WO2024051750A1 - 一种6000系铝合金板材制造方法及铝合金板材 - Google Patents

一种6000系铝合金板材制造方法及铝合金板材 Download PDF

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WO2024051750A1
WO2024051750A1 PCT/CN2023/117302 CN2023117302W WO2024051750A1 WO 2024051750 A1 WO2024051750 A1 WO 2024051750A1 CN 2023117302 W CN2023117302 W CN 2023117302W WO 2024051750 A1 WO2024051750 A1 WO 2024051750A1
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aluminum alloy
series aluminum
alloy plate
rolling
temperature
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PCT/CN2023/117302
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English (en)
French (fr)
Inventor
曹零勇
曹高辉
苑锡妮
杨晓琨
张文
杨兵
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宝山钢铁股份有限公司
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Publication of WO2024051750A1 publication Critical patent/WO2024051750A1/zh

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B3/00—Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences ; Rolling of aluminium, copper, zinc or other non-ferrous metals
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
    • C22F1/043—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon of alloys with silicon as the next major constituent
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
    • C22F1/05—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon of alloys of the Al-Si-Mg type, i.e. containing silicon and magnesium in approximately equal proportions

Definitions

  • the invention relates to an aluminum alloy plate and a manufacturing method thereof, in particular to a 6000 series aluminum alloy plate and a manufacturing method.
  • the 6000 series aluminum alloy has the advantages of high strength, good corrosion resistance, good surface quality after baking, and improved strength after baking. This series of alloys is increasingly used in the manufacture of exterior body panels.
  • the surface quality of 6000 series aluminum alloy automotive panels is as important as its mechanical properties. It is related to whether the appearance of the car is ideal after painting.
  • the weave defect is one of the factors that affects the surface quality of aluminum alloy automotive panels.
  • the publication number is CN101935785B, and the Chinese patent document titled "A highly formable aluminum alloy for automobile body panels” discloses an aluminum alloy with excellent formability that is obtained by adjusting the content and ratio of the main elements Si, Mg, and Cu. 6000 series aluminum alloy for automobile body panels.
  • the excellent formability described in this patent only focuses on yield strength, plasticity and work hardening rate, and does not pay attention to the r value, flanging performance and riveting performance that are closely related to the forming of automobile body panels.
  • the publication number is CN105074028B, and the publication date is June 6, 2017.
  • the Chinese patent document titled "Aluminum Alloy Plate with Excellent Characteristics after Room Temperature Aging” discloses a method that adds an appropriate amount of Sn element to the chemical composition.
  • An aluminum alloy whose properties are still excellent after aging at room temperature and a method for manufacturing the same, and the material prepared by it has excellent formability.
  • This patent achieves good technical effects by adding the alloy element Sn, but the patent does not focus on how to improve the flanging performance of the plate.
  • 6000 series aluminum alloy sheets have more or less problems such as poor flanging performance and obvious weave defects on the surface after stamping, which have affected the large-scale promotion and application of 6000 series automotive sheets.
  • One of the purposes of the present invention is to provide a manufacturing method for a 6000 series aluminum alloy plate that has high formability, high flanging performance and low ripple defects.
  • the manufacturing method of the 6000 series aluminum alloy plate adopts a reasonable process design. , through soaking, hot rolling, coiling, optional intermediate annealing and cold rolling processes, an alloy plate with a certain number and proportion of second phases and grain size can be obtained, and then in the subsequent solid solution pre-aging treatment process.
  • the medium-stimulated recrystallization nucleation (PSN) effect weakens the recrystallization texture content, especially the content of cubic texture components and Gaussian texture components, thereby significantly improving the formability and flanging performance of the final aluminum alloy sheet. , and improve the weave defects of aluminum alloy plates.
  • the present invention proposes a manufacturing method of 6000 series aluminum alloy plates with high formability, high flanging performance and low ripple defects, which includes the steps:
  • coarse second phase particles precipitate in the alloy, the coarse second phase will stimulate the recrystallization form.
  • Nucleation Particle Stimulated Nucleation
  • the content of structural components can be reduced, thereby reducing the degree of aggregation of the two and reducing the degree of ripple defects.
  • the inventor also found through research that the grain size decreases as the cold rolling reduction rate increases.
  • the manufacturing method of the present invention adopts controlled processing while ensuring the rationality of the process.
  • the soaking, hot rolling, coiling, and optional intermediate annealing process parameters during the process control the size and quantity of the coarse Mg 2 Si phase in the 6000 series aluminum alloy plate, giving full play to the particles of the coarse Mg 2 Si phase in the subsequent solid solution process.
  • the texture and grain size can also be further controlled by adjusting the cold rolling reduction rate and the cold rolling reduction rate in the subsequent cold rolling process, in order to weaken and control the recrystallization texture type, proportion, spatial distribution, and refine the grain size.
  • the purpose is to obtain 6000 series aluminum alloy sheets for automobile bodies with high formability, high flanging performance and low ribbing defects.
  • the non-equilibrium eutectic phase in the cast 6000 series aluminum alloy can easily lead to uneven composition or structure, which can lead to problems such as poor subsequent thermal deformation plasticity, which to a certain extent restricts the forming performance of the 6000 series aluminum alloy. . Therefore, this technical solution controls the soaking temperature during the homogenization process to exceed 530°C to ensure that most too coarse Mg 2 Si is dissolved. It also aims to improve the hot processing performance of the 6000 series aluminum alloy and eliminate non-equilibrium eutectic in the alloy. phase influence.
  • the inventor found through research that in this technical solution, if the hot finish rolling opening temperature is controlled to 400-480°C, the size of the second phase (i.e., Mg 2 Si precipitated phase) in the cold-rolled sheet can be controlled to be 1.3-480°C. 1.7 ⁇ m, the area density of the second phase is more than 55,000 pieces/mm; if the hot finish rolling opening temperature is too high, the size of the precipitated second phase will be too large and the number will be small; if the hot finish rolling opening temperature is too low, The size of the precipitated second phase is too small.
  • the present invention controls the cold rolling reduction rate to be 50% to 85%.
  • the non-equilibrium eutectic phase in the ingot is dissolved by soaking the ingot at a reasonable temperature and time, and then the homogenized ingot is directly subjected to hot rough rolling. , eliminate or reduce casting defects and process it into an intermediate billet that meets the hot finish rolling conditions, and then control the hot finish rolling, intermediate annealing and cold rolling processes to obtain a cold-rolled plate with a large number of coarse second phases and fine grains, and then deliver it later.
  • the recrystallization texture content is weakened through the PSN mechanism excited by the coarse second phase; on the other hand, the finished sheet with fine grains is obtained by regulating the cold rolling reduction rate, and then Obtain a 6000 aluminum alloy sheet with high formability, high flanging properties and low ribbing defects.
  • the manufacturing method of the present invention effectively regulates the quantity, distribution and grain size of the coarse second phase inside the aluminum alloy through specific process coordination, thereby regulating the texture of the final product T4P 6000 series aluminum alloy sheet. Structure and organization, and significantly improved the formability, flanging performance and weave defects of 6000 series aluminum alloy sheets.
  • the hot final rolling coiling temperature is controlled to be 250-350°C.
  • intermediate annealing is performed before cold rolling in step (3): the temperature of the intermediate annealing is controlled to 350 ⁇ 430°C, the holding time is 1 ⁇ 4h, and then The furnace is cooled to room temperature; when the hot final rolling coiling temperature is higher than 340°C, step (3) is performed directly without intermediate annealing.
