Preparation process of high-strength aluminum alloy

Abstract

The invention provides a preparation process of a high-strength aluminum alloy, and belongs to the technical field of automobile manufacturing, the preparation process uses the following aluminum alloy components in percentage by mass: 0.58 to 0.79 percent of Si, 0.04 to 0.08 percent of Fe, 1.77 to 1.98 percent of Cu, 0.93 to 1.16 percent of Mg, 0.57 to 0.87 percent of Mn, 0.11 to 0.16 percent of La, 0.02 to 0.06 percent of Ce, 0.04 to 0.09 percent of V, 0.006 to 0.009 percent of B and the balance of Al and inevitable impurities. By reasonably adjusting the element ratio of the aluminum alloy, controlling the technological process and reasonably setting parameters of the technological process, the high-strength and low-quenching-sensitivity aluminum alloy which can be achieved under the air cooling quenching condition is prepared.

Description

Technical Field

[0001] The invention belongs to the technical field of automobile manufacturing, and in particular relates to a preparation process of a high-strength aluminum alloy. Background Art

[0002] In order to achieve the goal of energy conservation and emission reduction, the automotive industry is urgently seeking lightweight solutions for vehicles, because this can not only help reduce energy consumption, but also improve the safety and handling of vehicles. In this regard, aluminum alloy sheets, as an ideal lightweight material, are increasingly used in automobile manufacturing. This trend is particularly evident in the field of new energy vehicles. The development of such models has greatly promoted the application of aluminum alloy sheets.

[0003] Among the aluminum alloy materials used in new energy vehicle aluminum alloy plates, the 6-series Al-Mg-Si alloy is the most widely used. However, the common 6-series aluminum alloys such as 6063, 6061, and 6082 on the market are mostly of medium strength, and their tensile strength is less than 300MPa.

[0004] In recent years, although some enterprises and research institutes have also developed some high-strength 6-series aluminum alloys, most of them need to use high-strength water quenching or offline quenching to meet the requirements when preparing profiles. However, these aluminum alloy materials have high quenching sensitivity. Under the premise of profile wall thickness > 3mm, they can achieve better performance and effect. For some high-precision profiles with wall thickness < 1.5mm, when online water cooling and offline quenching are performed, the cooling intensity is too high, which can easily cause profile deformation. After extrusion, they can only be quenched by air cooling, but this will result in insufficient strength.

[0005] Therefore, in order to solve the above problems, there is an urgent need for a 6 series aluminum alloy that can achieve high strength under air-cooled quenching conditions. Summary of the invention

[0006] The purpose of the present invention is to provide a preparation process of a high-strength aluminum alloy.

[0007] In order to achieve the above object, the present invention provides the following technical solutions: A preparation process of a high-strength aluminum alloy comprises the following steps: (1) Weigh the components of aluminum alloy according to the following mass percentage ratio: Si 0.58-0.79%, Fe 0.04-0.08%, Cu 1.77-1.98%, Mg 0.93-1.16%, Mn 0.57-0.87%, La 0.11-0.16%, Ce 0.02-0.06%, V 0.04-0.09%, B 0.006-0.009%, the balance being Al and unavoidable impurities; (2) heating and melting the aluminum alloy components at 770-790°C; adding a refining agent under a nitrogen atmosphere at a temperature of 720-730°C, and refining for 30-40 minutes to obtain an aluminum alloy melt; (3) casting the aluminum alloy melt to obtain an aluminum alloy ingot; (4) homogenizing the aluminum alloy ingot to obtain a homogenized ingot; (5) performing homogenization annealing on the homogenized ingot; (6) After annealing, first cool it with air cooling for 1-2 hours, then cool it with water cooling to 70-80℃, and then cool it naturally to room temperature to obtain a high-strength aluminum alloy.

[0008] Furthermore, the mass percentage ratio of Mg to Si is (1.46-1.63):1.

[0009] Furthermore, the mass percentage of Cu is greater than the sum of the mass percentages of Mg and Si.

