Al-Cu-Mg-Zn aluminum alloy profile for carrying traffic vehicle body structural component and preparation method of Al-Cu-Mg-Zn aluminum alloy profile

Abstract

The invention discloses an Al-Cu-Mg-Zn aluminum alloy profile for carrying traffic vehicle body structural components and a preparation method of the Al-Cu-Mg-Zn aluminum alloy profile, and relates to the technical field of metal materials and processing of the metal materials. The aluminum alloy comprises, by mass, 7.6%-8.4% of Zn, 1.8%-2.3% of Mg, 0.3%-0.4% of Mn, 0.16%-0.24% of Cr, 0.04%-0.08% of Ti, 0.12%-0.20% of Zr, smaller than or equal to 0.08% of Fe, smaller than or equal to 0.1% of Si and the balance Al, and the mass ratio of Zn to Mg is 3.7-4.2. The preparation method comprises the steps of smelting, purifying, casting, soaking treatment, saw cutting, turning, extruding, solid solution quenching, stretching and aging treatment. The Al-Cu-Mg-Zn alloy profile prepared by the preparation method provided by the invention has the characteristics of high toughness, corrosion resistance and easiness in processing, and can meet the operation requirements of carrying traffic vehicle bodies.

Description

Technical Field

[0001] The invention relates to the technical field of metal materials and processing thereof, in particular to an Al-Cu-Mg-Zn aluminum alloy profile for transportation vehicle body structural components and a preparation method thereof. Background Art

[0002] Aluminum alloy materials have been widely used in rail transit, new energy heavy trucks, engineering vehicles and other transportation vehicle bodies, which can increase the effective load of transportation vehicles, save fuel and reduce vehicle maintenance costs. Compared with traditional vehicle manufacturing materials such as weathering steel and stainless steel, aluminum profiles can reduce the body weight by 30%, and have good adaptability to high-speed lines, multi-bend lines, undulating lines and harsh environments, making them the preferred material for lightweight transportation vehicles. At present, aluminum profiles have been widely used in Japan's Shinkansen rail vehicles, and my country's "Fuxing" standard EMU body and axle box body and other structural load-bearing components are made of aluminum alloy. As a lightweight material with comprehensive excellent performance, aluminum alloy materials have also been widely adopted by domestic and foreign automakers, such as Volvo II-generation new energy heavy trucks, Dongfeng heavy trucks and Shenzhen Xingtu I-generation new energy heavy trucks, all of which have a high aluminumization rate. In addition, compared with other lightweight materials, aluminum alloys have excellent comprehensive characteristics such as corrosion resistance, low cost and recyclability.

[0003] Among them, Al-Cu-Mg-Zn alloy has high strength and excellent welding performance, and has become one of the current load-bearing structural materials for transportation vehicles; using Al-Cu-Mg-Zn alloy as a load-bearing structural material for transportation vehicles can not only ensure the use strength of the vehicle body, but also significantly reduce the vehicle weight and effectively reduce energy consumption. The high-strength and high-weldability Al-Zn-Mg alloy currently produced industrially has a high impurity content, and the hydrogen and slag content cannot be effectively controlled, resulting in low alloy toughness, fatigue resistance and stress corrosion resistance, which is difficult to meet the needs of transportation vehicles.

[0004] Therefore, there is an urgent need for an Al-Cu-Mg-Zn aluminum alloy profile for transportation vehicle body structural components and a preparation method thereof, which has a low impurity content and has better mechanical strength, toughness and weather resistance. Summary of the invention

[0005] The purpose of the present invention is to provide an Al-Cu-Mg-Zn aluminum alloy profile for transportation vehicle body structural components and a preparation method thereof. The aluminum alloy profile prepared by the preparation method of the present invention has a tensile strength greater than 650MPa, a yield strength greater than 600MPa, an elongation greater than 10%, and does not crack after four-point bending stress corrosion for 30 days. The profile can be widely used in transportation vehicle body structural components for products with high requirements on the mechanical strength, toughness and weather resistance of aluminum alloy materials, thereby solving the problems existing in the above-mentioned prior art.

