A low-carbon, high-strength and tough aluminum alloy for large integrated die-cast battery packs, its preparation method and die-casting process

Abstract

The present invention belongs to the technical field of aluminum alloy materials, and relates to a low-carbon, high-strength and tough aluminum alloy for large integrated die-cast battery packs, its preparation method and die-casting process. Based on the total weight of the aluminum alloy, it contains: Si 7.5% - 9.5%, Mg 0.15% - 0.45%, Cu 0.1% - 0.4%, Mn 0.25% - 0.65%, Fe 0.1% - 0.5%, Ti 0.05% - 0.15%, Ni 0.006 - 0.02%, Sm 0.003% - 0.02%, Ce 0.01% - 0.05%, Sr 0.01% - 0.04%, Zn ≤ 0.6%, and the balance is aluminum and inevitable trace impurities. The low-carbon, high-strength and tough aluminum alloy of the present invention has an ultimate tensile strength of 270 - 320 MPa, a yield strength of 140 - 170 MPa, and an elongation after fracture of 8 - 14%, meeting the use requirements of large integrated die-cast battery packs, and achieving a recycled aluminum addition amount of over 90%.

Description

Technical Field

[0001] The present invention belongs to the technical field of aluminum alloy materials, and relates to a low-carbon high-strength and tough aluminum alloy for large integrated die-cast battery packs, a preparation method thereof, and a die-casting process. Background Art

[0002] In 2020, Tesla first adopted the integrated die-casting technology for the rear floor of the Model Y vehicle body, successfully reducing the number of rear floor parts by 79, and shortening the manufacturing time from the traditional 1-2 hours to 3-5 minutes, thus triggering the rapid development of the integrated die-casting technology and the technological revolution of traditional automotive parts. As one of the key links in integrated die-casting, the heat-treatable aluminum alloy has become a research hotspot in the industry due to its high strength and toughness and the characteristics of not requiring heat treatment, which not only meets the technical requirements but also reduces the production cost, showing great development potential.

[0003] From the existing publicly disclosed alloy compositions, the high-strength and tough heat-treatable aluminum alloy materials for integrated die-casting can be divided into aluminum-silicon-magnesium series, aluminum-silicon series, aluminum-silicon-copper-magnesium series, aluminum-magnesium series, etc. The typical representative of the aluminum-silicon-magnesium series alloy is C611 of Alcoa, the typical representative of the aluminum-silicon series is the Castasil-37 alloy of Rheinmetall, the typical representative of the aluminum-silicon-copper-magnesium series is the alloy disclosed by Tesla in the Chinese patent WO2021150604A1, and the typical representative of the aluminum-magnesium series is the Magsimal-59 alloy of Rheinmetall. Many domestic and foreign enterprises and research institutions, including Xiaomi Motors, NIO Motors, Shanghai Jiao Tong University, Guangdong Hongtu, etc., are developing and promoting heat-treatable aluminum alloy materials, and the domestic R & D in recent years has mainly focused on the aluminum-silicon-magnesium series.

[0004] The research on heat-treatment-free aluminum alloy materials was initially to meet the requirements of the riveting process (SPR connection) of integrated structural parts, and the elongation must reach more than 10%. By looking at the heat-treatment-free aluminum alloy materials at home and abroad, they can be roughly divided into three categories. The first type of heat-free alloy does not add Mg elements, and typical representatives are Rhinefield's Castasil-37 alloy and Lizhong Group's LDHM-02 alloy. The main advantages are good thermal stability and good performance consistency before and after heat treatment, but it mainly relies on rapid cooling to improve strength, and the strength decreases significantly with increasing wall thickness. The second type adds Mg content of 0.15-0.22%, and typical representatives are: Alcoa C611 (patent publication number US6773666B2); Lizhong Group's AlSi7MnMg, etc. The main characteristics are good toughness and Mg2Si phase strengthening, but poor fluidity, and the performance of large integrated structural parts far away from the gate position is easily unsatisfactory. The third type adds Mg content of 0.22-0.35%, and the Fe content is further increased to increase the upper limit of the allowable impurity elements. Typical representatives are Tesla's alloy TeslaAlloy and Xiaomi Titan alloy. The main features are improved strength, with a higher upper limit of impurity elements such as iron and zinc, and a higher proportion of recycled aluminum can be added to achieve low carbon and low cost. The three types of heat-treatment-free alloys are ultimately mainly to meet the riveting process of large integrated structural parts, with an elongation of more than 10%, and the research and development of materials are subject to the connection method.

