High-strength aluminum alloy profile with low quenching sensitivity and good bending performance and preparation method of high-strength aluminum alloy profile

Abstract

The invention belongs to the technical field of aluminum alloy extruded profiles, and relates to a high-strength aluminum alloy profile with low quenching sensitivity and good bending performance and a preparation method thereof. According to the method, the strengthening effect of the aluminum alloy profile is optimized by controlling the formation of the beta phase and the Mg / Si ratio, especially in the peak aging state, the performance of the material in a bending test is improved by avoiding Si excess and reducing the risk of grain boundary embrittlement, and the tensile strength of the aluminum alloy profile is improved by reasonably selecting and controlling the adding amount of alloy elements (Mn, Zr, Sn and Cu). The bending performance, the surface quality and the extrudability are comprehensively optimized, the yield strength of the prepared aluminum alloy profile is larger than or equal to 350 Mpa, the bending angle in the L direction can be larger than 70 degrees, and the bending angle in the T direction can be larger than 50 degrees.

Description

Technical Field

[0001] The invention belongs to the technical field of aluminum alloy extruded profiles, and relates to a high-strength aluminum alloy profile with low quenching sensitivity and good bending performance and a preparation method thereof. Background Art

[0003] Lightweighting of vehicles is one of the effective ways to achieve energy conservation and emission reduction. Lightweighting of vehicles refers to reducing the overall weight of the vehicle as much as possible without sacrificing the strength and safety performance of the vehicle. By reducing the weight of the vehicle, it can not only reduce fuel consumption and exhaust emissions, but also improve the vehicle's power performance and handling. This not only meets the requirements of environmental protection, but also meets consumers' demand for higher energy efficiency and better driving experience.

[0004] Among many lightweight materials, 6xxx series aluminum alloys are widely used in automobile manufacturing due to their excellent mechanical properties and processing performance, especially in key structural parts such as battery trays, reinforcement beams, chassis and CMS (collision management system). However, although traditional 6xxx aluminum alloys have good comprehensive properties, their strength still needs to be improved. In order to further promote the lightweight process of automobiles, it is particularly important to develop 6xxx aluminum alloy materials with higher strength.

[0005] The development of high-strength 6xxx aluminum alloys is not only to reduce weight, but also to meet the increasingly high safety standards in modern car design. For example, in new energy vehicles, the battery tray must not only carry the heavy battery pack, but also protect the battery from damage in the event of a collision. This requires the material to have sufficient strength to withstand impact, but also good plasticity and toughness to absorb energy. In addition, reinforcing beams and chassis components also need to have high strength to ensure the stability of the vehicle at high speeds and under complex road conditions.

[0006] To achieve these goals, new alloy formulations and technologies are being explored to improve the strength of 6xxx aluminum alloys. These studies include, but are not limited to, introducing trace elements through microalloying technology to improve the microstructure of the alloy, using advanced heat treatment processes to optimize the mechanical properties of the material, and developing new forming technologies to ensure that parts do not deform during the forming process.

[0007] In short, automobile lightweighting has become an irreversible trend in the automotive industry. By continuously developing higher-strength 6xxx aluminum alloy materials, the automotive industry can not only achieve the goal of energy conservation and emission reduction, but also improve the safety and reliability of vehicles, laying a solid foundation for future sustainable transportation. Summary of the invention

[0008] The purpose of the present invention is to address the above-mentioned problems existing in the prior art and to propose a high-strength aluminum alloy profile with low quenching sensitivity and good bending performance, wherein the yield strength is ≥350Mpa, the bending angle L direction is >50°, and the bending angle T direction is >30°.

[0009] The purpose of the present invention can be achieved by the following technical solutions:

[0010] A high-strength aluminum alloy profile with low quenching sensitivity and high bending performance. The aluminum alloy extruded profile raw material is composed of the following elements in percentage by mass: 0.80-1.1% Mg, 0.75-1.0% Si, 0.35-0.60% Cu, 0.10-0.40% Mn, 0.10-0.25% Zr, 0.05-0.20% Sn, 0-0.25% Fe, and the balance is Al and unavoidable impurities.