[0006] An Al-Cu-Mg-Zn aluminum alloy profile for a transportation vehicle body structural component. The aluminum alloy material comprises the following element components by mass percentage: Cu: 2.0-2.6%; Zn: 7.6-8.4%; Mg: 1.8-2.3%, Mn: 0.3-0.4%, Cr: 0.16-0.24%, Ti: 0.04-0.08%, Zr: 0.12-0.20%, Fe≤0.08%, Si≤0.1%, and the balance is Al, wherein the mass percentage ratio of Zn to Mg is 3.7-4.2.

[0007] In the Al-Cu-Mg-Zn alloy of the present invention, Zn and Mg are the main alloying elements that form the strengthening phase. When the two exist at the same time, η(MgZn 2 ) phase and T(A1 2 Mg 2 Zn 3 ) phase, Zn, Mg and Al, Cu, Si, etc. can form Al 8 Mg 5 、S(Al 2 CuMg), T(Al 2 Mg 2 Zn 3 ) and β(Mg 2 As the content of Zn and Mg increases, the tensile strength of the alloy increases accordingly. However, when the Zn content exceeds a certain value, the welding performance and corrosion resistance deteriorate significantly. Therefore, when the Zn / Mg content ratio in this type of alloy is in the range of 3.7 to 4.2, the alloy has good tensile strength and good stress corrosion resistance.

[0008] Secondly, the elements Fe and Si are unavoidable harmful impurities in the alloy. Fe will reduce the corrosion resistance and mechanical properties of aluminum alloys, and Si will reduce the strength of aluminum alloys, reduce the bending properties of the alloy, and increase the tendency of welding cracks. 3 In addition to the Si phase, the main components are insoluble or poorly soluble Al 7 Cu 2 The presence of brittle phases and eutectic compounds such as Fe, AlFeMnSi, etc. increases the thermal cracking tendency of the alloy. Therefore, the content of Fe and Si must be controlled within a low range.

[0009] Also disclosed is a method for preparing an Al-Cu-Mg-Zn aluminum alloy profile for a transportation vehicle body structural component, the method comprising the following steps:

[0010] S1: Melting, weighing raw materials according to mass percentage and putting them into a melting furnace for melting;

[0011] S2: Purification, degassing and filtering the molten aluminum liquid;

[0012] S3: Casting, casting the degassed and filtered aluminum liquid, during which Al-Ti-C is added to the aluminum liquid in a launder in the form of online continuous wire feeding as a master alloy, and cooled to obtain a round ingot;

[0013] S4: Soaking treatment;

[0014] S5: Sawing;

[0015] S6: car skin;

[0016] S7: extrusion;

[0017] S8: solution quenching;

[0018] S9: stretching, stretching and straightening the profile after solution quenching, with a stretching rate of 1% to 3%;

[0019] S10: Aging treatment, subjecting the stretched profile to a regression aging treatment to obtain a finished product.

[0020] The strengthening of the Al-Cu-Mg-Zn alloy series of the present invention is mainly produced through the aging treatment process. The fine precipitates formed during the aging treatment process can inhibit the dislocation movement in the material and produce a strengthening effect. The GP zone is regarded as a metastable precipitate that is in a coherent relationship with the α (Al) matrix. As the aging treatment time increases, the GP zone can serve as a nucleation core to promote the formation of a metastable η' phase that is in a semi-coherent relationship with the α (Al) matrix, and can be transformed into an incoherent equilibrium η phase under further heat preservation or high temperature; the metastable η' phase rather than the stable η phase brings the best strengthening effect.

[0021] Preferably, in S1, the smelting temperature is 760-780° C., and the material is kept warm for 5-7 hours after melting.

[0022] Preferably, in S2, the melt is degassed by a degassing device to reduce the hydrogen content to 0.08%; and the melt is filtered by a plate filter having a foam ceramic filter plate.