[0005] With the development of the connection method of automobile parts, aluminum-aluminum connection and steel-aluminum connection have made great progress. For example, brazing, screw connection and other methods are applied to large integrated structural parts, and the toughness of heat-free alloys is required to be higher. Chinese patent CN117448634A discloses a renewable high-strength and toughness heat-free aluminum alloy and its preparation method and die-casting process. The heat-free aluminum alloy includes: Si 6.5% to 9.5%, Cu 0.8% to 1.2%, Mg 0.1% to 0.3%, Mn 0.2% to 0.4%, Fe0.20% to 0.45%, Sr 0.01% to 0.03%, Cr 0.01% to 0.15%, Ni 0.01-0.06%, Zn≤0.60%, Ti≤0.15%, and the rest are aluminum and inevitable trace impurities, wherein the content of a single element of the trace impurities is ≤0.05%, and the total amount of the trace impurities is ≤0.15%. The yield strength of the heat-treatment-free aluminum alloy provided is 120-140 MPa, which is difficult to meet the use of large-scale integrated die-cast battery packs. In addition, the alloy contains Cr and cannot meet export standards. The maximum amount of scrap aluminum added is only 50%, which is costly.

[0006] Therefore, there is a need for an aluminum alloy for large integrated die-cast battery packs that meets export standards, elongation and yield strength requirements and has low cost. Summary of the invention

[0007] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a low-carbon, high-strength and tough aluminum alloy for a large integrated die-cast battery pack and a preparation method and die-casting process thereof. From the perspective of the connection method being subject to material design, the alloy designed in the present invention will be used as the fourth type of heat-treatment-free alloy, further increasing the content of strengthening elements, while increasing the upper limit of impurity elements such as Fe, and the elongation will reach more than 8% while the strength is improved. The increase in strength allows the wall thickness of the part design to be further reduced, and the part structure design reduces unnecessary reinforcement ribs, thereby achieving part weight reduction. At the same time, the allowance of high impurity elements, the proportion of waste aluminum added in the present invention can reach up to 90%~100%, and the choice of waste material types is greatly relaxed, so that the cost of parts can be further reduced. This alloy material is mainly suitable for heat-treatment-free aluminum alloy materials for large integrated die-cast battery packs that require higher yield strength. The reduction in material cost will play an important role in the development of die-casting parts such as integrated large battery packs in China, and also provide the possibility for the decentralization of integrated die-casting technology from high-end models.

[0008] The technical solution adopted by the present invention to solve the technical problem is:

[0009] A first aspect of the present invention provides a low-carbon, high-strength and toughness aluminum alloy for a large integrated die-cast battery pack, which, relative to the total weight of the aluminum alloy, comprises: Si 7.5% to 9.5%, Mg 0.15% to 0.45%, Cu 0.1% to 0.4%, Mn 0.25% to 0.65%, Fe 0.1% to 0.5%, Ti 0.05% to 0.15%, Ni 0.006 to 0.02%, Sm 0.003% to 0.02%, Ce 0.01% to 0.05%, Sr 0.01% to 0.04%, Zn ≤ 0.6%, and the rest is aluminum and unavoidable trace impurities, wherein the content of a single element of the trace impurities is ≤ 0.05%, and the total amount of the trace impurities is ≤ 0.15%. The weight ratio of Cu and Mg is 0.5~1.5, the weight ratio of Mn and Fe is 1.5~2.5, the sum of the weights of Ni, Ce and Sm is 0.04~0.07%, and the weight ratio of Ni, Ce and Sm is 1:(1.6-2.6):(0.4-1.0). The ultimate tensile strength of the low-carbon, high-strength and tough aluminum alloy is 270~320MPa, the yield strength is 140~170MPa, and the elongation after fracture is 8~14%.

[0010] Furthermore, based on the total weight of the aluminum alloy, it contains: Si 8.5% to 9.0%, Mg 0.27% to 0.42%, Cu 0.10% to 0.36%, Mn 0.28% to 0.51%, Fe 0.15% to 0.35%, Ti 0.06% to 0.13%, Ni0.006% to 0.018%, Sm 0.003% to 0.012%, Ce 0.01% to 0.04%, Sr 0.015 to 0.04%, and Zn≤ 0.6%.

