6-series aluminum alloy thin-wall multi-cavity profile for vehicle and preparation method thereof

Abstract

The invention discloses a 6-series aluminum alloy thin-wall multi-cavity profile for a vehicle and a preparation method of the 6-series aluminum alloy thin-wall multi-cavity profile. The aluminum alloy profile comprises the following components in percentage by weight: 0.55-0.6% of Si; 0.10% to 0.15% of Fe; 0.20% to 0.25% of Cu; mn < = 0.1%; mg: 0.52 to 0.57%; less than or equal to 0.05% of Cr; the aluminum profile is prepared by the following steps of: smelting and casting, homogenizing treatment, extrusion, heat treatment and the like in sequence, so that the prepared aluminum profile has high strength and high plasticity, meets higher requirements of automobile thin-wall multi-cavity profiles, such as battery pack profiles and the like on mechanical properties and sizes, and avoids the technical problem of cracking.

Description

Technical Field

[0001] The invention belongs to the technical field of metal materials, and in particular relates to a 6 series aluminum alloy thin-wall multi-cavity profile for vehicles and a preparation method thereof. Background Art

[0002] With the rapid development of the automobile manufacturing industry, new energy vehicles are being used more and more widely. New energy vehicles use electricity as output power and need to be equipped with a large number of battery packs as power sources. With the advent of high-end new energy vehicles, higher performance standards are required for battery pack aluminum alloy profiles. Battery packs are mostly multi-cavity thin-walled profiles. At present, this type of profile produced by extrusion in my country is generally 6061 alloy. In actual production, due to the high degree of alloying and relatively poor formability of 6061, the internal ribs of the profile are prone to cracking, and the profile has crack defects after bending 90°. Summary of the invention

[0003] In view of this, the present invention discloses a 6 series aluminum alloy thin-wall multi-cavity profile for automobiles and a preparation method thereof, and the specific scheme is as follows:

[0004] A 6 series aluminum alloy thin-wall multi-cavity profile for vehicles, wherein the components and their weight percentages in the aluminum alloy profile are: Si: 0.55-0.6%; Fe: 0.10-0.15%; Cu: 0.20-0.25%; Mn≤0.1%; Mg: 0.52-0.57%; Cr≤0.05%; Zn≤0.05%, impurities total ≤0.03%, and the balance is Al.

[0005] As a supplement to the technical solution of the present invention, the method for preparing the above-mentioned 6 series aluminum alloy thin-walled multi-cavity profile for automobile comprises the following steps:

[0006] A. Ingredients: Prepare the raw materials according to the composition of 6 series aluminum alloy thin-walled multi-cavity profiles for automobiles;

[0007] B. Melting and casting: adding the prepared aluminum alloy raw materials into a melting furnace, mixing them evenly, and then melting them into liquid aluminum alloy, and then casting the liquid aluminum alloy into aluminum alloy casting rods;

[0008] C. Homogenization treatment: The aluminum alloy casting rod is homogenized at 555℃~565℃×8h, and then cooled by water cooling;

[0009] D. Extrusion: The aluminum alloy cast rod that has been homogenized is placed in an extruder for extrusion to obtain an aluminum alloy profile, and the extruded aluminum profile is quenched online and then stretched and straightened;

[0010] E. Heat treatment: The aluminum alloy profile after stretching and straightening is heat treated at a temperature of 165°C to 171°C for 6.5 hours.

[0011] As a supplement to the technical solution of the present invention, the extrusion process in step D is: the mold heating temperature is 480-510°C, the extrusion barrel heating temperature is 440-460°C, the cast rod heating temperature is 510-530°C, and the extrusion product speed is limited to 2-4m / min.

[0012] As a supplement to the technical solution of the present invention, the quenching cooling rate of the aluminum profile in step D is ≥120°C / min.

[0013] As a supplement to the technical solution of the present invention, in step C, the homogenization treatment system is specifically 560° C.×8 h.

[0014] As a supplement to the technical solution of the present invention, in step E, the heat treatment system is specifically 168°C×6.5h.

[0015] As a supplement to the technical solution of the present invention, the chamfer angle of the diverter bridge of the die in the extruder is α=30°, and the fillet of the bridge bottom is selected to be 6 mm.

[0016] As a supplement to the technical solution of the present invention, the height of the die welding chamber in the extruder is 45 mm.

[0017] Beneficial effects: The original automotive thin-walled multi-cavity profiles, such as battery pack profiles, have high requirements for mechanical properties and dimensions, so they are mostly produced with 6061 alloy, but cracking often occurs in actual production. Now, by designing a reasonable 6 series alloy, adjusting the casting rod homogenization system, strictly controlling the extrusion process parameters, and adjusting the aging system, the produced thin-walled multi-cavity profiles are free of cracking, and their mechanical properties can reach yield strength ≥ 255MPa, tensile strength ≥ 280MPa, and elongation after fracture A ≥ 13%; there is no crack in the profile after bending 90°; after 480h of neutral salt spray corrosion, the mechanical properties can meet the tensile strength ≥ 270MPa, and the mechanical properties decrease by <5% after salt spray corrosion; the Brinell hardness ≥ 85HBW, the exfoliation corrosion meets the GB / T22639 PA level, there is no intergranular corrosion, the extrusion cost is reduced, and the high performance requirements of thin-walled multi-cavity profiles for automobiles are met. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the rectangular chamfered structure of the mold diverter bridge.

[0019] Figure 2 It is a schematic diagram of the profile cross-section structure.

[0020] Figure 3 This is a real picture of Example 1 after the bending test.

[0021] Figure 4 Schematic diagram of the intergranular corrosion microstructure of Example 1.

[0022] Figure 5This is a real picture of Example 2 after the bending test.

[0023] Figure 6 Schematic diagram of the intergranular corrosion microstructure of Example 2.

[0024] Figure 7 This is a real picture of Example 3 after the bending test.

[0025] Figure 8 Schematic diagram of the intergranular corrosion microstructure of Example 3.

[0026] Fig. 9 This is the actual picture of comparative example 1 after the bending test.

