A 6xxx series aluminum alloy sheet strip with high bending performance and a method of manufacturing the same

Abstract

The application relates to a 6xxx series aluminum alloy plate strip with high bending performance, characterized by the following component mass percentage of the aluminum alloy plate strip: Si 0.5-1.3%, Mg 0.6-1.2%, Cu 0.5-1.1%, Mn 0.1-0.6%, Cr 0.1-0.3%, Fe<=0.50%, Ti 0.03-0.50%, and the balance being Al; the average grain size of the aluminum alloy plate strip in three directions is <=30 mu m, the average diameter of the second phase is <=3 mu m, the yield strength after baking is >=290 MPa, and the bending angle after baking is >=80 DEG. The application details the original grain size of the ingot, finally refines the grain size of the finished product, reasonably designs the quenching process, avoids the second phase precipitation, effectively controls the grain size of the 6xxx aluminum alloy and the precipitation of the second phase, greatly improves the bending performance of the plate strip, meanwhile, guarantees that the plate shape after quenching is not deteriorated, and makes the plate strip have the feasibility of industrial mass production.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy manufacturing, and in particular to a 6xxx series aluminum alloy sheet and strip with high bending performance and its preparation method. Background Technology

[0002] With the rise of the new energy vehicle industry, lightweighting of automobiles has become a current development trend. Aluminum alloys are widely used in the four doors and two covers of new energy vehicles as well as structural components due to their low density, easy recycling and good surface quality.

[0003] 6xxx aluminum alloys, as heat-treatable alloys, possess excellent bake-hardening properties, making them widely used in automotive internal structural components such as battery casings, crash beams, and floor reinforcement plates. To protect the safety of automotive battery packs, they require excellent energy absorption during collisions, necessitating both high strength and good bending performance.

[0004] Patent CN119082524A discloses a method for preparing a high-strength aluminum alloy with a high bending angle, but it is mainly an invention method for extruded profiles and does not involve aluminum alloy strips. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a 6xxx series aluminum alloy sheet and strip with high bending performance and its preparation method, which effectively controls the grain size and precipitation of the second phase of 6xxx aluminum alloy, and greatly improves the bending performance of the sheet and strip.

[0006] This invention is achieved using the following scheme: a 6xxx series aluminum alloy sheet and strip with high bending performance, comprising the following components by mass percentage: Si 0.5%–1.3%, Mg 0.6%–1.2%, Cu 0.5%–1.1%, Mn 0.1%–0.6%, Cr 0.1%–0.3%, Fe ≤ 0.50%, Ti 0.03%–0.50%, with the balance being Al; the average grain size in the three directions of the aluminum alloy sheet and strip is ≤ 30 μm, the average diameter of the second phase is ≤ 3 μm, the yield strength after baking is ≥ 290 MPa, and the bending angle after baking is ≥ 80°.

[0007] Another technical solution of the present invention: a method for preparing 6xxx series aluminum alloy sheet and strip with high bending performance as described above, comprising the following steps: (1) mixing, melting and casting the alloy components according to the proportion to obtain an aluminum alloy ingot; (2) homogenizing the aluminum alloy ingot; (3) hot rolling the homogenized aluminum alloy ingot to obtain a hot-rolled plate; (4) cold rolling the hot-rolled plate to obtain a cold-rolled plate; (5) solution quenching and pre-aging treatment of the cold-rolled plate to obtain an aluminum alloy sheet and strip.

[0008] Furthermore, in step (1), a continuous annealing furnace with an air cushion is used for solution quenching. The solution quenching process is as follows: First, the temperature is raised from room temperature to 500-560 ℃ at a rate of 50-100℃ / S. After holding at this temperature for 1-5 minutes, a three-stage cooling process is adopted. In the first stage, deionized water with a flow rate of 100-150 L / min is used for cooling, with a corresponding cooling rate of 40-60℃ / S, to cool the strip to 400-450℃. In the second stage, deionized water with a flow rate of 240-300 L / min is used for cooling, with a corresponding cooling rate of 80-120℃ / S, to cool the strip to 250-300℃. In the third stage, deionized water with a flow rate of 60-100 L / min is used for cooling, with a corresponding cooling rate of 20-40℃ / S, to cool the strip to below 50℃.

[0009] Furthermore, the cooling equipment used in the three-stage cooling system is a spray bar with a length of 2400mm, and nozzles with a diameter of 5-10mm are distributed at intervals of 10-20mm.

[0010] Furthermore, in step (2), the homogenization treatment is carried out at 540-580℃ for 1-10 hours.