[0011] The control range of Cu content is 0.1%~0.4%, the control range of Mg content is 0.15-0.45%, and the weight ratio of Cu and Mg is controlled in the range of 0.5~1.5, among which the weight ratio of Cu and Mg is lower than 0.5. At this time, the Cu content is low and the magnesium content is high, which is easy to precipitate Q-Al5Cu2Mg8Si6 phase and θ-Al2Cu phase. When the weight ratio of Cu and Mg is higher than 1.5, the Cu content is high and the magnesium content is low, which is easy to precipitate Q-Al5Cu2Mg8Si6 phase, and the θ-Al2Cu phase is reduced. At this time, Mg will form more Mg2Si phase with Si, which plays a supplementary strengthening role. The reason for reducing the θ-Al2Cu phase is that this phase often precipitates at the grain boundary, and the potential of this phase is higher than the base potential, which is easy to form intergranular corrosion at the grain boundary, which is very unfavorable to the corrosion resistance of parts. In addition to the role of supplementary strengthening, a more important purpose of adding Cu element is to increase the addition ratio of recycled scrap aluminum and the selection range of recycled scrap aluminum types. That is to say, it is necessary to minimize the impact of Cu addition on corrosion resistance while achieving the above two purposes. This is the most important purpose of controlling the weight ratio of Cu and Mg in the patent of this invention.

[0012] The control range of Mn content is 0.25% to 0.65%, and the control range of Fe content is 0.1% to 0.5%. The weight ratio of Mn to Fe is controlled within the range of 1.5 to 2.5. The content ratio of Mn and Fe is controlled. On the one hand, the Mn element can replace the Fe atoms in the needle-shaped AlFeSi phase to form a blocky AlFeMnSi phase, reducing the harm of the impurity Fe element. At the same time, too high a Mn element will cause the AlFeMnSi phase to coarsen, which is not conducive to material properties. Therefore, it is controlled within a certain range.

[0013] The control range of Ni content is 0.006 - 0.2%, the control range of Ce content is 0.01 - 0.05%, the control range of Sm content is 0.003 - 0.02%, the total weight of Ni, Ce, and Sm is 0.04 - 0.07%, and the weight ratio of Ni, Ce, and Sm is controlled as Ni:Ce:Sm = 1:(1.6 - 2.6):(0.4 - 1.0); Ni belongs to the Fe - affinity element, so some AlNiFe phases with high - temperature stability will be formed in the alloy, thus reducing the formation of acicular Fe - rich phases. In addition, Ce and Sm belong to rare - earth elements and have strong surface affinity, which can combine with elements such as O and H to purify the melt. At the same time, they can modify eutectic Si. Again, Ce and Sm elements adsorb at the boundaries of acicular Fe - rich phases during solidification, hindering the input of chemical elements into the AlFeSi phase. Therefore, they can play a role in hindering its production, turning the acicular phase into a granular phase, thereby reducing the harm of Fe - rich phases to the performance. Through reasonable element ratio, the harm of Fe can be further reduced, the melt can be purified, and the alloy performance can be improved. Through experiments, controlling Ni, Ce, and Sm in a certain proportion range has the best effect. Reducing the addition amount will lead to insufficient effect and poor performance, and adding more than the limit will result in the appearance of coarse rare - earth phases and performance degradation. It should be emphasized that the addition of trace elements Ni, Ce, and Sm plays a crucial role in the present invention. One of the main purposes of the present invention is to increase the proportion of recycled waste aluminum added and significantly broaden the selection range of recycled waste aluminum types. The technical means used is to effectively control the iron - rich phase, thereby relaxing the upper limit of the allowable Fe element. An important aspect of the innovation point of this invention patent is to add trace elements Ni, Ce, and Sm jointly, and through their respective range control, total amount range control, and weight ratio control of Ni, Ce, and Sm, so that the alloy can maintain excellent toughness while ensuring high strength, ensuring that the alloy of the present invention still has excellent strength - toughness balance when adding a higher proportion of recycled aluminum.

[0014] In the second aspect of the present invention, a preparation method of the low - carbon high - strength and high - toughness aluminum alloy is provided, including the following steps:

[0015] 1) Prepare aluminum alloy liquid;

[0016] 2) After the alloy composition is detected to be qualified, adjust the temperature of the aluminum liquid to 710 - 730 °C, weigh the particulate refining agent (weigh according to 0.15 - 0.25% of the total amount of the aluminum alloy liquid) and add it into the refining equipment. Adjust the parameters of the refining equipment, control the injection speed of the particulate refining agent to be 0.8 - 1.2 kg / min. After the refining equipment is connected to argon with a pressure of 0.6 - 0.8 MPa, uniformly inject the particulate refining agent into the aluminum alloy liquid, and let it stand for 10 - 20 min to make the particulate refining agent fully react and float, and conduct the first slag removal on the scum formed on the surface of the aluminum alloy liquid;

[0017] 3) Add 99.95% magnesium ingots, AlSr10 rods, and AlTiCB refiners to the degassed aluminum alloy liquid, stir, and conduct modification treatment and refinement treatment;