  • intermediate annealing can be added between the hot rolling and cold rolling processes.
  • the deformation resistance can be reduced and deformation can be easily achieved after intermediate annealing.
  • the inventor's research found that when the hot final rolling coiling temperature is 250 ⁇ 340°C, intermediate annealing is required to control the second phase, so that the average size of the Mg 2 Si precipitated phase is 1.3 ⁇ 1.7 ⁇ m, and its areal density is ⁇ 55000 pieces/mm 2 .
  • the second phase precipitates faster and the second phase size is larger; when the intermediate annealing temperature is below 350°C, the second phase precipitates slower and the second phase particle size It is also relatively small, which is not conducive to the occurrence of the PSN mechanism; but when the intermediate annealing temperature is higher than 430°C, the size of the precipitated second phase particles is too large, which will become the initiation point of microcracks during the processing, which is not conducive to subsequent sheet forming. , and at the same time, high temperatures often lead to a small number of second phase particles, which is not conducive to the subsequent formation of PSN texture.
  • the hot final rolling coiling temperature is higher than 340°C, intermediate annealing is not performed at this time, and the area density of the Mg 2 Si precipitated phase with an average size of 1.3 to 1.7 ⁇ m can also be obtained ⁇ 55000 pcs/mm 2 of the second phase.
  • step (2) hot rough rolling is performed at a temperature of 530 to 570°C, preferably at a temperature of 540 to 560°C.
  • step (2) when intermediate annealing is performed, the temperature rise rate of the intermediate annealing is 13 ⁇ 17°C/h, and the temperature decrease rate of the intermediate annealing is 12 ⁇ 15°C/h.
  • the heat preservation time of the homogenization treatment is 6 to 16 hours, preferably 8 to 12 hours.
  • step (1) of the 6000 series aluminum alloy plate manufacturing method of the present invention the temperature rise rate of the homogenization treatment is 20-50°C/h.
  • step (1) of the 6000 series aluminum alloy plate manufacturing method of the present invention the temperature of the homogenization treatment is 550 to 570°C.
  • step (2) of the 6000 series aluminum alloy plate manufacturing method of the present invention the total deformation amount of hot rough rolling is controlled to be greater than 70%, such as 70-95%; and/or the total deformation amount of hot finish rolling is greater than 80%, such as 85 ⁇ 90%.
  • step (2) of the 6000 series aluminum alloy plate manufacturing method of the present invention the opening rolling temperature of hot finish rolling is 440 to 480°C.
  • step (3) of the 6000 series aluminum alloy plate manufacturing method of the present invention the total cold rolling deformation is controlled to be 60 to 85%.
  • step (4) of the 6000 series aluminum alloy plate manufacturing method of the present invention the solution treatment temperature is 550-570°C, the solution heating rate is 15-30°C/s, and the solution treatment holding time is The time is 1 to 5 minutes, and the quenching method is water cooling.
  • step (5) of the 6000 series aluminum alloy plate manufacturing method of the present invention pre-aging treatment is performed within 3 minutes after step (4).
  • the pre-aging treatment is to raise the temperature to 80-100°C and then slowly drop it from 80-100°C to room temperature, with a cooling rate of 1-4 °C/h.
  • another object of the present invention is to provide a 6000 series aluminum alloy plate that has high formability, high flanging performance and low ripple defects.
  • the 6000 series aluminum alloy plate is easy to produce and the production cost is not high. It has very high formability, high flanging properties and low ribbing defects, so it can be effectively used in the vehicle manufacturing industry to meet the requirements of lightweight vehicles.
  • the present invention proposes a 6000 series aluminum alloy plate with high formability, high flanging performance and low ripple defects, which is produced by the above-mentioned manufacturing method of the 6000 series aluminum alloy plate of the present invention.
  • the average grain size of the 6000 series aluminum alloy plate according to the present invention is 20-32 ⁇ m
  • the recrystallization texture density is 6.5-10.0
  • the cubic texture component content is ⁇ 8%
  • the Gaussian texture component content is ⁇ 7%.
  • the properties of the 6000 series aluminum alloy plate according to the present invention meet: tensile strength ⁇ 210MPa, preferably ⁇ 215MPa, yield strength ⁇ 104MPa, preferably ⁇ 110MPa, and elongation ⁇ 24%, preferably ⁇ 24.5%.
  • the 6000 series aluminum alloy plate according to the present invention has the following properties: plastic strain ratio r ⁇ 0.68, preferably r ⁇ 0.70, preferably r ⁇ 0.72, more preferably ⁇ 0.74; plane anisotropy index ⁇ r ⁇ 0.10, preferably ⁇ 0.08, more preferably ⁇ 0.06, more preferably ⁇ 0.04; the flanging grade (flanging factor is 0.6) is evaluated as 1; the plain weave grade is evaluated as 1.
  • the 6000 series aluminum alloy is an aluminum alloy series containing elements such as silicon and magnesium, and its composition meets the GB/T33227-2016 standard.
  • Common 6000 series aluminum alloy grades include 6A16, 6111, 6013, 6014, 6016, 6022, 6061, 6063, 6181, 6082, etc.
  • the 6000 series aluminum alloy may contain: Si: 0.3 ⁇ 1.5%, Fe: 0.05 ⁇ 0.5%, Cu: 0.02 ⁇ 1.1%, Mg: 0.35 ⁇ 1.2%, Zn: ⁇ 0.8%, Mn: ⁇ 0.8%, Cr: ⁇ 0.35%, Ti: ⁇ 0.15%, V: ⁇ 0.20%, the balance is A1 and inevitable impurities, such as P, S and O, etc.
  • the elemental composition of the aluminum alloy sheet described herein is: 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%, the balance is Al and inevitable impurities.
  • the present invention provides a 6000 series aluminum alloy plate.
  • the average grain size of the 6000 series aluminum alloy plate is 20-32 ⁇ m
  • the recrystallization texture density is 6.5-10.0
  • the cubic texture component content ⁇ 8%
  • Gaussian texture component content ⁇ 7%.
  • the tensile strength of the 6000 series aluminum alloy plate is ⁇ 210MPa
  • the yield strength is ⁇ 104MPa
  • the elongation is ⁇ 24%.
  • the plastic strain ratio of the 6000 series aluminum alloy plate is r ⁇ 0.68, preferably r ⁇ 0.70, more preferably r ⁇ 0.72, and even more preferably ⁇ 0.74.
  • planar anisotropy index ⁇ r of the 6000 series aluminum alloy plate is ⁇ 0.10, preferably ⁇ r ⁇ 0.08, more preferably ⁇ 0.06, and even more preferably ⁇ 0.04.
  • the flanging grade of the 6000 series aluminum alloy plate is evaluated as 1, and the plain weave grade is evaluated as 1.
  • the 6000 series aluminum alloy may contain: Si: 0.3 ⁇ 1.5%, Fe: 0.05 ⁇ 0.5%, Cu: 0.02 ⁇ 1.1%, Mg: 0.35 ⁇ 1.2%, Zn: ⁇ 0.8% , Mn: ⁇ 0.8%, Cr: ⁇ 0.35%, Ti: ⁇ 0.15%, V: ⁇ 0.20%, the balance is Al and inevitable impurities; further preferably, the elemental composition of the aluminum alloy plate is: 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 %, the balance is Al and unavoidable impurities.