[0011] Mg and Si are the main additive elements of 6 series alloys. They interact and precipitate to form β" phase strengthening particles during the aging process to strengthen the matrix. If there is excess Si in the alloy, it is easy to segregate to the grain boundary, thereby causing grain boundary embrittlement and prone to cracks on the surface during the bending test. Therefore, the present invention tries to avoid excess Si and sets the lower limit of Mg / Si to 1 to ensure that there is no excess Si. At the same time, since the addition of Mg has a deteriorating effect on the extrudability of the material and aggravates the problem of quenching sensitivity, it is not conducive to large-scale mass production. Therefore, the present invention limits 1.0≤Mg / Si≤1.30 in the preferred embodiment.

[0012] Additive elements such as Mn, Cr, and Zr exist in the form of dispersed phase particles of submicron scale in aluminum alloys. These dispersed particles have a significant inhibitory effect on the recrystallization process, and their inhibitory efficiency is closely related to the size and number of particles. Specifically, the smaller the particle size and the greater the number, the stronger its ability to hinder recrystallization. Generally speaking, among the dispersed phase particles formed by these three elements, the dispersed phase particles formed by the Zr element are the smallest in size, so its ability to hinder recrystallization is the most prominent, followed by the Cr element, and the Mn element is relatively weak. During the aluminum extrusion process, recrystallization often occurs on the surface of the profile, forming a relatively coarse surface coarse-grained layer structure. This layer of structure has a serious negative impact on many properties of the profile product, including bending ability, corrosion resistance and surface quality. Therefore, by adding elements such as Mn, Cr, and Zr that can effectively inhibit recrystallization, it has a very significant effect on reducing or even eliminating the surface coarse-grained layer and thus improving the bending performance of the product.

[0013] However, the addition of Mn, Cr, and Zr elements will increase the quenching sensitivity of the alloy, resulting in an increase in the critical cooling rate during extrusion quenching. The increase in cooling rate will cause product deformation and cannot be adapted to large-scale mass production. The order of increasing quenching sensitivity is Cr>Mn>Zr. In order to reduce quenching sensitivity and facilitate large-scale industrial mass production, the present invention chooses not to add Cr elements, and mainly adds Mn and Zr elements.

[0014] If the amount of Mn and Zr added is too little, the ability to hinder recrystallization is insufficient, the surface coarse grain layer is too thick, and the bending performance is poor; if the amount of Mn and Zr added is too much, the extrusion pressure is large, the quenching sensitivity is large, and it is not conducive to large-scale mass production. In the preferred embodiment of the present invention, Mn is limited to 0.10-0.40%; Zr is limited to 0.10-0.25%.

[0015] The role of Sn in the present invention is to refine the Mn-containing dispersed phase particles, and its effects are twofold: 1. increase the number of precipitations, significantly enhance the role of Mn in hindering recrystallization; 2. simultaneously enhance the coherence between the Mn-containing dispersed phase particles and the matrix, so as to further reduce the influence of the Mn-containing dispersed phase particles on quenching sensitivity. In order to better play this role of Sn, after the aluminum rod is cast, the present invention adopts a two-stage homogenization process: the first stage homogenization process is 130-200℃ / 2-10h, and the second stage homogenization process is 370-450℃ / 2-12h. During the first stage homogenization, Sn forms a large number of atomic clusters, which serve to provide nucleation points for the precipitation of Mn during the second stage homogenization, thereby refining the Mn-containing dispersed phase particles by increasing the number of precipitations of the Mn-containing phase particles. When Sn is less than 0.05%, its ability to refine Mn-containing dispersed particles is insufficient, and when Sn is greater than 0.20%, the cost is too high. Therefore, the present invention controls the Sn content within the range of 0.05-0.20%.