[0018] 4) Maintain the temperature of the aluminum alloy liquid at 710 - 730 °C, use a rotary degasser in the melting furnace, connect argon gas with a pressure of 0.3 - 0.5 MPa, control the rotor speed at 380 - 400 r / min, and the argon gas flow rate at 15 - 20 m 3 / h;

[0019] 5) After refining and degassing, let it stand for 10 - 20 min, and remove the dross formed on the surface of the aluminum alloy liquid;

[0020] 6) The aluminum alloy liquid flows from the melting furnace along the launder into the degassing box. The degassing box is equipped with a double-rotor rotary degasser for full-process on-line degassing. The speed of the degasser is set at 430 - 450 r / min, and the argon gas flow rate is 15 - 25 L / min;

[0021] 7) After on-line degassing, the aluminum alloy liquid enters the filtration pool for filtration and purification, and the ceramic filter plate is 40 mesh;

[0022] 8) Control the temperature of the aluminum alloy liquid at 660 - 680 °C. The aluminum alloy liquid enters the preheated ingot mold through the distributor. Adjust the flow control valve to control the flow rate of the aluminum alloy liquid, and use the bottom rotary water spraying cooling method of the ingot mold for aluminum ingot die casting to obtain a low-carbon high-strength and tough aluminum alloy.

[0023] Further, the preparation method of the aluminum alloy liquid in step 1) is as follows: Put 99.97% A00 aluminum ingots, 3303 industrial silicon, electrolytic copper, AlMn10 master alloy, AlFe10 master alloy, AlTi10 master alloy, AlNi20 master alloy, AlSm10 master alloy, and AlCe40 master alloy into the melting furnace according to the ratio, evenly heat up the furnace chamber to 760 - 780 °C, stir 1 - 3 times during this period, stir for another 2 min after the aluminum ingots are completely melted, let it stand for 10 - 20 min, and then take samples to detect the composition to obtain the aluminum alloy liquid.

[0024] Further, the preparation method of the aluminum alloy liquid in step 1) is as follows: Put 30-40% of the total weight of waste automobile wheels, 30-40% of 1-series waste aluminum wires, 20-30% of waste A356 structural parts, and the remaining 1-5% of waste automobile water tanks or waste aluminum cans into a melting furnace, and uniformly heat the furnace chamber to 760-780 °C. Stir 3-5 times during this period, remove the waste slag generated during the melting process, stir again for 2 minutes after complete melting, and sample and detect the composition after standing for 10-20 minutes. If the detected components of Si, Cu, Mn, Ni, and Fe are lower than the required range, use AlSi40 master alloy, AlCu40 master alloy, AlMn10 master alloy, AlFe10 master alloy, AlTi10 master alloy, AlNi20 master alloy, AlSm10 master alloy, and AlCe40 master alloy to fine-tune the composition until it is qualified to obtain the aluminum alloy liquid.

[0025] The types of waste aluminum for the test are temporarily selected, which does not limit the types of recycled aluminum. In the future production, the original grade utilization or more types of recycled aluminum can be used.

[0026] The third aspect of the present invention provides a die-casting process suitable for the low-carbon high-strength and tough aluminum alloy, specifically: The die-casting machine uses a LK DCC500 die-casting machine, the die-casting temperature is 700-720 °C, the casting pressure is 1400-1600 bar, the slow injection speed is 0.2-0.5 m / s, the fast injection speed is 4-6 m / s, the mold temperature and the barrel temperature are 150-200 °C, the mold cavity vacuum degree is 20-40 mbar, and the dilution ratio of the mold release agent is 1:60.

[0027] The advantages and positive effects of the present invention are:

[0028] 1. Both Cu and Mg elements are the main strengthening elements in the material. Reasonably regulating the Cu / Mg ratio controls the strength and toughness of the material, and reasonably regulating the Mn / Fe ratio reduces the harm of the impurity Fe element.

[0029] 2. The Si element can improve the fluidity of the cast aluminum alloy, which is crucial for the fluidity of large integrated parts. However, an increase in the Si content will lead to a decrease in the elongation rate. The strength and toughness are controlled within a suitable range, and the Si element should not be too high, controlled within the range of 7.5-9.5%.

[0030] 3. Trace amounts of Ni element have a certain modification effect on the Fe-rich phase, changing the acicular phase into a fishbone shape and reducing the harm of the Fe-rich phase. Ce and Sm belong to rare earth elements, which play a role in refining the grains and modifying eutectic Si in the material. Among them, Ce and Sm elements form compounds with Al and enrich at the grain boundaries, resulting in constitutional supercooling, thereby refining the grain size of the alloy and simultaneously inhibiting the growth of eutectic Si. Control the total weight of Ni, Ce, and Sm to be 0.04 - 0.07%, and the weight ratio of Ni, Ce, and Sm to be 1:(1.6 - 2.6):(0.4 - 1.0). At the same time, reduce the weight ratio of Cu and Mg and increase the weight ratio of Mn and Fe, so as to ensure that the alloy still has excellent toughness while maintaining high strength, meeting the requirements for large integrated die-cast battery packs.