  • the 6000 series aluminum alloy plate manufacturing method of the present invention has the following advantages and beneficial effects:
  • the manufacturing method of the 6000 series aluminum alloy plate according to the present invention can obtain a large amount of larger second phase through homogenization, hot rolling, coiling, optional intermediate annealing, and cold rolling processes, so that it can be solidified in the subsequent process.
  • the PSN mechanism is induced to recrystallize nucleation, thereby reducing the density of the recrystallized texture, especially the content of the soft cubic texture and the hard Gaussian texture, thereby improving the formability of the sheet (among which , plastic strain ratio r ⁇ 0.68, plane anisotropy index ⁇ r ⁇ 0.10) and reduce the flat weave defects of the plate.
  • the manufacturing method of the 6000 series aluminum alloy plate according to the present invention can make the grains of the aluminum alloy plate fine by regulating the cold rolling process during the processing, thereby improving the flanging performance of the aluminum alloy plate.
  • the manufacturing method of the 6000 series aluminum alloy plate according to the present invention has a simple process. It can achieve process optimization by adjusting parameters on the basis of the existing aluminum alloy heat treatment production line. Its applicability is quite wide and can meet the needs of industrialization. Production needs.
  • the manufacturing method of the present invention can be used to quantify the structure and texture of the 6000 aluminum alloy sheet.
  • the produced 6000 series aluminum alloy sheet has high formability, high flanging performance, and low weave defects. It can be effectively used in the vehicle manufacturing industry to meet the requirements of lightweight vehicles and has very broad application prospects.
  • Figure 1 schematically shows the process flow chart of the manufacturing method of the 6000 series aluminum alloy plate according to the present invention.
  • Table 1 lists the chemical compositions of the 6000 series aluminum alloy sheets of Examples 1-8 and the aluminum alloy sheets of Comparative Examples 1-4.
  • Figure 1 schematically shows the process flow chart of the manufacturing method of the 6000 series aluminum alloy plate according to the present invention.
  • the aluminum alloy ingot is heated in a homogenization heat treatment furnace with the furnace, and heated to 530-580°C at a heating rate of 20-50°C/h; and the holding time of the homogenization treatment is preferably controlled. 6 to 16 hours;
  • Hot rough rolling is performed on the ingot at 530-570°C, and the total deformation of hot rough rolling is controlled to be greater than 70%;
  • Hot finish rolling perform hot finish rolling on the hot rough rolled plate, control the opening temperature of hot finish rolling to 400 ⁇ 480°C; control the coiling temperature of hot final rolling to above 250°C, and control the total deformation of hot finish rolling greater than 80%;
  • Intermediate annealing When the hot final rolling coiling temperature is 250 ⁇ 340°C, intermediate annealing is performed. The temperature of the intermediate annealing is controlled to be 350 ⁇ 430°C, the holding time is 1 ⁇ 4h, and the temperature rise rate of the intermediate annealing is 13 ⁇ 17°C/h, the cooling rate of intermediate annealing is 12 ⁇ 15°C/h; when the hot final rolling coiling temperature is higher than 340°C, the intermediate annealing is not performed and cold rolling is entered directly;
  • Solid solution treatment Control the solution treatment temperature to 550-570°C, the solution heating rate to 15-30°C/s, the solution treatment time to 1-5 minutes, and then use water cooling.
  • Pre-aging treatment After step (7), perform pre-aging treatment immediately within 3 minutes. It is to raise the temperature to 80-100°C and then slowly cool down from 80-100°C to room temperature. The cooling rate is 1-4°C/h. , to obtain T4P aluminum alloy sheet.
  • Comparative Examples 1-4 are similar to those of the present embodiment, but the process parameters do not meet the design scope of the present invention.
  • Table 2-1 and Table 2-2 list the specific process parameters of the 6000 series aluminum alloy plates of Examples 1-8 and the aluminum alloy plates of Comparative Examples 1-4 in the above process steps.
  • the size and distribution of the second phase (Mg 2 Si precipitated phase) in the longitudinal section of the aluminum alloy plates of each Example and Comparative Example were sampled from the cold-rolled plate, not the final of finished panels. This is because the recrystallization process occurs during the solution treatment of cold-rolled plates. Therefore, to observe the impact of the second phase on the recrystallization process and its microstructure, it is necessary to observe the second phase of the cold-rolled plates. .
  • 12mm (rolling direction) ⁇ 10mm (transverse) squares were cut from the cold-rolled plate samples corresponding to each embodiment and comparative example, and the longitudinal section of the plate was ground, using 320 mesh, 800 mesh and 1500 Use purpose water-grinding sandpaper for rough grinding; then use 800-grit metallographic sandpaper for fine grinding, and finally use polishing cloth to polish the longitudinal section of the plate. Then, use Sirion 200 field emission scanning electron microscope to examine the second phase (i.e., the longitudinal section of the aluminum alloy plate) Mg 2 Si precipitated phase) size and distribution were observed and analyzed. The relevant observation and analysis results are listed in Table 3 below.
  • Table 3 lists the average size and area density of the Mg 2 Si precipitated phase in the cold-rolled plates of Examples 1-8 and Comparative Examples 1-4.
  • the present invention also samples and detects the grain size of the finished T4P aluminum alloy sheets of each embodiment and comparative example.
  • the specific methods are as follows:
  • a rectangular sample of 15 mm (rolling direction) ⁇ 10 mm (transverse direction) was cut from the finished T4P aluminum alloy plate corresponding to each example and comparative example, and the statistical plane was the longitudinal section.
  • the sample was polished on a water mill with water-grinding sandpaper with a grit size of 320, 800, 1000, and 1500 and metallographic sandpaper with a grit size of 800 and 1000, diamond abrasive paste with a grit size of 0.5 ⁇ m was applied to the woolen cloth for mechanical testing. polishing. Use a DC power supply to perform anode coating on the polished sample.
  • a metallographic microscope was used to take metallographic photos at a magnification of 100 times, and the intercept method was used to detect the grain size of the aluminum alloy sheet through ImageJ software. The detection results are listed in Table 4.
  • the present invention also samples the finished 6000 series aluminum alloy plates of Examples 1-8 and the aluminum alloy plates of Comparative Examples 1-4, respectively, to conduct analysis of the macro texture. test.
  • the preparation and detection methods of XRD macro texture detection samples are as follows:
  • test conditions were 40kV tube voltage, 40mA tube current, CuK ⁇ radiation, and Ni filtering.
  • Corresponding background with center deviation of ⁇ ⁇ 1.4°; use Mtex-4.1.4 to perform background correction and defocus correction, and calculate the orientation distribution function (ODF).
  • ODF orientation distribution function
  • the present invention will also provide the finished 6000 series aluminum alloy sheets of Examples 1-8 and Comparative Example 1
  • the finished aluminum alloy plates of -4 were sampled again, and the mechanical properties, flanging properties and weave defects of the finished aluminum alloy plates of each example and comparative example were tested and evaluated.
  • the finished T4P aluminum alloy plate samples corresponding to each example and comparative example were subjected to a room temperature tensile property test after natural aging at room temperature for 7 days.
  • the room temperature tensile test was conducted in accordance with the requirements of ASTM E8/E8M-16a.
  • the room temperature tensile specimens were taken from the finished T4P aluminum alloy plate sample in three directions with angles of 0°, 45° and 90° to the rolling direction of the plate. .