[0016] Cu is also a major additive element in 6 series aluminum alloys, and it mainly plays a role in supplementary strengthening. However, excessive Cu content will deteriorate the intergranular corrosion performance of the material, while damaging the extrudability of the material and increasing quenching sensitivity. Therefore, in the present invention, Cu is controlled within a moderate range of 0.35-0.60%.

[0017] Further preferably, the aluminum alloy extruded profile raw material consists of the following elements in percentage by mass: 0.85-0.1.0% Mg, 0.80-0.95% Si, 0.40-0.50% Cu, 0.20-0.35% Mn, 0.12-0.20% Zr, 0.10-0.18% Sn, 0-0.15% Fe, and the balance is Al and unavoidable impurities.

[0018] In the above-mentioned high-strength aluminum alloy profile with low quenching sensitivity and high bending performance, as an optimization, the inevitable impurity elements in the aluminum alloy extrusion profile are less than 0.15wt%, and the single impurity element is less than 0.05%

[0019] In the above-mentioned high-strength aluminum alloy profile with low quenching sensitivity and high bending performance, as an optimization, Mg and Si also need to meet the following conditions: 1.0≤Mg / Si≤1.30.

[0020] The present invention also provides a method for preparing the high-strength aluminum alloy profile with low quenching sensitivity and high bending performance, the method comprising the following steps:

[0021] S1. Prepare raw materials;

[0022] S2, melting and casting the raw materials into aluminum bars, and then homogenizing them;

[0023] S3, then preheating the aluminum rod, and then hot extruding to obtain an extruded profile;

[0024] S4, then quenching the extruded profile and cooling it to room temperature;

[0025] S5. Finally, the extruded profile is subjected to aging treatment.

[0026] In the above-mentioned method for preparing a high-strength aluminum alloy profile with low quenching sensitivity and high bending performance, the homogenization treatment in step S2 adopts a two-stage homogenization process: the first stage homogenization process is 130-200℃ / 2-10h, and the second stage homogenization process is 370-450℃ / 2-12h.

[0027] In the above method for preparing a high-strength aluminum alloy profile with low quenching sensitivity and high bending performance, the preheating temperature in step S3 is 490-540°C.

[0028] In the above method for preparing a high-strength aluminum alloy profile with low quenching sensitivity and high bending performance, the quenching temperature in step S4 is 500-550°C.

[0029] In the above method for preparing a high-strength aluminum alloy profile with low quenching sensitivity and high bending performance, the cooling rate in step S4 is ≥4°C / s.

[0030] In the above-mentioned method for preparing a high-strength aluminum alloy profile with low quenching sensitivity and high bending performance, the aging treatment temperature in step S5 is 180-205° C. and the time is 2-16 hours.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The present invention optimizes the strengthening effect of the aluminum alloy profile by controlling the formation of the β" phase and the Mg / Si ratio. In particular, under the peak aging state, by avoiding excess Si, the risk of grain boundary embrittlement is reduced, and the performance of the material in the bending test is improved. By reasonably selecting and controlling the addition amount of alloying elements (Mn, Zr, Sn and Cu), the comprehensive optimization of bending performance, surface quality and extrudability is achieved. The yield strength of the prepared aluminum alloy profile is ≥350Mpa, and the bending angle can be >70° in the L direction and >50° in the T direction. DETAILED DESCRIPTION

[0033] The following are specific embodiments of the present invention, which further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

[0034] Embodiment 1-10:

[0035] S1. The raw material composition of the aluminum alloy profiles of Examples 1-10 is configured as shown in Table 1;

[0036] S2. Add the prepared alloy raw materials into a smelting furnace and smelt them at 780°C to make them all melt into liquid to form aluminum melt. After they are all melted into liquid, keep them warm for about half an hour to remove slag and refine the aluminum melt. After the components are adjusted to the required standard, reduce the temperature of the aluminum melt to 720°C, and perform standing, slag removal and casting in sequence to obtain round cast bars, and then perform two-stage homogenization treatment:

[0037] The first stage homogenization treatment is 185℃ / 6h, and the second stage homogenization treatment is 415℃ / 8h;

[0038] S3, then preheating the aluminum rod, and then using a hot extrusion die to make an extruded profile, wherein the preheating temperature is 490-540°C;

[0039] S4, then the extruded profile is quenched and then cooled to room temperature, wherein the quenching temperature is 530°C and the quenching cooling rate is 8°C / s;

[0040] S5. Finally, the extruded profile is subjected to aging treatment at 185°C for 10 hours.