[0023] The foam ceramic filter plate of the present invention has a uniform microporous structure and can create countless capillaries. It mainly realizes filtration by adsorbing and intercepting metal and non-metallic inclusions in the melt. The inclusions in the aluminum liquid include oxides, nitrides, carbides, borides, etc. Most of these inclusions exist in granular form, and the size is usually in the range of 1-30μm. They will reduce the purity of aluminum and affect the mechanical properties, processing properties and corrosion resistance of aluminum. Through filtering, these inclusions can be intercepted on the filter medium, thereby improving the purity of the aluminum liquid.

[0024] Preferably, in S3, the casting temperature is 700-720°C, and the maximum cross-sectional area of ​​the ingot is 77 cm 2 .

[0025] Preferably, in S4, the ingot is placed in a heat treatment furnace for heating and heat preservation for 10 to 12 hours, and subjected to low-temperature homogenization treatment at 380 to 390°C.

[0026] Preferably, in S5 and S6, the ingot after the soaking treatment is sawn and turned on a sawing machine and a lathe in turn to remove the segregation layer.

[0027] Preferably, in S7, the processed ingot is preheated in a permanent magnet heating furnace at a preheating temperature of 380-400°C for 1-2 hours, and the preheated ingot is extruded into shape using a reverse extrusion process at an extrusion speed of 0.3-1.0 m / min.

[0028] The invention adopts reverse extrusion process to reduce the thickness of the coarse grain layer.

[0029] Preferably, in S8, after the aluminum alloy is extruded, the extruded profile is immediately quenched offline using a vertical quenching furnace, wherein the solution process adopts a two-stage solution heat treatment, the first stage is 450-455°C, and the heat preservation is 3-4h, and the second stage is 470-475°C, and the heat preservation is 3-4h. The quenching medium is deionized water, the quenching cooling rate is 370-400°C / min, and the quenching transfer time is ≤5s.

[0030] Preferably, in S10, the aging heat treatment is a three-stage aging treatment: the first-stage aging temperature is 115-120° C., and the heat preservation is 16-24 hours; the second-stage aging temperature is 160-180° C., and the heat preservation is 20-60 minutes, and the air is cooled to room temperature; the third-stage aging temperature is 115-120° C., and the heat preservation is 16-24 hours, and the final product is obtained by air cooling after being taken out of the furnace.

[0031] The present invention discloses the following technical effects:

[0032] (1) The Cu element in the composition can increase the dispersion of the precipitated phase in the Al-Cu-Mg-Zn alloy. Cu and Mg elements can produce the strengthening phase S phase. Cu atoms can also dissolve into η' and η phases, reducing the potential difference between the grain boundary and the grain, and improving the alloy's resistance to stress corrosion.

[0033] (2) The element Zr can combine in Al-Cu-Mg-Zn alloy to form an intermetallic compound Al 3Zr, trace Zr can refine the grains, improve the strength, fracture toughness and stress corrosion resistance of the alloy; Mn can sharply increase the recrystallization temperature of hot-deformed semi-finished products, especially extruded products; at the same time, it can significantly improve the stress corrosion resistance of the alloy; elements Cr and Ti play a key role in microalloying, effectively controlling the grain structure during processing and heat treatment; trace Ti in the alloy can form TiA1 3 It can refine the weld cast structure to improve the resistance to welding cracks and improve the fine grain strengthening ability. Trace Cr in the alloy can form Al 7 Cr plays a role of precipitation strengthening.

[0034] (3) In the extrusion process, a reverse extrusion process is adopted; since Al-Cu-Mg-Zn aluminum alloy is a high-strength and hard aluminum alloy, it has a large resistance to extrusion deformation. Reverse extrusion can form a stable and small extrusion pressure, so that there is no friction between the billet and the extrusion barrel. In the full stroke range of the extrusion rod, the extrusion pressure remains unchanged. Compared with forward extrusion, there is no friction loss between the billet and the extrusion barrel, and the required maximum extrusion pressure is reduced. Difficult-to-deform materials can be extruded at a lower temperature with a higher extrusion coefficient. It has significant advantages for high-strength or high-deformation-resistance aluminum alloy materials, and in the actual production process, it can effectively reduce the wear of the extrusion barrel and the die and extend their service life.