  • the room temperature tensile test was conducted on an MTS810 tensile testing machine, and the tensile rate was controlled to 2mm/min.
  • the plastic strain ratio r value and the plane anisotropy index ⁇ r value were measured according to the GB/T 5027-2007 standard.
  • a rectangular sample of 250 mm (rolling direction) ⁇ 30 mm (transverse direction) was cut from the finished T4P aluminum alloy plate sample corresponding to each example and comparative example for flanging performance evaluation. Flanging performance evaluation is carried out according to the requirements of GMW 15421-2018. After pre-stretching the sample by 10% along the rolling direction, cut a rectangular sample of 50mm (rolling direction) ⁇ 30mm (transverse direction), and then use an indenter with a radius of 0.6mm to conduct a 180° bending experiment. During the experiment, ensure support The distance between rollers is 3.0 ⁇ 3.1mm.
  • Level 1 Smooth surface
  • Level 2 Discontinuous local shrinkage
  • Level 3 Microcrack morphology
  • Level 4 Obvious crack morphology, of which Levels 1 and 2 are acceptable. , Levels 3 and 4 are not acceptable.
  • the polishing of the Luo plain defect evaluation sample needs to be carried out on a flat work surface. First, put oil paper under the sample to facilitate cleaning after the test. Apply black ink evenly on the surface of the sample and wait for 10 to 15 seconds to evaporate. Then use a sponge pad with sandpaper on the surface to polish the surface of the sample. When polishing, you need to apply slight pressure on the surface of the sample. Generally, it is polished 2 to 3 times in one direction along the rolling direction, and then the Luoping weave defects are manually graded.
  • Level 1 The surface is required to have no vertical stripes parallel to the rolling direction; Level 2: The number of vertical stripes parallel to the rolling direction allowed on the surface is 1 to 5; Level 3: The number of vertical stripes parallel to the rolling direction is allowed on the surface. More than 5; Level 4: The number of vertical stripes on the surface parallel to the rolling direction exceeds 5 and the spacing between vertical stripes is less than 3 mm. Levels 1 and 2 are acceptable, but levels 3 and 4 are unacceptable.
  • Table 4 lists the structure, texture and performance testing results of the finished 6000 series aluminum alloy sheets of Examples 1-8 and the finished aluminum alloy sheets of Comparative Examples 1-4.
  • the 6xxx plate prepared according to the process of Examples 1-8 meets the requirements of the present invention.
  • the average size of the Mg 2 Si precipitated phase in the cold-rolled plate is 1.3 to 1.7 ⁇ m.
  • the areal density is ⁇ 55,000.
  • the average grain size of the finished sheet is 20 ⁇ 32 ⁇ m, the recrystallization texture density is 6.5 ⁇ 10.0, the cubic texture component content is ⁇ 8%, and the Gaussian texture component content is ⁇ 7%; the performance of the finished sheet meets the tensile strength requirements
  • the strength is ⁇ 210Mpa, the yield strength is ⁇ 104MPa, the elongation is ⁇ 24%, the plastic strain ratio r value is ⁇ 0.68, ⁇ r ⁇ 0.10, the flanging grade (flanging factor is 0.6) is all 1, and the plain weave grade is 1.
  • the 6xxx series plates prepared according to the process of Comparative Examples 1-4 do not meet the process scope of the present invention, resulting in the following results:
  • Comparative Example 2 Because the intermediate annealing temperature is too high, the second phase grows too much, making the coarse second phase too large in size. It is difficult to fully melt back during the subsequent solid solution process, and is left in the final product board, resulting in the flanging process. The sources of cracks increase, which leads to poor flanging performance (flanging grade 4).
