6N16 aluminum alloy for automobile inner plate and preparation method of 6N16 aluminum alloy

Abstract

The invention discloses a 6N16 aluminum alloy for an automobile inner plate and a preparation method of the 6N16 aluminum alloy, and belongs to the technical field of aluminum alloy preparation. The aluminum alloy comprises the following alloy components in percentage by weight: 0.9-1.2% of Si, 0.1-0.3% of Fe, 0.05-0.15% of Cu, 0.1-0.3% of Mn, 0.3-0.5% of Mg, 0.02-0.05% of Cr, less than or equal to 0.1% of Zn, less than or equal to 0.1% of Ti, less than or equal to 0.03% of V, less than or equal to 0.05% of single impurity, less than or equal to 0.15% of total impurity and the balance of Al. The aluminum alloy is prepared through smelting, casting, homogenization treatment, hot rolling, cold rolling, continuous annealing and pre-aging, and stretching is conducted in the continuous annealing process. By adjusting the alloy components and the preparation process, the 6-series aluminum alloy plate with high strength and good formability is obtained, and the performance index of the 6-series aluminum alloy automobile inner plate is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloy preparation, and particularly relates to a 6N16 aluminum alloy for automotive inner panels and a preparation method thereof. Background Art

[0002] Aluminum alloy automotive inner panels are important components in automotive manufacturing and have received relatively extensive attention and application in the automotive industry in recent years. Currently, it is widely recognized at home and abroad that using 5182 (Al-Mg series) as the material for automotive inner panels and 6016 (Al-Mg-Si series) alloy as the material for automotive body outer panels is beneficial to achieving vehicle body lightweighting. However, when using 5182 aluminum alloy as the automotive inner panel, there is a problem of intermittent cracking caused by out-of-control material flow during stamping, which is mainly related to its n value and r value, thus affecting the strength of the components. Based on this, a 6-series aluminum alloy for automotive inner panels is proposed. Summary of the Invention

[0003] To solve the above technical problems, the present invention provides a 6N16 aluminum alloy for automotive inner panels and a preparation method thereof.

[0004] The technical solution of the present invention is as follows:

[0005] The present invention provides a 6N16 aluminum alloy for automotive inner panels, including alloy components in the following weight percentages: Si 0.9 - 1.2%, Fe 0.1 - 0.3%, Cu 0.05 - 0.15%, Mn 0.1 - 0.3%, Mg 0.3 - 0.5%, Cr 0.02 - 0.05%, Zn ≤ 0.1%, Ti ≤ 0.1%, V ≤ 0.03%, the content of a single impurity ≤ 0.05%, the total impurity content ≤ 0.15%, and the balance is Al.

[0006] Further, Mg + Si is 1.2 - 1.7%.

[0007] Further, Cr + Zn + V ≤ 0.15%.

[0008] The present invention also provides a preparation method for a 6N16 aluminum alloy for automotive inner panels, including the steps of:

[0009] S1. According to the set alloy component range of the 6N16 aluminum alloy, batching is carried out, and the raw materials are melted and cast to obtain a 6N16 aluminum alloy ingot;

[0010] S2. Perform homogenization treatment on the 6N16 aluminum alloy ingot;

[0011] S3. Perform multi-pass hot rolling on the homogenized 6N16 aluminum alloy, and coil at 300 ± 10°C after hot rolling to obtain a hot-rolled coil;

[0012] S4. Perform multi-pass cold rolling on the hot-rolled coil to obtain cold-rolled sheets;

[0013] S5. Anneal the cold-rolled sheets on a continuous annealing line, and perform stretching simultaneously during the continuous annealing process;

[0014] S6. Perform pre-aging treatment on the annealed sheets, and then air-cool to room temperature to obtain 6N16 aluminum alloy coils.

[0015] Further, in step S1, during the melting process, control the melt heating temperature to 740 ± 20 °C. When all the raw materials are melted, take pre-analysis samples as needed, control the sampling temperature to 690 - 760 °C, and add manganese agent and / or iron agent and / or copper agent at 730 - 750 °C according to the sampling analysis results;

[0016] In step S1, the STAS process is also used to refine the melt during the melting process. During the refining process, control the melt temperature to 720 - 750 °C, use Cl2-Ar mixed gas to refine for at least 30 min, set the rotor speed to 200 - 400 rpm, the argon flow rate to 150 - 198 slpm, the chlorine flow rate to 0 - 48 slpm, and the input ratio of argon and chlorine to be 75 - 100% for argon and 0 - 25% for chlorine.