[0035] (4) In the solution aging process, vertical off-line water quenching is used for extruded profiles. The air circulation method in the vertical quenching furnace is conducive to uniform temperature distribution. In the vertical structure, hot air rises and cold air falls, forming a natural vertical circulation flow, so that the temperature difference between various parts in the furnace is relatively small. This uniform temperature environment can ensure that the cooling rate of each part of the aluminum alloy during the quenching process is basically the same, so that the material's organizational transformation and performance improvement are more uniform, avoiding problems such as local performance differences or deformation caused by uneven temperature; especially Al-Cu-Mg-Zn aluminum alloy high-strength and high-toughness aluminum alloy has high requirements for quenching transfer speed. In the aging process, a three-level regression aging heat treatment system is adopted to ensure that a higher proportion of η' strengthening phase is dispersed and precipitated during the aging process, and at the same time, relatively coarse discontinuous spherical precipitation phase particles are precipitated at the grain boundaries, thereby ensuring the coordinated improvement of strength and corrosion resistance.

[0036] (5) As a grain refining additive, Al-Ti-C master alloy plays an important role in refining the grains of aluminum and aluminum alloys. During the solidification process of aluminum alloy, TiC particles can serve as heterogeneous nucleation cores. Nucleation requires overcoming a certain energy barrier, and the energy barrier of heterogeneous nucleation is lower than that of homogeneous nucleation. When the liquid aluminum alloy is cooled and solidified, TiC particles provide a ready-made surface for the aggregation of aluminum atoms. Because the crystal structure of TiC has a certain lattice mismatch with aluminum, but within a suitable range, aluminum atoms can attach to the surface of TiC particles to nucleate. Within a unit volume, the increase in nucleation rate will lead to an increase in the number of grains, while the growth space of the grains is relatively limited, which ultimately leads to grain refinement. Without this step, the grains of the ingot will be coarse. In the actual industrial production of aluminum alloy casting, the addition of Al-Ti-C master alloy can effectively improve the microstructure of the casting and refine the grain size of the casting from millimeter level to micrometer level, thereby improving the mechanical properties of the aluminum alloy, such as strength, toughness and ductility.

[0037] In summary, the present invention provides a method for preparing Al-Cu-Mg-Zn aluminum alloy profiles for transport vehicle body structural components through microalloying design, preparation process optimization, and consideration of factors such as the comprehensive performance of the material and the feasibility of large-scale preparation. The prepared products can be widely used in the application field of aluminum alloy profiles for transport vehicle bodies that have high requirements on mechanical strength, toughness, weather resistance and other properties. DETAILED DESCRIPTION

[0038] 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 the embodiments. 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.

[0039] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below in conjunction with specific implementation methods.

[0040] Embodiment 1:

[0041] An Al-Cu-Mg-Zn aluminum alloy profile for a transportation vehicle body structural component, the chemical composition of the alloy is, by mass percentage, Cu: 2.5%, Zn: 8.4%, Mg: 2.2%, Mn: 0.4%, Cr: 0.24%, Ti: 0.08%, Zr: 0.20%, Fe: 0.06%, Si: 0.1%, and the balance is Al. The preparation method comprises the following steps:

[0042] Melting: Mix various raw materials according to mass percentage, heat to 780℃, melt the materials, and keep warm for 5 hours;

[0043] Purification: Degas the molten aluminum to reduce the percentage of hydrogen to 0.08%, and then filter out the infusible substances in the aluminum liquid;

[0044] Casting: The degassed and filtered aluminum liquid is cast, and Al-Ti-C is added to the aluminum liquid from the launder in the form of online continuous wire feeding. After cooling to room temperature, a cross-sectional area of ​​77cm 2 Ingots;

[0045] Heat treatment: Place the ingot in a heat treatment furnace and heat it for 10 hours, and perform low-temperature homogenization treatment at 380°C;

[0046] Sawing and lathe processing: the ingot after the soaking treatment is transported to the sawing machine and lathe for sawing and lathe processing to remove the segregation layer;

[0047] Preheating and extrusion: The processed ingot is preheated in a permanent magnet heating furnace at a temperature of 380°C for 1.5 hours. After preheating, the ingot is extruded at a speed of 0.3 m / min. The reverse extrusion process is used to reduce the thickness of the coarse grain layer.

