A multi-cavity thin-walled battery tray-type aluminum alloy profile for new energy vehicles and its preparation method.

Abstract

This invention discloses a multi-cavity thin-walled battery tray-type aluminum alloy profile for new energy vehicles and its preparation method, relating to the field of battery tray technology. The internal chemical composition of the aluminum alloy profile, by mass percentage, includes: Si: 0.65%–0.75%, Mg: 0.70%–0.85%, Cu: 0.10%–0.20%, Mn: 0.10%–0.18%, Cr: 0.06%–0.12%, Ti: 0.05%–0.10%, Sc: 0.02%–0.08%, Zr: 0.05%–0.12%, Fe≤0.20%, B≦0.10%, with the balance being Al. This invention successfully constructs a nanoscale dispersed reinforcing phase in the matrix through stepwise pretreatment of Sc / Ti elements and a two-stage aging process. Combined with an upward dual-medium quenching technology, the high-temperature zone utilizes a scandium oxide-containing water-based medium for rapid cooling, effectively freezing the supersaturated solid solution. The low-temperature zone utilizes an oil-based medium for slow cooling, eliminating harmful residual stress and significantly improving the load-bearing capacity and collision energy absorption safety of the battery tray.

Description

Technical Field

[0001] This invention relates to the field of battery tray technology, specifically to an aluminum alloy profile for a multi-cavity thin-walled battery tray for new energy vehicles and its preparation method. Background Technology

[0002] The battery system tray is one of the key components of new energy vehicles. Its main function is to support the battery system, preventing it from being bumped or damaged from below, while also providing heat dissipation and facilitating battery maintenance and assembly. As the core component of an electric vehicle, the performance and safety of the battery directly affect the overall operation and safety of the vehicle; therefore, the battery tray is a crucial component for supporting and protecting the battery.

[0003] For example, patent publication number "CN119121001A", entitled "Aluminum Alloy Profile for New Energy Vehicle Battery Tray and its Preparation Method", describes an aluminum alloy profile for a new energy vehicle battery tray that, by weight percentage, comprises the following components: Mg 0.5wt%–0.8wt%, Si 0.4wt%–0.6wt%, Fe 0.1wt%–0.35wt%, Ti 0.01wt%–0.08wt%, Sc 0.01wt%–0.09wt%, Mn ≤ 0.1wt%, Cu ≤ 0.1wt%, Zn ≤ 0.1wt%, total impurities ≤ 0.15wt%, and the balance being Al. The aluminum alloy profile for a new energy vehicle battery tray and its preparation method provided by the above patent effectively improve the mechanical properties and extrusion precision of aluminum by employing a newly designed alloy formula combined with a specific production process, solving the problem of reduced extrusion precision due to the large cross-section and irregular cavity structure of new energy vehicle battery trays.

[0004] The aforementioned patents use single water quenching to obtain high strength, which often leads to excessive residual stress inside the material, a significant decrease in elongation (usually below 15%), and increased brittleness, failing to meet the high energy absorption requirements of the battery tray under collision conditions. Conversely, if the cooling rate is reduced or single oil quenching is used in pursuit of high toughness, it will result in insufficient decomposition of the solid solution and coarse precipitates, causing a significant reduction in tensile strength and yield strength, making it unable to withstand the heavy load of the battery pack and road impact. Therefore, a multi-cavity thin-walled battery tray type aluminum alloy profile for new energy vehicles and its preparation method have been invented. Summary of the Invention

[0005] The purpose of this invention is to provide a multi-cavity thin-walled battery tray-type aluminum alloy profile for new energy vehicles and its preparation method, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a multi-cavity thin-walled battery tray-type aluminum alloy profile for new energy vehicles, wherein the internal chemical composition of the aluminum alloy profile, by mass percentage, includes: Si: 0.65%–0.75%, Mg: 0.70%–0.85%, Cu: 0.10%–0.20%, Mn: 0.10%–0.18%, Cr: 0.06%–0.12%, Ti: 0.05%–0.10%, Sc: 0.02%–0.08%, Zr: 0.05%–0.12%, Fe≤0.20%, B≦0.10%, with the balance being Al.