[0027] Fig.10 This is the actual picture of comparative example 2 after the bending test.

[0028] Fig.11 This is the actual picture of comparative example 3 after the bending test.

[0029] Fig.12 Schematic diagram of the intergranular corrosion microstructure of comparative example 4.

[0030] Fig.13 This is a real picture of comparative example 4 after the bending test.

[0031] Fig.14 This is a real picture of comparative example 5 after the bending test.

[0032] Fig.15 This is a real picture of comparative example 6 after the bending test.

[0033] Fig.16 This is a real picture of comparative example 7 after the bending test. DETAILED DESCRIPTION

[0034] The invention discloses a 6 series aluminum alloy thin-wall multi-cavity profile for vehicles and a preparation method thereof. The composition of the 6 series aluminum alloy thin-wall multi-cavity profile for vehicles is Si: 0.55-0.6%; Fe: 0.10-0.15%; Cu: 0.20-0.25%; Mn≤0.1%; Mg: 0.52-0.57%; Cr≤0.05%; Zn≤0.05%, the total impurities are ≤0.03%, and the balance is Al.

[0035] The preparation method specifically comprises the following steps:

[0036] A. Ingredients: Ingredients are prepared according to the above aluminum profile ingredients;

[0037] In order to ensure the strength of aluminum alloy, it is necessary to ensure the addition amount of the above-mentioned metal elements such as Si, Fe, Cu, Mn, Mg, Cr, and Zn, so that the prepared aluminum profile has a certain strength. When one or two of the alloying elements are reduced, the strength of the aluminum profile will not decrease significantly. In order to ensure the strength of the aluminum profile, it is necessary to limit the addition amount of the metal elements. When the addition amount of the metal elements is large, the strength of the prepared aluminum profile is large, but its plasticity is poor, and it is very easy to crack when deformed; when the addition amount of the metal elements is small, the strength of the aluminum profile will be greatly reduced, but its plasticity will be improved. On the basis of the above-mentioned prior art, the present invention reduces the content of Si, Mn, and Cr elements, and at the same time greatly reduces the content of Mg element (the content of Mg element in the national standard of 6061 aluminum alloy is 0.8-1.2%), so that the alloying elements of the aluminum profile are greatly reduced to ensure its plasticity requirements.

[0038] B. Melting and casting: adding the prepared aluminum alloy raw materials into a melting furnace, mixing them evenly, and then melting them into liquid aluminum alloy, and then casting the liquid aluminum alloy into aluminum alloy casting rods;

[0039] C. Homogenization treatment: The aluminum alloy casting rod is homogenized at a temperature of 555℃~565℃×8h, preferably 560℃×8h, and water cooling is used for rapid cooling. A high temperature and short time homogenization system of 560℃×8h is used, and rapid cooling of water cooling is used for cooling. The homogenization temperature is appropriately increased to fully integrate the strengthening phase Mg2Si into the matrix, which can eliminate the problems of component segregation and uneven organization generated during the casting process, help improve the mechanical properties and corrosion resistance of the alloy, and at the same time improve the extrudability of the casting rod, which can alleviate the problem of extrusion cracking;

[0040] The short-term homogenization system at 560℃×8h can eliminate the dendritic segregation in the cast rod and dissolve the non-equilibrium phase. This organizational change helps to improve the plasticity of the cast rod, reduce the extrusion force required during the extrusion process, improve the extrudability of the cast rod, and alleviate the problem of extrusion cracking. If the homogenization temperature is too high or the holding time is too long, the grains will grow excessively, the number of grain boundaries will decrease, and the plasticity of the alloy will be affected. At the same time, due to the high homogenization temperature, the microstructure becomes unstable, the corrosion sensitivity at the grain boundaries is increased, and the intergranular corrosion resistance of the aluminum alloy is affected. If the homogenization temperature is too low or the holding time is short, the dendritic network of the cast rod is partially broken, Mg2Si and the non-equilibrium eutectic phase are only partially dissolved into the α-Al matrix, the cast rod is not fully homogenized, and the mechanical properties of the alloy are reduced.

[0041] D. Extrusion: Place the homogenized aluminum alloy cast rod in the extruder for extrusion to obtain aluminum alloy profiles. The specific extrusion process is as follows: mold heating temperature 480-510℃, extrusion barrel heating temperature 440-460℃, cast rod heating temperature 510-530℃, and extrusion product speed is limited to 2-4m / min. While limiting the extrusion parameters, the mold structure is optimized. The mold diverter bridge adopts a rectangular chamfered cross-section design with a chamfer α=30°, the bridge bottom radius is selected to be 6mm, and the welding chamber height is 45mm.

[0042] In terms of mold design, the mold diverter bridge adopts a rectangular chamfered cross-section design. Compared with the traditional rectangular cross-section diverter bridge, it can alleviate the dead zone formed by metal accumulation under the diverter bridge during the extrusion process. Due to the large number of product cavities, the extrusion difficulty coefficient increases. The chamfer is selected as α=30° to ensure the welding quality, and the bottom radius of the bridge is selected as 6mm, which can significantly improve the strength of the diverter bridge and avoid the generation of dead zones. In order to reduce the extrusion resistance, the welding chamber adopts a special-shaped design with an unconventional cross-section according to the product section. The height of the welding chamber is increased to 45mm, which increases the welding pressure and ensures the strength and reliability of the weld.

[0043] In terms of extrusion technology, since the alloying degree of the aluminum profile of this application is low, high rod temperature extrusion production is used to improve the fluidity of the metal, reduce the extrusion resistance, and the extruded profile has no cracking. On the premise of ensuring that the profile size is qualified, the quenching temperature is ≥515°C and the cooling rate is ≥120°C / min, which reduces the precipitation and coarsening of the Mg2Si phase and excess Si in the profile, thereby improving the comprehensive performance of the profile.