[0048] Solution quenching: After the aluminum alloy is extruded, the extruded profile is immediately quenched offline in a vertical quenching furnace. The solution process adopts a two-stage solution heat treatment, with the first stage being 455℃ for 3h and the second stage being 470℃ for 4h.

[0049] Stretching: Control the stretching rate to 1% while ensuring the straightening of the profile;

[0050] Aging: The stretched profiles are subjected to regression aging treatment. The aging heat treatment is as follows: the first stage aging temperature is 115°C, and the temperature is kept at this temperature for 24 hours; the second stage aging temperature is 180°C, and the temperature is kept at this temperature for 20 minutes, and the profiles are cooled to room temperature by air; the third stage aging temperature is 115°C, and the temperature is kept at this temperature for 24 hours, and the profiles are cooled by air after being taken out of the furnace.

[0051] Embodiment 2:

[0052] Calculated by mass percentage, the chemical composition of the alloy is: Cu: 2.5%; Zn: 8.2%, Mg: 2.0%, Mn: 0.3%, Cr: 0.24%, Ti: 0.08%, Zr: 0.20%, Fe: 0.06%, Si: 0.1%, and the balance is Al.

[0053] The preparation method comprises the following steps:

[0054] Melting: Mix various raw materials according to mass percentage, heat to 760℃, melt the materials, and keep warm for 7h;

[0055] Purification: Degas the molten aluminum to reduce the percentage of hydrogen to 0.08%, and then filter out the infusible substances in the aluminum liquid;

[0056] Casting: The degassed and filtered aluminum liquid is cast, and Al-Ti-C is added to the aluminum liquid from the launder in the form of online continuous wire feeding. After cooling to room temperature, a cross-sectional area of ​​77cm is obtained. 2 Ingots;

[0057] Heat treatment: Place the ingot in a heat treatment furnace and heat it for 10 hours, and perform low-temperature homogenization treatment at 390°C;

[0058] Sawing and lathe processing: the ingot after the soaking treatment is transported to the sawing machine and lathe for sawing and lathe processing to remove the segregation layer;

[0059] Preheating and extrusion: The processed ingot is preheated in a permanent magnet heating furnace at a temperature of 390°C for 1.5 hours. After preheating, the ingot is extruded at a speed of 0.5 m / min. The reverse extrusion process is used to reduce the thickness of the coarse grain layer.

[0060] Solution quenching: After the aluminum alloy is extruded, the extruded profile is immediately quenched offline in a vertical quenching furnace. The solution process adopts a two-stage solution heat treatment, with the first stage being 455℃ for 3h and the second stage being 470℃ for 4h.

[0061] Stretching: Control the stretching rate to 1% while ensuring the straightening of the profile;

[0062] Aging: The stretched profiles are subjected to regression aging treatment. The aging heat treatment is as follows: the first stage aging temperature is 115℃, and the temperature is kept for 24 hours; the second stage aging temperature is 180℃, and the temperature is kept for 30 minutes, and the profiles are cooled to room temperature by air; the third stage aging temperature is 115℃, and the temperature is kept for 24 hours, and the profiles are cooled by air after being taken out of the furnace.

[0063] Embodiment 3:

[0064] The chemical composition of the alloy is, by mass percentage, Cu: 2.2%, Zn: 8.0%, Mg: 2.1%, Mn: 0.3%, Cr: 0.24%, Ti: 0.08%, Zr: 0.20%, Fe: 0.06%, Si: 0.1%, and the balance is Al.