[0007] A method for preparing a multi-cavity thin-walled battery tray-type aluminum alloy profile for new energy vehicles, comprising the above-mentioned method, wherein the preparation method includes: S01: Based on the internal chemical composition of aluminum alloy profiles, Sc is divided into Sc Part 1 and Sc Part 2 by weight. Sc Part 1 accounts for 85% to 88% of the total weight of Sc. Sc Part 2 is processed to obtain scandium oxide. Ti is divided into Ti Part 1 and Ti Part 2 according to its weight. Ti Part 1 accounts for 3% to 8% of the total weight of Ti. Prepare raw material No. 1, which is a mixture of Si, Mg, Cu, Mn, Cr and Zr; S02: When the aluminum ingot is melted to a temperature of 700°C, the first part of Sc is added and stirred for 0.4 to 0.5 hours. Then, the second part of Ti and the first raw material are added to obtain the first aluminum liquid. The first aluminum liquid is then refined. S03: Cast the No. 1 aluminum liquid into aluminum alloy ingots, and perform homogenization treatment on the aluminum alloy ingots for 12 to 18 hours. S04: The first Ti powder with a particle size of 0.5μm to 2.0μm is sprayed onto the surface of the aluminum alloy ingot and diffused at 145℃ to 155℃ for 5 to 10 minutes. S05: The diffusion-treated aluminum alloy ingot is fed into an extrusion press for extrusion molding to obtain a shaped aluminum alloy. S06: The formed aluminum alloy is quenched by the upward-passing dual-medium graded quenching method, wherein the upward-passing dual-medium graded quenching includes: pulling the formed aluminum alloy upward from the bottom of the quenching tank and passing through the lower rapid cooling zone and the upper slow cooling zone in sequence. The lower rapid cooling zone and the upper slow cooling zone inside the quenching tank are naturally separated according to density. The lower rapid cooling zone is a water-based quenching fluid, and the upper slow cooling zone is an oil-based quenching fluid. Scandium oxide and B are added to the water-based quenching fluid. The formed aluminum alloy passes through the lower water-based quenching liquid and rapidly passes through the quenching-sensitive temperature range of the aluminum alloy at a cooling rate of ≥50℃ / s during the high-temperature stage until the surface temperature of the formed aluminum alloy drops to 260℃-330℃. The formed aluminum alloy is moved upward into the upper oil-based quenching liquid and slowly cooled at a cooling rate of ≤10℃ / s in the low-temperature stage until the surface temperature of the formed aluminum alloy drops to room temperature, thus obtaining the quenched profile. S07: After quenching, the profiles are stretched and straightened by 1.5% to 2.5%, and then sawn to length. S08: The cut profiles are subjected to a two-stage aging treatment at 175℃~185℃ for 12 hours~16 hours to obtain the final product.

[0008] Furthermore, the diffusion treatment includes: after the metallic Ti powder is sprayed, the aluminum alloy ingot is sent into a controlled gas protection furnace, heated to 145°C to 150°C under nitrogen protection, and held at that temperature for 5 to 10 minutes.

[0009] Furthermore, the depth of the water-based quenching fluid is greater than the thickness of the formed aluminum alloy, the depth of the upper oil-based quenching fluid is greater than the thickness of the formed aluminum alloy, and the water-based quenching fluid contains B, which is used to synergistically improve the surface quenching uniformity of the profile with scandium oxide.

[0010] Furthermore, the quenching tank includes: The first circulation system is connected to the lower water-based quenching fluid and is used to control the temperature and level of the water-based quenching fluid. The second circulation system is connected to the upper oil-based quenching fluid and is used to control the temperature and level of the oil-based quenching fluid. A liquid level sensor, placed at the oil-water interface, is used to monitor the interface height between water-based quenching fluid and oil-based quenching fluid. The controller is electrically connected to the liquid level sensor, the first circulation system, and the second circulation system to maintain a highly stable oil-water interface.

[0011] Furthermore, the two-stage timeliness processing includes: First stage: Heat the sawn profiles to 120℃~130℃ at a heating rate of 30℃ / h~50℃ / h, and keep them warm for 4~6 hours; Second stage: Transition to the second stage of high temperature aging at a controlled heating rate of 50℃ / h to 80℃ / h, heating to 175℃ to 185℃, and holding for 8 to 10 hours.

[0012] Furthermore, the homogenization treatment includes a two-stage heating process, which includes: a first stage heating the ingot to 480℃~490℃ at a heating rate of ≤50℃ / h and holding it at that temperature for 4~6 hours, so as to initially dissolve the low-melting-point eutectic phase and prevent the ingot from cracking; and a second stage continuing to heat the ingot to 565℃~575℃ at a heating rate of ≤30℃ / h and holding it at that temperature for 8~12 hours.

[0013] Furthermore, the refining process includes: after adding alloying elements and stirring evenly, adjusting the temperature of the molten aluminum to 730℃~750℃, first introducing nitrogen gas for rotary degassing treatment for 15 minutes to 25 minutes, adding environmentally friendly refining agent for melt purification, allowing it to stand and removing slag, and then filtering it through a ceramic filter plate.