[0044] E. Heat treatment: The aluminum alloy profile after stretching and straightening is heat treated at 165℃~171℃×6.5h, preferably 168℃×6.5h. In order to ensure the mechanical properties and bending properties of the profile, an aging system of 168℃×6.5h is adopted. During the aging process, β' and stable Mg2Si phase are precipitated, which can ensure the mechanical properties of the profile. The aging temperature is appropriately reduced to make the precipitated phase small and evenly distributed, and improve the bending properties of the profile. Under the above alloy composition, the aging temperature is increased / the insulation aging time is increased, and more rod-shaped β' will be formed during the peak aging, which effectively hinders the dislocation movement and can improve the mechanical properties of the profile, but at the same time it will affect the plasticity of the profile, causing subsequent bending of the profile to crack; reduce the aging temperature / shorten the insulation time, and the precipitates during the aging process are mainly β" and a small amount of β' and Mg2Si phase. At this time, the mechanical properties of the profile are low and cannot meet the requirements.

[0045] The use of a higher extrusion temperature in the previous extrusion production helps to promote the recrystallization process of the aluminum alloy, refine the grains, thereby reducing the stress concentration coefficient at the grain boundary, inhibiting cracking, and storing more energy. The subsequent use of a lower aging temperature can obtain good mechanical properties and plasticity. In order to ensure the plasticity and bending properties of the profile, the aging temperature and aging time need to be appropriately reduced. Therefore, when designing the composition in the early stage, a small amount of Cu element is added to improve the fluidity of the aluminum alloy. During the aging process, some specific precipitation phases, such as β″ phase, will be formed, which can significantly improve the aging hardening effect and rate of the alloy, thereby increasing the strength of the alloy.

[0046] If low rod temperature is used for extrusion, the metal fluidity will deteriorate and the energy storage will be less. In order to improve the mechanical properties later, a higher aging temperature will be required, which will cause cracking problems in subsequent bending.

[0047] Example 1.

[0048] A. Ingredients: Ingredients are made according to the alloy elements in Table 1.1.

[0049] Table 1.1 Chemical composition

[0050] element Si Fe Cu Mn Mg Cr Zn Impurities Al content 0.57 0.14 0.22 0.006 0.56 0.003 0.005 0.05 margin

[0051] B. Melting and casting process: melting temperature 720℃, refining temperature 740℃, 1.5% aluminum-titanium-boron refiner is added to the melting furnace, the aluminum alloy raw materials in the melting furnace are completely melted and evenly stirred by a stirring device, and then cast into aluminum alloy rods by a casting equipment.

[0052] C. Homogenization treatment: The cast rod is homogenized at a temperature of 565°C for 8 hours, and then cooled by water cooling.

[0053] D. Extrusion: Use 36MN double-action horizontal aluminum extruder to produce 131mm×114mm, 2-3mm thick automotive 6 series aluminum alloy thin-walled multi-cavity profiles, with a maximum extrusion force of 28MN, online spray production, a casting rod diameter of 310mm, a casting rod heating temperature of 522℃, a mold heating temperature of 500℃, an extrusion barrel temperature of 452℃, and a profile outlet temperature of 525℃. The above-mentioned mold diverter bridge adopts a rectangular chamfer design, with chamfer α=30°, a bridge bottom radius of 6mm, a welding chamber height of 45mm, an extrusion speed of 3m / min, and a quenching cooling rate of 152℃ / min.

[0054] E. Heat treatment: The aluminum alloy profile after stretching and straightening is heat treated at a temperature of 171°C × 6.5h.

[0055] The 6 series aluminum alloy thin-walled multi-cavity profiles for automobiles prepared by the above process were tested:

[0056] 1. Mechanical properties test: The test equipment is AG-X 100KN electronic universal testing machine. Test method: GB / T228.1-2010 Metal material tensile test Part 1: Room temperature test method. The mechanical properties test is shown in Table 2 below:

[0057] Table 1.2 Mechanical properties results

[0058]

[0059] 2. Salt spray corrosion: Test equipment: Q-FOG cyclic salt spray corrosion tester, AG-X 100KN electronic universal testing machine. Test method: GB / T 10125-2021 Artificial atmosphere corrosion test salt spray test, GB / T228.1-2010 Metal material tensile test Part 1: Room temperature test method. The mechanical properties of the product after salt spray corrosion are shown in the following table:

[0060] Table 1. Mechanical properties after 3480h neutral salt spray corrosion

[0061]

[0062] 3. Brinell hardness: Test equipment: HB-3000C electronic Brinell hardness tester. Test method: GB / T231.1-2018 Brinell hardness test for metal materials Part 1: Test method. The Brinell hardness test results are as follows:

[0063] Table 1.4 Brinell hardness

[0064]

[0065] 4. Bending test: Test equipment: AG-X 250KN electronic universal testing machine. Test method: GB / T232-2010 metal material bending test method. Test standard: bending angle 90°, no cracking. Figure 3 As shown, there is no crack after bending at an angle of 90°.

[0066] 5. Exfoliation corrosion: Test equipment: HH-6 digital constant temperature water bath. Test method: GB / T22639-2008 Exfoliation corrosion test method for aluminum alloy products. The exfoliation corrosion test results are as follows:

[0067] Table 1.5 Exfoliation corrosion

[0068]

[0069] 6. Intergranular corrosion: Test equipment: DK-98-H electric constant temperature water bath. Test method: GB / T7998-2005 aluminum alloy intergranular corrosion determination method. Test standard: Intergranular corrosion level ≤ 4 (≤ 300μm). Figure 4As shown, the intergranular corrosion after the test is 20.34μm

[0070] Example 2.

[0071] A. Ingredients: Ingredients are made according to the alloy elements in Table 2.1.

[0072] Table 2.1 Chemical composition

[0073] element Si Fe Cu Mn Mg Cr Zn Impurities Al content 0.57 0.14 0.22 0.006 0.56 0.003 0.005 0.05 margin

[0074] B. Melting and casting process: melting temperature 720℃, refining temperature 740℃, 1.5% aluminum-titanium-boron refiner is added to the melting furnace, the aluminum alloy raw materials in the melting furnace are completely melted and evenly stirred by a stirring device, and then cast into aluminum alloy rods by a casting equipment.