[0065] The preparation method comprises the following steps:

[0066] Melting: Mix various raw materials according to mass percentage, heat to 780℃, melt the materials, and keep warm for 6 hours;

[0067] Purification: Degas the molten aluminum to reduce the percentage of hydrogen to 0.08%, and then filter out the infusible substances in the aluminum liquid;

[0068] Casting: The degassed and filtered aluminum liquid is cast, and Al-Ti-C is added to the aluminum liquid from the launder in the form of online continuous wire feeding, and cooled to room temperature. The cross-sectional area is 77cm 2 Ingots;

[0069] Heat treatment: Place the ingot in a heat treatment furnace and heat it for 10 hours, and perform low-temperature homogenization treatment at 380°C;

[0070] Sawing and lathe processing: the ingot after the soaking treatment is transported to the sawing machine and lathe for sawing and lathe processing to remove the segregation layer;

[0071] Preheating and extrusion: The processed ingot is preheated in a permanent magnet heating furnace at a temperature of 400°C for 1 hour. After preheating, the ingot is extruded at a speed of 1.0 m / min. The reverse extrusion process is used to reduce the thickness of the coarse grain layer.

[0072] Solution quenching: After the aluminum alloy is extruded, the extruded profile is immediately quenched offline in a vertical quenching furnace. The solution process adopts a two-stage solution heat treatment, with the first stage being 455℃ for 3h and the second stage being 470℃ for 4h.

[0073] Stretching: Control the stretching rate to 2% while ensuring the straightening of the profile;

[0074] Aging: The stretched profiles are subjected to regression aging treatment. The aging heat treatment is as follows: the first stage aging temperature is 120℃, and the temperature is kept for 16 hours; the second stage aging temperature is 180℃, and the temperature is kept for 40 minutes, and the profiles are cooled to room temperature by air; the third stage aging temperature is 120℃, and the temperature is kept for 24 hours, and the profiles are cooled by air after being taken out of the furnace.

[0075] Embodiment 4:

[0076] The chemical composition of the alloy is, by mass percentage, Cu: 2.6%, Zn: 7.6%, Mg: 1.8%, Mn: 0.4%, Cr: 0.24%, Ti: 0.08%, Zr: 0.20%, Fe: 0.06%, Si: 0.1%, and the balance is Al.

[0077] The preparation method comprises the following steps:

[0078] Melting: Mix various raw materials according to mass percentage, heat to 780℃, melt the materials, and keep warm for 6 hours;

[0079] Purification: Degas the molten aluminum to reduce the percentage of hydrogen to 0.08%, and then filter out the infusible substances in the aluminum liquid;

[0080] Casting: The degassed and filtered aluminum liquid is cast, and Al-Ti-C is added to the aluminum liquid from the launder in the form of online continuous wire feeding. After cooling to room temperature, a cross-sectional area of ​​77cm is obtained. 2 Ingots;

[0081] Heat treatment: Place the ingot in a heat treatment furnace and heat it for 10 hours, and perform low-temperature homogenization treatment at 380°C;

[0082] Sawing and lathe processing: the ingot after the soaking treatment is transported to the sawing machine and lathe for sawing and lathe processing to remove the segregation layer;

[0083] Preheating and extrusion: The processed ingot is preheated in a permanent magnet heating furnace at a temperature of 400°C for 1 hour. After preheating, the ingot is extruded at a speed of 1.0 m / min. The reverse extrusion process is used to reduce the thickness of the coarse grain layer.

[0084] Solution quenching: After the aluminum alloy is extruded, the extruded profile is immediately quenched offline in a vertical quenching furnace. The solution process adopts a two-stage solution heat treatment, with the first stage being 455℃ for 3h and the second stage being 470℃ for 4h.

[0085] Stretching: Control the stretching rate to 2% while ensuring the straightening of the profile;

[0086] Aging: The stretched profiles are subjected to regression aging treatment. The aging heat treatment is as follows: the first stage aging temperature is 115℃, and the temperature is kept for 24 hours; the second stage aging temperature is 180℃, and the temperature is kept for 20 minutes, and the profiles are cooled to room temperature by air; the third stage aging temperature is 115℃, and the temperature is kept for 24 hours, and the profiles are cooled by air after being taken out of the furnace.