[0031] 4. Ti element will form Al3Ti phase with Al, which is mainly a grain-refining element.

[0032] 5. Sr element is mainly a eutectic Si modification element, which changes the lamellar eutectic Si into granular shape and improves the plasticity of the alloy.

[0033] Compared with Patent CN117448634A, by reducing the weight ratio of Cu and Mg, increasing the weight ratio of Mn and Fe, and at the same time controlling the total weight of Ni, Ce, and Sm to be 0.04 - 0.07%, and the weight ratio of Ni, Ce, and Sm to be 1:(1.6 - 2.6):(0.4 - 1.0), through the reasonable ratio of main elements and trace elements, the synergistic effect of each element ensures high strength of the aluminum alloy while also having good toughness, achieving a recycled aluminum addition of more than 90%. The ultimate tensile strength of the low-carbon high-strength and tough aluminum alloy of the present invention is 270 - 320 MPa, the yield strength is 140 - 170 MPa, and the elongation after fracture is 8 - 14%.

[0034] The advantages of the high strength and toughness of the materials of the present invention provide more space for part design, reduce the wall thickness of parts and reduce redundant stiffeners, which plays a positive role in reducing the weight of parts. Therefore, "recycling" + "lightweight" further reduces the cost of parts and increases the installation volume of integrated structural parts in automobiles, which will play a positive role in promoting and leading the development of large integrated structural parts in our country. Brief Description of the Drawings

[0035] Figure 1 It is the microstructure diagram of the low-carbon high-strength and tough aluminum alloy prepared in Example 1;

[0036] Figure 2 It is the composition diagram of the Fe-rich phase in the low-carbon high-strength and tough aluminum alloy prepared in Example 1. Detailed Description of the Invention

[0037] The present invention will be further described in detail below through specific embodiments. The following embodiments are only descriptive and not restrictive, and the protection scope of the present invention cannot be limited thereby.

[0038] Embodiment 1

[0039] A low-carbon, high-strength and tough aluminum alloy for large integrated die-cast battery packs, based on the total weight of the aluminum alloy, contains: Si 8.72%, Mg 0.35%, Cu 0.27%, Mn 0.45%, Fe 0.21%, Ti 0.12%, Ni 0.018%, Sm 0.011%, Ce 0.032%, Sr 0.031%, Zn ≤ 0.6%, and the rest is aluminum and inevitable trace impurities. The content of a single element of the trace impurities ≤ 0.05%, and the total amount of the trace impurities ≤ 0.15%. The weight ratio of Cu to Mg is 0.77, the weight ratio of Mn to Fe is 2.16, and the sum of the weights of Ni, Ce, and Sm is 0.062%.

[0040] The preparation method is as follows:

[0041] 1) Prepare aluminum alloy liquid from electrolytic aluminum; put A00 aluminum ingot 99.97%, 3303 industrial silicon, electrolytic copper, AlMn10 master alloy, AlFe10 master alloy, AlTi10 master alloy, AlNi20 master alloy, AlSm10 master alloy, AlCe40 master alloy into the melting furnace according to the above ratio, and uniformly heat up the furnace chamber to 780 °C. Stir 3 times during this period. After the aluminum ingot is completely melted, stir for another 2 minutes, let it stand for 10 - 20 minutes, and then take a sample to detect the composition to obtain the aluminum alloy liquid.

[0042] 2) After the alloy composition is detected to be qualified, adjust the temperature of the aluminum liquid to 710 °C, weigh the Siton STJ-A1 granular refining agent (weigh according to 0.15% of the total amount of the melted aluminum liquid) and add it to the refining equipment. Adjust the parameters of the refining equipment, control the spraying speed of the granular refining agent to be 1.0 kg / min. After the refining equipment is connected to argon gas with a pressure of 0.8 MPa, uniformly spray the granular refining agent into the aluminum alloy liquid, let it stand for 20 minutes to make the granular refining agent fully react and float, and conduct the first slag removal on the slag formed on the surface of the aluminum alloy liquid;

[0043] 3) Add 99.95% magnesium ingot, AlSr10 rod, and AlTiCB grain refiner to the slag-removed aluminum alloy liquid, stir, and conduct modification treatment and grain refinement treatment;

[0044] 4) Keep the temperature of the aluminum alloy liquid at 710 - 730 °C, use the rotary degasser in the melting furnace, connect it to argon gas with a pressure of 0.5 MPa, control the rotor speed at 400 r / min, and the argon gas flow rate at 20 m 3 / h;

[0045] 5) After refining and degassing, let it stand for 20 min, and remove the dross formed on the surface of the aluminum alloy liquid.