[0010] In 6 series aluminum alloys, Mg and Si are the main strengthening elements, forming a strengthening phase Mg 2 Si. Therefore, the ratio of Mg to Si affects the strength of aluminum alloys. At present, the ratio of Mg to Si in aluminum alloys on the market is mostly in the range of 1.0-1.3. For example, patent CN115505794B defines the Mg / Si atomic ratio as 1.0-1.2, but the tensile strength of its aluminum alloy is still lower than 300MPa, which cannot meet the market demand. In the system of the present invention, the tensile strength of aluminum alloys can be improved by adjusting the mass percentage ratio of Mg to Si to (1.46-1.63): 1 and limiting the addition amount between Cu and Mg and Si. Analysis shows that in the system of the present invention, Si may also form different phases with other elements such as Fe, and by reasonably designing and controlling the ratio of Mg and Si in the alloy composition, the Mg can be controlled. 2 The amount and size of Si phases affect the tensile strength of aluminum alloy materials. Although copper can increase the strength of aluminum alloys, excessive copper can make the material brittle and affect its ductility.

[0011] The present invention can ensure the formation of effective strengthening phase by adjusting the ratio between Cu, Mg and Si without causing unnecessary brittleness or other negative effects, and can also improve the elongation at break of aluminum alloy. However, the improvement of the yield strength of aluminum alloy under this condition is not ideal.

[0012] Furthermore, the sum of the mass percentages of La, Ce and V is 0.18-0.26%.

[0013] By rationally designing the addition of La, Ce and V in the system of the present invention, the yield strength of the aluminum alloy can be improved. La and Ce are rare earth elements, which can effectively refine the grains of the aluminum alloy, thereby reducing the formation of coarse phases and improving the microstructure of the aluminum alloy. The addition of V can improve the morphology and distribution of the second phase, making these phases finer and more evenly distributed, thereby increasing the yield strength of the material. At the same time, when the sum of the mass percentages of La, Ce and V is controlled to be 0.18-0.26%, the yield strength of the aluminum alloy after baking can also be improved. Analysis shows that the addition of La, Ce and V can affect Mg 2 The morphology and distribution of secondary phases such as Si make these phases more dispersed and fine, which can reduce the adverse effects of temperature on the material; by adding a certain amount of La, Ce and V, it helps to improve the response of the alloy during heat treatment, so that the material can better retain its strengthening effect during the paint curing process.

[0014] Furthermore, the refining agent comprises the following raw materials in parts by weight: 35-38 parts of KCl, 15-19 parts of LiCl, 25-28 parts of AlF 3 , 12-17 parts CaF 2 , 2-6 parts of carbon powder, 10-15 parts of CaO and 10-15 parts of La 2 O 3 .

[0015] Furthermore, the preparation method of the refining agent comprises the following steps: S1. Crush the raw materials of the refining agent into 50-60 mesh respectively; S2. The crushed raw materials of the refining agent are put into a blender according to the mass ratio and mixed evenly, then baked at 100-103° C. for 2-3 hours, crushed to less than 70 meshes, and cooled to room temperature to obtain the refining agent.

[0016] Furthermore, the amount of the refining agent added is 0.22-0.26% of the total mass of the aluminum alloy components.

[0017] The refining agent of the present invention can refine the elements of the grains. The fine grains help to improve the strength and plasticity of the aluminum alloy. At the same time, it can also improve the fluidity of the aluminum alloy melt of the present invention, and can ensure that the aluminum alloy can evenly fill the mold during pouring, thereby obtaining good casting surface quality and dimensional accuracy.

[0018] Furthermore, the temperature rise process of the homogenization treatment is a gradient temperature rise, firstly the temperature is raised to 420°C-450°C, kept warm for 2-3 hours, then the temperature is raised to a holding temperature of 550°C-570°C, kept warm for 15-18 hours.

[0019] Furthermore, the homogenization annealing adopts a three-stage homogenization treatment, with the first stage being kept at a temperature of 450-470°C for 4-6 hours, the second stage being kept at a temperature of 530-550°C for 7-9 hours after the first stage, and the third stage being kept at a temperature of 570-590°C for 11-13 hours after the second stage.

[0020] Furthermore, the air cooling rate is 270-280°C / h, and the water cooling rate is 310-320°C / h.