[0087] Comparative Example 1:

[0088] A high-strength and tough Al-Cu-Mg-Zn aluminum alloy profile for transportation vehicle body structural components comprises 3.0% Cu, 8.4% Zn, 2.3% Mg, 0.4% Mn, 0.24% Cr, 0.08% Ti, 0.20% Zr, 0.08% Fe, 0.1% Si, and the balance is Al; the other steps are the same as those in Example 1.

[0089] Comparative Example 2

[0090] A high-strength and tough Al-Cu-Mg-Zn aluminum alloy profile for transport vehicle body structural components comprises 2.5% Cu, 7.0% Zn, 1.6% Mg, 0.4% Mn, 0.24% Cr, 0.08% Ti, 0.20% Zr, 0.08% Fe, 0.1% Si, and the remainder is Al; the other steps are the same as those in Example 1.

[0091] Comparative Example 3

[0092] A high-strength and tough Al-Cu-Mg-Zn aluminum alloy profile for transport vehicle body structural components does not use the Al-Ti-C intermediate alloy wire feeding process for melting and casting in the S3 casting process, and the other steps are the same as those in Example 1.

[0093] Comparative Example 4

[0094] A high-strength and tough Al-Cu-Mg-Zn aluminum alloy profile for a transportation vehicle body structural component is water quenched by online water penetration during the solid solution quenching process in S8; the other steps are the same as those in Example 1.

[0095] Comparative Example 5

[0096] A high-strength and tough Al-Cu-Mg-Zn aluminum alloy profile for transportation vehicle body structural components adopts a single-stage process system for S8 and S10 solid solution and aging: solid solution at 455°C, insulation for 7 hours, and vertical water quenching; aging temperature is 120°C, insulation for 24 hours, and air cooling after being taken out of the furnace; other steps are the same as Example 1.

[0097] The performance items of the aluminum alloy profiles of Examples 1 to 4 are shown in Table 1 below.

[0098]

[0099] Table 1

[0100] The performance items tested for Comparative Examples 1 to 5 are shown in Table 2 below;

[0101]

[0102] Table 2

[0103] It can be seen from the test results in Table 1 that the present invention proposes a high-strength and tough Al-Cu-Mg-Zn aluminum alloy profile for transport vehicle body structural components, and a 600Mpa-grade Al-Cu-Mg-Zn aluminum alloy profile can be prepared, which has stable mechanical properties and excellent stress corrosion resistance; according to the comparative example in Table 2, it can be seen that when the content of Mg and Zn elements is reduced, more η phase cannot be provided during the aging precipitation process, which affects the mechanical strength of the aluminum alloy material; when the Cu content is increased, the strengthening effect in the alloy is mainly achieved through the precipitation strengthening of Mg and Zn. The addition of element content, Cu can effectively reduce the electrode potential difference of the alloy and improve the corrosion resistance in the early stage of the homogenization heat treatment process. As the addition amount increases further, the corrosion resistance is greatly reduced; when the solid solution aging process adopts the method of online water quenching after extrusion of the extruded profile, it fails to meet the high requirements of the alloy quenching sensitivity for quenching speed and transfer time, resulting in a decrease in the mechanical properties of the material; when the single-stage aging heat treatment system is adopted in the aging process, it is impossible to effectively precipitate relatively coarse discontinuous spherical precipitation phase particles at the grain boundaries during the aging process, thereby reducing the corrosion resistance of the material.

[0104] In summary, since the improvement of the comprehensive mechanical properties of alloy materials is a comprehensive reflection of the synergistic effect of phase precipitation strengthening, it is necessary to match the corresponding pressure processing and aging heat treatment processes to comprehensively improve the mechanical strength and corrosion resistance of aluminum alloys.

