Aluminum alloy sheet and method for manufacturing the same

Abstract

The application provides an aluminum alloy plate and a preparation method thereof. The preparation method comprises the following steps: after ingredients of the aluminum alloy plate are proportioned, melting, casting, integrated treatment of soaking and heating, hot rolling and cold rolling are sequentially performed to obtain a cold-rolled coil; the ingredients of the aluminum alloy plate comprise the following components in percentage by mass: 0.6-1.3% of Si element, 0.5-1.1% of Cu element, 0.6-1.2% of Mg element, 0.25% of Cr element, 0.7% of Zn element, 0.2% of Ti element, 0.2% of Zr element and the balance of Al element; the cold-rolled coil is sequentially subjected to solid solution, quenching (multi-stage cooling), straightening and pre-aging to obtain a first finished coil; and the first finished coil is subjected to differential temperature heating artificial aging treatment to obtain the aluminum alloy plate. The production efficiency of the above preparation method is high, and the comprehensive performance of the obtained aluminum alloy plate is good.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aluminum alloy, in particular to an aluminum alloy plate and a preparation method thereof. BACKGROUND

[0002] Aluminum alloy plate is considered to be an ideal material for automobile lightweight due to its light weight, high specific strength, excellent comprehensive performance and easy recycling. The strength of aluminum alloy material needs to be further improved when replacing steel parts with aluminum alloy parts.

[0003] High-strength alloys usually add alloying elements to improve mechanical properties, but these elements may reduce the corrosion resistance of the material. Simply pursuing the strength of the alloy may affect its corrosion resistance, so a balance needs to be found between the two. At the same time, when a vehicle is involved in a collision, the material needs to deform plastically by bending to absorb energy, thereby reducing the impact on the occupants, which requires the aluminum alloy to have good forming performance while maintaining strength.

[0004] Therefore, there is an urgent need to develop a corrosion-resistant aluminum alloy plate and a preparation method thereof that can balance strength performance, corrosion performance and forming performance, which can not only meet the lightweighting demand but also ensure the durability and safety of the vehicle. SUMMARY

[0005] The main purpose of the present application is to provide an aluminum alloy plate and a preparation method thereof to solve the problem of low production efficiency of aluminum alloy in the prior art and the problem that the prepared aluminum alloy for automobiles cannot balance strength, corrosion resistance and forming performance.

[0006] In order to achieve the above object, according to one aspect of the present application, a method for preparing an aluminum alloy plate is provided, which comprises: step S1, after ingredients of the aluminum alloy plate are proportioned, sequentially performing melting, casting, homogenizing heating integrated treatment, hot rolling and cold rolling to obtain a cold-rolled coil; wherein the ingredients of the aluminum alloy plate comprise, in percentage by mass: 0.6-1.3% of Si element; Fe element ≤0.5%; 0.5-1.1% of Cu element; Mn element ≤1.0%; 0.6-1.2% of Mg element; Cr element ≤0.25%; Zn element ≤0.7%; Ti element ≤0.2%; Zr element ≤0.2%, total content of unavoidable impurities ≤0.15%, content of unavoidable impurities of a single kind ≤0.05%, and the balance being Al element; step S2, sequentially performing solid solution, quenching, straightening and pre-aging treatment on the cold-rolled coil to obtain a first finished coil; step S3, performing differential temperature heating artificial aging treatment on the first finished coil to obtain the aluminum alloy plate; wherein the quenching is in the form of multi-stage cooling, and the quenching comprises sequentially performed first-stage cooling, second-stage cooling and third-stage cooling, and the cooling rate in the temperature range of 300-400°C during the second-stage cooling is 100-300°C / s; the differential temperature heating artificial aging treatment comprises sequentially performed first artificial aging treatment and second artificial aging treatment, and the temperature of the first artificial aging treatment is 30-50°C higher than that of the second artificial aging treatment.

[0007] Further, in the step S3, the differential temperature heating artificial aging treatment is performed by using a car bottom heating furnace, the car bottom heating furnace comprises sequentially connected first heating zone, second heating zone, third heating zone, fourth heating zone, fifth heating zone and sixth heating zone; the first artificial aging treatment is performed in the first heating zone and the second heating zone, and the second artificial aging treatment is performed in the third heating zone, the fourth heating zone, the fifth heating zone and the sixth heating zone; wherein the heating rate of the first artificial aging treatment is 30-100°C / h; the time of the first artificial aging treatment is 1.4-5.6h; the temperature of the second artificial aging treatment is 165-195°C, and the time of the second artificial aging treatment is 4-20h.

[0008] Further, in the step S1, the homogenizing heating integrated treatment comprises sequentially performed homogenizing heat treatment and heating treatment; wherein the heating rate of the homogenizing heat treatment is 20-100°C / h, the temperature of the homogenizing heat treatment is 540-570°C, and the time of the homogenizing heat treatment is 4-30h; the temperature of the heating treatment is 535-560°C, and the time of the heating treatment is 1-18h.

[0009] Further, in the step S1, the hot rolling is performed at a starting temperature of 535-560℃ and a finishing temperature of 240-360℃, and the thickness of the hot-rolled coil is 2-8mm; and / or, the cold rolling is performed at a cold rolling rate of 50-90%, and the thickness of the cold-rolled coil is 0.6-3.0mm.

[0010] Further, the step S1 further comprises: performing intermediate annealing during the multi-pass cold rolling; wherein the intermediate annealing is performed at a temperature of 410-520℃ for a time of 10-60s.

[0011] Further, in the step S2, the solution treatment is performed at a temperature of 535-570℃ for a time of 10-150s; and / or, the straightening is performed at a straightening amount of 0.2-1.0%.

[0012] Further, in the step S2, the pre-aging treatment is isothermal pre-aging treatment or cooling pre-aging treatment; wherein the isothermal pre-aging treatment is performed at a temperature of 70-100℃ for a time of 4-10h; the cooling pre-aging treatment is performed at a starting temperature of 90-110℃ at a cooling rate of 1-3℃ / h.

[0013] Further, in the step S2, the first finished coil has a yield strength of 145-200MPa, a tensile strength ≥275MPa, an elongation at break ≥20%, a work hardening index n (5-15) ≥0.26, and a Lankford coefficient r 10 ≥0.6; after being subjected to a pre-stretching of 2% and a baking at 185℃ for 20min, the first finished coil has a yield strength ≥290MPa, a tensile strength ≥350MPa, a maximum intergranular corrosion depth ≤250μm, and an average intergranular corrosion depth ≤150μm.