[0021] Compared with the prior art, the advantages and beneficial effects of the present invention are: 1. The present invention prepares a high-strength aluminum alloy with high strength and low quenching sensitivity that can be achieved under air-cooled quenching conditions by adjusting the element ratio of the aluminum alloy and controlling the process and reasonably setting its parameters.

[0022] 2. In the system of the present invention, by adjusting the mass percentage ratio of Mg to Si to (1.46-1.63):1 and limiting the addition amount of Cu to Mg and Si, the tensile strength of the aluminum alloy can be improved. At the same time, the elongation at break of the aluminum alloy can be improved.

[0023] 3. The yield strength of aluminum alloy can be improved by adding La, Ce and V in the system in a reasonable design. At the same time, when the sum of the mass percentages of La, Ce and V is controlled to be 0.18-0.26%, the yield strength of aluminum alloy after baking can also be improved. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Example 1 This embodiment provides a preparation process of a high-strength aluminum alloy, comprising the following steps: (1) Weigh the components of aluminum alloy according to the following mass percentage ratio: Si 0.72%, Fe 0.06%, Cu 1.87%, Mg 1.11%, Mn 0.72%, La 0.13%, Ce 0.03%, V 0.06%, B 0.007%, the balance being Al and unavoidable impurities; (2) heating the aluminum alloy components to melt at 780°C; adding a refining agent under a nitrogen atmosphere at a temperature of 725°C and refining for 35 minutes to obtain an aluminum alloy melt; The refining agent includes the following raw materials in parts by weight: 36 parts KCl, 17 parts LiCl, 27 parts AlF 3 、14 parts CaF 2 , 4 parts carbon powder, 13 parts CaO and 12 parts La 2 O 3 .

[0026] The preparation method of the refining agent comprises the following steps: S1. Crush the raw materials of the refining agent into 50-60 mesh respectively; S2. The crushed raw materials of the refining agent are put into a blender according to the mass ratio and mixed evenly, then baked at 102° C. for 2.5 hours, crushed to less than 70 meshes, and cooled to room temperature to obtain the refining agent.

[0027] The amount of the refining agent added is 0.24% of the total mass of the aluminum alloy components.

[0028] (3) casting the aluminum alloy melt to obtain an aluminum alloy ingot; (4) homogenizing the aluminum alloy ingot. The heating process of the homogenization treatment is a gradient heating process, first heating to 430°C and keeping it warm for 2.5 hours, then heating to a holding temperature of 560°C and keeping it warm for 17 hours to obtain a homogenized ingot; (5) performing homogenization annealing on the homogenized ingot; the homogenization annealing adopts a three-stage homogenization treatment, wherein the first stage is kept at a temperature of 460° C. for 5 hours, the second stage is kept at a temperature of 540° C. for 8 hours, and the third stage is kept at a temperature of 580° C. for 12 hours after the second stage; (6) After annealing, the alloy is first cooled by air cooling for 1.5 h at a cooling rate of 275 °C / h, then cooled by water cooling to 75 °C at a cooling rate of 315 °C / h, and then naturally cooled to room temperature to obtain a high-strength aluminum alloy.

[0029] Example 2 This embodiment provides a preparation process of a high-strength aluminum alloy, comprising the following steps: (1) Weigh the components of aluminum alloy according to the following mass percentage ratio: Si 0.79%, Fe 0.04%, Cu 1.97%, Mg 1.16%, Mn 0.57%, La 0.11%, Ce 0.02%, V 0.05%, B 0.006%, the balance being Al and unavoidable impurities; (2) heating the aluminum alloy components to melt at 770°C; adding a refining agent under a nitrogen atmosphere at a temperature of 720°C and refining for 30 minutes to obtain an aluminum alloy melt; The refining agent includes the following raw materials by weight: 35 parts of KCl, 15 parts of LiCl, 25 parts of AlF 3 、12 parts CaF 2 , 2 parts carbon powder, 10 parts CaO and 10 parts La 2 O 3 .

[0030] The preparation method of the refining agent comprises the following steps: S1. Crush the raw materials of the refining agent into 50-60 mesh respectively; S2. The crushed raw materials of the refining agent are put into a blender according to the mass ratio and mixed evenly, then baked at 100° C. for 2 hours, crushed to less than 70 meshes, and cooled to room temperature to obtain the refining agent.