[0014] Compared with the prior art, the beneficial effects of the present invention are: This invention relates to a multi-cavity thin-walled battery tray aluminum alloy profile for new energy vehicles and its preparation method. Through stepwise pretreatment of Sc / Ti elements and a two-stage aging process, a nanoscale dispersed reinforcing phase was successfully constructed in the matrix. Combined with an upward dual-medium quenching technology, the high-temperature zone utilizes a scandium oxide-containing water-based medium for rapid cooling, effectively freezing the supersaturated solid solution. The low-temperature zone utilizes an oil-based medium for slow cooling, eliminating harmful residual stress and significantly improving the load-bearing capacity and collision energy absorption safety of the battery tray.

[0015] Meanwhile, the upward-flowing dual-medium graded quenching process effectively controls the temperature gradient on the profile cross-section through the gentle cooling effect of the oil-based quenching fluid at low temperatures after rapid cooling quenching, minimizing thermal stress and structural stress during the cooling process.

[0016] Adding scandium oxide microparticles and synergistic element B to water-based quenching fluid further refines the surface grains, improves surface quenching uniformity, and eliminates surface ripple defects by utilizing their heterogeneous nucleation effect during the quenching process. The surface diffusion treatment of Ti element promotes grain boundary strengthening, inhibits intergranular corrosion tendency, and significantly improves its fatigue resistance. This enables it to better adapt to the complex vibration conditions throughout the entire life cycle of new energy vehicles, thereby improving the overall reliability and durability of the battery system. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the preparation method of the present invention; Figure 2 This is a schematic diagram of the quenching process of the present invention; Figure 3 This is a front view of the quenching tank of the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] like Figure 1 - Figure 3 As shown, the present invention provides a technical solution: a multi-cavity thin-walled battery tray-type aluminum alloy profile for new energy vehicles. The internal chemical composition of the aluminum alloy profile, by mass percentage, includes: Si: 0.65%–0.75%, Mg: 0.70%–0.85%, Cu: 0.10%–0.20%, Mn: 0.10%–0.18%, Cr: 0.06%–0.12%, Ti: 0.05%–0.10%, Sc: 0.02%–0.08%, Zr: 0.05%–0.12%, Fe≤0.20%, B≦0.10%, with the balance being Al.

[0020] A method for preparing a multi-cavity thin-walled battery tray-type aluminum alloy profile for new energy vehicles, comprising the following steps: S01: Based on the internal chemical composition of aluminum alloy profiles, Sc is divided into Sc Part 1 and Sc Part 2 by weight. Sc Part 1 accounts for 85% to 88% of the total weight of Sc. Sc Part 2 is processed to obtain scandium oxide. Ti is divided into Ti Part 1 and Ti Part 2 according to its weight. Ti Part 1 accounts for 3% to 8% of the total weight of Ti. Prepare raw material No. 1, which is a mixture of Si, Mg, Cu, Mn, Cr and Zr; S02: When the aluminum ingot is melted to a temperature of 700°C, the first part of Sc is added and stirred for 0.4 to 0.5 hours. Then, the second part of Ti and the first raw material are added to obtain the first aluminum liquid. The first aluminum liquid is then refined. S03: Cast the No. 1 aluminum liquid into aluminum alloy ingots, and perform homogenization treatment on the aluminum alloy ingots for 12 to 18 hours. S04: The first Ti powder with a particle size of 0.5μm to 2.0μm is sprayed onto the surface of the aluminum alloy ingot and diffused at 145℃ to 155℃ for 5 to 10 minutes. S05: The diffusion-treated aluminum alloy ingot is fed into an extrusion press for extrusion molding to obtain a shaped aluminum alloy. S06: Quenching of shaped aluminum alloy by the upward-passing dual-medium graded quenching method, the upward-passing dual-medium graded quenching includes: pulling the shaped aluminum alloy upward from the bottom of the quenching tank, passing through the lower rapid cooling zone and the upper slow cooling zone in sequence. The lower rapid cooling zone and the upper slow cooling zone inside the quenching tank are naturally separated according to density. The lower rapid cooling zone is water-based quenching fluid, and the upper slow cooling zone is oil-based quenching fluid. Scandium oxide and B are added to the water-based quenching fluid. The formed aluminum alloy passes through the lower water-based quenching liquid and rapidly passes through the quenching-sensitive temperature range of the aluminum alloy at a cooling rate of ≥50℃ / s during the high-temperature stage until the surface temperature of the formed aluminum alloy drops to 260℃-330℃. The formed aluminum alloy is moved upward into the upper oil-based quenching liquid and slowly cooled at a cooling rate of ≤10℃ / s in the low-temperature stage until the surface temperature of the formed aluminum alloy drops to room temperature, thus obtaining the quenched profile. S07: After quenching, the profiles are stretched and straightened by 1.5% to 2.5%, and then sawn to length. S08: The cut profiles are subjected to a two-stage aging treatment at 175℃~185℃ for 12 hours~16 hours to obtain the final product.