  • the manufacturing method of the 6000 series aluminum alloy plate according to the present invention which has high formability, high flanging properties and low ribbing defects, on the one hand, through reasonable control of soaking and hot rolling during the processing , coiling, and intermediate annealing process parameters to regulate the size and quantity of the coarse Mg 2 Si precipitated phase in the 6000 series aluminum alloy sheet, giving full play to the PSN effect of the coarse Mg 2 Si phase in the subsequent solid solution process, thereby adjusting the texture; in addition
  • the texture and grain size of the finished sheet are further controlled by adjusting the cold rolling reduction rate, ultimately achieving the purpose of weakening the recrystallization texture density of the finished sheet and refining the grain size of the finished sheet. This resulted in a 6000 series aluminum alloy sheet for automobile bodies with high formability, high flanging properties and low ribbing defects.

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Abstract

公开了一种兼具高成形性能、高翻边性能以及低罗平纹缺陷的6000系铝合金板材及其制造方法，所述板材的平均晶粒尺寸为20～32μm，再结晶织构密度为6.5～10.0，立方织构组分含量≤8％，高斯织构组分含量≤7％。所述方法包括：(1)对铸锭进行均匀化处理，均匀化处理的温度为530～580℃；(2)对均匀化处理后的铸锭直接进行热粗轧、热精轧和热终轧卷取，控制热精轧的开轧温度为400～480℃，控制热终轧卷取温度为250℃以上；(3)冷轧：控制冷轧总变形量为50～85％；(4)固溶处理；(5)预时效处理，随后空冷，获得6000系铝合金板材。

Description

一种6000系铝合金板材制造方法及铝合金板材 技术领域
本发明涉及一种铝合金板材及其制造方法，尤其涉及一种6000系铝合金板材及制造方法。
背景技术
6000系铝合金具有强度高，耐蚀性好，烘烤后表面质量良好且烘烤后强度提高等优点，该系合金被越来越多地应用于车身外覆盖件的制造。
作为车身覆盖件，6000系铝合金汽车板的表面质量与其力学性能同等重要，关系到汽车涂漆后的外观是否理想，罗平纹缺陷就是影响铝合金汽车板表面质量的因素之一。
此外，铝合金板材在翻边过程中，粗大金属间化合物与铝板基体之间的界面常会造成严重应力集中，诱发微裂纹的萌生，从而会降低合金板的翻边性能，因此提高铝合金板材的翻边性能也具有重要意义。
公开号为CN101935785B，名称为“一种高成形性汽车车身板用铝合金”的中国专利文献，公开了一种通过调整主元素Si、Mg、Cu的含量及配比获得了具有优异成形性能的6000系汽车车身板用铝合金。该专利所述的优异成形性能仅关注于屈服强度、塑性以及加工硬化率，并没有关注与汽车车身覆盖件成形密切相关的r值、翻边性能以及罗平纹性能。
公开号为CN105074028B，公开日为2017年6月6日，名称为“室温时效后的特性优异的铝合金板”的中国专利文献，公开了一种通过在化学成分中增加了适量的Sn元素使得板材室温时效后性能仍然很优异的铝合金及其板材制造方法，其所制备的材料具有优良的成形性能。该专利通过增加合金元素Sn来实现良好的技术效果，但是该专利并未关注如何提高板材的翻边性能。
因此，在现有技术中，6000系铝合金板材都或多或少的存在着翻边性能差，冲压后表面存在明显罗平纹缺陷等问题，影响了6000系汽车板的大规模推广应用。
基于此，期望获得一种使6000系铝合金板材具有高成形性能、高翻边性能以及 低罗平纹缺陷的制造方法。
发明内容
本发明的目的之一在于提供一种兼具高成形性能、高翻边性能以及低罗平纹缺陷的6000系铝合金板材的制造方法，该6000系铝合金板材的制造方法采用了合理的工艺设计，其通过均热、热轧、卷取、可选的中间退火以及冷轧工艺，可以得到具有一定的第二相数量和比例以及晶粒尺寸的合金板，进而在后续固溶预时效处理过程中激发再结晶形核(PSN)效应，削弱再结晶织构含量，尤其立方织构组分和高斯织构组分的含量，进而使最终得到的铝合金板材的成形性能和翻边性能显著提高，以及改善铝合金板材的罗平纹缺陷。
为了实现上述目的，本发明提出了一种兼具高成形性能、高翻边性能以及低罗平纹缺陷的6000系铝合金板材的制造方法，其包括步骤：
(1)对铸锭进行均匀化处理，均匀化处理的温度为530～580℃；
(2)对均匀化处理后的铸锭直接进行热粗轧、热精轧和热终轧卷取，控制热精轧的开轧温度为400～480℃，控制热终轧卷取温度为250℃以上；
(3)冷轧：控制冷轧总变形量为50～85％，获得的冷轧板内的Mg2Si析出相的平均尺寸为1.3～1.7μm，Mg2Si析出相的面密度≥55000个/mm2；
(4)固溶处理；
(5)预时效处理，随后空冷，获得6000系铝合金板材。
发明人经过大量的研究发现第二相颗粒会对6000系铝合金的再结晶织构有很大影响，当合金中析出有粗大的第二相颗粒时，粗大的第二相会激发再结晶形核(PSN，Particle Stimulated Nucleation)，从而促进再结晶且会使得再结晶后织构组分以随机织构为主，降低织构强度，以及典型再结晶织构中立方织构组分和高斯织构组分的含量，从而降低两者的聚集程度，降低罗平纹缺陷程度。此外，发明人通过研究还发现，晶粒尺寸随着冷轧压下率的增加而降低。
基于此，为了克服现有6000系铝合金板成形性能不足、翻边性能较差、易出现罗平纹缺陷这些技术问题，在保证工艺合理性的前提下，本发明所述的制造方法通过调控加工过程中的均热、热轧、卷取、以及可选的中间退火工艺参数调控6000系铝合金板内粗大Mg2Si相尺寸和数量，充分发挥粗大Mg2Si相在后续固溶过程中粒子诱发再结晶形核(PSN，Particle Stimulated Nucleation)效应，从而调节织构；其 次还可以通过调控后续冷轧过程中的冷轧压下率和来进一步调控织构和晶粒尺寸，以期达到弱化和调控再结晶织构类型、比例、空间分布，以及细化晶粒尺寸的目的，从而获得高成形性能、高翻边性能以及低罗平纹缺陷的汽车车身用6000系铝合金板材。
具体来说，铸态6000系铝合金中的非平衡共晶相容易导致成分或者组织不均匀，而引起后续热变形可塑性差等问题，这在一定程度上制约了6000系铝合金的成形加工性能。因此，本技术方案控制均匀化过程中的均热温度超过530℃，以确保多数过于粗大的Mg2Si溶解，同时也旨在改善6000系铝合金的热加工性能以及消除合金中非平衡共晶相的影响。
此外，经发明人研究发现，在本技术方案中，若控制热精轧开轧温度为400～480℃，可以控制冷轧板材内的第二相(即Mg2Si析出相)尺寸为1.3～1.7μm，第二相的面密度为55000个/mm以上；若热精轧开轧温度过高，则析出第二相的尺寸过大且数量少；若热精轧开轧温度过低，则析出的第二相尺寸过小。
另外，经发明人研究发现，在本技术方案中，若冷轧压下率低于50％，则会导致成品板材中的晶粒粗大，一方面会使合金板材翻边后外板面出现微裂纹或连续颈缩等缺陷，降低翻边性能，另一方面，会使板材在冲制成形后形成橘皮状粗糙表面，降低表面质量；若冷轧压下率高于85％，粗大第二相粒子周围的局部变形区太大，该区域在成形过程中，会成为微裂纹的萌生区域，不利于成形性能。故本发明控制冷轧压下率为50％～85％。
由此，在本发明的上述技术方案中，通过对铸锭进行合理温度及时间的均热处理，使得铸锭中的非平衡共晶相溶解，随后对均匀化后的铸锭直接进行热粗轧，消除或减少铸造缺陷以及加工成满足热精轧条件的中间坯，然后控制热精轧、中间退火以及冷轧工艺以得到具有大量粗大第二相和晶粒细小的冷轧板材，在后续交货前的固溶预时效过程中，一方面通过粗大第二相激发的PSN机制，削弱再结晶织构含量；另一方面，通过调控冷轧压下率获得晶粒细小的成品态板材，进而获得兼具高成形性、高翻边性和低罗平纹缺陷的6000铝合金板材。
换句话说，本发明所述的制造方法通过特定的工艺配合，有效调控了铝合金内部粗大第二相的数量及分布和晶粒尺寸，进而调控了最终成品T4P态6000系铝合金板材的织构和组织，并显著改善了6000系铝合金板材的成形性能、翻边性能和罗平纹缺陷。
进一步地，在本发明所述的6000系铝合金板材制造方法的步骤(2)中，控制热终轧卷取温度为250～350℃。进一步地，当热终轧卷取温度为250～340℃时，在步骤(3)冷轧之前先进行中间退火：控制中间退火的温度为350～430℃，保温时间为1～4h，随后随炉冷却至室温；当热终轧卷取温度高于340℃时，不进行中间退火而直接进行步骤(3)。
