Low-carbon high-toughness aluminum alloy for large-scale integrated die-casting battery pack and preparation method and die-casting process of low-carbon high-toughness aluminum alloy

Abstract

The invention belongs to the technical field of aluminum alloy materials, and relates to a low-carbon high-strength and high-toughness aluminum alloy for a large integrated die-casting battery pack and a preparation method and die-casting process of the low-carbon high-strength and high-toughness aluminum alloy, and the low-carbon high-strength and high-toughness aluminum alloy comprises, by weight, 7.5%-9.5% of Si, 0.15%-0.45% of Mg, 0.1%-0.4% of Cu, 0.25%-0.65% of Mn, 0.1%-0.5% of Fe, 0.05%-0.15% of Ti, 0.006%-0.02% of Ni, 0.003%-0.02% of Sm, 0.01%-0.05% of Ce, 0.01%-0.04% of Sr, smaller than or equal to 0.6% of Zn and the balance aluminum and inevitable trace impurities. The ultimate tensile strength of the low-carbon high-strength and high-toughness aluminum alloy ranges from 270 MPa to 320 MPa, the yield strength ranges from 140 MPa to 170 MPa, the percentage elongation after fracture ranges from 8% to 14%, the low-carbon high-strength and high-toughness aluminum alloy can be used for a large-scale integrated die-casting battery pack, and the addition amount of secondary aluminum can reach 90% or above.

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 toughness aluminum alloy for a large integrated die-cast battery pack, and a preparation method and a die-casting process thereof. Background Art

[0002] In 2020, Tesla used integrated die-casting technology for the first time on the rear floor of the Model Y, 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, which triggered the rapid development of integrated die-casting technology and a technological revolution in traditional auto parts. As one of the key links in integrated die-casting, heat-free aluminum alloy has become a hot topic in industry research due to its high strength and toughness and the characteristics of no need for heat treatment. It not only meets technical needs but also reduces production costs, showing great development potential.

[0003] Judging from the existing disclosed alloy compositions, high-strength and tough heat-treatment-free 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. A typical representative of aluminum-silicon-magnesium alloys is Alcoa's C611, a typical representative of aluminum-silicon series is Rheinfeld's Castasil-37 alloy, a typical representative of aluminum-silicon-copper-magnesium series is the alloy disclosed by Tesla in the Chinese patent WO2021150604A1, and a typical representative of aluminum-magnesium series is Rheinfeld's Magsimal-59 alloy. Many domestic and foreign companies and research institutes, including Xiaomi Motors, NIO, Shanghai Jiaotong University, Guangdong Hongtu, etc., are developing and promoting heat-treatment-free aluminum alloy materials. Domestic research and development in recent years has mainly focused on 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 to be Ni:Ce:Sm=1:(1.6-2.6):(0.4-1.0); Ni is an Fe-philic element, so some AlNiFe phases with high temperature stability will be formed in the alloy, thereby reducing the formation of needle-shaped Fe-rich phases. In addition, Ce and Sm are rare earth elements with strong surface affinity, which can be combined with elements such as O and H to purify the melt and modify the eutectic Si. Again, Ce and Sm elements are adsorbed at the needle-shaped Fe-rich phase boundary during solidification, which hinders the input of chemical elements into the AlFeSi phase, so it can hinder its production and transform the needle-shaped phase into granular phase, thereby reducing the harm of Fe-rich phase to performance. Through reasonable element ratio, Fe harm can be further reduced, melt purification can be achieved, and alloy performance can be improved. Through experiments, it is found that the best effect is achieved when Ni, Ce, and Sm are controlled in a certain range in proportion. Reducing the amount of addition leads to insufficient effect and poor performance. Excessive addition will result in a decrease in the performance of the coarse rare earth phase. It should be emphasized that the addition of trace elements Ni, Ce, and Sm in the present invention is crucial. One of the main purposes of the present invention is to increase the proportion of recycled scrap aluminum addition and greatly relax the selection range of recycled scrap aluminum types. The technical means used is to relax the upper limit of the Fe element through effective control of the iron-rich phase. An important aspect of the innovation of the present invention is to add trace elements Ni, Ce, and Sm together, and through respective range control, total range control, and Ni, Ce, Sm weight ratio control, 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] The second aspect of the present invention provides a method for preparing the low-carbon high-strength and toughness aluminum alloy, comprising the following steps:

[0015] 1) Preparing aluminum alloy liquid;