[0011] Furthermore, in step (3), the thickness of the hot-rolled plate is 6.0 to 8.0 mm.

[0012] Furthermore, in step (4), the thickness of the cold-rolled sheet is 1.0 to 3.0 mm.

[0013] Furthermore, in step (5), the pre-aging treatment is to keep warm at 80-120℃ for 12-24 hours.

[0014] Furthermore, in step (1), the mass percentage of each component alloy material is as follows: Si 0.5%~1.3%, Mg 0.6%~1.2%, Cu 0.5%~1.1%, Mn 0.1%~0.6%, Cr 0.1%~0.3%, Fe≤0.50%, Ti 0.03%~0.50%, with the balance being Al.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention refines the original grain size of the ingot and ultimately refines the grain size of the finished product. By rationally designing the quenching process, the precipitation of the second phase is avoided, effectively controlling the grain size and the precipitation of the second phase of 6xxx aluminum alloy, greatly improving the bending performance of the strip and sheet, and ensuring that the shape of the strip after quenching does not deteriorate, making it feasible for industrial mass production.

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below through specific embodiments and related drawings. Attached Figure Description

[0017] Figure 1 Schematic diagram of bending test of xxx series aluminum alloy sheet and strip in Embodiment 6 of the present invention; Detailed Implementation

[0018] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0019] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0020] A high-bending-performance 6xxx series aluminum alloy sheet and strip comprises the following components by mass percentage: Si 0.5%–1.3%, Mg 0.6%–1.2%, Cu 0.5%–1.1%, Mn 0.1%–0.6%, Cr 0.1%–0.3%, Fe ≤0.50%, Ti 0.03%–0.50%, with the balance being Al; the average grain size in the three directions of the aluminum alloy sheet and strip is ≤30 μm, the average diameter of the second phase is ≤3 μm, the yield strength after baking is ≥290 MPa, and the bending angle after baking is ≥80°.

[0021] Test methods for various properties of 6xxx series aluminum alloy sheets and strips:

[0022] (1) Average grain size: The average grain size was measured according to the national standard method GB / T3246.1. One 10*10mm sample was taken, and after the cut sample was cold-mounted, it was polished with a polishing machine, then anodized and coated. Then, a metallographic microscope was used to take pictures under 100x magnification, and the average grain size of the sample was calculated using the intercept method.

[0023] (2) Average diameter of the second phase: Take one 10*10mm sample, cold mount the cut sample, polish the sample with a polishing machine, and observe the second phase in a scanning electron microscope. Use backscattered electron mode for observation, randomly select 9 fields of view for photography, magnification of 500 times, and use professional analysis software to calculate the average diameter of the second phase.

[0024] (3) Yield strength after baking: Prepare A50 / A80 size samples, first perform 2% pre-stretching on a tensile testing machine, then bake at 185℃ for 20min, and then measure the yield strength according to the requirements of national standard GB / T16865.

[0025] (4) Bending angle after baking: Take a 60*60mm sample, bake it at 185℃ for 20 minutes, and then conduct a bending angle test according to VDA238-100 standard. Figure 1 As shown. After the experiment, the bending angle was measured using a protractor.

[0026] A method for preparing 6xxx series aluminum alloy sheet and strip with high bending performance as described above includes the following steps: (1) mixing, melting and casting the alloy components according to the proportion to obtain an aluminum alloy ingot; (2) homogenizing the aluminum alloy ingot; (3) hot rolling the homogenized aluminum alloy ingot to obtain a hot-rolled plate; (4) cold rolling the hot-rolled plate to obtain a cold-rolled plate; (5) solution quenching and pre-aging treatment of the cold-rolled plate to obtain an aluminum alloy sheet and strip.

[0027] In this embodiment, in step (1), a continuous air-cushion annealing furnace is used for solution quenching. The solution quenching process is as follows: First, the temperature is increased from room temperature to 500-560℃ at a rate of 50-100℃ / s. After holding at this temperature for 1–5 minutes, a three-stage cooling process is employed. The first stage uses deionized water at a flow rate of 100–150 L / min, corresponding to a cooling rate of 40–60 °C / s, to cool the strip to 400–450 °C. The main purpose is to control the strip shape while ensuring the temperature remains above the precipitation temperature. The second stage uses deionized water at a flow rate of 240–300 L / min, corresponding to a cooling rate of 80–120 °C / s, to cool the strip to 250–300 °C. The main purpose is to avoid the nose temperature range of the C-curve and to cool rapidly to prevent the precipitation of the second phase. The third stage uses deionized water at a flow rate of 60–100 L / min, corresponding to a cooling rate of 20–40 °C / s, to cool the strip to below 50 °C. The main purpose is to control the strip shape and prevent burns to the equipment rollers.