为了有利于后续进一步的冷加工，可以在热轧及冷轧工序间增加中间退火。在本技术方案中，中间退火后可以降低变形抗力和易于变形的实现。经发明人研究发现，当热终轧卷取温度为250～340℃时，需要进行中间退火，以控制第二相，使得Mg2Si析出相的平均尺寸为1.3～1.7μm，且其面密度≥55000个/mm2。其中当中间退火温度为350℃以上时，第二相析出速度比较快，第二相尺寸也较大；当中间退火温度为350℃以下时，第二相析出速度比较慢，第二相粒子尺寸也比较小，不利于PSN机制的发生；但当中间退火温度高于430℃时，析出的第二相粒子尺寸过大，在加工过程中会成为微裂纹的萌生点，不利于后续的板材成形，同时高温下往往还导致第二相粒子数量少不利于后续的PSN织构的形成。
此外，在另外的实施方式中，如果热终轧卷取温度高于340℃时，此时不进行中间退火，也可以获得平均尺寸为1.3～1.7μm的Mg2Si析出相的面密度≥55000个/mm2的第二相。
进一步地，在步骤(2)中，在530～570℃的温度下，优选在540～560℃的温度下进行热粗轧。
进一步地，在步骤(2)中，当进行中间退火时，中间退火的升温速率为13～17℃/h，中间退火的降温速率为12～15℃/h。
进一步地，在本发明所述的6000系铝合金板材制造方法的步骤(1)中，均匀化处理的保温时间为6～16h，优选8～12h。
进一步地，在本发明所述的6000系铝合金板材制造方法的步骤(1)中，均匀化处理的升温速率为20-50℃/h。
进一步地，在本发明所述的6000系铝合金板材制造方法的步骤(1)中，均匀化处理的温度为550～570℃。
进一步地，在本发明所述的6000系铝合金板材制造方法的步骤(2)中，控制热粗轧总变形量大于70％，如70～95％；并且/或者热精轧总变形量大于80％，如85～90％。
进一步地，在本发明所述的6000系铝合金板材制造方法的步骤(2)中，热精轧的开轧温度为440～480℃。
进一步地，在本发明所述的6000系铝合金板材制造方法的步骤(3)中，控制冷轧总变形量为60～85％。
进一步地，在本发明所述的6000系铝合金板材制造方法的步骤(4)中，固溶处理温度为550～570℃，固溶升温速率为15～30℃/s，固溶处理保温时间为1～5min，淬火方式为水冷。
进一步地，在本发明所述的6000系铝合金板材制造方法的步骤(5)中，步骤(4)结束后在3min内进行预时效处理。
进一步地，在本发明所述的6000系铝合金板材制造方法的步骤(5)中，预时效处理为升温至80～100℃后从80～100℃缓慢降至室温，降温速率为1～4℃/h。
相应地，本发明的另一目的在于提供一种兼具高成形性能、高翻边性能以及低罗平纹缺陷的6000系铝合金板材，该6000系铝合金板材易于生产，且生产成本不高，其具有相当高的成形性，高的翻边性和低的罗平纹缺陷，从而可以有效应用于车辆制造行业中，满足车辆轻量化的要求。
为了实现上述目的，本发明提出了一种兼具高成形性能、高翻边性能以及低罗平纹缺陷的6000系铝合金板材，其采用本发明上述的6000系铝合金板材的制造方法制得。
进一步地，本发明所述的6000系铝合金板材的平均晶粒尺寸为20～32μm，再结晶织构密度为6.5～10.0，立方织构组分含量≤8％，高斯织构组分含量≤7％。
进一步地，本发明所述的6000系铝合金板材的性能满足：抗拉强度≥210MPa、优选≥215MPa，屈服强度≥104MPa、优选≥110MPa，延伸率≥24％、优选≥24.5％。
进一步地，本发明所述的6000系铝合金板材的还性能满足：塑性应变比r≥0.68，优选r≥0.70，优选r≥0.72，更优选≥0.74；平面各向异性指数Δr≤0.10，优选≤0.08，更优选≤0.06，更优选≤0.04；翻边等级(翻边因子为0.6)评定为1；罗平纹等级评定为1。
本文中，6000系列铝合金是一种含有硅和镁等元素的铝合金系列，其成分满足GB/T33227-2016标准。常见的6000系列铝合金牌号有6A16、6111、6013、6014、6016、6022、6061、6063、6181、6082等。本文中，以质量百分比计，所述6000系列铝合金可含有：Si：0.3～1.5％，Fe：0.05～0.5％，Cu：0.02～1.1％，Mg：0.35～1.2％， Zn：≤0.8％，Mn：≤0.8％，Cr：≤0.35％，Ti：≤0.15％，V：≤0.20％，余量为A1和不可避免的杂质，如P、S和O等。
在一些实施方案中，本文所述的铝合金板材的元素组成为：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％，余量为Al和不可避免的杂质。
在一些实施方案中，本发明提供一种6000系铝合金板材，所述6000系铝合金板材的平均晶粒尺寸为20～32μm，再结晶织构密度为6.5～10.0，立方织构组分含量≤8％，高斯织构组分含量≤7％。优选地，所述6000系铝合金板材的抗拉强度≥210MPa，屈服强度≥104MPa，延伸率≥24％。进一步优选地，所述6000系铝合金板材的塑性应变比r≥0.68，优选r≥0.70，更优选r≥0.72，更优选≥0.74。进一步优选地，所述6000系铝合金板材的平面各向异性指数Δr≤0.10，优选Δr≤0.08，更优选≤0.06，更优选≤0.04。进一步优选地，所述6000系铝合金板材的翻边等级评定为1，罗平纹等级评定为1。优选地，以质量百分比计，所述6000系列铝合金可含有：Si：0.3～1.5％，Fe：0.05～0.5％，Cu：0.02～1.1％，Mg：0.35～1.2％，Zn：≤0.8％，Mn：≤0.8％，Cr：≤0.35％，Ti：≤0.15％，V：≤0.20％，余量为Al和不可避免的杂质；进一步优选地，所述铝合金板材的元素组成为：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％，余量为Al和不可避免的杂质。
相较于现有技术，本发明所述的6000系铝合金板材制造方法具有如下所述的优点以及有益效果：
(1)本发明所述的6000系铝合金板材的制造方法，其通过均匀化、热轧、卷取、可选的中间退火、冷轧工艺可以获得大量较大第二相，从而在后续固溶处理和预时效过程中诱发PSN机制再结晶形核，从而降低再结晶织构的密度，尤其是软织构立方织构和硬织构高斯织构的含量，进而提高板材的成形性能(其中，塑性应变比r≥0.68，平面各向异性指数Δr≤0.10)和降低板材的罗平纹缺陷。
(2)本发明所述的6000系铝合金板材的制造方法，其通过调控加工过程中的冷轧工艺，可以使铝合金板材的晶粒细小，进而提高铝合金板材的翻边性能。
(3)本发明所述的6000系铝合金板材的制造方法的工艺简便，其可以在现有铝合金热处理生产线的基础上进行参数调整即可实现工艺优化，其适用性相当广泛，可以满足工业化生产需要。
(4)采用本发明所述的制造方法可以对6000铝合金板材的组织和织构进行量化，所制得的6000系铝合金板材具有高成形性能，高翻边性能，以及低罗平纹缺陷，其可以有效应用于车辆制造行业中，满足车辆轻量化的要求，具有十分广阔的应用前景。
附图说明
图1示意性地显示了本发明所述的6000系铝合金板材制造方法的工艺流程图。
具体实施方式
下面将结合具体的实施例和说明书附图对本发明所述的6000系铝合金板材及其制造方法做进一步的解释和说明，然而该解释和说明并不对本发明的技术方案构成不当限定。
实施例1-8和对比例1-4
表1列出了实施例1-8的6000系铝合金板材和对比例1-4的铝合金板材的化学成分。
表1.(wt.％，余量为Al和其他不可避免的杂质)
需要说明的是，由于本发明不对铝合金板材的成分配比进行限制，因此上述表1的作用仅用于完整纰漏本发明所述的制造方法，而并非对本发明所述的制造方法和铝合金板材进行限制。
图1示意性地显示了本发明所述的6000系铝合金板材制造方法的工艺流程图。
如图1所示的，本发明所述的实施例1-8的6000系铝合金板材采用下述步骤制得：
(1)熔炼和铸造：按照表1所示的化学成分进行配料，在熔炼炉中熔化后铸造制备铝合金铸锭；
(2)均匀化处理：将铝合金铸锭在均匀化热处理炉中随炉升温，并以20-50℃/h的升温速率升温到530～580℃；并优选地控制均匀化处理的保温时间为6～16小时；
(3)热粗轧：于530-570℃对铸锭进行热粗轧，控制热粗轧总变形量大于70％；
(4)热精轧：对热粗轧态板材进行热精轧，控制热精轧开轧温度为400～480℃；控制热终轧卷取温度为250℃以上，控制热精轧总变形量大于80％；
(5)中间退火：当热终轧卷取温度为250～340℃时，进行中间退火，控制中间退火的温度为350～430℃，保温时间为1～4h，中间退火的升温速率为13～17℃/h，中间退火的降温速率为12～15℃/h；当热终轧卷取温度高于340℃时，不进行中间退火而直接进入冷轧；
(6)冷轧：控制冷轧总变形量为50～85％；
(7)固溶处理：控制固溶处理温度为550～570℃，固溶升温速率为15～30℃/s，固溶处理时间为1～5min，然后采用水冷。
(8)预时效处理：步骤(7)结束后在3min内立即进行预时效处理，其为升温至80～100℃后从80～100℃缓慢降温至室温，降温速率为1～4℃/h，得到T4P态铝合金板材。
需要说明的是，对比例1-4的制造步骤流程与本案实施例类似，但是其工艺参数不符合本发明的设计范围。
表2-1和表2-2列出了实施例1-8的6000系铝合金板材和对比例1-4的铝合金板材在上述工艺步骤中的具体工艺参数。
表2-1.