[0014] According to another aspect of the present application, there is provided an aluminum alloy plate prepared by the above method.

[0015] Further, the aluminum alloy plate has a yield strength ≥340MPa, a tensile strength ≥390MPa, and an elongation at break ≥12%; the aluminum alloy plate has a maximum intergranular corrosion depth ≤250μm and an average intergranular corrosion depth ≤150μm.

[0016] The aluminum alloy plate prepared by the preparation method has high strength, good corrosion resistance and forming property, can meet the demand of light weight of the aluminum alloy for automobile, and can guarantee the durability and safety of the vehicle. Specifically, 1) the aluminum alloy component constructs a new Al-Mg-Si-Cu quaternary strengthening alloy system with the mass content of Cu element in the above range. The mass content of Cu element can reduce the nucleation barrier of precipitated strengthening phase, promote the formation of precipitated strengthening phase, thereby accelerating the aging hardening rate, and further improving the strength property of the aluminum alloy plate, and the synergistic improvement of the strength property under various use conditions while maintaining good forming property. Meanwhile, the aging kinetics is accelerated, and the heat treatment time can be shortened, thereby improving the production efficiency. By adding the micro-alloying elements Mn element, Cr element, Ti element and Zr element, the synergistic effect of the main alloying elements and the micro-alloying elements can be improved, and the effects of precipitated strengthening and grain refinement can be fully played, thereby further synergistically improving the strength, formability and corrosion resistance of the aluminum alloy plate. Therefore, the aluminum alloy plate solves the core problems of insufficient strength and slow baking response of the traditional Al-Mg-Si automobile plate, and has high industrial application value. 2) Based on JMatPro thermodynamic calculation and TTT curve analysis, and combined with the characteristics of the continuous annealing line field cooling equipment, a solid solution quenching multi-stage cooling process is innovatively developed, and especially the cooling rate of the second stage cooling in the quenching is controlled in the above range, so that high-speed cooling can be realized, thereby effectively inhibiting the continuous network precipitation of the grain boundary Q' phase (AlCuMgSi phase), and changing the morphology from continuous distribution to intermittent distribution. The optimized and controlled grain boundary microstructure can improve the intergranular corrosion resistance of the aluminum alloy plate, and can also improve the forming property, thereby realizing the balance of the comprehensive properties such as strength, formability and corrosion resistance. 3) Compared with the traditional isothermal artificial aging treatment, the temperature of the first artificial aging treatment is 30-50 DEG C higher than that of the second artificial aging treatment in the differential temperature heating artificial aging treatment of the application, which can accelerate the heating rate of the heating section (the first artificial aging treatment), reduce the time required in the heating section, and thereby significantly improve the production efficiency. 4) The storage time between the solid solution quenching and the artificial aging has a certain influence on the performance of the alloy T6 state. The traditional process requires strict control of the consistent storage time to ensure the performance stability between batches, but this requirement is often difficult to achieve in actual production scheduling due to factors such as equipment scheduling and process connection. The pre-aging process introduced in the application can improve the stability of the aluminum alloy plate, reduce the sensitivity of the aluminum alloy performance to the storage time after solid solution, ensure the consistency of the performance of the materials with different storage time batches, and thereby improve the flexibility of the production scheduling, and provide convenience for the actual production management.The pre-aging process is designed after solid solution. On the one hand, the supersaturated vacancies are actively utilized to form small and uniform solute atom clusters or transition phases, thereby reducing the free vacancy concentration and hindering the formation of harmful coarse clusters in the natural aging process, so as to improve the stability of the aluminum alloy material. On the other hand, the small clusters formed by the pre-aging process can act as nucleation sites for strengthening phases during subsequent differential temperature heating artificial aging, thereby promoting more intensive and uniform precipitation and further improving the response efficiency of the differential temperature heating artificial aging process, and further improving the final strength of the aluminum alloy sheet. 5) The preparation method of the present application can not need to add an intermediate annealing process between multiple cold rolling processes, thereby shortening the production cycle, improving the production efficiency and reducing the production cost. At the same time, the intermediate annealing process can significantly increase the cold rolling rate of cold rolling, thereby further refining the grain structure and further improving the comprehensive performance of the aluminum alloy sheet. In summary, the preparation method of the present application has high production efficiency, low energy consumption, and can reduce carbon emissions, and the comprehensive performance and quality stability of the prepared aluminum alloy sheet are good, thereby better applying in the fields of automobile lightweight, rail transportation, aerospace, ship and marine engineering, etc. DETAILED DESCRIPTION

[0017] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments.

[0018] As analyzed in the background art, the production efficiency of the aluminum alloy in the prior art is low, and the automobile aluminum alloy prepared has the problem of being difficult to balance the strength, corrosion resistance and forming performance. In order to solve the above problems, the present application provides an aluminum alloy sheet and a preparation method thereof.

[0019] In a typical embodiment of the present application, a preparation method of an aluminum alloy plate is provided, which comprises: step S1, after compounding according to the composition of the aluminum alloy plate, sequentially performing melting, casting, homogenizing heating integrated treatment, hot rolling and cold rolling to obtain a cold-rolled coil; wherein the composition of the aluminum alloy plate comprises, in mass percentage: 0.6-1.3% of Si element, Fe element ≤0.5%, 0.5-1.1% of Cu element, Mn element ≤1.0%, 0.6-1.2% of Mg element, Cr element ≤0.25%, Zn element ≤0.7%, Ti element ≤0.2%, Zr element ≤0.2%, total content of unavoidable impurities ≤0.15%, content of unavoidable single kind of impurities ≤0.05%, and the balance being Al element; step S2, sequentially performing solid solution, quenching, straightening and pre-aging treatment on the cold-rolled coil to obtain a first finished coil; step S3, performing differential temperature heating artificial aging treatment on the first finished coil to obtain the aluminum alloy plate; wherein the quenching mode is multi-stage cooling, the quenching comprises sequentially performing first-stage cooling, second-stage cooling and third-stage cooling, and the cooling rate in the temperature range of 300-400°C during the second-stage cooling is 100-300°C / s, preferably 100-200°C / s; the differential temperature heating artificial aging treatment comprises sequentially performing first artificial aging treatment and second artificial aging treatment, and the temperature of the first artificial aging treatment is 30-50°C higher than that of the second artificial aging treatment.