[0017] Further, in step S2, the homogenization treatment process is to heat the aluminum alloy ingot to 560 ± 5 °C and hold for at least 8 hours, and the total heating time in the homogenization furnace cannot exceed 36 hours.

[0018] Further, the hot rolling process in step S3 includes rough rolling and finish rolling;

[0019] The number of rough rolling passes is 20 - 30 passes, and the maximum reduction ratio during rough rolling is 25 - 55 mm. The thickness of the intermediate plate obtained after rough rolling is 45 - 58 mm, and the temperature of the intermediate plate is 360 - 400 °C;

[0020] The number of finish rolling passes is 3 - 7 passes, and the maximum reduction ratio during finish rolling is 2 - 20 mm. The thickness of the hot-rolled final rolling plate obtained after finish rolling is 3.5 - 7.5 mm;

[0021] In step S4, during the cold rolling process, first roll 2 - 3 passes with a rolling mill, and then roll 1 pass with EDT to obtain cold-rolled sheets with a thickness of 0.8 - 1.5 mm.

[0022] Further, in step S5, during continuous annealing line annealing, the annealing temperature is 540 - 560 °C, and the annealing time is 10 - 30 s of holding time starting from when the annealing temperature is reached.

[0023] Further, in step S5, the stretching rate is 0.2 - 0.5%.

[0024] Further, in step S6, the pre-aging temperature is 65 ± 5°C.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] The present invention provides a 6N16 aluminum alloy for automotive inner panels and its preparation method. By adjusting the alloy composition and preparation process, a 6-series aluminum alloy sheet with high strength and good formability is obtained, enabling the 6-series aluminum alloy to be used for preparing automotive inner panels and further improving the performance indicators of automotive inner panels. Specific Embodiments

[0027] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0028] The present invention provides a 6N16 aluminum alloy for automotive inner panels, including alloy components with the following weight percentages: Si 0.9 - 1.2%, Fe 0.1 - 0.3%, Cu 0.05 - 0.15%, Mn 0.1 - 0.3%, Mg 0.3 - 0.5%, Cr 0.02 - 0.05%, Zn ≤ 0.1%, Ti ≤ 0.1%, V ≤ 0.03%, the content of a single impurity ≤ 0.05%, the total impurity content ≤ 0.15%, and the balance is Al.

[0029] In the preferred embodiment of the present invention, the content of Mg + Si is controlled to be 1.2 - 1.7%. By controlling the contents of Mg and Si, the total amount of the formed Mg2Si phase is controlled, and controlling the total amount of Mg + Si ≤ 1.7% also avoids the precipitation of coarse phases.

[0030] In the preferred embodiment of the present invention, it is also controlled that Cr + Zn + V ≤ 0.15%. By adding microalloying elements Cr, Zn, and V in the present invention, a (Cr,Zn,V)Al3 composite precipitation phase can be formed during the heat treatment process. The (Cr,Zn,V)Al3 composite precipitation phase can maintain a dispersed distribution of less than 50 nm at 200°C (where Cr inhibits recrystallization, and Zn / V synergistically improves the thermal stability of the precipitation phase), thereby improving the mechanical properties of the aluminum alloy through dispersion strengthening.

[0031] Based on the above 6N16 aluminum alloy, the present invention also provides a preparation method for this alloy, including the steps:

[0032] S1. According to the set alloy composition range of 6N16 aluminum alloy, the raw materials are mixed, smelted and cast to obtain 6N16 aluminum alloy ingots; wherein, during the smelting process, the melt heating temperature is controlled to be 740±20°C, and when all the raw materials are melted, a pre-analysis sample is taken as needed, and the sampling temperature is controlled at 690-760°C, and according to the sampling analysis results, a manganese agent and / or an iron agent and / or a copper agent is added at 730-750°C; during refining, the STAS process is used to refine the melt, and the melt temperature is controlled to be 720-750°C during the refining process, and Cl2-Ar mixed gas is used for refining for at least 30 minutes, and the rotor speed is set to 200-400rpm, the argon flow rate is 150-198slpm, the chlorine flow rate is 0-48slpm, and the introduction ratio of argon and chlorine is 75-100% for argon and 0-25% for chlorine;