表2-2.
需要说明的是，在本发明中，观察各实施例和对比例铝合金板材纵截面第二相(Mg2Si析出相)的尺寸及分布情况是在冷轧态板材上取样的，而不是最终的成品板材。这是因为：再结晶过程是在对冷轧板进行固溶处理的过程中发生的，所以观察第二相对再结晶过程及其组织织构的影响，需要对冷轧板的第二相进行观察。
在本发明中，从各实施例和对比例对应的冷轧态板材样品上截取12mm(轧向)×10mm(横向)的方块，对板材的纵截面进行研磨，依次使用320目、800目和1500 目的水磨砂纸进行粗磨；然后使用800目的金相砂纸进行细磨，最后用抛光布对板材的纵截面进行抛光，之后利用Sirion 200场发射扫描电子显微镜对铝合金板材纵截面第二相(即Mg2Si析出相)尺寸及分布进行观察和分析，相关观察分析结果列于下述表3之中。
表3列出了实施例1-8和对比例1-4的冷轧态板材中Mg2Si析出相的平均尺寸和面密度。
表3.
本发明还对各实施例和对比例的成品T4P态铝合金板材的晶粒尺寸进行了取样检测。具体方法如下：
从各实施例和对比例对应的成品T4P态铝合金板材上切取15mm(轧向)×10mm(横向)的矩形试样，统计面为纵截面。试样在水磨机上一次用粒度为320、800、1000、1500的水磨砂纸和粒度为800、1000的金相砂纸进行打磨后，再在呢子布上涂抹粒度为0.5μm的金刚石研磨膏进行机械抛光。利用直流电源对抛光后的样品进行阳极覆膜。之后利用金相显微镜在放大倍率100倍条件下拍摄金相照片，通过ImageJ软件采用截距法对铝合金板材的晶粒尺寸进行检测，检测结果列于表4中。
此外，为了描述组织及织构与性能之间的关系，本发明还对实施例1-8的成品6000系铝合金板材和对比例1-4的铝合金板材分别取样，以对宏观织构进行测试。 XRD宏观织构检测样品的制备以及检测手段如下所述：
从各实施例1-8和对比例1-4对应的1mm厚的成品T4P态铝合金板材样品上切取15mm(轧向)×10mm(横向)的方块，测试面为板平面。样品需要经过水磨砂纸及金相砂纸打磨，测试面磨至接近板材厚度中心，之后放入30％NaOH水溶液中浸泡8～15min，取出后置于10％HNO3水溶液中浸泡5s，取出试样后用水清洗并吹干。宏观织构测试在Bruker D8 Discover型X射线衍射仪上进行，测试条件为40kV的管电压，40mA的管电流，CuKα辐射，Ni滤波。按照Shulz反射法分别测定纯铝粉及各试样的{111}、{200}、{220}三个不完整极图(α＝0°～75°；β＝0°～360°)及峰中心偏离Δθ＝±1.4°的相应背底；用Mtex-4.1.4进行背底修正和散焦校正，并计算取向分布函数(ODF)。检测结果列于表4中。
另外，为了进一步地说明本发明所述的成品6000系铝合金板材的力学性能、翻边性能和表面质量，本发明还将得到的实施例1-8的成品6000系铝合金板材和对比例1-4的成品对比铝合金板材再次取样，并对各实施例和对比例的成品铝合金板材的力学性能、翻边性能和罗平纹缺陷进行测试和评价。
相关力学性能检测手段如下所述：
将各实施例和对比例对应的成品T4P态铝合金板材样品在室温自然时效7天后进行室温拉伸性能测试。室温拉伸试验根据ASTM E8/E8M-16a要求进行，室温拉伸试样分别从成品T4P态铝合金板材样品上与板材轧制方向夹角为0°、45°和90°的三个方向截取。室温拉伸试验在MTS810拉伸试验机上进行，控制拉伸速率为2mm/min。相应地，塑性应变比r值和平面各向异性指数Δr值根据GB/T 5027-2007标准进行测定。
相关翻边性能评价手段如下所述：
从各实施例和对比例对应的成品T4P态铝合金板材样品上切取250mm(轧向)×30mm(横向)的矩形试样进行翻边性能评价。翻边性能评价根据GMW 15421-2018的要求进行。将样品沿轧向预拉伸10％后，再切取50mm(轧向)×30mm(横向)的矩形试样，然后利用半径为0.6mm的压头进行180°弯曲实验，实验过程中，保证支承辊间距为3.0～3.1mm。弯曲后对外表面按照图的标准进行等级评价：1级：表面光滑；2级：不连续局部收缩；3级：微裂纹形貌；4级：明显裂纹形貌，其中1级和2级可接受，3级和4级不可接受。
相关罗平纹缺陷评价手段，如下所述：
从各实施例1-8和对比例1-4对应的成品T4P态铝合金板材样品上截取250mm(轧向)×35mm(横向)的矩形试样进行罗平纹缺陷评价。罗平纹缺陷评价试样的打磨需要在平坦的工作台面上进行，首先在试样下方垫上油纸，方便测试后清理，将黑色油墨均匀涂抹在试样表面，等待10～15s的挥发时间。然后使用表面带有砂纸的海绵垫在试样表面上进行打磨，打磨时需要在试样表面施加轻微的压力，一般沿其轧向单向打磨2～3次，随后人工对罗平纹缺陷进行等级评价：1级：表面要求无平行于轧向的竖行条纹；2级：表面允许平行于轧向的竖行条纹数量为1～5条；3级：表面平行于轧向的竖行条纹数量超过5条；4级：表面平行于轧向的竖行条纹数量超过5条切竖行条纹间距小于3mm，其中1级和2级可接受，3级和4级不可接受。
表4列出了实施例1-8的成品6000系铝合金板材和对比例1-4的成品铝合金板材的组织、织构及性能检测结果。
表4.