[0020] The aluminum alloy plate obtained by the preparation method has high strength, good corrosion resistance and forming property, can meet the demand of light weight of aluminum alloy for automobile, and can guarantee the durability and safety of the vehicle. Specifically, 1) the aluminum alloy component of the application constructs a new Al-Mg-Si-Cu quaternary strengthening alloy system with Cu element mass content in the above range. The increase of the mass content of Cu element can reduce the nucleation barrier of precipitated strengthening phase, promote the formation of precipitated strengthening phase, thereby accelerating the aging hardening rate, and thus improving the strength performance of the aluminum alloy plate, and the synergistic improvement of the strength performance under various use conditions while maintaining good forming property. At the same time, the aging kinetics is accelerated, and the time of heat treatment can be shortened, thereby improving the production efficiency. By adding micro-alloying elements Mn, Cr, Ti and Zr, the synergistic effect of the main alloying elements and the micro-alloying elements can be improved, and the effects of precipitated strengthening and grain refinement can be fully played, thereby further synergistically improving the strength, formability and corrosion resistance of the aluminum alloy plate. Therefore, the aluminum alloy plate of the application solves the core problems of insufficient strength and slow baking response of traditional Al-Mg-Si automobile plate, and has high industrial application value. 2) Based on JMatPro thermodynamic calculation and TTT curve analysis, combined with the characteristics of continuous annealing line field cooling equipment, the application innovatively develops a solid solution quenching multi-stage cooling process, especially controlling the cooling rate of the second stage cooling in quenching in the above range, which can realize high-speed cooling, thereby effectively inhibiting the continuous network precipitation of grain boundary Q' phase (AlCuMgSi phase), and changing its morphology from continuous distribution to intermittent distribution. The optimized grain boundary microstructure can improve the intergranular corrosion resistance of the aluminum alloy plate, and can also improve its forming property, thereby realizing the balance of strength, formability and corrosion resistance. 3) Compared with the traditional isothermal artificial aging treatment, the temperature of the first artificial aging treatment in the differential temperature heating artificial aging treatment of the application is 30-50℃ higher than that of the second artificial aging treatment, which can accelerate the heating rate of the heating section (the first artificial aging treatment) and reduce the time required in the heating section, thereby significantly improving the production efficiency. 4) The storage time between solid solution quenching and artificial aging has a certain influence on the performance of the alloy in T6 state. The traditional process requires strict control of consistent storage time to ensure the performance stability between batches, but in actual production scheduling, this requirement is often difficult to achieve due to factors such as equipment scheduling and process connection. The introduction of pre-aging process in the application can improve the stability of the aluminum alloy plate, reduce the sensitivity of the aluminum alloy performance to the storage time after solid solution, ensure the consistency of the performance of the materials with different storage time batches, and thereby improve the flexibility of production scheduling, providing convenience for actual production management. Generally, Al-Mg-Si system aluminum alloy material has natural aging phenomenon after solid solution, which can reduce the stability of the aluminum alloy material.The pre-aging process is designed after solid solution. On the one hand, the over-saturated vacancies are actively utilized to form small and uniform solute atom clusters or transition phases, so as to reduce the free vacancy concentration and hinder the formation of harmful coarse clusters in the natural aging process, thereby improving the stability of the aluminum alloy material. On the other hand, the small clusters formed by the pre-aging process can act as nucleation sites for the strengthening phase during subsequent differential temperature heating artificial aging, thereby promoting more intensive and uniform precipitation and further improving the response efficiency of the differential temperature heating artificial aging process and the final strength of the aluminum alloy sheet. 5) The preparation method of the present application can eliminate the need for intermediate annealing process between multiple cold rolling processes, thereby shortening the production cycle, improving the production efficiency and reducing the production cost. At the same time, the intermediate annealing process can significantly increase the cold rolling rate of the cold rolling process, thereby further refining the grain structure and improving the comprehensive performance of the aluminum alloy sheet. In summary, the preparation method of the present application has high production efficiency, low energy consumption, and can reduce carbon emissions, and the comprehensive performance and quality stability of the aluminum alloy sheet prepared by the preparation method are good, thereby better applying in the fields of automobile lightweight, rail transportation, aerospace, ship and marine engineering, etc.

[0021] In addition, the first and third stages of cooling in the quenching process are not particularly required. According to the analysis and calculation of the precipitation kinetics TTT curve, the precipitation nose temperature of the Q' phase (AlCuMgSi phase) in the alloy is 300-400℃, i.e., the temperature range of the second stage of cooling is 300-400℃, the temperature range of the first stage is 400-570℃, and the temperature range of the third stage is room temperature-300℃. The Q' phase (AlCuMgSi phase) has a small precipitation rate, and therefore, the cooling rate is not particularly required.

[0022] Preferably, the aluminum alloy sheet contains the following elements in mass percentage: 0.65-0.95% of Si element, 0-0.3% of Fe element, 0.6-0.9% of Cu element, 0-0.3% of Mn element, 0.7-1.0% of Mg element, 0-0.3% of Cr element, 0-0.5% of Zn element, 0-0.1% of Ti element, 0-0.1% of Zr element, the total content of unavoidable impurities is ≤0.15%, the content of each single kind of unavoidable impurities is ≤0.05%, and the balance is Al element.

[0023] The mass contents of Mg element, Si element and Cu element have an important influence on the performance of the alloy. The mass content of Mg element is X%, the mass content of Si element is Y%, and the mass content of Cu element is Z%. (X+Y)×Z is 0.87-1.76, which helps to balance the strength, formability and corrosion resistance of the aluminum alloy sheet, and comprehensively improves the performance of the aluminum alloy.

[0024] In an embodiment of the present application, in the step S3, the differential temperature heating artificial aging treatment is performed by using a trolley type heating furnace, the trolley type heating furnace comprises first heating zone, second heating zone, third heating zone, fourth heating zone, fifth heating zone and sixth heating zone connected in sequence; the first artificial aging treatment is performed in the first heating zone and the second heating zone, and the second artificial aging treatment is performed in the third heating zone, the fourth heating zone, the fifth heating zone and the sixth heating zone; wherein the heating rate of the first artificial aging treatment is 30-100℃ / h; the time of the first artificial aging treatment is 1.4-5.6h; the temperature of the second artificial aging treatment is 165-195℃, and the time of the second artificial aging treatment is 4-20h.