[0033] S2. Perform homogenization treatment on the 6N16 aluminum alloy ingot, specifically, heating the aluminum alloy ingot to 560±5°C and keeping it warm for 8 hours, and the total heating time in the homogenization furnace shall not exceed 36 hours;

[0034] S3, the 6N16 aluminum alloy after homogenization treatment is subjected to multiple hot rolling, the hot rolling process includes rough rolling and finish rolling, wherein the rough rolling passes are 20 to 30 passes, the maximum reduction during the rough rolling process is 25 to 55 mm, the thickness of the intermediate plate obtained after the rough rolling is 45 to 58 mm, and the temperature of the intermediate plate is 360 to 400 ° C; the finish rolling passes are 3 to 7 passes, and the maximum reduction during the finish rolling process is 2 to 20 mm, the thickness of the rolled plate obtained after the finish rolling is 3.5 to 7.5 mm, and the finish rolling is followed by coiling, and the coiling temperature is 300 ± 10 ° C;

[0035] S4, performing multiple cold rolling on the hot rolled coil, specifically first using a rolling mill for 2 to 3 passes, and then EDT rolling for 1 pass, to obtain a cold rolled sheet with a thickness of 0.8 to 1.5 mm;

[0036] S5. After cold rolling, continuous annealing is performed at a temperature of 540 to 560°C. The annealing time is 10 to 30 seconds from the time the annealing temperature is reached. After annealing, air cooling is performed. During the continuous annealing, stretching is performed at the same time, and the stretching rate is 0.2 to 0.5%.

[0037] S6. The annealed sheet is subjected to a pre-aging treatment at a temperature of 65±5°C, and then air-cooled to room temperature to obtain a 6N16 aluminum alloy coil.

[0038] Example 1

[0039] This embodiment provides a 6N16 aluminum alloy, and its alloy composition is as follows:

[0040] Si 1.0827%, Fe 0.2104%, Cu 0.0723%, Mn 0.1312%, Mg 0.4336%, Cr 0.0302%, Zn 0.0090%, Ti 0.0209%, V 0.0139%. The content of other single impurities is ≤0.02%, and the total impurity content is ≤0.1%. The balance is Al.

[0041] The preparation method of the above 6N16 aluminum alloy is as follows:

[0042] S1. Weigh materials according to the alloy composition range of the set 6N16 aluminum alloy, melt and cast the raw materials to obtain a 6N16 aluminum alloy ingot. During the melting process, set the melt heating temperature at 740°C. When all the raw materials are melted, take a pre-analysis sample as needed. Control the sampling temperature at 730°C, and add manganese agent and / or iron agent and / or copper agent at 740°C according to the sampling analysis results. During refining, use the STAS process to refine the melt. Control the melt temperature at 735°C during the refining process. Refine with a Cl2-Ar mixed gas for 30 minutes, set the rotor speed at 300 rpm, the argon flow rate at 150 slpm, the chlorine flow rate at 48 slpm, and the volume ratio of argon to chlorine for introduction is 75% argon and 25% chlorine.

[0043] S2. Carry out homogenization treatment on the 6N16 aluminum alloy ingot. Specifically, heat the aluminum alloy ingot to 560±5°C and hold for 10 hours before taking it out of the furnace.

[0044] S3. Directly carry out multi-pass hot rolling on the 6N16 aluminum alloy after homogenization treatment and taken out of the furnace. This hot rolling process includes rough rolling and finish rolling. Among them, the number of rough rolling passes is 27. For the first 9 passes: the maximum reduction per pass is 55 mm; for the middle 12 passes: the reduction gradually decreases from 35 mm to 25 mm; for the last 6 passes: the stable reduction is 15 mm. The thickness of the intermediate plate obtained after rough rolling is 45 mm, and the temperature of the intermediate plate is 392°C. The number of finish rolling passes is 5, and the maximum reduction during finish rolling is 20 mm. The thickness of the rolled sheet obtained after finish rolling is 5.0 mm. After finish rolling, coiling is carried out, and the coiling temperature is 300±10°C.