[0041] Comparative Examples 1-5:

[0042] S1. The raw material components of the aluminum alloy profiles of Comparative Examples 1-5 are configured as shown in Table 1;

[0043] S2. Add the prepared alloy raw materials into a smelting furnace and smelt them at 780°C to make them all melt into liquid to form aluminum melt. After they are all melted into liquid, keep them warm for about half an hour to remove slag and refine the aluminum melt. After the components are adjusted to the required standard, reduce the temperature of the aluminum melt to 720°C, and perform standing, slag removal and casting in sequence to obtain round cast bars, and then perform two-stage homogenization treatment:

[0044] The first stage homogenization treatment is 185℃ / 6h, and the second stage homogenization treatment is 415℃ / 8h;

[0045] S3, then preheating the aluminum rod, and then using a hot extrusion die to make an extruded profile, wherein the preheating temperature is 490-540°C;

[0046] S4, then the extruded profile is quenched and then cooled to room temperature, wherein the quenching temperature is 530°C and the quenching cooling rate is 8°C / s;

[0047] S5. Finally, the extruded profile is subjected to aging treatment at 185°C for 10 hours.

[0048] Comparative Example 6:

[0049] The only difference from Example 6 is that the homogenization treatment of Comparative Example 5 is to keep the temperature at 565° C. for 6 hours.

[0050] Table 1: Elemental composition of aluminum alloy profiles prepared in Examples 1-10 and Comparative Examples 1-4

[0051]

[0052] Table 2: Performance test results of aluminum alloy profiles prepared in Examples 1-10 and Comparative Examples 1-5

[0053]

[0054]

[0055] From the above data, it can be seen that the aluminum alloy profile studied in this invention mainly focuses on several key chemical elements (Mg, Si, Sn, Mn, Fe, Cu, Cr, Zr) and their effects on material properties. In particular, the ratio of Mg / Si and the specific content of each element are crucial to obtain ideal mechanical properties (such as yield strength Rm, yield strength R0.2, elongation A50, bending angle).

[0056] Examples 1-10 adopt the composition requirements and preparation scheme of the present invention. All examples exceed 50° in the L direction and 30° in the T direction, indicating that these materials have good formability. Examples 6-10 achieve a good balance between strength and bending angle and have the best comprehensive performance.

[0057] In Comparative Example 1, the Mg and Si contents are relatively low, resulting in poor overall mechanical properties and a yield strength of less than 350 MPa. In Comparative Example 2, compared with Example 6, the Zr content is significantly reduced, which affects the microstructure of the material and thereby reduces the bending performance. In Comparative Example 3, the Sn content is insufficient. As one of the important strengthening elements, the reduction of Sn also leads to a decrease in the bending performance of the material. In Comparative Example 4, the Mn content is reduced. Mn can effectively improve the toughness of the material, so its insufficient content will also affect the deformation performance of the material. It can be seen from Comparative Example 5 that under conventional homogenization treatment, the bending angle of the prepared aluminum alloy profile is unqualified.

[0058] In summary, the present invention optimizes the strengthening effect of the aluminum alloy profile by controlling the formation of the β" phase and the Mg / Si ratio, especially in the peak aging state, by avoiding excess Si, reducing the risk of grain boundary embrittlement, and improving the performance of the material in the bending test. By reasonably selecting and controlling the addition amount of alloying elements (Mn, Zr, Sn and Cu), the comprehensive optimization of bending performance, surface quality and extrudability is achieved. The yield strength of the prepared aluminum alloy profile is ≥350Mpa, and the bending angle satisfies the L direction>50° and the T direction>30°.

