6xxx series aluminum alloy plate strip with high bending performance and preparation method of 6xxx series aluminum alloy plate strip

Abstract

The invention relates to a 6xxx series aluminum alloy plate strip with high bending performance. The 6xxx series aluminum alloy plate strip is characterized by comprising the following components in percentage by mass: 0.5%-1.3% of Si, 0.6%-1.2% of Mg, 0.5%-1.1% of Cu, 0.1%-0.6% of Mn, 0.1%-0.3% of Cr, less than or equal to 0.50% of Fe, 0.03%-0.50% of Ti and the balance of Al, the average grain size of the aluminum alloy plate strip in three directions is smaller than or equal to 30 microns, the average diameter of a second phase is smaller than or equal to 3 microns, the yield strength after baking is larger than or equal to 290 MPa, and the bending angle after baking is larger than or equal to 80 degrees. According to the method, the original grain size of a cast ingot is refined, the grain size of a finished product is finally refined, the quenching process is reasonably designed, second phase precipitation is avoided, the grain size of the 6xxx aluminum alloy and second phase precipitation are effectively regulated and controlled, the bending performance of a plate strip is greatly improved, meanwhile, it is guaranteed that the quenched plate shape cannot deteriorate, and the product quality is improved. The feasibility of industrial mass production is realized.

Description

Technical Field

[0001] The invention relates to the field of aluminum alloy manufacturing, and in particular to a 6xxx series aluminum alloy plate and strip with high bending performance and a preparation method thereof. Background Art

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

[0003] As a heat-treatable alloy, 6xxx aluminum alloy has good bake hardening properties, so it is widely used in automotive internal structural parts, such as battery housings, anti-collision beams, floor reinforcement plates, etc. In order to protect the safety of automotive battery packs, it is necessary to have good energy absorption effect during collisions, that is, the material must have high strength and good bending performance.

[0004] Patent CN119082524A discloses a method for preparing a high-strength and high-bending-angle aluminum alloy, 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 object of the present invention is to provide a 6xxx series aluminum alloy plate and strip with high bending performance and a preparation method thereof, effectively control the grain size of the 6xxx aluminum alloy and the precipitation of the second phase, and greatly improve the bending performance of the plate and strip.

[0006] The present invention is implemented by the following scheme: a 6xxx series aluminum alloy plate and strip with high bending performance, comprising the following components: 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 remainder is Al; the average grain size of the aluminum alloy plate and 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°.

[0007] Another technical solution of the present invention: A method for preparing a 6xxx series aluminum alloy sheet and strip with high bending performance as above, comprising the following steps: (1) mixing, smelting and casting the alloy components according to a 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 the cold-rolled plate to obtain an aluminum alloy sheet and strip.

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

[0009] Furthermore, the cooling device used for the three-stage cooling is a spray rod, which has a length of 2400 mm and nozzles with a diameter of 5 to 10 mm are distributed at intervals of 10 to 20 mm.

[0010] Furthermore, in step (2), the homogenization treatment is carried out at 540-580° C. 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 performed at 80 to 120° C. for 12 to 24 hours.

[0014] Furthermore, in step (1), the mass percentage of each component alloy material is: 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.

[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, avoids the precipitation of the second phase by reasonably designing the quenching process, 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 and strip, and at the same time ensures that the plate shape after quenching will not deteriorate, making it feasible for industrial mass production.

[0016] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below through specific embodiments and related drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of a bending test of a 6xxx series aluminum alloy sheet and strip according to an embodiment of the present invention; DETAILED DESCRIPTION

[0018] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0019] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0020] A 6xxx series aluminum alloy plate and strip with high bending performance, comprising the following components: 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; the average grain size of the aluminum alloy plate and 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°.

[0021] Test methods for various properties of 6xxx series aluminum alloy sheets and strips: (1) Average grain size: The average grain size is measured in accordance with the national standard method of GB / T3246.1. Take a 10*10mm sample, cold mount the cut sample, polish it with a grinder, and then anodize it. Then take a photo with a metallographic microscope at 100 times magnification, and use the intercept method to calculate the average grain size of the sample.

[0022] (2) Average diameter of the second phase: Take a 10*10 mm sample, cold mount the cut sample, polish it with a grinder and polisher, put it into a scanning electron microscope to observe the second phase, use the backscattered electron mode for observation, randomly select 9 fields of view to take pictures, and use the magnification of 500 times to calculate the average diameter of the second phase using professional analysis software.

[0023] (3) Yield strength after baking: Prepare A50 / A80 size samples, first perform 2% pre-stretching on a tensile testing machine, then bake at 185°C for 20 min, and then measure the yield strength according to the requirements of the national standard GB / T16865.