[0031] The amount of the refining agent added is 0.22% of the total mass of the aluminum alloy components.

[0032] (3) casting the aluminum alloy melt to obtain an aluminum alloy ingot; (4) homogenizing the aluminum alloy ingot, wherein the temperature is gradually increased, firstly the temperature is increased to 420°C, kept at this temperature for 2 hours, then the temperature is increased to a holding temperature of 550°C, kept at this temperature for 15 hours, and a homogenized ingot is obtained; (5) performing homogenization annealing on the homogenized ingot; the homogenization annealing adopts a three-stage homogenization treatment, wherein the first stage is kept at a temperature of 450° C. for 4 hours, the second stage is kept at a temperature of 530° C. for 7 hours after the first stage, and the third stage is kept at a temperature of 570° C. for 11 hours after the second stage; (6) After annealing, the alloy is first cooled by air cooling for 1 h at a cooling rate of 270 °C / h, then cooled by water cooling to 70 °C at a cooling rate of 310 °C / h, and then naturally cooled to room temperature to obtain a high-strength aluminum alloy.

[0033] Example 3 This embodiment provides a preparation process of a high-strength aluminum alloy, comprising the following steps: (1) Weigh the components of aluminum alloy according to the following mass percentage ratio: Si 0.75%, Fe 0.08%, Cu 1.97%, Mg 1.13%, Mn 0.87%, La 0.16%, Ce 0.02%, V 0.07%, B 0.009%, and the balance is Al and unavoidable impurities; (2) heating the aluminum alloy components to melt at 790°C; adding a refining agent under a nitrogen atmosphere at a temperature of 730°C and refining for 40 minutes to obtain an aluminum alloy melt; The refining agent includes the following raw materials in parts by weight: 38 parts KCl, 19 parts LiCl, 28 parts AlF3 、17 parts CaF 2 , 6 parts carbon powder, 15 parts CaO and 15 parts La 2 O 3 .

[0034] The preparation method of the refining agent comprises the following steps: S1. Crush the raw materials of the refining agent into 50-60 mesh respectively; S2. The crushed raw materials of the refining agent are put into a blender according to the mass ratio and mixed evenly, then baked at 103° C. for 3 hours, crushed to less than 70 meshes, and cooled to room temperature to obtain the refining agent.

[0035] The amount of the refining agent added is 0.26% of the total mass of the aluminum alloy components.

[0036] (3) casting the aluminum alloy melt to obtain an aluminum alloy ingot; (4) homogenizing the aluminum alloy ingot, wherein the temperature is gradually increased, firstly the temperature is increased to 450°C, kept at this temperature for 3 hours, then the temperature is increased to a holding temperature of 570°C, kept at this temperature for 18 hours, and a homogenized ingot is obtained; (5) performing homogenization annealing on the homogenized ingot; the homogenization annealing adopts a three-stage homogenization treatment, wherein the first stage is kept at a temperature of 470°C for 6 hours, the second stage is kept at a temperature of 550°C for 9 hours after the first stage, and the third stage is kept at a temperature of 590°C for 13 hours after the second stage; (6) After annealing, the alloy is first cooled by air cooling for 2 h at a cooling rate of 280 °C / h, then cooled by water cooling to 80 °C at a cooling rate of 320 °C / h, and then naturally cooled to room temperature to obtain a high-strength aluminum alloy.

[0037] Comparative Example 1 The difference between this comparative example and Example 1 is that the proportions of the components of the aluminum alloy are different.

[0038] Specifically: weigh the components of the aluminum alloy according to the following mass percentage ratio: Si0.81%, Fe0.02%, Cu1.60%, Mg1.18%, Mn0.88%, La0.08%, Ce0.07%, V0.11%, B0.007%, and the balance is Al and unavoidable impurities.

[0039] Comparative Example 2 The difference between this comparative example and Example 1 is that the mass percentage contents of Mg and Si are different.