[0046] 6) The aluminum alloy liquid flows from the melting furnace into the degassing tank along the launder. A double-rotor rotary degasser is installed in the degassing tank for full-process on-line degassing. The rotational speed of the degasser is set at 450 r / min, and the argon flow rate is 25 L / min.

[0047] 7) After on-line degassing, the aluminum alloy liquid enters the filtration pool for filtration and purification, and the ceramic filter plate is 40 mesh.

[0048] 8) Control the temperature of the aluminum alloy liquid at 680 °C. The aluminum alloy liquid enters the preheated ingot mold through the distributor. Adjust the flow control valve to control the flow rate of the aluminum alloy liquid. The aluminum ingot is produced by the method of spraying water for cooling at the bottom of the ingot mold in a rotating manner, and a low-carbon high-strength and tough aluminum alloy is obtained.

[0049] The low-carbon high-strength and tough aluminum alloy obtained by the above preparation is die-cast by a LK DCC500 die-casting machine. The die-casting temperature is 720 °C, the casting pressure is 1400 bar, the slow injection speed is 0.5 m / s, the fast injection speed is 6 m / s, the mold temperature and the barrel temperature are 200 °C, the vacuum degree of the mold cavity is 40 mbar, and the dilution ratio of the mold release agent is 1:60. The specific element contents are shown in Table 1, and the performance parameters are shown in Table 3.

[0050] The microstructure of the low-carbon high-strength and tough aluminum alloy prepared in Example 1 is as Figure 1 shown, Figure 2 which is the composition diagram of the iron-rich phase of the low-carbon high-strength and tough aluminum alloy prepared in Example 1.

[0051] Examples 2 to 6

[0052] The preparation method and die-casting process are the same as those in Example 1, except that the element contents are different. The specific element contents are shown in Table 1, and the performance parameters are shown in Table 3.

[0053] Example 7

[0054] A low-carbon high-strength and tough aluminum alloy for large integrated die-casting battery packs, based on the total weight of the aluminum alloy, contains: Si 8.89%, Mg 0.28%, Cu 0.30%, Mn 0.50%, Fe 0.23%, Ti 0.13%, Ni 0.016%, Sm 0.012%, Ce 0.033%, Sr 0.033%, Zn ≤ 0.6%, and the rest are aluminum and inevitable trace impurities, where the content of each single element of the trace impurities ≤ 0.05%, and the total amount of the trace impurities ≤ 0.15%. The weight ratio of Cu to Mg is 1.08, the weight ratio of Mn to Fe is 2.2, and the sum of the weights of Ni, Ce, and Sm is 0.061%.

[0055] The difference in the preparation method from Example 1 lies in step 1), specifically: Put 30% of the total weight of waste automobile wheels and 30% of Series 1 waste aluminum wires into the melting furnace, and evenly heat the furnace chamber to 780 °C. Stir 5 times during this period. Skim off the waste residue generated during the melting process. After the waste is completely melted, stir for another 2 minutes, and then let it stand for 20 minutes and take samples for composition detection. If the detected Si, Cu, Mn, Ni, and Fe in the composition are lower than the required range, use AlSi40 master alloy, electrolytic copper, AlMn10 master alloy, AlFe10 master alloy, AlTi10 master alloy, AlNi20 master alloy, AlSm10 master alloy, and AlCe40 master alloy to finely adjust the composition until it is qualified to obtain aluminum alloy liquid.

[0056] The die-casting process is the same as that of Example 1. The specific element contents are shown in Table 1, and the performance parameters are shown in Table 3.

[0057] Example 8

[0058] A low-carbon, high-strength and tough aluminum alloy for large integrated die-cast battery packs, based on the total weight of the aluminum alloy, contains: Si 8.87%, Mg 0.29%, Cu 0.30%, Mn 0.51%, Fe 0.23%, Ti 0.12%, Ni 0.017%, Sm 0.011%, Ce 0.035%, Sr 0.033%, Zn ≤ 0.6%, and the rest is aluminum and unavoidable trace impurities. The content of a single element of the trace impurities ≤ 0.05%, and the total amount of the trace impurities ≤ 0.15%. The weight ratio of Cu to Mg is 1.03, the weight ratio of Mn to Fe is 2.22, and the sum of the weights of Ni, Ce, and Sm is 0.063%.