[0028] In this embodiment, the cooling device used for the three-stage cooling is a spray bar with a length of 2400mm, and nozzles with a diameter of 5-10mm are distributed at intervals of 10-20mm.

[0029] In this embodiment, in step (2), the homogenization process is to keep warm at 540-580°C for 1-10 hours.

[0030] In this embodiment, in step (3), the thickness of the hot-rolled plate is 6.0 to 8.0 mm.

[0031] In this embodiment, in step (4), the thickness of the cold-rolled sheet is 1.0 to 3.0 mm.

[0032] In this embodiment, in step (5), the pre-aging treatment is to keep warm at 80-120°C for 12-24 hours.

[0033] In this embodiment, in step (1), the mass percentage of each component alloy material is as follows: Si 0.5%~1.3%, Mg 0.6%~1.2%, Cu 0.5%~1.1%, Mn 0.1%~0.6%, Cr 0.1%~0.3%, Fe≤0.50%, Ti 0.03%~0.50%, and the balance is Al.

[0034] The high bending performance 6xxx series aluminum alloy sheet and strip of the present invention has a specially designed composition, which refines the original grain size of the ingot and ultimately refines the grain size of the finished product through a genetic mechanism. By rationally designing the quenching process, the precipitation of the second phase is avoided, and the shape of the sheet after quenching is not deteriorated, making it feasible for industrial mass production.

[0035] The following examples and comparative examples of sample experiments provide a comparative explanation.

[0036] Table 1

[0037]

[0038] Table 2

[0039]

[0040] Table 3

[0041]

[0042] The components and production process parameters of Examples 1, 2, and 3 are shown in Tables 1 and 2, respectively. All were trial-produced in accordance with the requirements of this invention, and the performance of the finished products is shown in Table 3. All of them meet the requirements.

[0043] The composition and production process parameters of Comparative Example 1 are shown in Table 1 and Table 2, respectively. The main problem in this case is that the cooling rate of the first stage after quenching is too high, which leads to a sharp deterioration in the plate shape and scrapping of the finished product.

[0044] The composition and production process parameters of Comparative Example 2 are shown in Tables 1 and 2, respectively, and its finished product performance is shown in Table 3. The average diameter of its second phase and the bending angle after baking do not meet the requirements. This is mainly because the cooling rate of the second stage after quenching is too high, leading to a large precipitation of the Al-Cu-Mg phase and an excessively large second phase size, thus affecting the final bending angle performance after baking.

[0045] The composition and production process parameters of Comparative Example 3 are shown in Table 1 and Table 2, respectively. The main reason for this scheme is that the cooling rate of the third stage is too slow, the strip cannot be cooled to room temperature, there is a risk of scalding the equipment, online shutdown for cooling, and scrapping of finished products.

[0046] The composition and production process parameters of Comparative Example 4 are shown in Tables 1 and 2, respectively, and the performance of its finished product is shown in Table 3. The baking performance of the finished product of this scheme is low, mainly because the Mg and Cu in its composition are far below the target requirements, resulting in insufficient strengthening phase formed during the subsequent baking process and low material strength.

[0047] The composition and production process parameters of Comparative Example 5 are shown in Tables 1 and 2, respectively, and its finished product performance is shown in Table 3. The finished product of this scheme has a larger grain size and lower bending performance. This is mainly due to the lower Ti content in its composition, which leads to poor grain digestion during the casting process, resulting in a larger grain size in the finished product and affecting the bending performance of the material.

[0048] This invention effectively controls the grain size and second phase precipitation of 6xxx aluminum alloy through composition design and quenching process control, greatly improving the bending performance of sheet and strip materials. The resulting sheet and strip materials can be widely used in internal structural components of new energy vehicles.

[0049] Unless otherwise stated, if any of the technical solutions disclosed in this invention specify a numerical range, then the disclosed numerical range is a preferred numerical range. Anyone skilled in the art should understand that the preferred numerical range is merely one among many feasible numerical values ​​that has a more obvious or representative technical effect. Because there are many numerical values, it is impossible to list them all. Therefore, this invention discloses only some numerical values ​​to illustrate the technical solutions of this invention. Furthermore, the numerical values ​​listed above should not constitute a limitation on the scope of protection of this invention.