[0075] C. Homogenization treatment: The cast rod is homogenized at a temperature of 560°C for 8 hours, and then cooled by water cooling.

[0076] D. Extrusion: A 36MN double-action horizontal aluminum extruder is used to produce 131mm×114mm, 2-3mm thick automotive 6 series aluminum alloy thin-walled multi-cavity profiles with a maximum extrusion force of 28MN. The production is carried out by online spraying. The diameter of the casting rod is 310mm, the heating temperature of the casting rod is 522℃, the heating temperature of the mold is 500℃, the temperature of the extrusion barrel is 452℃, and the profile outlet temperature is 525℃. The above-mentioned mold diverter bridge adopts a rectangular chamfer design with chamfer α=30°, the bottom radius of the bridge is 6mm, the height of the welding chamber is 45mm, the extrusion speed is 3m / min, and the quenching cooling rate is 153℃ / min.

[0077] E. Heat treatment: The aluminum alloy profile after stretching and straightening is heat treated at a temperature of 168°C × 6.5h.

[0078] The 6 series aluminum alloy thin-walled multi-cavity profiles for automobiles prepared by the above process were tested:

[0079] 1. Mechanical properties test: The test equipment is AG-X 100KN electronic universal testing machine. Test method: GB / T228.1-2010 Metal material tensile test Part 1: Room temperature test method. The mechanical properties test is shown in Table 2 below:

[0080] Table 2.2 Mechanical properties results

[0081]

[0082] 2. Salt spray corrosion: Test equipment: Q-FOG cyclic salt spray corrosion tester, AG-X 100KN electronic universal testing machine. Test method: GB / T 10125-2021 Artificial atmosphere corrosion test salt spray test, GB / T228.1-2010 Metal material tensile test Part 1: Room temperature test method. The mechanical properties of the product after salt spray corrosion are shown in the following table:

[0083] Table 2. Mechanical properties after 3480h neutral salt spray corrosion

[0084]

[0085] 3. Brinell hardness: Test equipment: HB-3000C electronic Brinell hardness tester. Test method: GB / T231.1-2018 Brinell hardness test for metal materials Part 1: Test method. The Brinell hardness test results are as follows:

[0086] Table 2.4 Brinell hardness

[0087]

[0088] 4. Bending test: Test equipment: AG-X 250KN electronic universal testing machine. Test method: GB / T232-2010 metal material bending test method. Test standard: bending angle 90°, no cracking. Figure 5 As shown, there is no crack after bending at an angle of 90°.

[0089] 5. Exfoliation corrosion: Test equipment: HH-6 digital constant temperature water bath. Test method: GB / T22639-2008 Exfoliation corrosion test method for aluminum alloy products. The exfoliation corrosion test results are as follows:

[0090] Table 2.5 Exfoliation corrosion

[0091]

[0092] 6. Intergranular corrosion: Test equipment: DK-98-H electric constant temperature water bath. Test method: GB / T7998-2005 aluminum alloy intergranular corrosion determination method. Test standard: Intergranular corrosion level ≤ 4 (≤ 300μm). After the test, the intergranular corrosion is as follows Figure 6 As shown, there is no intergranular corrosion.

[0093] Example 3.

[0094] A. Ingredients: Ingredients should be made according to the alloy elements in Table 3.1.

[0095] Table 3.1 Chemical composition

[0096] element Si Fe Cu Mn Mg Cr Zn Impurities Al content 0.57 0.14 0.22 0.006 0.56 0.003 0.005 0.05 margin

[0097] B. Melting and casting process: melting temperature 720℃, refining temperature 740℃, 1.5% aluminum-titanium-boron refiner is added to the melting furnace, the aluminum alloy raw materials in the melting furnace are completely melted and evenly stirred by a stirring device, and then cast into aluminum alloy rods by a casting equipment.

[0098] C. Homogenization treatment: The cast rod is homogenized at a temperature of 555°C for 8 hours, and then cooled by water cooling.

[0099] D. Extrusion: A 36MN double-action horizontal aluminum extruder is used to produce 131mm×114mm, 2-3mm thick automotive 6 series aluminum alloy thin-walled multi-cavity profiles with a maximum extrusion force of 28MN. The production is carried out by online spraying. The diameter of the casting rod is 310mm, the heating temperature of the casting rod is 522℃, the heating temperature of the mold is 500℃, the temperature of the extrusion barrel is 452℃, and the profile outlet temperature is 525℃. The above-mentioned mold diverter bridge adopts a rectangular chamfer design with chamfer α=30°, the bottom radius of the bridge is 6mm, the height of the welding chamber is 45mm, the extrusion speed is 3m / min, and the quenching cooling rate is 152℃ / min.

[0100] E. Heat treatment: The aluminum alloy profile after stretching and straightening is heat treated, and the heat treatment system is: 165℃×6.5h.

[0101] The 6 series aluminum alloy thin-walled multi-cavity profiles for automobiles prepared by the above process were tested:

[0102] 1. Mechanical properties test: The test equipment is AG-X 100KN electronic universal testing machine. Test method: GB / T228.1-2010 Metal material tensile test Part 1: Room temperature test method. The mechanical properties test is shown in Table 2 below:

[0103] Table 3.2 Mechanical properties results

[0104]

[0105] 2. Salt spray corrosion: Test equipment: Q-FOG cyclic salt spray corrosion tester, AG-X 100KN electronic universal testing machine. Test method: GB / T 10125-2021 Artificial atmosphere corrosion test salt spray test, GB / T228.1-2010 Metal material tensile test Part 1: Room temperature test method. The mechanical properties of the product after salt spray corrosion are shown in the following table:

[0106] Table 3. Mechanical properties after 3480h neutral salt spray corrosion

[0107]

[0108]

[0109] 3. Brinell hardness: Test equipment: HB-3000C electronic Brinell hardness tester. Test method: GB / T231.1-2018 Brinell hardness test for metal materials Part 1: Test method. The Brinell hardness test results are as follows:

[0110] Table 3.4 Brinell hardness

[0111]

[0112] 4. Bending test: Test equipment: AG-X 250KN electronic universal testing machine. Test method: GB / T232-2010 metal material bending test method. Test standard: bending angle 90°, no cracking. Figure 7 As shown, there is no crack after bending at an angle of 90°.