[0040] Specifically: weigh the components of the aluminum alloy according to the following mass percentage ratio: Si0.79%, Fe0.06%, Cu1.87%, Mg0.94%, Mn0.72%, La0.13%, Ce0.03%, V0.06%, B0.007%, and the balance is Al and unavoidable impurities.

[0041] Comparative Example 3 The difference between this comparative example and Example 1 is that the mass percentage contents of Cu, Mg and Si are different.

[0042] Specifically: weigh the components of the aluminum alloy according to the following mass percentage ratio: Si0.77%, Fe0.06%, Cu1.77%, Mg1.16%, Mn0.72%, La0.13%, Ce0.03%, V0.06%, B0.007%, and the balance is Al and unavoidable impurities.

[0043] Comparative Example 4 The difference between this comparative example and Example 1 is that the total mass percentage of La, Ce and V is different.

[0044] Specifically: weigh the components of the aluminum alloy according to the following mass percentage ratio: Si0.72%, Fe0.06%, Cu1.87%, Mg1.11%, Mn0.72%, La0.16%, Ce0.06%, V0.09%, B0.007%, and the balance is Al and unavoidable impurities.

[0045] Comparative Example 5 The difference between this comparative example and Example 1 is that the added amounts of La, Ce and V are different.

[0046] Specifically: weigh the components of the aluminum alloy according to the following mass percentage ratio: Si0.72%, Fe0.06%, Cu1.87%, Mg1.11%, Mn0.72%, La0.07%, Ce0.13%, V0.02%, B0.007%, and the balance is Al and unavoidable impurities.

[0047] Comparative Example 6 The difference between this comparative example and Example 1 is that the composition of the refining agent is different.

[0048] The refining agent includes the following raw materials in parts by weight: 26 parts KCl, 27 parts LiCl, 17 parts AlF 3 , 24 parts CaF 2 , 14 parts carbon powder, 19 parts CaO and 8 parts La 2 O 3 .

[0049] Comparative Example 7 The difference between this comparative example and Example 1 is that the homogenization treatment method is different.

[0050] The homogenization treatment method is: heating to a holding temperature of 560°C and keeping the temperature for 19.5 hours.

[0051] Comparative Example 8 The difference between this comparative example and Example 1 is that the homogenization annealing method is different.

[0052] The homogenization annealing adopts a three-stage homogenization treatment, with the first stage being kept at a temperature of 490°C for 9 hours, the second stage being kept at a temperature of 520°C for 6 hours, and the third stage being kept at a temperature of 560°C for 10 hours.

[0053] Performance Testing The aluminum alloy profiles were prepared using the aluminum alloys prepared in Examples 1-3 and Comparative Examples 1-8, respectively, and specifically included the following steps: The aluminum alloy is heated to 475°C and then extruded into a thin-walled square tube (wall thickness 1.2 mm). The extrusion ratio is 41, the extrusion speed is 3.5 mm / s, the outlet profile temperature before extrusion is 527°C, and the profile is cooled to 200°C online by strong wind after extrusion, and then naturally cooled to room temperature to obtain an aluminum profile semi-finished product, wherein the cooling rate in the interval of cooling to 200°C is 7.8°C / s; artificial aging treatment is performed, the aging system is 155°C, and the heat preservation is performed for 12 hours to obtain an aluminum alloy profile.

[0054] The aluminum alloy profile products prepared in Examples 1-3 and Comparative Examples 1-8 were subjected to mechanical property tests in accordance with GB / T228.1-2021 "Tensile Test of Metallic Materials Part 1: Room Temperature Test Method", and the yield strength after baking paint was tested: the baking paint conditions were 2% pre-stretching, and the temperature and time for baking paint curing were: 185°C×20min.

[0055] Among them, Rm represents tensile strength, Rp0.2 represents yield strength, that is, the strength when the non-proportional elongation is 0.2%, and A50 represents elongation after fracture, that is, the elongation at a gauge length of 50 mm.

[0056] Table 1 Performance test results It can be seen from the above performance test results that the aluminum alloys prepared in Examples 1-3 have excellent comprehensive performance, especially the comprehensive performance of Example 1 is the most outstanding. This is mainly due to the synergistic effect of adjusting the element ratio of the aluminum alloy, controlling the process and reasonably setting its parameters.