[0025] Preferably, the differential temperature heating artificial aging treatment is performed by using a trolley type heating furnace, the furnace of the trolley type heating furnace is divided into six zones (first heating zone, second heating zone, third heating zone, fourth heating zone, fifth heating zone and sixth heating zone), and the temperature of each zone can be independently controlled, which is helpful for accurately controlling the differential temperature heating process, thereby better optimizing the distribution and size of precipitated phase and achieving better aging effect. Preferably, the temperature of the first two zones is higher than that of the last four zones, which is helpful for accelerating the aging process of different zones in the aluminum alloy and improving the production efficiency. Preferably, the heating rate of the differential temperature heating artificial aging treatment, the time of the first artificial aging treatment, the temperature and time of the second artificial aging treatment are controlled in the above-mentioned ranges, which is helpful for orderly gathering of solute atoms in the aluminum alloy to form stable precipitated phase, thereby improving the comprehensive performance of the aluminum alloy plate.

[0026] The trolley speed of the trolley type heating furnace is determined by the furnace length / (heating time + holding time), which is helpful for realizing rapid heating in the artificial aging process and continuous automatic production. One end of the trolley type heating furnace is the entrance, and the other end is the exit. Compared with the traditional heating furnace with the same end relative to the entrance and exit, or the isothermal heating artificial aging process (the temperature of the furnace is consistent), the production efficiency of the present application is improved by 30-40%.

[0027] The differential temperature heating artificial aging treatment is naturally cooled, which is helpful for relieving the internal stress concentration caused by rapid cooling, thereby maintaining the stability and consistency of the aluminum alloy material.

[0028] In an embodiment of the present application, in the step S1, the integrated homogenization heating treatment comprises homogenization heat treatment and heating treatment performed in sequence; wherein the heating rate of the homogenization heat treatment is 20-100℃ / h, the temperature of the homogenization heat treatment is 540-570℃, and the time of the homogenization heat treatment is 4-30h; the temperature of the heating treatment is 535-560℃, and the time of the heating treatment is 1-18h.

[0029] The heating treatment process is directly transitioned from the homogenization heat treatment process, i.e., integrated treatment of soaking and heating. This direct transition avoids the cooling and reheating processes after traditional heat treatment, reduces energy consumption, improves efficiency, and also avoids performance degradation caused by phase changes during the cooling process.

[0030] Preferably, the temperature and time of the homogenization heat treatment are controlled in the above ranges, which helps the solute atoms in the aluminum alloy to fully diffuse, reduces composition segregation, dissolves and destroys the hard phases formed during casting, and thus makes the microstructure of the aluminum alloy more uniform. In particular, in the Al-Mg-Si system, it helps to effectively redissolve Mg2Si phases and Q' phases, thereby facilitating the subsequent formation of uniform and fine precipitates, and further improving the strength and formability of the aluminum alloy sheet. Preferably, the temperature and time of the heating treatment are controlled in the above ranges, which helps to maintain the thermal stability of the aluminum alloy, reduces cracks and other defects during hot rolling, and at the same time provides plasticity for the aluminum alloy sheet to facilitate hot rolling.

[0031] In an embodiment of the present application, in the step S1, the hot rolling is performed at a starting temperature of 535-560°C and a finishing temperature of 240-360°C, and the thickness of the hot-rolled coil is 2-8 mm; and / or, the cold rolling is performed at a cold rolling rate of 50-90%, preferably 60-80%, and the thickness of the cold-rolled coil is 0.6-3.0 mm.

[0032] Hot rolling helps to optimize the microstructure of the aluminum alloy, thereby improving the mechanical properties of the aluminum alloy sheet. Preferably, the starting temperature of the hot rolling is controlled in the above range, which helps to reduce the deformation resistance of the aluminum alloy sheet, so that it has good flowability at the initial stage of hot rolling, thereby facilitating the control of the thickness and the smooth progress of the subsequent processes. Preferably, the finishing temperature is controlled in the above range, which helps to suppress the occurrence of recrystallization and maintain the metastable structure of the aluminum alloy sheet at the end of hot rolling. This structure is rich in dislocations, which helps to provide more plastic deformation space for subsequent cold rolling and solid solution, thereby helping to obtain finer grains and more uniform precipitate distribution. In addition, it also helps to reduce the oxidation and surface damage of the aluminum alloy sheet during hot rolling, thereby improving the surface quality and corrosion resistance of the finished product.

[0033] Preferably, the cold rolling rate of the cold rolling is controlled in the above range, which helps to increase the dislocation density of the cold-rolled sheet, break and elongate the original grains, and accumulate a large amount of deformation energy. This high-energy state helps to promote the formation of a large number of recrystallization nuclei during annealing, and finally obtain a fine and uniform grain structure. The optimization of this microstructure helps to simultaneously improve various properties of the aluminum alloy sheet: the fine-grain strengthening effect helps to improve the strength of the material; the uniform and fine grain structure helps to improve the deformation coordination, thereby enhancing the formability of the material; in addition, the fine-grain structure can hinder the expansion of grain boundary corrosion, thereby improving the intergranular corrosion resistance of the material. This method of controlling the grain size by adjusting the cold rolling rate provides an effective way to comprehensively improve the strength, formability and corrosion resistance of the aluminum alloy sheet.

[0034] In an embodiment of the present application, the step S1 further comprises: performing intermediate annealing during the multi-pass cold rolling; wherein the temperature of the intermediate annealing is 410-520℃, and the time of the intermediate annealing is 10-60s.

[0035] According to the actual production needs, intermediate annealing can be arranged between the multi-pass cold rolling, and the temperature and time of the intermediate annealing are controlled in the above range, which helps to restore the plasticity of the aluminum alloy sheet, reduce cold work hardening, and reduce the generation of cracks.

[0036] In an embodiment of the present application, in the step S2, the temperature of the solution treatment is 535-570℃, and the time of the solution treatment is 10-150s; and / or, the amount of straightening of the straightening is 0.2-1.0%.