[0113] 5. Exfoliation corrosion: Test equipment: HH-6 digital constant temperature water bath. Test method: GB / T22639-2008 Exfoliation corrosion test method for aluminum alloy products. The exfoliation corrosion test results are as follows:

[0114] Table 3.5 Exfoliation corrosion

[0115]

[0116] 6. Intergranular corrosion: Test equipment: DK-98-H electric constant temperature water bath. Test method: GB / T7998-2005 aluminum alloy intergranular corrosion determination method. Test standard: Intergranular corrosion level ≤ 4 (≤ 300μm). After the test, the intergranular corrosion is as follows Figure 8 As shown, there is no intergranular corrosion.

[0117] Comparative example 1.

[0118] A. Ingredients: Ingredients should be made according to the alloy elements in Table 4.1.

[0119] Table 4.1 Chemical composition

[0120] element Si Fe Cu Mn Mg Cr Zn Impurities Al content 0.64 0.14 0.18 0.08 0.94 0.09 0.004 0.05 margin

[0121] B. Melting and casting process: melting temperature 720℃, refining temperature 740℃, 1.5% aluminum-titanium-boron refiner is added to the melting furnace, the aluminum alloy raw materials in the melting furnace are completely melted and evenly stirred by a stirring device, and then cast into aluminum alloy rods by a casting equipment.

[0122] C. Homogenization treatment: The cast rod is homogenized at a temperature of 570°C for 12 hours, and then cooled by water cooling.

[0123] D. Extrusion: Use 36MN double-action horizontal aluminum extruder to produce 131mm×114mm, 2-3mm thick automotive 6 series aluminum alloy thin-walled multi-cavity profiles, with a maximum extrusion force of 29MN, online air cooling production, a casting rod diameter of 310mm, a casting rod heating temperature of 500℃, a mold heating temperature of 495℃, an extrusion barrel temperature of 450℃, and a profile outlet temperature of 505℃. The above mold uses a rectangular diverter bridge, a welding chamber height of 30mm, an extrusion speed of 3m / min, and a quenching cooling rate of 105℃ / min.

[0124] E. Heat treatment: The aluminum alloy profile after stretching and straightening is heat treated at a temperature of 175°C for 8 hours.

[0125] The 6 series aluminum alloy thin-walled multi-cavity profiles for automobiles prepared by the above process were tested:

[0126] 1. Mechanical properties test: The test equipment is AG-X 100KN electronic universal testing machine. Test method: GB / T228.1-2010 Metal material tensile test Part 1: Room temperature test method. The mechanical properties test is shown in Table 2 below:

[0127] Table 4.2 Mechanical properties results

[0128]

[0129] 2. Bending test: Test equipment: AG-X 250KN electronic universal testing machine. Test method: GB / T232-2010 metal material bending test method. Test standard: bending angle 90°, no cracking.

[0130] The test results are as follows Fig. 9 As shown, cracks appear after bending at an angle of 90°.

[0131] Comparative example 2.

[0132] A. Ingredients: Ingredients should be made according to the alloy elements in Table 5.1.

[0133] Table 5.1 Chemical composition

[0134] element Si Fe Cu Mn Mg Cr Zn Impurities Al content 0.56 0.14 0.20 0.08 0.56 0.003 0.004 0.05 margin

[0135] B. Melting and casting process: melting temperature 720℃, refining temperature 740℃, 1.5% aluminum-titanium-boron refiner is added to the melting furnace, the aluminum alloy raw materials in the melting furnace are completely melted and evenly stirred by a stirring device, and then cast into aluminum alloy rods by a casting equipment.

[0136] C. Homogenization treatment: The cast rod is homogenized at a temperature of 570°C for 12 hours, and then cooled by water cooling.

[0137] D. Extrusion: Use 36MN double-action horizontal aluminum extruder to produce 131mm×114mm, 2-3mm thick automotive 6 series aluminum alloy thin-walled multi-cavity profiles, with a maximum extrusion force of 28MN, online air cooling production, a casting rod diameter of 310mm, a casting rod heating temperature of 502℃, a mold heating temperature of 495℃, an extrusion barrel temperature of 450℃, a profile outlet temperature of 505℃, a rectangular shunt bridge mold, a welding chamber height of 30mm, an extrusion speed of 3m / min, and a quenching cooling rate of 105℃ / min.

[0138] E. Heat treatment: The aluminum alloy profile after stretching and straightening is heat treated at a temperature of 175°C for 8 hours.

[0139] The 6 series aluminum alloy thin-walled multi-cavity profiles for automobiles prepared by the above process were tested:

[0140] 1. Mechanical properties test: The test equipment is AG-X 100KN electronic universal testing machine. Test method: GB / T228.1-2010 Metal material tensile test Part 1: Room temperature test method. The mechanical properties test is shown in Table 2 below:

[0141] Table 5.2 Mechanical properties results

[0142]

[0143] 2. Bending test: Test equipment: AG-X 250KN electronic universal testing machine. Test method: GB / T232-2010 metal material bending test method. Test standard: bending angle 90°, no cracking.

[0144] The test results are as follows Fig.10 As shown, cracks appear after bending at an angle of 90°.

[0145] Comparative example 3.

[0146] A. Ingredients: Ingredients shall be made according to the alloy elements in Table 6.1.

[0147] 6.1 Chemical composition

[0148] element Si Fe Cu Mn Mg Cr Zn Impurities Al content 0.57 0.15 0.21 0.08 0.56 0.003 0.004 0.05 margin

[0149] B. Melting and casting process: melting temperature 720℃, refining temperature 740℃, 1.5% aluminum-titanium-boron refiner is added to the melting furnace, the aluminum alloy raw materials in the melting furnace are completely melted and evenly stirred by a stirring device, and then cast into aluminum alloy rods by a casting equipment.