[0057] However, since the necessary technical solutions were not adopted in the comparative examples, the corresponding performance tests were obviously worse than those of the embodiments. In comparative example 1, the ratio of aluminum alloy elements was changed, and it can be seen that the strength effect of the aluminum alloy decreased, proving that the element ratio scheme of the aluminum alloy has an important influence on the strength of the aluminum alloy; in comparative example 2, the mass percentage scheme of Mg and Si was changed, and in comparative example 3, the sum of the mass percentages of Cu, Mg and Si was changed. From the results, it can be seen that the tensile strength effect of the aluminum alloy decreased, indicating that only the addition of these three elements can obtain a high-strength aluminum alloy under certain conditions; in comparative example 4, the total mass percentage of La, Ce and V was changed, resulting in a decrease in the yield strength after baking paint, indicating that in the system of the present invention, the total mass percentage of La, Ce and V is controlled within a certain range, which can improve the yield strength after baking paint; in comparative example 5, the addition of La, Ce and V exceeds the addition range of the present invention, resulting in a decrease in the performance of the aluminum alloy. It can be seen from Comparative Examples 6-8 that high-performance aluminum alloy can be obtained only under the conditions of controlling the process of the present invention and reasonably setting its parameters. The above experimental results further prove the importance of the technical scheme defined in the present invention to its technical effect.

[0058] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A process for preparing a high-strength aluminum alloy, characterized in that: The following steps are involved: (1) Weigh the aluminum alloy components according to the following mass percentage ratio: Si 0.58-0.79%, Fe 0.04-0.08%, Cu 1.77-1.98%, Mg 0.93-1.16%, Mn 0.57-0.87%, La 0.11-0.16%, Ce 0.02-0.06%, V 0.04-0.09%, B 0.006-0.009%, the balance being Al and unavoidable impurities; The mass percentage ratio of Mg to Si is (1.46-1.63):1; the mass percentage of Cu is greater than the sum of the mass percentages of Mg and Si; the sum of the mass percentages of La, Ce and V is 0.18-0.26%; (2) heating and melting the aluminum alloy components at 770-790°C; adding a refining agent under a nitrogen atmosphere at a temperature of 720-730°C, and refining for 30-40 minutes to obtain an aluminum alloy melt; The refining agent comprises the following raw materials in parts by mass: 35-38 parts of KCl, 15-19 parts of LiCl, 25-28 parts of AlF3, 12-17 parts of CaF2, 2-6 parts of carbon powder, 10-15 parts of CaO and 10-15 parts of La2O3; (3) casting the aluminum alloy melt to obtain an aluminum alloy ingot; (4) homogenizing the aluminum alloy ingot to obtain a homogenized ingot; The temperature rise process of homogenization treatment is gradient temperature rise, firstly heating to 420℃-450℃, keeping warm for 2-3h, then heating to the warming temperature of 550℃-570℃, keeping warm for 15-18h; Homogenization annealing adopts three-stage homogenization treatment, the first stage is kept at 450-470℃ for 4-6h, the second stage is kept at 530-550℃ for 7-9h, and the third stage is kept at 570-590℃ for 11-13h. (6) After annealing, the aluminum alloy is first cooled by air cooling for 1-2 hours, then cooled by water cooling to 70-80°C, and then naturally cooled to room temperature to obtain a high-strength aluminum alloy.

2. The process for preparing the high-strength aluminum alloy according to claim 1, characterized in that: The preparation method of the refining agent comprises the following steps: S1. Crush the raw materials of the refining agent into 50-60 mesh respectively; S2. The crushed raw materials of the refining agent are put into a blender according to the mass ratio and mixed evenly, then baked at 100-103° C. for 2-3 hours, crushed to less than 70 meshes, and cooled to room temperature to obtain the refining agent.

3. The process for preparing the high-strength aluminum alloy according to claim 1, characterized in that: The amount of the refining agent added is 0.22-0.26% of the total mass of the aluminum alloy components.

4. The process for preparing a high-strength aluminum alloy according to claim 1, characterized in that: The air cooling rate is 270-280℃ / h, and the water cooling rate is 310-320℃ / h.

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