[0024] (4) Bending angle after baking: Take a 60*60mm sample, bake it at 185℃ for 20min, and then perform a bending angle test according to VDA238-100 standard. Figure 1 When the test is finished, use an angle measuring tool to check the bending angle value.

[0025] A method for preparing a 6xxx series aluminum alloy sheet and strip with high bending performance as described above comprises the following steps: (1) mixing, smelting and casting the alloy components according to a 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 sheet; (4) cold rolling the hot-rolled sheet to obtain a cold-rolled sheet; (5) solution quenching and pre-aging the cold-rolled sheet to obtain an aluminum alloy sheet and strip.

[0026] In this embodiment, in step (1), an air cushion continuous annealing furnace is used for solution quenching. The solution quenching process is as follows: first, the temperature is raised from room temperature to 500-560°C / s at a rate of 50-100°C / s. ℃, keep it at this temperature for 1 to 5 minutes, and then adopt three-stage cooling, in which the first stage uses deionized water with a flow rate of 100 to 150 l / min for cooling, and the corresponding cooling rate is 40 to 60 ℃ / S, and the strip is cooled to 400 to 450 ℃. The main purpose is to control the strip shape while ensuring that the temperature is above the precipitation temperature; the second stage uses deionized water with a flow rate of 240-300 l / min for cooling, and the corresponding cooling rate is 80 to 120 ℃ / S, and the strip is cooled to 250 to 300 ℃. The main purpose is to avoid the temperature range of the nose of the C curve, cool it quickly, and avoid the precipitation of the second phase; the third stage uses deionized water with a flow rate of 60 to 100 l / min for cooling, and the corresponding cooling rate is 20 to 40 ℃ / S, and the strip is cooled to below 50 ℃. The main purpose is to control the plate shape and avoid scalding the equipment roller.

[0027] In this embodiment, the cooling device used for the three-stage cooling is a spray rod, which is 2400 mm long and has nozzles with a diameter of 5 to 10 mm distributed at intervals of 10 to 20 mm.

[0028] In this embodiment, in step (2), the homogenization treatment is carried out at 540-580° C. for 1-10 hours.

[0029] In this embodiment, in step (3), the thickness of the hot-rolled plate is 6.0 to 8.0 mm.

[0030] In this embodiment, in step (4), the thickness of the cold-rolled sheet is 1.0 to 3.0 mm.

[0031] In this embodiment, in step (5), the pre-aging treatment is carried out by keeping the temperature at 80-120° C. for 12-24 hours.

[0032] In this embodiment, in step (1), the mass percentage of each component alloy material is: 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%, Ti0.03-0.50%, and the balance is Al.

[0033] The high bending performance 6xxx series aluminum alloy plate and strip of the present invention has a special designed composition, which refines the original grain size of the ingot, and finally refines the grain size of the finished product through a genetic mechanism; by reasonably designing the quenching process, the precipitation of the second phase is avoided, and at the same time, it is ensured that the plate shape after quenching will not deteriorate, making it feasible for industrial mass production.

[0034] The following is a comparative explanation through examples and comparative examples of sample experiments.

[0035] Table 1 Table 2 Table 3 The ingredients and production process parameters of Example 1, Example 2 and Example 3 are shown in Table 1 and Table 2, respectively. All of them are trial-produced within the scope required by the present invention. The performance of the finished products is shown in Table 3, and all items meet the requirements.

[0036] The composition and production process parameters of Comparative Example 1 are shown in Table 1 and Table 2 respectively. This solution mainly causes the plate shape to deteriorate sharply and the finished product to be scrapped due to the excessive cooling rate in the first stage after quenching.

[0037] The composition and production process parameters of Comparative Example 2 are shown in Tables 1 and 2, respectively, and the performance of the finished product is shown in Table 3. The average diameter of the 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, resulting in a large amount of precipitation of Al-Cu-Mg phase and a large size of the second phase, which affects the bending angle performance after the final baking.

[0038] The ingredients and production process parameters of Comparative Example 3 are shown in Tables 1 and 2, respectively. This solution is mainly due to the third stage cooling rate is too slow, the strip can not be cooled to room temperature, there is a risk of scalding equipment, the online shutdown cooling, the finished product scrapped.

[0039] The composition and production process parameters of Comparative Example 4 are shown in Tables 1 and 2, respectively, and the performance of the finished product is shown in Table 3. The baking performance of the finished product of this solution is relatively low, mainly because the Mg and Cu in its composition are far below the target requirement range, resulting in insufficient strengthening phase formed in the subsequent baking process and low material strength.

[0040] The composition and production process parameters of Comparative Example 5 are shown in Table 1 and Table 2, respectively, and the performance of the finished product is shown in Table 3. The grain size of the finished product of this solution is relatively large, and the bending performance is relatively low. This is mainly due to the low Ti content of its composition, which leads to poor grain digestion during the casting process, resulting in a large grain size of the finished product, affecting the bending performance of the material.