[0150] C. Homogenization treatment: The cast rod is homogenized at a temperature of 560°C for 8 hours, and then cooled by water cooling.

[0151] D. Extrusion: Use 36MN double-action horizontal aluminum extruder to produce 131mm×114mm, 2-3mm wall thickness automotive 6 series aluminum alloy thin-walled multi-cavity profiles, with a maximum extrusion force of 27MN, online air cooling production, a casting rod diameter of 310mm, a casting rod heating temperature of 500℃, a mold heating temperature of 495℃, an extrusion barrel temperature of 450℃, a profile outlet temperature of 506℃, a rectangular shunt bridge mold, a welding chamber height of 30mm, an extrusion speed of 3m / min, and a quenching cooling rate of 106℃ / min.

[0152] E. Heat treatment: The aluminum alloy profile after stretching and straightening is heat treated at a temperature of 175°C for 8 hours.

[0153] The 6 series aluminum alloy thin-walled multi-cavity profiles for automobiles prepared by the above process were tested:

[0154] 1. Mechanical properties test: The test equipment is AG-X 100KN electronic universal testing machine. Test method: GB / T228.1-2010 Metal material tensile test Part 1: Room temperature test method. The mechanical properties test is shown in Table 2 below:

[0155] Table 6.2 Mechanical properties results

[0156]

[0157] 2. Bending test: Test equipment: AG-X 250KN electronic universal testing machine. Test method: GB / T232-2010 metal material bending test method. Test standard: bending angle 90°, no cracking.

[0158] The test results are as follows Fig.11 As shown, cracks appear after bending at an angle of 90°.

[0159] Comparative example 4.

[0160] A. Ingredients: Ingredients shall be made according to the alloy elements in Table 7.1.

[0161] 7.1 Chemical composition

[0162] element Si Fe Cu Mn Mg Cr Zn Impurities Al content 0.56 0.15 0.21 0.007 0.55 0.003 0.005 0.05 margin

[0163] B. Melting and casting process: melting temperature 720℃, refining temperature 740℃, 1.5% aluminum-titanium-boron refiner is added to the melting furnace, the aluminum alloy raw materials in the melting furnace are completely melted and evenly stirred by a stirring device, and then cast into aluminum alloy rods by a casting equipment.

[0164] C. Homogenization treatment: The cast rod is homogenized at a temperature of 570°C for 12 hours, and then cooled by water cooling.

[0165] D. Extrusion: Use a 36MN double-action horizontal aluminum extruder to produce 131mm×114mm, 2-3mm thick automotive 6 series aluminum alloy thin-walled multi-cavity profiles, with a maximum extrusion force of 28MN, online spray production, a casting rod diameter of 310mm, a casting rod heating temperature of 521℃, a mold heating temperature of 500℃, an extrusion barrel temperature of 452℃, a profile outlet temperature of 524℃, a mold diverter bridge with a rectangular chamfer, a chamfer α=30°, a bridge bottom radius of 6mm, the welding chamber height increased to 45mm, the extrusion speed of 3m / min, and the quenching cooling rate of 150℃ / min.

[0166] E. Heat treatment: The aluminum alloy profile after stretching and straightening is heat treated at a temperature of 168°C × 6.5h.

[0167] The 6 series aluminum alloy thin-walled multi-cavity profiles for automobiles prepared by the above process were tested:

[0168] 1. Mechanical properties test: The test equipment is AG-X 100KN electronic universal testing machine. Test method: GB / T228.1-2010 Metal material tensile test Part 1: Room temperature test method. The mechanical properties test is shown in Table 2 below:

[0169] Table 7.2 Mechanical properties results

[0170]

[0171]

[0172] 2. Intergranular corrosion: Test equipment: DK-98-H electric constant temperature water bath. Test method: GB / T7998-2005 determination method of intergranular corrosion of aluminum alloy. Test standard: intergranular corrosion grade ≤ 4 (≤ 300μm).

[0173] like Fig.12 As shown, the intergranular corrosion depth is 356.61μm.

[0174] 3. Bending test: Test equipment: AG-X 250KN electronic universal testing machine. Test method: GB / T232-2010 metal material bending test method. Test standard: bending angle 90°, no cracking.

[0175] Test results such as Fig.13 As shown, the crack occurs when bent 90°.

[0176] Comparative Example 5.

[0177] A. Ingredients: Ingredients shall be made according to the alloy elements in Table 8.1.

[0178] 8.1 Chemical composition

[0179] element Si Fe Cu Mn Mg Cr Zn Impurities Al content 0.56 0.15 0.21 0.007 0.55 0.003 0.005 0.05 margin

[0180] B. Melting and casting process: melting temperature 720℃, refining temperature 740℃, 1.5% aluminum-titanium-boron refiner is added to the melting furnace, the aluminum alloy raw materials in the melting furnace are completely melted and evenly stirred by a stirring device, and then cast into aluminum alloy rods by a casting equipment.

[0181] C. Homogenization treatment: The cast rod is homogenized at a temperature of 560°C for 8 hours, and then cooled by water cooling.

[0182] D. Extrusion: Use a 36MN double-action horizontal aluminum extruder to produce 131mm×114mm, 2-3mm thick automotive 6 series aluminum alloy thin-walled multi-cavity profiles, with a maximum extrusion force of 28MN, online spray production, a casting rod diameter of 310mm, a casting rod heating temperature of 521℃, a mold heating temperature of 500℃, an extrusion barrel temperature of 452℃, a profile outlet temperature of 525℃, a mold diverter bridge with a rectangular chamfer, a chamfer α=30°, a bridge bottom radius of 6mm, the welding chamber height increased to 45mm, the extrusion speed of 3m / min, and the quenching cooling rate of 153℃ / min.

[0183] E. Heat treatment: The aluminum alloy profile after stretching and straightening is heat treated at a temperature of 175°C for 8 hours.