[0059] The parts of the embodiments herein that are not exhaustive of the midpoint values ​​of the technical scope claimed for protection by the present invention and the new technical solutions formed by equivalent replacement of single or multiple technical features in the technical solutions of the embodiments are also within the scope claimed for protection by the present invention; at the same time, in all the listed or unlisted embodiments of the scheme of the present invention, each parameter in the same embodiment merely represents an example of its technical solution (i.e., a feasible solution), and there is no strict coordination and limitation relationship between the parameters, wherein the parameters can be replaced with each other without violating the axioms and the claims of the present invention, unless otherwise stated.

[0060] The technical means disclosed in the scheme of the present invention are not limited to the technical means disclosed in the above technical means, but also include technical schemes composed of any combination of the above technical features. The above is a specific implementation 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 principle of the present invention, and these improvements and modifications are also regarded as the protection scope of the present invention.

[0061] The specific embodiments described herein are merely examples of the spirit of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, but they will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A high-strength aluminum alloy profile with low quenching sensitivity and high bending performance, characterized in that: The aluminum alloy extruded profile raw material is composed of the following elements in percentage by mass: 0.80-1.1% Mg, 0.75-1.0% Si, 0.35-0.60% Cu, 0.10-0.40% Mn, 0.10-0.25% Zr, 0.05-0.20% Sn, 0-0.25% Fe, and the balance is Al and unavoidable impurities.

2. According to claim 1, a high-strength aluminum alloy profile with low quenching sensitivity and high bending performance is characterized in that: The aluminum alloy extruded profile raw material is composed of the following elements in percentage by mass: 0.85-1.0% Mg, 0.80-0.95% Si, 0.40-0.50% Cu, 0.20-0.35% Mn, 0.12-0.20% Zr, 0.10-0.18% Sn, 0-0.15% Fe, and the balance is Al and unavoidable impurities.

3. A high-strength aluminum alloy profile with low quenching sensitivity and high bending performance according to claim 1 or 2, characterized in that: The inevitable impurity elements in the aluminum alloy extruded profile are less than 0.15wt%, of which a single impurity element is less than 0.05%.

4. A high-strength aluminum alloy profile with low quenching sensitivity and high bending performance according to claim 1 or 2, characterized in that: Mg and Si must also meet the following conditions: 1.0≤Mg / Si≤1.

30.

5. A method for preparing a high-strength aluminum alloy profile with low quenching sensitivity and high bending performance as claimed in claim 1 or 2, characterized in that: The method comprises the following steps: S1. Prepare raw materials; S2, melting and casting the raw materials into aluminum bars, and then homogenizing them; S3, then preheating the aluminum rod, and then hot extruding to obtain an extruded profile; S4, then quenching the extruded profile and cooling it to room temperature; S5. Finally, the extruded profile is subjected to aging treatment.

6. The method for preparing a high-strength aluminum alloy profile with low quenching sensitivity and high bending performance according to claim 5, characterized in that: The homogenization treatment in step S2 adopts a two-stage homogenization process: the first stage homogenization process is 130-200°C / 2-10h, and the second stage homogenization process is 370-450°C / 2-12h.

7. The method for preparing a high-strength aluminum alloy profile with low quenching sensitivity and high bending performance according to claim 5, characterized in that: The preheating temperature in step S3 is 490-540°C.

8. The method for preparing a high-strength aluminum alloy profile with low quenching sensitivity and high bending performance according to claim 5, characterized in that: The quenching temperature in step S4 is 500-550°C.

9. The method for preparing a high-strength aluminum alloy profile with low quenching sensitivity and high bending performance according to claim 5, characterized in that: The cooling rate in step S4 is ≥4°C / s.

10. The method for preparing a high-strength aluminum alloy profile with low quenching sensitivity and high bending performance according to claim 5, characterized in that: The aging treatment temperature in step S5 is 180-205°C and the time is 2-16h.

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