[0021] The diffusion process includes: after the Ti metal powder is sprayed, the aluminum alloy ingot is sent into a controlled gas protection furnace, heated to 145℃~150℃ under nitrogen protection, and held at that temperature for 5 minutes~10 minutes.

[0022] The depth of the water-based quenching fluid is greater than the thickness of the formed aluminum alloy, and the depth of the upper oil-based quenching fluid is also greater than the thickness of the formed aluminum alloy. The water-based quenching fluid contains B, which is added to synergistically improve the surface quenching uniformity of the profile with scandium oxide.

[0023] The quenching tank includes: The first circulation system is connected to the lower water-based quenching fluid and is used to control the temperature and level of the water-based quenching fluid. The second circulation system is connected to the upper oil-based quenching fluid and is used to control the temperature and level of the oil-based quenching fluid. A liquid level sensor, placed at the oil-water interface, is used to monitor the interface height between water-based quenching fluid and oil-based quenching fluid. The controller, electrically connected to the level sensor, the first circulation system, and the second circulation system, is used to maintain a highly stable oil-water interface.

[0024] Two-level timeliness processing includes: First stage: Heat the sawn profiles to 120℃~130℃ at a heating rate of 30℃ / h~50℃ / h, and keep them warm for 4~6 hours; Second stage: Transition to the second stage of high temperature aging at a controlled heating rate of 50℃ / h to 80℃ / h, heating to 175℃ to 185℃, and holding for 8 to 10 hours.

[0025] The homogenization process includes a two-stage heating process, which consists of: in the first stage, the ingot is heated to 480℃~490℃ at a heating rate of ≤50℃ / h and held for 4~6 hours to allow the low-melting-point eutectic phase to initially dissolve and prevent the ingot from cracking; in the second stage, the ingot is heated to 565℃~575℃ at a heating rate of ≤30℃ / h and held for 8~12 hours.

[0026] The refining process includes: after adding alloying elements and stirring evenly, adjusting the temperature of the molten aluminum to 730℃~750℃, first introducing nitrogen gas for rotary degassing for 15 minutes to 25 minutes, adding environmentally friendly refining agents for melt purification, allowing it to stand and removing slag, and then filtering it through a ceramic filter plate.

[0027] The total weight of Sc is divided into two parts: Sc Part 1 and Sc Part 2. Sc Part 1, which accounts for 85% to 88% of the total weight of Sc, is used for subsequent smelting and mainly plays a role in microalloying within the matrix (refining grains and age hardening). The remaining Sc Part 2 is processed into scandium oxide powder through chemical methods (such as precipitation and calcination), which will be used in the subsequent quenching step.

[0028] To optimize the absorption rate and metallurgical quality of alloying elements, the preferred order of adding other reinforcing alloying elements is as follows: after adding the first portion of Sc and stirring for 5 minutes, add the second portion of Ti, and then add the remaining alloying elements. This helps to utilize the initial refining effect of Ti on the melt, creating better conditions for the uniform distribution of other elements in the future.

[0029] The refining process includes: first, high-purity nitrogen is introduced for rotary blowing degassing for 15-25 minutes to efficiently remove hydrogen and some non-metallic inclusions from the melt; then, environmentally friendly sodium-free refining agent is sprinkled onto the surface of the melt for flux refining to further adsorb inclusions; after settling and slag removal, the melt is filtered online through a ceramic foam filter plate to remove tiny inclusions and obtain clean aluminum melt.

[0030] To improve the microstructure uniformity and extrusion performance of aluminum alloy ingots, a homogenization treatment is performed for 12 to 18 hours. A two-stage heating homogenization process is preferred to better control the evolution of microstructure. The first stage involves slowly heating the ingot to 480 to 490°C at a low heating rate not exceeding 50°C / h and holding it at this temperature for 4 to 6 hours. The purpose of this stage is to initially dissolve the low-melting-point eutectic phase formed by non-equilibrium solidification in the ingot, while preventing cracking due to excessive internal stress caused by rapid heating. The second stage involves continuing heating to a high temperature of 565 to 575°C at an even slower heating rate not exceeding 30°C / h, and holding it at this temperature for 8 to 12 hours. This stage aims to fully dissolve and spheroidize the sparingly soluble compounds rich in Fe, Mn, and other elements, while simultaneously allowing the fine and uniform precipitation of the Al3(Sc,Zr) dispersed phase, providing a good microstructure basis for subsequent extrusion deformation.