[0184] The 6 series aluminum alloy thin-walled multi-cavity profiles for automobiles prepared by the above process were tested:

[0185] 1. Mechanical properties test: The test equipment is AG-X 100KN electronic universal testing machine. Test method: GB / T228.1-2010 Metal material tensile test Part 1: Room temperature test method. The mechanical properties test is shown in Table 2 below:

[0186] Table 8.2 Mechanical properties results

[0187]

[0188]

[0189] 2. Bending test: Test equipment: AG-X 250KN electronic universal testing machine. Test method: GB / T232-2010 metal material bending test method. Test standard: bending angle 90°, no cracking.

[0190] Test results such as Fig.14 As shown, cracks appear after bending 90°.

[0191] Comparative Example 6.

[0192] A. Ingredients: Ingredients shall be made according to the alloy elements in Table 9.1.

[0193] 9.1 Chemical composition

[0194] element Si Fe Cu Mn Mg Cr Zn Impurities Al content 0.47 0.12 0.005 0.006 0.48 0.004 0.005 0.05 margin

[0195] B. Melting and casting process: melting temperature 720℃, refining temperature 740℃, 1.5% aluminum-titanium-boron refiner is added to the melting furnace, the aluminum alloy raw materials in the melting furnace are completely melted and evenly stirred by a stirring device, and then cast into aluminum alloy rods by a casting equipment.

[0196] C. Homogenization treatment: The cast rod is homogenized at a temperature of 560°C for 8 hours, and then cooled by water cooling.

[0197] D. Extrusion: Use 36MN double-action horizontal aluminum extruder to produce 131mm×114mm, 2-3mm thick automotive 6 series aluminum alloy thin-walled multi-cavity profiles, with a maximum extrusion force of 28MN, online spray production, a casting rod diameter of 310mm, a casting rod heating temperature of 522℃, a mold heating temperature of 490℃, an extrusion barrel temperature of 440℃, a profile outlet temperature of 525℃, a mold diverter bridge with rectangular chamfer, chamfer α=30°, a bridge bottom radius of 6mm, the welding chamber height increased to 45mm, the extrusion speed of 3m / min, and the quenching cooling rate of 154℃ / min.

[0198] E. Heat treatment: The aluminum alloy profile after stretching and straightening is heat treated at a temperature of 168°C × 6.5h.

[0199] The 6 series aluminum alloy thin-walled multi-cavity profiles for automobiles prepared by the above process were tested:

[0200] 1. Mechanical properties: Test equipment: AG-X 100KN electronic universal testing machine. Test method: GB / T228.1-2010 Tensile test of metallic materials Part 1: Room temperature test method.

[0201] Table 9.2 Mechanical properties results

[0202]

[0203] 2. Salt spray corrosion: Test equipment: Q-FOG cyclic salt spray corrosion tester, AG-X 100KN electronic universal testing machine. Test method: GB / T 10125-2021 Artificial atmosphere corrosion test salt spray test, GB / T228.1-2010 Metal material tensile test Part 1: Room temperature test method.

[0204] Table 9. Mechanical properties after 3480h neutral salt spray corrosion

[0205]

[0206] 3. Brinell hardness: Test equipment: HB-3000C electronic Brinell hardness tester. Test method: GB / T231.1-2018 Brinell hardness test for metallic materials Part 1: Test method.

[0207] Table 9.4 Brinell hardness

[0208]

[0209] 4. Bending test: Test equipment: AG-X 250KN electronic universal testing machine. Test method: GB / T232-2010 metal material bending test method. Test standard: bending angle 90°, no cracking.

[0210] Test results such as Fig.15 As shown, there is no crack at a bending angle of 90°.

[0211] Comparative Example 7.

[0212] A. Ingredients: Ingredients shall be made according to the alloy elements in Table 10.1.

[0213] 10.1 Chemical composition

[0214] element Si Fe Cu Mn Mg Cr Zn Impurities Al content 0.64 0.14 0.18 0.08 0.94 0.09 0.004 0.05 margin

[0215] B. Melting and casting process: melting temperature 720℃, refining temperature 740℃, 1.5% aluminum-titanium-boron refiner is added to the melting furnace, the aluminum alloy raw materials in the melting furnace are completely melted and evenly stirred by a stirring device, and then cast into aluminum alloy rods by a casting equipment.

[0216] C. Homogenization treatment: The cast rod is homogenized at a temperature of 560°C for 8 hours, and then cooled by water cooling.

[0217] D. Extrusion: A 36MN double-action horizontal aluminum extruder is used to produce 131mm×114mm, 2-3mm thick automotive 6 series aluminum alloy thin-walled multi-cavity profiles with a maximum extrusion force of 28MN. The production is carried out by online spraying. The diameter of the casting rod is 310mm, the heating temperature of the casting rod is 522℃, the heating temperature of the mold is 490℃, the temperature of the extrusion barrel is 440℃, and the profile outlet temperature is 524℃. The above-mentioned mold diverter bridge adopts a rectangular chamfer design with chamfer α=30°, the bottom radius of the bridge is 6mm, the height of the welding chamber is 45mm, the extrusion speed is 3m / min, and the quenching cooling rate is 148℃ / min.

[0218] E. Heat treatment: The aluminum alloy profile after stretching and straightening is heat treated at a temperature of 168°C × 6.5h.

[0219] The 6 series aluminum alloy thin-walled multi-cavity profiles for automobiles prepared by the above process were tested:

[0220] 1. Mechanical properties test: The test equipment is AG-X 100KN electronic universal testing machine. Test method: GB / T228.1-2010 Metal material tensile test Part 1: Room temperature test method. Mechanical properties test is shown in Table 10.2 below:

[0221] Table 10.2 Mechanical properties results

[0222]

[0223] 2. Bending test: Test equipment: AG-X 250KN electronic universal testing machine. Test method: GB / T232-2010 metal material bending test method. Test standard: bending angle 90°, no cracking.

[0224] The test results are as follows Fig.16 As shown, cracks appear after bending at an angle of 90°.

[0225] The results of the above embodiments and comparative examples are analyzed. Comparative Example 1 is an aluminum profile prepared by conventional 6061 aluminum alloy composition and conventional production method. The internal ribs of the extruded profile are cracked. After testing, its mechanical properties meet the requirements, but its plasticity is poor, and cracks occur in the bending test.