[0105] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. An Al-Cu-Mg-Zn aluminum alloy profile for transportation vehicle body structural components, characterized in that: The aluminum alloy material contains the following elements in percentage by mass: Cu: 2.0-2.6%; Zn: 7.6-8.4%; Mg: 1.8-2.3%, Mn: 0.3-0.4%, Cr: 0.16-0.24%, Ti: 0.04-0.08%, Zr: 0.12-0.20%, Fe≤0.08%, Si≤0.1%, and the balance is Al, wherein the mass percentage ratio of Zn to Mg is 3.7-4.

2.

2. A method for preparing the Al-Cu-Mg-Zn aluminum alloy profile for transportation vehicle body structural components according to claim 1, characterized in that: The method comprises the following steps: S1: Melting, weighing raw materials according to mass percentage and putting them into a melting furnace for melting; S2: Purification, degassing and filtering the molten aluminum liquid; S3: Casting, casting the degassed and filtered aluminum liquid, during which Al-Ti-C is added to the aluminum liquid in a launder in the form of online continuous wire feeding as a master alloy, and cooled to obtain a round ingot; S4: Soaking treatment; S5: Sawing; S6: car skin; S7: extrusion; S8: solution quenching; S9: stretching, stretching and straightening the profile after solution quenching, with a stretching rate of 1% to 3%; S10: Aging treatment, subjecting the stretched profile to a regression aging treatment to obtain a finished product.

3. The method for preparing an Al-Cu-Mg-Zn aluminum alloy profile for a transportation vehicle body structural component according to claim 2, characterized in that: In S1, the smelting temperature is 760-780°C, and the material is kept warm for 5-7 hours after melting.

4. The method for preparing an Al-Cu-Mg-Zn aluminum alloy profile for a transportation vehicle body structural component according to claim 2, characterized in that: In S2, the melt is degassed and filtered by the cooperation of a degassing device and a filtering device.

5. The method for preparing an Al-Cu-Mg-Zn aluminum alloy profile for a transportation vehicle body structural component according to claim 2, characterized in that: In S3, the casting temperature is 700-720°C, and the maximum cross-sectional area of ​​the ingot is 77 cm 2 .

6. The method for preparing an Al-Cu-Mg-Zn aluminum alloy profile for a vehicle body structural component according to claim 2, characterized in that: In S4, the ingot is placed in a heat treatment furnace for heating and heat preservation for 10 to 12 hours, and subjected to low-temperature homogenization treatment at 380 to 390°C.

7. The method for preparing Al-Cu-Mg-Zn aluminum alloy profiles for transportation vehicle body structural components according to claim 2, characterized in that: In S5 and S6, the ingot after the soaking treatment is sawn and turned on a sawing machine and a lathe in turn to remove the segregation layer.

8. The method for preparing Al-Cu-Mg-Zn aluminum alloy profiles for transportation vehicle body structural components according to claim 2, characterized in that: In S7, the processed ingot is preheated in a permanent magnet heating furnace at a temperature of 380-400° C. for 1-2 hours, and the preheated ingot is extruded by a reverse extrusion process at an extrusion speed of 0.3-1.0 m / min.

9. The method for preparing Al-Cu-Mg-Zn aluminum alloy profiles for transportation vehicle body structural components according to claim 2, characterized in that: In S8, after the aluminum alloy is extruded, the extruded profile is immediately quenched offline using a vertical quenching furnace, wherein the solution process adopts a two-stage solution heat treatment, the first stage is 450-455°C, and the heat preservation is 3-4h, the second stage is 470-475°C, and the heat preservation is 3-4h, the quenching medium is deionized water, the quenching cooling rate is 370-400°C / min, and the quenching transfer time is ≤5s.

10. The method for preparing Al-Cu-Mg-Zn aluminum alloy profiles for transportation vehicle body structural components according to claim 2, characterized in that: In S10, the aging treatment is a three-stage aging treatment: the first-stage aging temperature is 115-120° C., and the temperature is kept for 16-24 hours; the second-stage aging temperature is 160-180° C., and the temperature is kept for 20-60 minutes, and the product is cooled to room temperature by air; the third-stage aging temperature is 115-120° C., and the temperature is kept for 16-24 hours, and the product is cooled by air after being taken out of the furnace to obtain the final product.

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