[0031] The first portion of Ti reserved in step S01 (accounting for 3% to 8% of the total Ti) is ground into a fine powder with a particle size of 0.5 μm to 2.0 μm. This powder is then uniformly sprayed onto the pre-treated surface of the ingot using electrostatic spraying or other methods. After spraying, the ingot is placed in a controlled gas furnace and subjected to diffusion treatment at 145℃ to 155℃ for 5 to 10 minutes under the protection of an inert gas (such as nitrogen). During this process, the fine Ti powder forms a Ti-rich diffusion layer on the surface of the ingot through thermal diffusion. This Ti-rich layer is then incorporated into the surface and near-surface layers of the profile during subsequent extrusion due to intense shear deformation, forming a fine grain structure. This significantly improves the surface quality and fatigue resistance of the profile, while also providing good metallurgical compatibility for subsequent welding.

[0032] The diffusion-treated aluminum alloy ingot is heated to the extrusion temperature and fed into a large extrusion press. It is then extruded through a complex cross-section die specifically designed for multi-cavity, thin-walled structures to obtain shaped aluminum alloy profiles. Parameters such as extrusion speed and exit temperature are precisely controlled according to the specific profile cross-section and alloy properties.

[0033] An upward-moving, dual-medium, graded quenching device and method are used to quench high-temperature formed aluminum alloy profiles from an extruder online. The quenching tank contains two immiscible quenching media that naturally separate into layers based on density: the lower layer is a denser water-based quenching fluid (forming a rapid cooling zone), and the upper layer is a less dense oil-based quenching fluid (forming a slow cooling zone). The quenching tank is equipped with a traction device that can vertically pull the formed aluminum alloy from the bottom upwards, sequentially passing through the lower rapid cooling zone and the upper slow cooling zone. The interior of the quenching tank has a U-shaped design. Since the density of the water-based quenching fluid is greater than that of the oil-based quenching fluid, it will contact the water-based quenching fluid through one end of the U-shape inside the quenching tank, thus achieving quenching. Afterwards, it moves along the U-shape to contact the oil-based quenching fluid and exits from the U-shaped end inside the quenching tank.

[0034] In the lower water-based quenching fluid, scandium oxide powder prepared from the second part of Sc was added and evenly dispersed. To further improve the quenching uniformity, boron (B) was also added to the water-based quenching fluid. Boron and scandium oxide work synergistically to form a more uniform vapor film on the profile surface, reducing soft spots and deformation caused by uneven cooling during quenching. The high-temperature profile (usually above 500℃) enters the lower water-based quenching fluid. Due to the extremely strong cooling capacity of water and the addition of scandium oxide and other additives promoting the uniformity of boiling, the profile rapidly passes through the quenching-sensitive temperature range of aluminum alloy (about 300℃~400℃) at an extremely high cooling rate of ≥50℃ / s during the high-temperature stage. This process aims to "freeze" the supersaturated vacancies and solute atoms in the high-temperature solid solution state, providing the maximum driving force for subsequent aging precipitation and ensuring the final strength of the profile. The profile continues to rise into the upper oil-based quenching fluid. Oil cools much slower than water. At this low temperature stage, the profile is cooled to room temperature at a slow cooling rate of ≤10℃ / s. This slow cooling method greatly reduces the profile deformation and residual stress caused by phase transformation stress and thermal stress, which is especially important for thin-walled multi-cavity structures that are poor in rigidity and easily deformed.

[0035] During the refining process, nitrogen gas is introduced for rotary degassing for 15 to 25 minutes to remove hydrogen and inclusions. After quenching, the profiles are subjected to 1.5% to 2.5% tensile straightening at room temperature to eliminate macroscopic deformations such as longitudinal bending and twisting, and to further reduce residual stress. After straightening, the profiles are precision sawed to the customer's required length. The sawn profiles are then placed in an aging furnace for artificial aging treatment. This invention employs a two-stage aging process, which can optimize grain boundary precipitates and improve the alloy's corrosion resistance and microstructure stability while achieving high strength. The specific steps are as follows: First stage (low temperature pre-aging): The profile is heated to 120℃~130℃ at a heating rate of 30℃ / h~50℃ / h and held at this temperature for 4~6 hours. This stage aims to form high-density fine GP regions to provide nucleation sites for the uniform precipitation of the subsequent strengthening phase.

[0036] Second stage (high temperature final aging): After completing the first stage of heat preservation, the material is transitioned to the second stage of high temperature aging at a controlled heating rate of 50℃ / h to 80℃ / h. The material is heated to 175℃ to 185℃ and held for 8 to 10 hours. This treatment imparts high strength to the material, coarsens the grain boundary precipitates and make them discontinuously distributed, thereby improving the alloy's resistance to intergranular corrosion and stress corrosion.