[0045] S4. Cold roll the hot-rolled coil in multiple passes. Specifically, first roll it 3 times with a rolling mill, and then roll it 1 time with EDT, obtaining a cold-rolled sheet with a thickness of 1.15 mm, that is, 5.0 mm - 3.0 mm - 1.9 mm - 1.19 mm - 1.15 mm (EDT); in addition, during the cold rolling process, the reduction rate of the EDT pass can be adjusted within the range of 3 - 5%; except for the EDT pass, the reduction rate of each of the other passes can be adjusted within the range of 35 - 50% and a tolerance of ±2% is allowed; during the EDT rolling process, control the surface quality to meet Ra: 0.7 - 1.3 um, Rpc > 55 per cm;

[0046] S5. After cold rolling, perform continuous annealing on the continuous production line. The annealing temperature is 550 °C, and the annealing time is calculated starting from when the annealing temperature of 550 °C is reached and holding for 20 s. After annealing is completed, air-cool to the pre-aging temperature, and at the same time, perform stretching in a pure stretching mode during the continuous annealing process, with a stretching rate of 0.2%;

[0047] S6. Perform pre-aging treatment on the annealed sheet on the continuous production line. The pre-aging temperature is 65 ± 5 °C, the line speed is 40.5 m / min, and after exiting the pre-aging furnace, air-cool to room temperature to obtain 6N16 aluminum alloy coil.

[0048] Example 2

[0049] This example provides a 6N16 aluminum alloy, and its alloy composition is as follows:

[0050] Si 1.0507%, Fe 0.1703%, Cu 0.0666%, Mn 0.1201%, Mg 0.3902%, Cr 0.0262%, Zn 0.0073%, Ti 0.0192%, V 0.0145%, the content of other single impurities ≤ 0.02%, the total impurity content ≤ 0.1%, and the balance is Al.

[0051] The preparation method of the above 6N16 aluminum alloy is as follows:

[0052] S1. According to the set alloy composition range of 6N16 aluminum alloy, the raw materials are prepared, and the raw materials are melted and cast to obtain 6N16 aluminum alloy ingots; wherein, during the smelting process, the melt heating temperature is set to 740°C. When all the raw materials are melted, a pre-analysis sample is taken as needed, and the sampling temperature is controlled at 730°C. According to the sampling analysis results, a manganese agent and / or an iron agent and / or a copper agent is added at 740°C; during refining, the STAS process is used to refine the melt, and the melt temperature is controlled to 735°C during the refining process. Cl2-Ar mixed gas is used for refining for 30 minutes, and the rotor speed is set to 300rpm, the argon flow rate is 150slpm, the chlorine flow rate is 48slpm, and the introduction ratio (volume ratio) of argon and chlorine is 75% argon and 25% chlorine;

[0053] S2. Performing homogenization treatment on the 6N16 aluminum alloy ingot, specifically heating the aluminum alloy ingot to 560±5°C and keeping the temperature for 10 hours before taking out of the furnace;

[0054] S3, directly subjecting the 6N16 aluminum alloy after homogenization treatment to multiple hot rolling, the hot rolling process includes rough rolling and finish rolling, wherein the rough rolling passes are 27 passes, the first 9 passes: the maximum reduction of a single pass is 55mm; the middle 12 passes: the reduction decreases step by step, from 35mm to 25mm; the last 6 passes: the stable reduction is 15mm, the thickness of the intermediate plate obtained after rough rolling is 45mm, and the temperature of the intermediate plate is 386℃; the finish rolling passes are 5 passes, and the maximum reduction during the finish rolling process is 20mm, the thickness of the rolled plate obtained after the finish rolling is 5.0mm, and the coiling is performed after the finish rolling, and the coiling temperature is 300±10℃;

[0055] S4, the hot rolled coil is subjected to multiple cold rolling, specifically, firstly 2 passes of rolling by a rolling mill, and then 1 pass of EDT rolling, and the thickness of the obtained cold rolled sheet is 1.15mm, i.e. 4.0mm-2.2mm-1.19mm-1.15mm (EDT); in addition, during the cold rolling process, the reduction rate of the EDT pass can be adjusted within the range of 3-5%; except for the EDT pass, the reduction rate of each other pass can be adjusted within the range of 35-50% and a tolerance of ±2% is allowed; during the EDT rolling process, the surface quality is controlled to meet Ra: 0.7-1.3um, Rpc>55 pieces / cm;

[0056] S5. After cold rolling, continuous annealing is performed on a continuous production line. The annealing temperature is 550°C. The annealing time is 20 seconds starting from the annealing temperature of 550°C. After annealing, the steel is air-cooled to the pre-aging temperature. During the continuous annealing, pure stretching mode is used for stretching, and the stretching rate is 0.2%.