[0050] If this invention discloses or relates to mutually fixedly connected components or structural parts, then, unless otherwise stated, a fixed connection can be understood as: a detachable fixed connection (e.g., using bolts or screws), or a non-detachable fixed connection (e.g., riveting, welding). Of course, mutually fixed connections can also be replaced by an integral structure (e.g., manufactured in one piece using a casting process) (except where it is obviously impossible to use an integral molding process).

[0051] In addition, unless otherwise stated, the terms used in any of the technical solutions disclosed in this invention to indicate positional relationships or shapes include states or shapes that are similar to, close to, or approximate with those states or shapes.

[0052] Any component provided by this invention can be assembled from multiple individual components or can be a single component manufactured by a one-piece molding process.

[0053] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A high-bend performance 6xxx series aluminum alloy sheet strip characterized by: The aluminum alloy plate strip comprises the following components in percentage by mass: Si 0.5% to 1.3%, Mg 0.6% to 1.2%, Cu 0.5% to 1.1%, Mn 0.1% to 0.6%, Cr 0.1 to 0.3%, Fe ≤0.50%, Ti 0.03 to 0.50%, and the balance being Al; the average grain size of the aluminum alloy plate strip in three directions is ≤30 μm, the average diameter of the second phase is ≤3 μm, the yield strength after baking is ≥290 MPa, and the bending angle after baking is ≥80°.

2. A method of producing a high-bend performance 6xxx series aluminum alloy sheet strip as claimed in claim 1, characterized by: The method comprises the following steps: (1) mixing, smelting and casting alloy components according to the proportion to obtain an aluminum alloy ingot; (2) homogenizing the aluminum alloy ingot; (3) hot-rolling the homogenized aluminum alloy ingot to obtain a hot-rolled plate; (4) cold-rolling the hot-rolled plate to obtain a cold-rolled plate; and (5) solid solution quenching and pre-aging the cold-rolled plate to obtain the aluminum alloy plate strip.

3. The method of making a high-bend-formability 6xxx-series aluminum alloy sheet or strip as defined in claim 2, wherein: In step (1), the solid solution quenching is performed by using a gas cushion type continuous annealing furnace, and the solid solution quenching process is as follows: first, the temperature is raised from room temperature to 500-560 ℃ at a rate of 50-100 ℃ / s, and then the temperature is kept at this temperature for 1-5 min, and then three-stage cooling is performed, in which the first stage uses deionized water with a flow rate of 100-150 l / min to cool the strip at a corresponding cooling rate of 40-60 ℃ / s to 400-450 ℃; the second stage uses deionized water with a flow rate of 240-300 l / min to cool the strip at a corresponding cooling rate of 80-120 ℃ / s to 250-300 ℃; and the third stage uses deionized water with a flow rate of 60-100 l / min to cool the strip at a corresponding cooling rate of 20-40 ℃ / s to below 50 ℃.

4. The method of making a high-bend-formability 6xxx-series aluminum alloy sheet or strip as defined in claim 3, wherein: The cooling equipment used in the three-stage cooling is a spray rod, the length of which is 2400 mm, and the spray rod is distributed with nozzles with a diameter of 5-10 mm at an interval of 10-20 mm.

5. The method of making a high-bend-formability 6xxx-series aluminum alloy sheet or strip as defined in claim 2, wherein: In step (2), the homogenization treatment is performed at 540-580 ℃ for 1-10 h.

6. The method of making a high-bend-formability 6xxx-series aluminum alloy sheet or strip as defined in claim 2, wherein: In step (3), the thickness of the hot-rolled plate is 6.0-8.0 mm.

7. The method of making a high-bend-formability 6xxx-series aluminum alloy sheet or strip as defined in claim 2, wherein: In step (4), the thickness of the cold-rolled plate is 1.0-3.0 mm.

8. The method of making a high-bend-formability 6xxx-series aluminum alloy sheet or strip as defined in claim 2, wherein: In step (5), the pre-aging treatment is performed at 80-120 ℃ for 12-24 h.

9. The method of making a high-bend-formability 6xxx-series aluminum alloy sheet or strip as defined in claim 2, wherein: In step (1), the alloy components comprise the following components in percentage by mass: Si 0.5% to 1.3%, Mg 0.6% to 1.2%, Cu 0.5% to 1.1%, Mn 0.1% to 0.6%, Cr 0.1 to 0.3%, Fe ≤0.50%, Ti 0.03 to 0.50%, and the balance being Al.

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