[0037] The aluminum alloy profiles must have an elongation of ≥18%, tensile strength of ≥320MPa, and airtightness meeting IP69K standards. Battery trays need sufficient strength to support the weight of the battery pack and withstand external impacts, while also possessing good plasticity (elongation) to absorb energy and prevent brittle fracture. Tensile strength is typically ≥280MPa, with advanced processes reaching ≥310MPa. It measures the material's maximum resistance to tensile fracture and is a fundamental guarantee of safety. Yield strength is typically ≥245MPa, with high-performance requirements exceeding 260MPa. This is the critical point at which the material begins to undergo permanent deformation, determining whether the tray can maintain its shape under stress. Elongation: Generally between 9% and 14%, with some designs requiring high toughness needing 10%. This indicator directly corresponds to a higher plastic elongation, which means the material can undergo greater plastic deformation before fracture, resulting in better energy absorption and higher safety. Through stepwise pretreatment of Sc / Ti elements and a two-stage aging process, a nanoscale dispersed reinforcing phase was successfully constructed in the matrix. Combined with an upward dual-medium quenching technology, the high-temperature zone utilizes a scandium oxide-containing water-based medium for rapid cooling, effectively freezing the supersaturated solid solution. The low-temperature zone utilizes an oil-based medium for slow cooling, eliminating harmful residual stress and significantly improving the load-bearing capacity and collision energy absorption safety of the battery tray.

[0038] During tensile straightening, the stretching amount is precisely controlled (1.5%–2.5%). By applying tensile stress exceeding the material's yield strength, the profile undergoes uniform micro-plastic elongation. This process promotes internal grain slippage, thereby redistributing and significantly reducing the macroscopic residual stress caused by uneven temperature and asynchronous phase transformation during extrusion and quenching. After straightening, the profile is precisely sawn to the designed length of the battery tray. This step requires a smooth, burr-free cut end to ensure positioning accuracy for subsequent welding or machining. Scandium oxide microparticles and synergistic element B are added to the water-based quenching fluid. Utilizing their heterogeneous nucleation effect during quenching, the surface grains are further refined, improving surface quenching uniformity and eliminating surface ripple defects. Surface diffusion treatment of Ti promotes grain boundary strengthening, inhibits intergranular corrosion, and significantly improves fatigue resistance. This allows the profile to better adapt to the complex vibration conditions throughout the entire life cycle of new energy vehicles, improving the overall reliability and durability of the battery system.

[0039] Example 1: S01: Based on the internal chemical composition of aluminum alloy profiles, Sc is divided into Sc Part 1 and Sc Part 2 by weight. Sc Part 1 accounts for 85% of the total weight of Sc. Sc Part 2 is processed to obtain scandium oxide. Ti is divided into Ti Part 1 and Ti Part 2 according to its weight. Ti Part 1 accounts for 8% of the total weight of Ti. S02: When the aluminum ingot is melted to the point where the temperature of the molten aluminum reaches 700℃, the first part of Sc is added and stirred for 0.4 hours. Then, the second part of Ti and the first raw material are added to obtain the first molten aluminum. The first molten aluminum is then refined. S03: Cast the No. 1 aluminum liquid into aluminum alloy ingots, and homogenize the aluminum alloy ingots for 12 hours. S04: The first Ti powder with a particle size of 0.5 μm was sprayed onto the surface of the ingot and diffused at 145°C for 5 minutes; S05: The diffusion-treated aluminum alloy ingot is fed into an extrusion press for extrusion molding to obtain a shaped aluminum alloy. S06: Quenching of shaped aluminum alloy by the upward-passing dual-medium graded quenching method, the upward-passing dual-medium graded quenching includes: pulling the shaped aluminum alloy upward from the bottom of the quenching tank, passing through the lower rapid cooling zone and the upper slow cooling zone in sequence. The formed aluminum alloy passes through the lower water-based quenching liquid and rapidly passes through the quenching-sensitive temperature range of the aluminum alloy at a cooling rate of ≥50℃ / s during the high-temperature stage until the surface temperature of the profile drops to 260℃. The formed aluminum alloy rises into the upper oil-based quenching liquid and is slowly cooled at a cooling rate of ≤10℃ / s in the low-temperature stage until the surface temperature of the profile drops to room temperature. S07: After quenching, the profile is stretched and straightened by 1.5% and then sawn to length. S08: The sawn profiles are subjected to a two-stage aging treatment at 175℃ for 12 hours to obtain the final product; The two-level timeliness processing includes: First stage: Heat the sawn profiles to 120℃ at a heating rate of 30℃ / h and keep them warm for 4 hours; Second stage: Transition to the second stage of high temperature aging at a controlled heating rate of 50℃ / h, heating to 175℃ and holding for 8 hours; The two-stage heating process includes: in the first stage, the ingot is heated to 480°C at a heating rate of 50°C / h and held for 4 hours to allow the low-melting-point eutectic phase to initially dissolve and prevent the ingot from cracking; in the second stage, the ingot is heated to 565°C at a heating rate of 30°C / h and held for 8 hours.