[0057] S6. Perform pre-aging treatment on the annealed sheet on a continuous production line. The pre-aging temperature is 65 ± 5 °C, the linear speed is 40.5 m / min, and after exiting the pre-aging furnace, it is air-cooled to room temperature to obtain 6N16 aluminum alloy coils.

[0058] Example 3

[0059] This example provides a 6N16 aluminum alloy, and its alloy composition is as follows:

[0060] Si 1.0636%, Fe 0.1948%, Cu 0.0767%, Mn 0.1323%, Mg 0.4176%, Cr 0.0323%, Zn 0.0093%, Ti 0.0213%, V 0.0145%, the content of other single impurities ≤ 0.02%, the total impurity content ≤ 0.1%, and the balance is Al.

[0061] The preparation method of the above 6N16 aluminum alloy is as follows:

[0062] S1. According to the set alloy composition range of 6N16 aluminum alloy, charge materials, melt and cast the raw materials to obtain 6N16 aluminum alloy ingots; among them, during the melting process, set the melt heating temperature to 740 °C. When all the raw materials are melted, take pre-analysis samples as needed, control the sampling temperature at 730 °C, and according to the sampling analysis results, add manganese agent and / or iron agent and / or copper agent at 740 °C; during refining, use the STAS process to refine the melt, control the melt temperature at 735 °C during the refining process, refine with Cl2-Ar mixed gas for 30 min, set the rotor speed to 300 rpm, the argon flow rate to 150 slpm, the chlorine flow rate to 48 slpm, and the input ratio (volume ratio) of argon to chlorine to be 75% argon and 25% chlorine;

[0063] S2. Perform homogenization treatment on the 6N16 aluminum alloy ingots. Specifically, heat the aluminum alloy ingots to 560 ± 5 °C and hold for 15 hours before taking them out of the furnace;

[0064] S3. Directly perform multi-pass hot rolling on the 6N16 aluminum alloy after homogenization treatment. This hot rolling process includes rough rolling and finish rolling. Among them, the rough rolling pass is 27 passes. For the first 9 passes: the maximum reduction per pass is 55 mm; for the middle 12 passes: the reduction decreases step by step from 35 mm to 25 mm; for the last 6 passes: the stable reduction is 15 mm. The thickness of the intermediate plate obtained after rough rolling is 45 mm, and the temperature of the intermediate plate is 389 °C; the finish rolling pass is 5 passes, and the maximum reduction during finish rolling is 20 mm. The thickness of the rolled sheet obtained after finish rolling is 5.0 mm. After finish rolling, coiling is carried out, and the coiling temperature is 300 ± 10 °C;

[0065] S4. The hot-rolled coil is cold-rolled in multiple passes. Specifically, it is first rolled 3 passes by a rolling mill and then 1 pass by EDT, and the thickness of the cold-rolled sheet obtained is 0.8 mm, that is, 3.5 mm - 2.1 mm - 1.3 mm - 0.825 mm - 0.8 mm (EDT); in addition, during the cold rolling process, the reduction rate of the EDT pass can be adjusted within the range of 3% - 5%; except for the EDT pass, the reduction rate of each pass can be adjusted within the range of 35 - 50% and a tolerance of ±2% is allowed; during the EDT rolling process, the surface quality is controlled to meet Ra: 0.7 - 1.3 um, Rpc > 55 pieces / cm;

[0066] S5. After cold rolling, continuous annealing is carried out on a continuous production line. The annealing temperature is 550 °C, and the annealing time is 20 s of heat preservation starting from when the annealing temperature of 550 °C is reached. After annealing is completed, it is air-cooled to the pre-aging temperature, and during the continuous annealing process on the continuous production line, pure tension mode is simultaneously used for stretching, and the stretching rate is 0.2%;

[0067] S6. The annealed sheet is subjected to pre-aging treatment on a continuous production line. The pre-aging temperature is 65 ± 5 °C, the linear speed is 45 m / min, and after coming out of the pre-aging furnace, it is air-cooled to room temperature to obtain 6N16 aluminum alloy coil.