[0059] The difference in the preparation method from Example 1 lies in step 1), specifically: Put 35% of the total weight of waste automobile wheels, 30% of Series 1 waste aluminum wires, 25% of waste A356 structural parts, and the remaining 2% of waste aluminum cans into the melting furnace, and evenly heat the furnace chamber to 780 °C. Stir 5 times during this period. Skim off the waste residue generated during the melting process. After the waste is completely melted, stir for another 2 minutes, and then let it stand for 20 minutes and take samples for composition detection. If the detected Si, Cu, Mn, Ni, and Fe in the composition are lower than the required range, use AlSi40 master alloy, electrolytic copper, AlMn10 master alloy, AlFe10 master alloy, AlTi10 master alloy, AlNi20 master alloy, AlSm10 master alloy, and AlCe40 master alloy to finely adjust the composition until it is qualified to obtain aluminum alloy liquid.

[0060] The specific element contents are shown in Table 1, and the performance parameters are shown in Table 3.

[0061] Comparative Example 1

[0062] The preparation method and die-casting process are the same as those in Example 8, except that the sum of the weights of Ni, Ce, and Sm is 0.021%. The specific element contents are shown in Table 2, and the performance parameters are shown in Table 3.

[0063] Comparative Example 2

[0064] The preparation method and die-casting process are the same as those in Example 8, except that the sum of the weights of Ni, Ce, and Sm is 0.084%. The specific element contents are shown in Table 2, and the performance parameters are shown in Table 3.

[0065] Comparative Example 3

[0066] The preparation method and die-casting process are the same as those in Example 8, except that the weight ratio of Ni, Ce, and Sm is 1:2.9:1.2. The specific element contents are shown in Table 2, and the performance parameters are shown in Table 3.

[0067] Comparative Example 4

[0068] The preparation method and die-casting process are the same as those in Example 8, except that the weight ratio of Cu and Mg is 0.3. The specific element contents are shown in Table 2, and the performance parameters are shown in Table 3.

[0069] Comparative Example 5

[0070] The preparation method and die-casting process are the same as those in Example 8, except that the weight ratio of Cu and Mg is 1.6. The specific element contents are shown in Table 2, and the performance parameters are shown in Table 3.

[0071] Comparative Example 6

[0072] The preparation method and die-casting process are the same as those in Example 8, except that the weight ratio of Mn and Fe is 1.4. The specific element contents are shown in Table 2, and the performance parameters are shown in Table 3.

[0073] Comparative Example 7

[0074] The preparation method and die-casting process are the same as those in Example 8, except that the weight ratio of Mn and Fe is 2.7. The specific element contents are shown in Table 2, and the performance parameters are shown in Table 3.

[0075] Comparative Example 8

[0076] Based on the formula disclosed in Patent CN117448634A, Ni, Ce, and Sm are added, and the formula is as follows: Si 8.6%, Cu 0.9%, Mg 0.25%, Mn 0.3%, Fe 0.30%, Sr 0.022%, Cr 0.014%, Zn 0.10%, Ti 0.12%, Ni 0.01%, Sm 0.01%, Ce 0.04%. The preparation method and die-casting process are the same as those in Example 8, and the performance parameters are shown in Table 3.

[0077] Table 1 Element contents of Examples 1 to 8 (%)

[0078]

[0079] Table 2 Element contents of Comparative Examples 1 to 7 (%)

[0080]

[0081] Table 3 Mechanical properties of Examples 1 to 8 and Comparative Examples 1 to 8

[0082]

[0083] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the inventive concept, several modifications and improvements can be made, and these all belong to the protection scope of the present invention.

Claims

1. A low-carbon, high-strength and tough aluminum alloy for large integrated die-cast battery packs, characterized in that, Based on the total weight of the aluminum alloy, it contains: Si 8.5% - 9.0%, Mg 0.27% - 0.42%, Cu 0.10% - 0.36%, Mn 0.28% - 0.51%, Fe 0.15% - 0.35%, Ti 0.06% - 0.13%, Ni 0.006% - 0.018%, Sm 0.003% - 0.012%, Ce 0.01% - 0.04%, Sr 0.015 - 0.04%, Zn ≤ 0.6%, and the rest is aluminum and inevitable trace impurities. The content of each single element of the trace impurities ≤ 0.05%, and the total amount of the trace impurities ≤ 0.15%. The weight ratio of Cu to Mg is 0.5 - 1.5, the weight ratio of Mn to Fe is 1.5 - 2.5, the sum of the weights of Ni, Ce, and Sm is 0.04% - 0.07%, the weight ratio of Ni, Ce, and Sm is 1:(1.6 - 2.6):(0.4 - 1.0). The ultimate tensile strength of the low-carbon high-strength and tough aluminum alloy is 270 - 320 MPa, the yield strength is 140 - 170 MPa, the elongation after fracture is 8 - 14%, and the addition amount of recycled aluminum is more than 90%.