[0037] Preferably, the temperature and time of the solution treatment are controlled in the above range, which not only helps to promote the dissolution of Cu and Mg elements and form a supersaturated state, thereby helping to rapidly precipitate fine strengthening phases during subsequent aging treatment, thereby improving the strength of the aluminum alloy sheet. At the same time, it also helps to make the microstructure more uniform, thereby improving the plasticity and formability of the aluminum alloy sheet. Preferably, the amount of straightening of the straightening is controlled in the above range, which helps to reduce the residual stress inside the aluminum alloy sheet, reduce the warping of the aluminum alloy sheet during storage and transportation, and at the same time maintain the strength and plasticity of the material.

[0038] In an embodiment of the present application, in the step S2, the pre-aging treatment is isothermal pre-aging treatment or cooling pre-aging treatment; wherein the temperature of the isothermal pre-aging treatment is 70-100℃, and the time of the isothermal pre-aging treatment is 4-10h; the starting temperature of the cooling pre-aging treatment is 90-110℃, and the cooling rate of the cooling pre-aging treatment is 1-3℃ / h.

[0039] Preferably, the temperature and time of the isothermal pre-aging treatment are controlled in the above ranges, which not only helps to stabilize the microstructure of the material, reduce the strength change caused by natural aging, and thus improve the stability of the material during subsequent processing and use, but also helps to promote the formation of atomic clusters or transition phases, which serve as nucleation centers for precipitated phases during differential temperature heating artificial aging treatment, and promote the uniform distribution of precipitated phases, thereby improving the final strength of the aluminum alloy sheet. Preferably, the starting temperature of the cooling pre-aging treatment is controlled in the above range, which helps to promote the formation of atomic clusters or transition phases, and the cooling rate is controlled in the above range, which helps to promote the uniform distribution and stable growth of clusters, thereby balancing the strength and plasticity of the aluminum alloy sheet.

[0040] In an embodiment of the present application, in the step S2, the yield strength of the first finished coil is 145-200 MPa, the tensile strength of the first finished coil is ≥275 MPa, the elongation at break of the first finished coil is ≥20%, the work hardening index n of the first finished coil is ≥0.26, and the Lankford coefficient r of the first finished coil is ≥0.6; after the 2% pre-stretching and the baking at 185°C for 20 min, the yield strength of the first finished coil is ≥290 MPa, the tensile strength of the first finished coil is ≥350 MPa, the maximum intergranular corrosion depth of the first finished coil is ≤250 μm, and the average intergranular corrosion depth of the first finished coil is ≤150 μm. (5-15) ≥0.26, and the Lankford coefficient r 10 of the first finished coil is ≥0.6; after the 2% pre-stretching and the baking at 185°C for 20 min, the yield strength of the first finished coil is ≥290 MPa, the tensile strength of the first finished coil is ≥350 MPa, the maximum intergranular corrosion depth of the first finished coil is ≤250 μm, and the average intergranular corrosion depth of the first finished coil is ≤150 μm.

[0041] The present application optimizes the alloy composition and process of the Al-Mg-Si-Cu quaternary strengthening system, so that the sheet has excellent strength performance in each state.

[0042] Preferably, the yield strength of the first finished coil is 145-200 MPa, the tensile strength of the first finished coil is ≥285 MPa, the elongation at break of the first finished coil is ≥25%, the work hardening index n of the first finished coil is ≥0.27, and the Lankford coefficient r of the first finished coil is ≥0.65; after the 2% pre-stretching and the baking at 185°C for 20 min, the yield strength of the first finished coil is ≥295 MPa, the tensile strength of the first finished coil is ≥355 MPa, the maximum intergranular corrosion depth of the first finished coil is ≤150 μm, and the average intergranular corrosion depth of the first finished coil is ≤100 μm. (5-15) ≥0.27, and the Lankford coefficient r 10 of the first finished coil is ≥0.65; after the 2% pre-stretching and the baking at 185°C for 20 min, the yield strength of the first finished coil is ≥295 MPa, the tensile strength of the first finished coil is ≥355 MPa, the maximum intergranular corrosion depth of the first finished coil is ≤150 μm, and the average intergranular corrosion depth of the first finished coil is ≤100 μm.

[0043] In another typical embodiment of the present application, an aluminum alloy sheet is provided, which is prepared by the above preparation method.

[0044] The aluminum alloy plate obtained by the preparation method has high strength, good corrosion resistance and forming performance, can meet the demand of light weight of aluminum alloy for automobile, guarantee the durability and safety of the vehicle, and can be applied in the fields of rail transit, aerospace, ship and marine engineering and the like.

[0045] In an embodiment of the present application, the yield strength of the aluminum alloy plate is ≥ 340 MPa, the tensile strength of the aluminum alloy plate is ≥ 390 MPa, and the fracture elongation of the aluminum alloy plate is ≥ 12%; the maximum intergranular corrosion depth of the aluminum alloy plate is ≤ 250 μm, and the average intergranular corrosion depth of the aluminum alloy plate is ≤ 150 μm.

[0046] Compared with the 6451 alloy which is the strongest among the current Al-Mg-Si system automobile plates, the mechanical properties of the aluminum alloy plate of the present application are improved by more than 20%, and the aluminum alloy plate becomes a high-strength automobile plate material in the current Al-Mg-Si system and Al-Mg-Si-Cu system.

[0047] Preferably, the yield strength of the aluminum alloy plate is ≥ 345 MPa, the tensile strength of the aluminum alloy plate is ≥ 400 MPa, and the fracture elongation of the aluminum alloy plate is ≥ 14%; the maximum intergranular corrosion depth of the aluminum alloy plate is ≤ 200 μm, and the average intergranular corrosion depth of the aluminum alloy plate is ≤ 140 μm.

[0048] It should be particularly pointed out that due to the particularity of the alloy field and the limitation of the existing test and characterization means, the microstructure of the obtained aluminum alloy plate is difficult to be comprehensively quantitatively characterized, but experiments show that the aluminum alloy plate obtained by the present application has higher comprehensive mechanical properties and corrosion resistance.

[0049] The beneficial effects of the present application will be further illustrated in combination with the embodiments.