[0040] The diffusion process includes: after the Ti metal powder is sprayed, the ingot is sent into a controlled gas protection furnace, heated to 145°C under nitrogen protection, and held for 5 minutes.

[0041] The refining process includes: after adding all alloying elements and stirring evenly, adjusting the temperature of the molten aluminum to 730°C, first introducing nitrogen gas for rotary degassing for 15 minutes to remove hydrogen and inclusions, then adding an environmentally friendly refining agent for melt purification, allowing it to stand and remove slag, and then filtering it online through a ceramic filter plate.

[0042] Example 2: The preparation process is the same as that of Example 1, but Sc is divided into Sc Part 1 and Sc Part 2 according to weight. Sc Part 1 accounts for 88% of the total weight of Sc. Sc Part 2 is processed to obtain scandium oxide. Example 3: The preparation process is the same as that of Example 1, but Ti is divided into Ti Part 1 and Ti Part 2 according to weight, with Ti Part 1 accounting for 3% of the total weight of Ti; Comparative Example 1: Its preparation process is the same as that of Example 1. Only water-based quenching liquid is used for quenching until the surface temperature of the profile drops to room temperature. Comparative Example 2: Its preparation process is the same as that of Example 1. Only oil-based quenching fluid is used for quenching until the surface temperature of the profile drops to room temperature.

[0043] The mechanical properties of the aluminum alloy profiles for new energy vehicle battery trays prepared in Examples 1-3, Comparative Examples 1 and 2 were tested. Then, the battery pack trays were prepared by extrusion molding. The dimensions of the extruded products were measured, and the yield rate was statistically analyzed. The test results are shown in Table 1. Table 1

[0044] Based on the data in the table, it can be concluded that the data from Examples 1 to 3 show that the tensile strength of the profiles prepared by this invention exceeds 320 MPa, the yield strength exceeds 260 MPa, and the elongation remains between 18.8% and 19.5%. The upward-flowing dual-medium staged quenching successfully solves the contradiction of "high strength but low toughness" or "good toughness but low strength" in traditional single-medium quenching, perfectly meeting the safety requirements of battery trays that require both high strength to bear load and high elongation to absorb energy. Compared with the low yield (88.0%) caused by Comparative Example 1 (water quenching), the yield of the finished products in the embodiments of this invention all reach more than 95%. This is due to the slow cooling effect of the oil-based quenching fluid at low temperature (≤10℃ / s), which effectively reduces the residual stress and thermal deformation of the thin-walled multi-cavity structure. Compared with Comparative Example 2 (oil quenching), the cooling of single oil quenching is too slow, and the alloying elements undergo coarse precipitation during the quenching process, resulting in poor solid solution strengthening effect and tensile strength and yield strength far below the standard.

[0045] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended embodiments and their equivalents.

Claims

1. A multi-cavity thin-walled battery tray-type aluminum alloy profile for new energy vehicles, characterized in that, The internal chemical composition of the aluminum alloy profile, by mass percentage, includes: Si: 0.65%–0.75%, Mg: 0.70%–0.85%, Cu: 0.10%–0.20%, Mn: 0.10%–0.18%, Cr: 0.06%–0.12%, Ti: 0.05%–0.10%, Sc: 0.02%–0.08%, Zr: 0.05%–0.12%, Fe≤0.20%, B≦0.10%, with the balance being Al.