如表3和表4所示，按照实施例1-8工艺制备的6xxx板材满足本发明要求，冷轧态板材内的平均尺寸为1.3～1.7μm的Mg2Si析出相的面密度≥55000个/mm2；成品 态板材的平均晶粒尺寸为20～32μm，再结晶织构密度为6.5～10.0，立方织构组分含量≤8％，高斯织构组分含量≤7％；成品态板材的性能满足抗拉强度≥210Mpa，屈服强度≥104MPa，延伸率≥24％，塑性应变比r值≥0.68，Δr≤0.10，翻边等级(翻边因子为0.6)评定均为1，罗平纹等级评定均为1。而比较例中，按比较例1-4工艺制备的6xxx系板材因不满足本发明的工艺范围，导致如下结果：
对比例1因热精轧的终轧卷取温度在340℃以下但未进行中间退火，析出过多细小第二相，而粗大第二相数量过低，从而抑制了粗大第二相在后续固溶过程中激发的PSN效应，从而导致再结晶织构密度过高，进而使成品板的成形性能差(r值低，Δr值高)；尤其是立方织构软取向组分和高斯织构硬取向组分含量较高，且两种织构组分沿轧向聚集交替分布，导致在垂直于轧向方向进行10％预拉伸时具有高斯织构硬取向的晶粒不易变形，呈现山脊，而具有立方织构软取向的晶粒易变形减薄，呈现山谷，从而沿轧向出现高低起伏的罗平纹缺陷。
对比例2因中间退火温度过高，第二相过分长大，使粗大第二相尺寸过大，在后续固溶过程中难以充分回融，遗留在最终成品板内，导致在翻边过程中裂纹源增多，进而导致翻边性能差(翻边等级为4)。
对比例3因冷轧压下率过低，导致成品板内的晶粒尺寸过大，粗大的晶粒会促进翻边过程中剪切带的产生和传播，进而翻边性能差(翻边等级为4)。
对比例4因冷轧压下率过高，导致冷轧板中的变形织构密度过高，由于织构的遗传效应，成品板中的再结晶织构密度也高，尤其是立方织构软取向组分和高斯织构硬取向组分含量较高，进而导致出现严重的罗平纹缺陷(罗平纹缺陷评级为3)。
由此可以看出，本发明所述的兼具高成形性、高翻边性和低罗平纹缺陷的6000系铝合金板材制造方法，一方面通过合理的调控加工过程中的均热、热轧、卷取、中间退火工艺参数，调控了6000系铝合金板材内粗大Mg2Si析出相的尺寸和数量，充分发挥粗大Mg2Si相在后续固溶过程中PSN效应，从而调节织构；另一方面还通过调控冷轧压下率来进一步调控成品态板材的织构和晶粒尺寸，最终实现了弱化成品态板材的再结晶织构密度和细化成品态板材的晶粒尺寸的目的，进而获得了高成形性、高翻边性和低罗平纹缺陷的汽车车身用6000系铝合金板材。
需要说明的是，本案中各技术特征的组合方式并不限本案权利要求中所记载的组合方式或是具体实施例所记载的组合方式，本案记载的所有技术特征可以以任何方式进行自由组合或结合，除非相互之间产生矛盾。
还需要注意的是，以上所列举的实施例仅为本发明的具体实施例。显然本发明不局限于以上实施例，随之做出的类似变化或变形是本领域技术人员能从本发明公开的内容直接得出或者很容易便联想到的，均应属于本发明的保护范围。

Claims (15)

  1. 一种6000系铝合金板材，其特征在于，所述6000系铝合金板材的平均晶粒尺寸为20～32μm，再结晶织构密度为6.5～10.0，立方织构组分含量≤8％，高斯织构组分含量≤7％。
  2. 如权利要求1所述的6000系铝合金板材，其特征在于，所述6000系铝合金板材的抗拉强度≥210MPa，屈服强度≥104MPa，延伸率≥24％。
  3. 如权利要求1或2所述的6000系铝合金板材，其特征在于，所述6000系铝合金板材的塑性应变比r≥0.68，平面各向异性指数Δr≤0.10，翻边等级评定为1，罗平纹等级评定为1。
  4. 如权利要求3所述的6000系铝合金板材，其特征在于，所述6000系铝合金板材的塑性应变比r≥0.70，优选r≥0.72，更优选≥0.74。
  5. 如权利要求3或4所述的6000系铝合金板材，其特征在于，所述6000系铝合金板材的平面各向异性指数Δr≤0.08，优选≤0.06，更优选≤0.04。
  6. 如权利要求1～5中任一项所述的6000系铝合金板材，其特征在于，以质量百分比计，所述6000系列铝合金可含有：Si：0.3～1.5％，Fe：0.05～0.5％，Cu：0.02～1.1％，Mg：0.35～1.2％，Zn：≤0.8％，Mn：≤0.8％，Cr：≤0.35％，Ti：≤0.15％，V：≤0.20％，余量为Al和不可避免的杂质；优选地，所述铝合金板材的元素组成为：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％，余量为Al和不可避免的杂质。
  7. 一种兼具高成形性能、高翻边性能以及低罗平纹缺陷的6000系铝合金板材制造方法，其特征在于，包括步骤：
    (1)对铸锭进行均匀化处理，均匀化处理的温度为530～580℃，优选550～570℃；
    (2)对均匀化处理后的铸锭直接进行热粗轧、热精轧和热终轧卷取，控制热精轧的开轧温度为400～480℃、优选440～480℃，控制热终轧卷取温度为250℃以上；
    (3)冷轧：控制冷轧总变形量为50～85％，获得的冷轧板内的Mg2Si析出相的平均尺寸为1.3～1.7μm，Mg2Si析出相的面密度≥55000个/mm2；
    (4)固溶处理；
    (5)预时效处理，随后空冷，获得6000系铝合金板材。
  8. 如权利要求7所述的6000系铝合金板材制造方法，其特征在于，在步骤(2)中，热终轧卷取温度为250～340℃，在步骤(3)冷轧之前先进行中间退火：控制中间退火的温度为350～430℃，保温时间为1～4h，随后随炉冷却至室温，优选地，中间退火的升温速率为13～17℃/h，中间退火的降温速率为12～15℃/h；或热终轧卷取温度高于340℃，不进行中间退火而直接进行步骤(3)。
  9. 如权利要求7所述的6000系铝合金板材制造方法，其特征在于，在步骤(1)中，均匀化处理的保温时间为6～16h。
  10. 如权利要求7所述的6000系铝合金板材制造方法，其特征在于，在步骤(2)中，控制热粗轧温度为530～570℃；和/或，控制热粗轧总变形量大于70％；并且/或者热精轧总变形量大于80％。
  11. 如权利要求7所述的6000系铝合金板材制造方法，其特征在于，在步骤(3)中，控制冷轧总变形量为60～85％。
  12. 如权利要求7所述的6000系铝合金板材制造方法，其特征在于，在步骤(4)中，固溶处理温度为550～570℃，固溶升温速率为15～30℃/s，固溶处理保温时间为1～5min，淬火方式为水冷。
  13. 如权利要求7所述的6000系铝合金板材制造方法，其特征在于，在步骤(5)中，步骤(4)结束后在3min内进行预时效处理；和/或预时效处理为升温至80～100℃后从80～100℃缓慢降至室温，降温速率为1～4℃/h。
  14. 如权利要求7～13中任一项所述的6000系铝合金板材制造方法，其特征在于，所述6000系铝合金板材为权利要求1～6中任一项所述的6000系铝合金板材。
  15. 一种6000系铝合金板材，其采用如权利要求8-13中任一项所述的制造方法制得；优选地，所述6000系铝合金板材的平均晶粒尺寸为20～32μm，再结晶织构密度为6.5～10.0，立方织构组分含量≤8％，高斯织构组分含量≤7％；更优选地，所述6000系铝合金板材的性能还满足：
    抗拉强度≥210MPa，屈服强度≥104MPa，延伸率≥24％；
    塑性应变比r≥0.68，平面各向异性指数Δr≤0.10，翻边等级评定为1，罗平纹等级评定为1。
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