2. The preparation method of the low-carbon high-strength and tough aluminum alloy according to claim 1, characterized in that It includes the following steps: 1) Prepare aluminum alloy liquid; 2) After the alloy composition is detected to be qualified, adjust the temperature of the aluminum liquid to 710 - 730 °C, add 0.15 - 0.25% of the total amount of the aluminum alloy liquid of the granular refining agent into the refining equipment, adjust the parameters of the refining equipment, control the spraying speed of the granular refining agent to be 0.8 - 1.2 kg / min. After the refining equipment is connected to argon with a pressure of 0.6 - 0.8 MPa, spray the granular refining agent evenly into the aluminum alloy liquid, and let it stand for 10 - 20 min to make the granular refining agent fully react and float up, and conduct the first slag removal on the dross formed on the surface of the aluminum alloy liquid; 3) Add 99.95% magnesium ingots, AlSr10 rods, and AlTiCB refining agents to the slag-removed aluminum alloy liquid, stir, and conduct modification treatment and refinement treatment; 4) Keep the temperature of the aluminum alloy liquid at 710~730 °C, use a rotary degasser in the melting furnace, connect argon gas with a pressure of 0.3~0.5 MPa, control the rotor speed at 380~400 r / min, and the argon gas flow rate at 15~20 m 3 / h; 5) After refining and degassing, let it stand for 10 - 20 min, and conduct slag removal on the dross formed on the surface of the aluminum alloy liquid; 6) The aluminum alloy liquid flows from the melting furnace along the launder into the degassing tank. The degassing tank is equipped with a double-rotor rotary degasser for full-process on-line degassing. The rotation speed of the degasser is set at 430 - 450 r / min, and the argon gas flow rate is 15 - 25 L / min; 7) After the aluminum alloy liquid is on-line degassed, it enters the filter pool for filtration and purification, and the ceramic filter plate is 40 mesh; 8) Control the temperature of the aluminum alloy liquid at 660 - 680 °C. The aluminum alloy liquid enters the preheated ingot mold for die casting through the distributor. Adjust the flow control valve to control the flow rate of the aluminum alloy liquid, and use the bottom rotary water spraying cooling method of the ingot mold for aluminum ingot die casting to obtain the low-carbon high-strength and tough aluminum alloy.

3. The preparation method according to claim 2, characterized in that, The preparation method of step 1) is as follows: Put 99.97% A00 aluminum ingot, 3303 industrial silicon, electrolytic copper, AlMn10 master alloy, AlFe10 master alloy, AlTi10 master alloy, AlNi20 master alloy, AlSm10 master alloy, and AlCe40 master alloy into the melting furnace according to the ratio, and uniformly heat up the furnace chamber to 760 - 780 °C. Stir 1 - 3 times during this period. After the aluminum ingot is completely melted, stir for another 2 minutes. After standing for 10 - 20 minutes, sample and detect the composition to obtain the aluminum alloy liquid.

4. The preparation method according to claim 2, characterized in that, The preparation method of step 1) is as follows: Put 30 - 40% of the total weight of waste automobile wheels, 30 - 40% of 1 - series waste aluminum wires, 20 - 30% of waste A356 structural parts, and the remaining 1 - 5% of waste automobile radiators or waste aluminum cans into the melting furnace. Uniformly heat up the furnace chamber to 760 - 780 °C. Stir 3 - 5 times during this period. Skim off the slag generated during the melting process. After the waste aluminum is completely melted, stir for another 2 minutes. After standing for 10 - 20 minutes, sample and detect the composition. If the content of Si, Cu, Mn, Ni, Sm, and Ce in the composition detection is lower than the required range, adjust the composition by using AlSi40 master alloy, AlCu40 master alloy, AlMn10 master alloy, AlFe10 master alloy, AlTi10 master alloy, AlNi20 master alloy, AlSm10 master alloy, and AlCe40 master alloy until the composition is qualified to obtain the aluminum alloy liquid.

5. A die-casting process applicable to the low-carbon high-strength and tough aluminum alloy described in claim 1, characterized in that, The die - casting temperature is 700 - 720 °C, the casting pressure is 1400 - 1600 bar, the slow injection speed is 0.2 - 0.5 m / s, the fast injection speed is 4 - 6 m / s, the mold temperature and the barrel temperature are 150 - 200 °C, the mold cavity vacuum degree is 20 - 40 mbar, and the dilution ratio of the mold release agent is 1:60.

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