[0050] Embodiment 1

[0051] The aluminum alloy plate is prepared by the following steps. After the composition of the aluminum alloy plate is allocated, the cast ingot is obtained by sequentially melting and casting at 750℃. The cast ingot is subjected to soaking heating integrated treatment, which is sequentially carried out homogenizing heat treatment and heating treatment. The temperature of the homogenizing heat treatment is 560℃, the time is 8h, and the heating rate is 30℃ / h. The temperature of the heating treatment is 540℃, and the time is 2h. Then, the hot-rolled coil is obtained by hot rolling. The starting temperature of the hot rolling is 540℃, and the final temperature of the hot rolling is 270℃. The thickness of the hot-rolled coil is 7mm. The cold-rolled coil is obtained by multi-pass cold rolling of the hot-rolled coil. The cold rolling rate is 79%, and the thickness of the cold-rolled coil is 1.5mm. The first finished coil is obtained by sequentially subjecting the cold-rolled coil to solid solution, quenching, straightening and pre-aging treatment. The temperature of the solid solution is 555℃, and the time is 30s. The quenching is carried out by a multi-stage cooling process. The tempering is sequentially carried out first-stage cooling, second-stage cooling and third-stage cooling. The cooling rate of the second-stage cooling is 100℃ / s at a temperature range of 300-400℃. The straightening amount of the straightening is 0.5%. The pre-aging treatment is temperature decreasing pre-aging, the starting temperature is 100℃, and the cooling rate is 2℃ / h. The aluminum alloy plate is obtained by slicing the first finished coil after the difference temperature heating artificial aging treatment in the bogie hearth furnace. The difference temperature heating artificial aging treatment is sequentially carried out first artificial aging treatment and second artificial aging treatment. The bogie hearth furnace includes sequentially connected first heating zone, second heating zone, third heating zone, fourth heating zone, fifth heating zone and sixth heating zone. The first artificial aging treatment is carried out in the first heating zone and the second heating zone, and the second artificial aging treatment is carried out in the third heating zone, the fourth heating zone, the fifth heating zone and the sixth heating zone. The temperature of the first heating zone and the second heating zone is set to 220℃, and the temperature of the third heating zone, the fourth heating zone, the fifth heating zone and the sixth heating zone is set to 180℃. The temperature of the first artificial aging treatment is 220℃, the time is 3.3h, and the heating rate is 60℃ / h. The temperature of the second artificial aging treatment is 180℃, and the time is 8h.

[0052] The composition of the aluminum alloy plate is shown in Table 1, and the parameters of the preparation method are shown in Tables 2 and 3.

[0053] Examples 2-6

[0054] The difference between Example 1 and the present embodiment is that the element composition of the aluminum alloy plate is different, which is shown in Table 1.

[0055] Examples 7-15

[0056] The difference between Example 1 and the present embodiment is that the parameters of the preparation method of the aluminum alloy plate are different, which are shown in Tables 2 and 3.

[0057] The intermediate annealing in Example 9 and Example 14 is carried out in the process of multi-pass cold rolling.

[0058] Example 16

[0059] The difference from Example 1 is that the cooling rate in the temperature range of 300-400℃ during the second cooling in the quenching process is 200℃ / s, and finally the aluminum alloy plate is obtained.

[0060] Example 17

[0061] The difference from Example 1 is that the heating rate of the first artificial aging treatment is 100℃ / h, the temperature of the first artificial aging treatment is 215℃, and the time is 19h; the temperature of the second artificial aging treatment is 165℃, and the time of the second artificial aging treatment is 20h, and finally the aluminum alloy plate is obtained.

[0062] Example 18

[0063] The difference from Example 1 is that the heating rate of the first artificial aging treatment is 30℃ / h, the temperature of the first artificial aging treatment is 225℃, and the time is 5h; the temperature of the second artificial aging treatment is 195℃, and the time of the second artificial aging treatment is 4h, and finally the aluminum alloy plate is obtained.

[0064] Example 19

[0065] The difference from Example 1 is that the mass content of Mg element is 1.0(X)%, the mass content of Si element is 0.95(Y)%, and the mass content of Cu element is 0.9(Z)%, (X+Y)×Z is 1.76, and finally the aluminum alloy plate is obtained.

[0066] Example 20

[0067] The difference from Example 1 is that the mass content of Mg element is 0.6(X)%, the mass content of Si element is 0.6(Y)%, and the mass content of Cu element is 0.5(Z)%, (X+Y)×Z is 0.6, and finally the aluminum alloy plate is obtained.

[0068] Comparative Examples 1-5

[0069] The difference from Example 1 is that the element composition of the aluminum alloy plate is different, and the specific see Table 1.

[0070] Comparative Examples 6-8

[0071] The difference from Example 1 is that the parameters of the preparation method of the aluminum alloy plate are different, and the specific see Table 2 and Table 3.

[0072] Test method:

[0073] The first finished plate and the aluminum alloy plate are placed at room temperature 25℃ for 7 days, and then the mechanical properties, baking properties and intergranular corrosion properties are evaluated.

[0074] Yield strength, tensile strength, and elongation at break: Refer to GB / T 228-2010 Metallic materials, tensile test, room temperature test method.

[0075] Work hardening index n ((5-15) Tested according to GB / T 5028-2008 Determination of tensile strain hardening index (n value) of thin plates and strips of metallic materials.

[0076] Lankford coefficient r 10 Tested according to GB / T 5027-2016 Determination of Plastic Strain Ratio (r value) of Thin Plates and Strips of Metallic Materials.

[0077] Baking performance: Tested according to GB / T 33227-2016 Aluminum and aluminum alloy sheets and strips for automobiles.

[0078] Intergranular corrosion:

[0079] According to the test of "BMW Group AA0255-2017-02 Testing the Sensitivity of 6xxxAluminum Alloys for Integranular Corrosion".

[0080] The test results are shown in Tables 4 and 5.

[0081] Table 1

[0082]

[0083] Table 2

[0084]

[0085] Table 3

[0086]

[0087] Table 4

[0088]

[0089] Table 5

[0090]

[0091] As can be seen from the above, the high Cu content in Comparative Example 1 leads to increased element segregation and continuous distribution of Cu-containing precipitates at grain boundaries. Although the strength of the aluminum alloy sheet is improved, the elongation decreases and the corrosion resistance is significantly reduced.

