is 30-45mm.

12. A 6000 series aluminum alloy plate prepared by the method of any one of claims 1-11.

13. The 6000-series aluminum alloy sheet of claim 12, wherein The performance satisfies: tensile strength ≥275MPa, yield strength ≥173MPa, and elongation ≥21.7%; The plastic strain ratios r0, r45, and r90 in three directions with the included angle of 0°, 45°, and 90° with the rolling direction of the plate respectively satisfy r0≥0.61, r 45 ≥0.38, and r 90 ≥0.62.

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