[0226] Comparative Example 2 is an aluminum profile prepared by using the newly designed aluminum alloy composition of the present application and a conventional production method. By analyzing its experimental results, due to the reduced degree of alloying, the internal ribs of the profile did not crack during extrusion production. The conventional peak aging system was still used, and its mechanical properties could meet the requirements. The plasticity of the profile was poor, and a higher homogenization temperature was used, resulting in excessive grain growth, affecting the plasticity of the alloy, and cracking occurred in subsequent bending.

[0227] Comparative Example 3 adopts the new alloy composition designed in this application, adopts the optimized homogenization treatment system, and combines the traditional extrusion process, extrusion die, and heat treatment system to analyze the test results. More rod-shaped β' will be formed during peak aging, which effectively hinders the dislocation movement. Although its mechanical properties meet the requirements, it affects the plasticity of the profile, and cracking occurs in subsequent bending. Since its plasticity does not meet the requirements, it is no longer subjected to salt spray corrosion, Brinell hardness, exfoliation corrosion, intergranular corrosion and other tests.

[0228] Comparative Example 4 adopts the new alloy composition designed in the present application, adopts the traditional homogenization treatment system, and adopts the optimized extrusion parameters, die design and heat treatment system. The test results are analyzed. Although its mechanical properties meet the requirements, due to the use of too high homogenization temperature, the grains in the aluminum alloy grow, affecting the plasticity of the profile, cracking occurs after bending, and the number of grain boundaries decreases, reducing the aluminum alloy's resistance to intergranular corrosion. Its intergranular corrosion does not meet the requirements, so it is no longer subjected to salt spray corrosion, Brinell hardness, exfoliation corrosion and other tests.

[0229] Comparative Example 5 adopts the new alloy composition designed in this application, adopts the optimized homogenization treatment system, extrusion parameters, die design, and traditional heat treatment system, analyzes the test results, and adopts a high-temperature aging system. Its mechanical properties can meet the requirements, but the aging temperature is too high, resulting in coarse aluminum alloy grains, which makes it more fragile and cracks appear during the bending process. Since its plasticity does not meet the requirements, it is not tested for salt spray corrosion, Brinell hardness, and exfoliation corrosion.

[0230] Comparative Example 6 adopts the new alloy composition designed in the present application, further reduces its alloy composition, specifically reduces the alloy components such as Si, Cu, and Mg, and selects the optimized homogenization treatment system, extrusion parameters, mold design, and heat treatment system. The test results are analyzed. Due to the low content of Si, Cu, and Mg elements in the alloy, the formed strengthening phase Mg2Si is small, and its mechanical properties, mechanical properties after salt spray corrosion, and Brinell hardness do not meet the use requirements.

[0231] Comparative Example 7 uses the traditional 6061 aluminum alloy composition, and cooperates with the homogenization treatment system, extrusion parameters, die design, and heat treatment system optimized by this application. The test results are analyzed and its mechanical properties can meet the requirements, but due to the high alloying degree of the original composition, the toughness of the aluminum alloy is reduced, and crack defects are generated during bending. Since its plasticity does not meet the requirements, it is not tested for salt spray corrosion, Brinell hardness, exfoliation corrosion, etc.

[0232] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and inventive concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A 6 series aluminum alloy thin-walled multi-cavity profile for automobiles, characterized in that: The components and their weight percentages in the aluminum alloy profile are: Si: 0.55-0.6%; Fe: 0.10-0.15%; Cu: 0.20-0.25%; Mn≤0.1%; Mg: 0.52-0.57%; Cr≤0.05%; Zn≤0.05%, total impurities ≤0.03%, the balance is Al.

2. A method for preparing the 6 series aluminum alloy thin-walled multi-cavity profile for vehicles according to claim 1, characterized in that: The preparation method comprises: A. Ingredients: Prepare the raw materials according to the composition of 6 series aluminum alloy thin-walled multi-cavity profiles for automobiles; B. Melting and casting: adding the prepared aluminum alloy raw materials into a melting furnace, mixing them evenly, and then melting them into liquid aluminum alloy, and then casting the liquid aluminum alloy into aluminum alloy casting rods; C. Homogenization treatment: The aluminum alloy casting rod is homogenized at 555℃~565℃×8h, and then cooled by water cooling; D. Extrusion: The aluminum alloy cast rod that has been homogenized is placed in an extruder for extrusion to obtain an aluminum alloy profile, and the extruded aluminum profile is quenched online and then stretched and straightened; E. Heat treatment: The aluminum alloy profile after stretching and straightening is heat treated at a temperature of 165°C to 171°C for 6.5 hours.

3. The method for preparing a 6 series aluminum alloy thin-walled multi-cavity profile for vehicles according to claim 2, characterized in that: The extrusion process in step D is as follows: the mold heating temperature is 480-510° C., the extrusion barrel heating temperature is 440-460° C., the casting rod heating temperature is 510-530° C., and the extrusion product speed is limited to 2-4 m / min.

4. The method for preparing a 6 series aluminum alloy thin-walled multi-cavity profile for vehicles according to claim 2, characterized in that: The quenching cooling rate of the aluminum profile in step D is ≥120°C / min.

5. The method for preparing a 6 series aluminum alloy thin-walled multi-cavity profile for vehicles according to claim 2, characterized in that: In the step C, the homogenization treatment system is specifically 560° C.×8 h.

6. The method for preparing a 6 series aluminum alloy thin-walled multi-cavity profile for vehicles according to claim 2, characterized in that: In the step E, the heat treatment system is specifically 168° C.×6.5 h.

7. The method for preparing a 6 series aluminum alloy thin-walled multi-cavity profile for vehicles according to claim 2, characterized in that: The chamfer angle of the diverter bridge of the die in the extruder is α=30°, and the fillet of the bridge bottom is selected to be 6mm.

8. The process for producing a 6 series aluminum alloy thin-walled multi-cavity profile for vehicles according to claim 7, characterized in that: The die welding chamber height in the extruder is 45 mm.

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