[0092] The mass content of Cu element in Comparative Example 2 is low, which leads to the reduction of the strength performance of the aluminum alloy plate.

[0093] The mass content of Si element in Comparative Example 3 is high, which is not conducive to the formability and corrosion resistance of the aluminum alloy plate, and the elongation and corrosion resistance are reduced.

[0094] The mass content of Mg element in Comparative Example 4 is high, which belongs to the Mg excessive system, the driving force of Mg2Si generated in each process is greater, the Mg2Si phase is left in the finished plate, and the effective dispersion strengthening phase density is low, which leads to the reduction of the strength performance of the aluminum alloy plate.

[0095] The mass content of Zn element in Comparative Example 5 is high, which leads to the reduction of the corrosion resistance of the aluminum alloy plate.

[0096] In Comparative Example 6, the cooling rate of the second cooling in quenching is small, which causes the continuous network precipitation of grain boundary Q' phase (AlCuMgSi), and leads to the significant reduction of the corrosion resistance of the aluminum alloy plate.

[0097] In Comparative Example 7, the temperature of the first artificial aging treatment is 20℃ higher than that of the second artificial aging treatment, and the difference is small, which reduces the production efficiency. At the same time, the temperature of the second artificial aging treatment is low, and the aluminum alloy plate is in the under-aged state, which leads to the reduction of the mechanical properties of the aluminum alloy plate.

[0098] In Comparative Example 8, the temperature of the first artificial aging treatment is the same as that of the second artificial aging treatment, which is isothermal artificial aging treatment, and the production efficiency is obviously reduced. The temperature of the second artificial aging treatment is high, and the aluminum alloy plate is in the over-aged state, which leads to the poor elongation of the aluminum alloy plate.

[0099] In Example 12, the homogenization temperature is low, the as-cast structure uniformity is not high, the soluble phase Mg2Si phase and Q' phase (AlCuMgSi) are not completely dissolved, the difficult-to-dissolve AlFeMnSi phase is not high in discontinuity, and the initial phase is left in the finished plate. The opening rolling temperature of hot rolling is low, Mg2Si is precipitated, the solid solution process cannot be completely dissolved, Mg2Si phase is left in the finished plate, and the properties of the aluminum alloy plate are reduced.

[0100] In Example 13, the final rolling temperature of hot rolling is high, which causes a large amount of Mg2Si to precipitate after hot rolling and winding, which has an adverse effect on the subsequent processing and heat treatment process, the solid solution process cannot be completely dissolved, Mg2Si phase is left in the finished plate, and at the same time, the recrystallization grains grow after hot rolling and winding, the genetic effect causes the finished plate to have coarse grains, and the properties of the aluminum alloy plate are reduced.

[0101] The intermediate annealing temperature in the embodiment 14 is low, the recrystallization degree in the intermediate annealing process is low, meanwhile, Mg2Si precipitates and grows, which has an adverse effect on subsequent processing and heat treatment process, and the comprehensive performance of the aluminum alloy plate is reduced.

[0102] The solid solution temperature in the embodiment 15 is low, the recrystallization degree of the cold-rolled plate is low, the Mg2Si resolubility is poor, and the strength performance and corrosion resistance of the alloy plate are reduced.

[0103] From the above description, it can be seen that the above-mentioned embodiments of the present application achieve the following technical effects:

[0104] The aluminum alloy sheet prepared by the method described in this application exhibits high strength, good corrosion resistance, and formability, meeting the lightweight requirements of automotive aluminum alloys while ensuring vehicle durability and safety. Specifically, 1) the aluminum alloy composition of this application constructs a novel Al-Mg-Si-Cu quaternary strengthening alloy system with Cu content within the aforementioned range. Increasing the Cu content lowers the nucleation barrier of the precipitation strengthening phase, promoting its formation and accelerating the aging hardening rate, thereby improving the strength properties of the aluminum alloy sheet. This achieves a synergistic improvement in strength properties under various service conditions while maintaining good formability. Simultaneously, it accelerates aging kinetics, shortening heat treatment time and improving production efficiency. The addition of microalloying elements Mn, Cr, Ti, and Zr enhances the synergistic effect between the main alloying elements and microalloying elements, fully leveraging precipitation strengthening and grain refinement to further synergistically improve the strength, formability, and corrosion resistance of the aluminum alloy sheet. Therefore, the aluminum alloy sheet of this application solves the core problems of insufficient strength and slow baking response in traditional Al-Mg-Si automotive sheets, possessing high industrial application value. 2) Based on JMatPro thermodynamic calculations and TTT curve analysis, and combined with the characteristics of the on-site cooling equipment in the continuous annealing line, this application innovatively develops a multi-stage cooling process for solution quenching. In particular, by controlling the cooling rate of the second stage of quenching within the aforementioned range, high-speed cooling can be achieved, thereby effectively suppressing the continuous network precipitation of the Q' phase (AlCuMgSi phase) at the grain boundaries, changing its morphology from a continuous distribution to a discontinuous distribution. The optimized and controlled grain boundary microstructure can improve the intergranular corrosion resistance of aluminum alloy sheets on the one hand, and enhance their formability on the other hand, thus achieving a balance between comprehensive properties such as strength, formability, and corrosion resistance. 3) Compared with traditional isothermal artificial aging treatment, the differential temperature heating artificial aging treatment in this application controls the temperature of the first artificial aging treatment to be 30~50℃ higher than that of the second artificial aging treatment, which can accelerate the heating rate of the heating stage (first artificial aging treatment) and reduce the time required for the heating stage, thereby significantly improving production efficiency. 4) The dwell time between solution quenching and artificial aging has a certain impact on the properties of the alloy in the T6 state. Traditional processes require strict control of consistent dwell time to ensure batch-to-batch performance stability. However, in actual production scheduling, this requirement is often difficult to achieve due to factors such as equipment scheduling and process integration. This application introduces a pre-aging process, which can improve the stability of aluminum alloy sheets, reduce the sensitivity of aluminum alloy properties to the dwell time after solution treatment, and ensure the consistency of material properties in batches with different dwell times. This improves the flexibility of production scheduling and provides convenience for actual production management. Typically, Al-Mg-Si system aluminum alloys undergo natural aging after solution treatment, which reduces the stability of the aluminum alloy material.The pre-aging process is designed after solid solution, on the one hand, the supersaturated vacancies are actively utilized to form small and uniform solute atom clusters or transition phases, the free vacancy concentration is reduced, the formation of harmful coarse clusters in the natural aging process is hindered, and thus the stability of the aluminum alloy material is improved. On the other hand, the small clusters formed by the pre-aging process can act as nucleation sites for strengthening phases during subsequent differential temperature heating artificial aging, promoting more intensive and uniform precipitation, thereby enhancing the response efficiency of the differential temperature heating artificial aging process and further improving the final strength of the aluminum alloy plate. 5) The preparation method of the present application can not need to add an intermediate annealing process between multiple cold rolling processes, thereby shortening the production cycle, improving the production efficiency and reducing the production cost. At the same time, the intermediate annealing process can significantly increase the cold rolling rate of cold rolling, thereby further refining the grain structure and improving the comprehensive performance of the aluminum alloy plate. In summary, the production efficiency of the preparation method of the present application is higher, the energy consumption is lower, and the carbon emission can be reduced, and the comprehensive performance and quality stability of the aluminum alloy plate prepared are better, so that it is better applied in the fields of automobile lightweight, rail transportation, aerospace and ship and marine engineering.