[0041] The present invention effectively controls the grain size of 6xxx aluminum alloy and the precipitation of the second phase through composition design and quenching process control, greatly improving the bending performance of the plate and strip material. The obtained plate and strip material can be widely used in internal structural parts of new energy vehicles.

[0042] Unless otherwise stated, any technical solution disclosed in the present invention disclosed above, if it discloses a numerical range, then the disclosed numerical range is a preferred numerical range, and any technician in the field should understand that the preferred numerical range is only a numerical value with a more obvious technical effect or representative value among many implementable numerical values. Since there are too many numerical values ​​to be exhaustive, the present invention discloses some numerical values ​​to illustrate the technical solution of the present invention, and the numerical values ​​listed above should not constitute a limitation on the scope of protection of the present invention.

[0043] If the present invention discloses or involves components or structures that are fixedly connected to each other, then, unless otherwise stated, the fixed connection can be understood as: a detachable fixed connection (for example, connection using bolts or screws), and can also be understood as: a non-detachable fixed connection (for example, riveting, welding). Of course, the mutual fixed connection can also be replaced by an integrated structure (for example, manufactured by integrated molding using a casting process) (except when it is obviously impossible to use an integrated molding process).

[0044] In addition, unless otherwise stated, the terms used to indicate positional relationships or shapes in any of the technical solutions disclosed in the present invention include states or shapes that are approximate, similar, or close to them.

[0045] Any component provided by the present invention may be assembled from a plurality of separate components, or may be a separate component manufactured by an integral forming process.

[0046] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A 6xxx series aluminum alloy sheet and strip with high bending performance, characterized in that: The aluminum alloy plate and 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 is Al; the average grain size of the aluminum alloy plate and 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 for preparing a 6xxx series aluminum alloy sheet and strip with high bending performance as claimed in claim 1, characterized in that: The following steps are involved: (1) The alloy components are mixed, smelted and cast according to the proportion to obtain an aluminum alloy ingot; (2) The aluminum alloy ingot is homogenized; (3) The aluminum alloy ingot after homogenization is hot-rolled to obtain a hot-rolled plate; (4) The hot-rolled plate is cold-rolled to obtain a cold-rolled plate; (5) The cold-rolled plate is solution quenched and pre-aged to obtain an aluminum alloy plate and strip.

3. The method for preparing the 6xxx series aluminum alloy sheet and strip with high bending performance according to claim 2, characterized in that: In step (1), an air cushion continuous annealing furnace is used for solution quenching, and the solution quenching process is as follows: first, the temperature is raised from room temperature to 500-560°C at a rate of 50-100°C / S, and the temperature is kept at this temperature for 1-5 minutes, and then a three-stage cooling is adopted, wherein the first stage uses deionized water with a flow rate of 100-150 l / min for cooling, and the corresponding cooling rate is 40-60°C / S, and the strip is cooled to 400-450°C; the second stage uses deionized water with a flow rate of 240-300 l / min for cooling, and the corresponding cooling rate is 80-120°C / S, and the strip is cooled to 250-300°C; the third stage uses deionized water with a flow rate of 60-100 l / min for cooling, and the corresponding cooling rate is 20-40°C / S, and the strip is cooled to below 50°C.

4. The method for preparing the 6xxx series aluminum alloy sheet and strip with high bending performance according to claim 3, characterized in that: The cooling equipment used for the three-stage cooling is a spray rod, which is 2400 mm long and has nozzles with a diameter of 5 to 10 mm distributed at intervals of 10 to 20 mm.

5. The method for preparing the 6xxx series aluminum alloy sheet and strip with high bending performance according to claim 2, characterized in that: In step (2), the homogenization treatment is carried out at 540-580° C. for 1-10 hours.

6. The method for preparing the 6xxx series aluminum alloy sheet and strip with high bending performance according to claim 2, characterized in that: In step (3), the thickness of the hot-rolled plate is 6.0 to 8.0 mm.

7. The method for preparing a 6xxx series aluminum alloy sheet and strip with high bending performance according to claim 2, characterized in that: In step (4), the thickness of the cold-rolled sheet is 1.0 to 3.0 mm.

8. The method for preparing a 6xxx series aluminum alloy sheet and strip with high bending performance according to claim 2, characterized in that: In step (5), the pre-aging treatment is carried out at 80 to 120° C. for 12 to 24 hours.

9. The method for preparing a 6xxx series aluminum alloy sheet and strip with high bending performance according to claim 2, characterized in that: In step (1), the mass percentage of the alloy components is: 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 is Al.

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