[0068] Example 4

[0069] The difference between this example and Example 1 is that this example provides a 6N16 aluminum alloy, and its alloy composition is as follows:

[0070] Si 0.9521%, Fe 0.1254%, Cu 0.1017%, Mn 0.1946%, Mg 0.3422%, Cr 0.0409%, Zn 0.0079%, Ti 0.0314%, V 0.0132%, the content of other single impurities ≤ 0.02%, the total impurity content ≤ 0.1%, and Al is the balance.

[0071] Example 5

[0072] The difference between this example and Example 1 is that this example provides a 6N16 aluminum alloy, and its alloy composition is as follows:

[0073] Si 1.1874%, Fe 0.2716%, Cu 0.1375%, Mn 0.2642%, Mg 0.4752%, Cr 0.0411%, Zn 0.0082%, Ti 0.03361%, V 0.0210%, the content of other single impurities ≤ 0.02%, the total impurity content ≤ 0.1%, and Al is the balance.

[0074] Comparative Example 1

[0075] The difference between this comparative example and Example 1 is that the Mg content in this comparative example is 0.2083%.

[0076] Comparative Example 2

[0077] The difference between this comparative example and Example 1 is that the Si content in this comparative example is 1.5126%.

[0078] Comparative Example 3

[0079] The difference between this comparative example and Example 1 is that the Mn content in this comparative example is 0.0537%.

[0080] Comparative Example 4

[0081] The difference between this comparative example and Example 1 is that in the preparation process of this comparative example, stretching is carried out first, and then annealing is carried out. The annealing process and the stretching rate are the same as those in Example 1.

[0082] Comparative Example 5

[0083] The difference between this comparative example and Example 1 is that in the preparation process of this comparative example, continuous annealing line annealing is carried out first, and then stretching is carried out. The annealing process and the stretching rate are the same as those in Example 1.

[0084] Samples of the aluminum alloy sheets prepared in the above Examples 1-5 and Comparative Examples 1-6 were taken for mechanical property testing, as shown in Table 1 below.

[0085] Table 1

[0086]

[0087] Samples of the aluminum alloy sheets prepared in the above Examples 1-5 were taken for baking. The baking temperature was 180 °C and the baking time was 8 hours, and the mechanical properties after baking were detected, as shown in Table 2 below.

[0088] Table 2

[0089]

[0090]

[0091] By analyzing the mechanical property test results in Table 1 and Table 2 above:

[0092] The mechanical properties of the aluminum alloy sheets prepared in Examples 1-5 before and after baking both meet the standard requirements, and their strain hardening index and plastic strain ratio are relatively high, indicating that they have good formability and can be applied to the preparation of automotive inner panels;

[0093] The mechanical properties of the aluminum alloy sheets prepared in Comparative Examples 1-3 before baking could not meet the standard requirements. The main reasons were analyzed as follows: In Comparative Example 1, the low Mg content resulted in insufficient formation of Mg2Si phase, leading to a decrease in strength; in Comparative Example 2, the high Si content caused excess Si to form plate-like free phases, resulting in an increase in strength but a decrease in elongation; in Comparative Example 3, the low Mn content led to an increase in grain size and a reduction in substructure, resulting in a decrease in strength; moreover, the aluminum alloy sheets prepared in Comparative Examples 1-3 had a low strain hardening index and poor uniform deformation ability.

[0094] The mechanical properties of the aluminum alloy sheets prepared in Comparative Examples 4 and 5 before baking also could not meet the standard requirements. The main reasons were analyzed as follows: In Comparative Example 4, the process of stretching first and then annealing was adopted. During the stretching process, a high density of dislocations was generated. On this basis, recrystallization occurred during annealing, forming coarse recrystallized grains, resulting in a decrease in strength, an increase in elongation, and obvious anisotropy; in Comparative Example 5, the process of annealing first and then stretching was adopted. During the annealing process, recrystallization occurred to form uniform equiaxed grains. On this basis, stretching would generate a high density of dislocations and cold work hardening would occur, resulting in an increase in strength but a decrease in elongation; moreover, the aluminum alloy sheets prepared in Comparative Examples 4 and 5 had a low strain hardening index and poor uniform deformation ability.

[0095] It should be noted that the parts not described in the present invention can be realized by adopting or referring to the existing technologies.

[0096] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by those skilled in the art within the essence of the present invention should also fall within the protection scope of the present invention.