[0105] The above only describes the embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various changes and variations. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method of producing an aluminum alloy sheet, characterized by, The preparation method comprises: Step S1, after the aluminum alloy plate is proportioned according to the composition, sequentially performing melting, casting, homogenizing heating integrated treatment, hot rolling and cold rolling to obtain a cold-rolled coil, wherein the composition of the aluminum alloy plate comprises, in percentage by mass: 0.6-1.3% of Si element; Fe element ≤0.5%; 0.5-1.1% of Cu element; Mn element ≤1.0%; 0.6-1.2% of Mg element; Cr element ≤0.25%; Zn element ≤0.7%; Ti element ≤0.2%; Zr element ≤0.2%, the total content of unavoidable impurities ≤0.15%, the content of unavoidable single kind of impurities ≤0.05%, and the balance being Al element; Step S2, sequentially performing solid solution, quenching, straightening and pre-aging treatment on the cold-rolled coil to obtain a first finished coil; Step S3, performing differential temperature heating artificial aging treatment on the first finished coil to obtain the aluminum alloy plate; Wherein, the quenching mode is multi-stage cooling, the quenching comprises sequentially performing first-stage cooling, second-stage cooling and third-stage cooling, and the cooling rate in the temperature range of 300-400 DEG C in the second-stage cooling is 100-300 DEG C / s; The differential temperature heating artificial aging treatment comprises sequentially performing first artificial aging treatment and second artificial aging treatment, the temperature of the first artificial aging treatment is 30-50 DEG C higher than that of the second artificial aging treatment; in the step S3, the differential temperature heating artificial aging treatment is performed by using a car-type heating furnace, the car-type heating furnace comprises sequentially connected first heating zone, second heating zone, third heating zone, fourth heating zone, fifth heating zone and sixth heating zone; the first artificial aging treatment is performed in the first heating zone and the second heating zone, and the second artificial aging treatment is performed in the third heating zone, the fourth heating zone, the fifth heating zone and the sixth heating zone; The heating rate of the first artificial aging treatment is 30-100 DEG C / h, the time of the first artificial aging treatment is 1.4-5.6 h, the temperature of the second artificial aging treatment is 165-195 DEG C, and the time of the second artificial aging treatment is 4-20 h; The open rolling temperature of the hot rolling is 535-560 DEG C.

2. The production method according to claim 1, characterized by, In the step S1, the homogenizing heating integrated treatment comprises sequentially performing homogenizing heat treatment and heating treatment; wherein, the heating rate of the homogenizing heat treatment is 20-100 DEG C / h, the temperature of the homogenizing heat treatment is 540-570 DEG C, and the time of the homogenizing heat treatment is 4-30 h; the temperature of the heating treatment is 535-560 DEG C, and the time of the heating treatment is 1-18 h.

3. The method of claim 1, wherein, In the step S1, the finish rolling temperature of the hot rolling is 240-360 DEG C, and the thickness of the coil after hot rolling is 2-8 mm; And / or, the cold rolling rate of the cold rolling is 50-90%, and the thickness of the cold-rolled coil is 0.6-3.0 mm.

4. The method of claim 1, wherein, The step S1 further comprises: performing intermediate annealing in the multi-pass cold rolling process; wherein the intermediate annealing temperature is 410-520℃, and the intermediate annealing time is 10-60s.

5. The preparation method according to claim 1, characterized in that, In the step S2, the solution temperature is 535-570℃, and the solution time is 10-150s; and / or the straightening amount is 0.2-1.0%.

6. The method of claim 1, wherein, In the step S2, the pre-aging treatment is isothermal pre-aging treatment or cooling pre-aging treatment; wherein the isothermal pre-aging treatment temperature is 70-100℃, and the isothermal pre-aging treatment time is 4-10h; the cooling pre-aging treatment starting temperature is 90-110℃, and the cooling pre-aging treatment cooling rate is 1-3℃ / h.

7. The preparation method according to claim 1, characterized in that, In the step S2, the yield strength of the first finished coiled material is 145-200 MPa, the tensile strength of the first finished coiled material is ≥275 MPa, the elongation at break of the first finished coiled material is ≥20%, the work hardening index n of the first finished coiled material is ≥0.26, and the Lankford coefficient r of the first finished coiled material is ≥0.

6. (5-15) 10 ≥0.6.​ After 2% pre-stretching and baking at 185℃ for 20min, the yield strength of the first finished coil is ≥290MPa, the tensile strength of the first finished coil is ≥350MPa, the maximum intergranular corrosion depth of the first finished coil is ≤250μm, and the average intergranular corrosion depth of the first finished coil is ≤150μm.

8. An aluminum alloy sheet characterized by, The aluminum alloy plate is prepared by the preparation method in any one of claims 1-7.

9. The aluminum alloy sheet of claim 8, wherein, The yield strength of the aluminum alloy plate is ≥340MPa, the tensile strength of the aluminum alloy plate is ≥390MPa, the fracture elongation of the aluminum alloy plate is ≥12%, the maximum intergranular corrosion depth of the aluminum alloy plate is ≤250μm, and the average intergranular corrosion depth of the aluminum alloy plate is ≤150μm.

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