2. A method for preparing a multi-cavity thin-walled battery tray-type aluminum alloy profile for new energy vehicles, comprising the multi-cavity thin-walled battery tray-type aluminum alloy profile for new energy vehicles as described in claim 1, characterized in that: The preparation method includes: S01: Based on the internal chemical composition of aluminum alloy profiles, Sc is divided into Sc Part 1 and Sc Part 2 by weight. Sc Part 1 accounts for 85% to 88% of the total weight of Sc. Sc Part 2 is processed to obtain scandium oxide. Ti is divided into Ti Part 1 and Ti Part 2 according to its weight. Ti Part 1 accounts for 3% to 8% of the total weight of Ti. Prepare raw material No. 1, which is a mixture of Si, Mg, Cu, Mn, Cr and Zr; S02: When the aluminum ingot is melted to a temperature of 700°C, the first part of Sc is added and stirred for 0.4 to 0.5 hours. Then, the second part of Ti and the first raw material are added to obtain the first aluminum liquid. The first aluminum liquid is then refined. S03: Cast the No. 1 aluminum liquid into aluminum alloy ingots, and perform homogenization treatment on the aluminum alloy ingots for 12 to 18 hours. S04: The first Ti powder with a particle size of 0.5μm to 2.0μm is sprayed onto the surface of the aluminum alloy ingot and diffused at 145℃ to 155℃ for 5 to 10 minutes. S05: The diffusion-treated aluminum alloy ingot is fed into an extrusion press for extrusion molding to obtain a shaped aluminum alloy. S06: The formed aluminum alloy is quenched by the upward-passing dual-medium graded quenching method, wherein the upward-passing dual-medium graded quenching includes: pulling the formed aluminum alloy upward from the bottom of the quenching tank and passing through the lower rapid cooling zone and the upper slow cooling zone in sequence. The lower rapid cooling zone and the upper slow cooling zone inside the quenching tank are naturally separated according to density. The lower rapid cooling zone is a water-based quenching fluid, and the upper slow cooling zone is an oil-based quenching fluid. Scandium oxide and B are added to the water-based quenching fluid. The formed aluminum alloy passes through the lower water-based quenching liquid and rapidly passes through the quenching-sensitive temperature range of the aluminum alloy at a cooling rate of ≥50℃ / s during the high-temperature stage until the surface temperature of the formed aluminum alloy drops to 260℃-330℃. The formed aluminum alloy is moved upward into the upper oil-based quenching liquid and slowly cooled at a cooling rate of ≤10℃ / s in the low-temperature stage until the surface temperature of the formed aluminum alloy drops to room temperature, thus obtaining the quenched profile. S07: After quenching, the profiles are stretched and straightened by 1.5% to 2.5%, and then sawn to length. S08: The cut profiles are subjected to a two-stage aging treatment at 175℃~185℃ for 12 hours~16 hours to obtain the final product.

3. The method for preparing a multi-cavity thin-walled battery tray-type aluminum alloy profile for new energy vehicles according to claim 2, characterized in that: The diffusion process includes: after the Ti powder coating is completed, the aluminum alloy ingot is sent into a controlled gas protection furnace, heated to 145℃~150℃ under nitrogen protection, and held at that temperature for 5 minutes~10 minutes.

4. The method for preparing a multi-cavity thin-walled battery tray-type aluminum alloy profile for new energy vehicles according to claim 2, characterized in that: The depth of the water-based quenching fluid is greater than the thickness of the formed aluminum alloy, and the depth of the upper oil-based quenching fluid is greater than the thickness of the formed aluminum alloy. The water-based quenching fluid contains B, which is used to synergistically improve the surface quenching uniformity of the profile with scandium oxide.

5. The method for preparing a multi-cavity thin-walled battery tray-type aluminum alloy profile for new energy vehicles according to claim 2, characterized in that: The quenching tank includes: The first circulation system is connected to the lower water-based quenching fluid and is used to control the temperature and level of the water-based quenching fluid. The second circulation system is connected to the upper oil-based quenching fluid and is used to control the temperature and level of the oil-based quenching fluid. A liquid level sensor, placed at the oil-water interface, is used to monitor the interface height between water-based quenching fluid and oil-based quenching fluid. The controller is electrically connected to the liquid level sensor, the first circulation system, and the second circulation system to maintain a highly stable oil-water interface.

6. The method for preparing a multi-cavity thin-walled battery tray-type aluminum alloy profile for new energy vehicles according to claim 2, characterized in that: The two-level timeliness processing includes: First stage: Heat the sawn profiles to 120℃~130℃ at a heating rate of 30℃ / h~50℃ / h, and keep them warm for 4~6 hours; Second stage: Transition to the second stage of high temperature aging at a controlled heating rate of 50℃ / h to 80℃ / h, heating to 175℃ to 185℃, and holding for 8 to 10 hours.

7. The method for preparing a multi-cavity thin-walled battery tray-type aluminum alloy profile for new energy vehicles according to claim 2, characterized in that: The homogenization process includes a two-stage heating process, which includes: in the first stage, the ingot is heated to 480℃~490℃ at a heating rate of ≤50℃ / h and held for 4~6 hours to allow the low-melting-point eutectic phase to initially dissolve and prevent the ingot from cracking; in the second stage, the ingot is heated to 565℃~575℃ at a heating rate of ≤30℃ / h and held for 8~12 hours.

8. The method for preparing a multi-cavity thin-walled battery tray-type aluminum alloy profile for new energy vehicles according to claim 2, characterized in that: The refining process includes: after adding alloying elements and stirring evenly, adjusting the temperature of the molten aluminum to 730℃~750℃, first introducing nitrogen gas for rotary degassing treatment for 15 minutes to 25 minutes, adding environmentally friendly refining agent for melt purification, allowing it to stand and removing slag, and then filtering it through a ceramic filter plate.

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