Claims

1. A 6N16 aluminum alloy for automotive inner panels, characterized in that, It includes alloy components with the following weight percentages: Si 0.9 - 1.2%, Fe 0.1 - 0.3%, Cu 0.05 - 0.15%, Mn 0.1 - 0.3%, Mg 0.3 - 0.5%, Cr 0.02 - 0.05%, Zn ≤ 0.1%, Ti ≤ 0.1%, V ≤ 0.03%, the content of a single impurity ≤ 0.05%, the total impurity content ≤ 0.15%, and Al is the balance.

2. The 6N16 aluminum alloy for automotive inner panel according to claim 1, wherein, Mg + Si is 1.2 - 1.7%.

3. A 6N16 aluminum alloy for automotive inner panels according to claim 1, characterized in that, Cr + Zn + V ≤ 0.15%.

4. A preparation method of 6N16 aluminum alloy for automotive inner panel according to any one of claims 1-3, characterized in that, It includes the steps: S1. According to the set alloy composition range of 6N16 aluminum alloy, charge materials, melt and cast the raw materials to obtain a 6N16 aluminum alloy ingot; S2. Carry out homogenization treatment on the 6N16 aluminum alloy ingot; S3. Carry out multi-pass hot rolling on the homogenized 6N16 aluminum alloy, and coil at 300 ± 10 °C after hot rolling to obtain a hot-rolled coil; S4. Carry out multi-pass cold rolling on the hot-rolled coil to obtain a cold-rolled sheet; S5. Carry out continuous annealing on the cold-rolled sheet, and simultaneously carry out stretching during the continuous annealing process; S6. Carry out pre-aging treatment on the annealed sheet, and then air-cool to room temperature to obtain a 6N16 aluminum alloy coil.

5. The preparation method of 6N16 aluminum alloy for automobile inner panel according to claim 4, characterized in that, In step S1, during the melting process, control the melt heating temperature at 740 ± 20 °C. When all the raw materials are melted, take a pre-analysis sample as needed, control the sampling temperature at 690 - 760 °C, and add manganese agent and / or iron agent and / or copper agent at 730 - 750 °C according to the sampling analysis results; In step S1, during the melting process, also use the STAS process to refine the melt. During the refining process, control the melt temperature at 720 - 750 °C, use Cl2 - Ar mixed gas to refine for at least 30 min, set the rotor speed at 200 - 400 rpm, the argon flow rate at 150 - 198 slpm, and the chlorine flow rate at 0 - 48 slpm.

6. The preparation method of 6N16 aluminum alloy for automotive inner panel according to claim 4, characterized in that, In step S2, the homogenization treatment process is to heat the aluminum alloy ingot to 560 ± 5 °C and keep it warm for at least 8 hours, and the total heating time in the homogenization furnace shall not exceed 36 hours.

7. The preparation method of 6N16 aluminum alloy for automotive inner panel according to claim 4, characterized in that, In step S3, the hot rolling process includes rough rolling and finish rolling; The number of rough rolling passes is 20 - 30 passes, and the maximum reduction in the rough rolling process is 25 - 55 mm. The thickness of the intermediate plate obtained after rough rolling is 45 - 58 mm, and the temperature of the intermediate plate is 360 - 400 °C; The number of finish rolling passes is 3 - 7 passes, and the maximum reduction in the finish rolling process is 2 - 20 mm. The thickness of the hot-rolled final rolling plate obtained after finish rolling is 3.5 - 7.5 mm; In step S4, during the cold rolling process, first use the rolling mill to roll 2 - 3 passes, and then EDT roll 1 pass. The thickness of the obtained cold-rolled sheet is 0.8 - 1.5 mm.

8. The preparation method of 6N16 aluminum alloy for automotive inner panel according to claim 4, characterized in that, In step S5, during continuous annealing, the annealing temperature is 540 - 560 °C, and the annealing time is 10 - 30 s starting from when the annealing temperature is reached for heat preservation.

9. The preparation method of 6N16 aluminum alloy for automobile inner panel according to claim 4, characterized in that, In step S5, the stretching rate is 0.2 - 0.5%.

10. A preparation method of 6N16 aluminum alloy for automotive inner panel according to claim 4, characterized in that, In step S6, the pre-aging temperature is 65 ± 5 °C.

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