[0016] 2) After the alloy composition is tested to be qualified, adjust the aluminum liquid temperature to 710~730℃, weigh the particle refining agent (0.15~0.25% of the total amount of aluminum alloy liquid) and add it to the refining equipment, adjust the parameters of the refining equipment, control the speed of spraying the particle refining agent to 0.8~1.2kg / min, and after the refining equipment is connected to the argon gas with a pressure of 0.6~0.8MPa, spray the particle refining agent evenly into the aluminum alloy liquid, let it stand for 10~20min, so that the particle refining agent fully reacts and floats, and remove the slag formed on the surface of the aluminum alloy liquid for the first time;

[0017] 3) adding 99.95% magnesium ingot, AlSr10 rod and AlTiCB refiner to the aluminum alloy liquid after slag removal, stirring, and performing modification and refinement treatment;

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

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

[0020] 6) The aluminum alloy liquid flows from the smelting furnace along the flow channel into the degassing box. The degassing box is equipped with a double-rotor rotary degasser for online degassing throughout the whole process. The speed of the degasser is set at 430~450r / min, and the argon flow rate is 15~25L / min;

[0021] 7) After online degassing, the aluminum alloy liquid enters the filter tank for filtration and purification, with a ceramic filter plate of 40 mesh;

[0022] 8) The temperature of the aluminum alloy liquid is controlled at 660-680°C. The aluminum alloy liquid enters the preheated ingot mold through the distributor. The flow control valve is adjusted to control the flow of the aluminum alloy liquid. The aluminum ingot is die-casted by a rotating water spray cooling method at the bottom of the ingot mold to obtain a low-carbon, high-strength and tough aluminum alloy.

[0023] Furthermore, the preparation method of the aluminum alloy liquid in step 1) is: 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 are put into a smelting furnace according to a proportion, and the temperature in the furnace is uniformly raised to 760-780°C, and stirred 1-3 times during the period. After the aluminum ingot is completely melted, it is stirred again for 2 minutes, and after standing for 10-20 minutes, a sample is taken to detect the composition to obtain an aluminum alloy liquid.

[0024] Further, the preparation method of the aluminum alloy liquid in step 1) is: 30-40% of the total weight of waste automobile wheels, 30-40% of 1 series waste aluminum wire, 20-30% of waste A356 structural parts, and the remaining 1-5% of waste automobile water tanks or waste cans are added into a smelting furnace, and the furnace is evenly heated to 760-780°C, stirred 3-5 times during the period, and the waste slag produced during the melting process is scraped out, and stirred again for 2 minutes after the waste is completely melted, and then sampled and tested for composition after standing for 10-20 minutes. If the composition detection Si, Cu, Mn, Ni, and Fe are lower than the required range, the composition is fine-tuned to the qualified 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 to obtain aluminum alloy liquid.

[0025] The types of scrap aluminum being tested are temporarily selected, and do not limit the types of recycled aluminum. In future production, the original grade aluminum can be utilized 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 toughness aluminum alloy, specifically: the die-casting machine adopts a Lijin DCC500 die-casting machine, the die-casting temperature is 700~720℃, the casting pressure is 1400~1600bar, the slow injection speed is 0.2~0.5m / s, the fast injection speed is 4~6m / s, the mold temperature and the barrel temperature are 150~200℃, the mold cavity vacuum is 20~40mbar, and the release agent dilution ratio is 1:60.

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

[0028] 1. Cu and Mg are the main strengthening elements in the material. Reasonable Cu / Mg ratio regulates the strength and toughness of the material, and reasonable regulation of Mn / Fe ratio reduces the harm of impurity Fe element.

[0029] 2. The Si element can improve the fluidity of cast aluminum alloys, which is the key to large-scale integrated fluidity. However, an increase in Si content will lead to a decrease in elongation. The strength and toughness should be controlled within an appropriate range. The Si element should not be too high and should be controlled within the range of 7.5~9.5%.

[0030] 3. Trace amounts of Ni have a certain metamorphic effect on the Fe-rich phase, with the needle-like phase changing to a fishbone shape, reducing the harm of the Fe-rich phase. Ce and Sm are rare earth elements, which play a role in refining the grains and modifying the eutectic Si. Ce and Sm elements form compounds with Al and are enriched at the grain boundaries, resulting in supercooling of the concentration, thereby refining the alloy grain size and inhibiting the growth of eutectic Si. The total weight of Ni, Ce, and Sm is controlled to be 0.04~0.07%, and the weight ratio of Ni, Ce, and Sm is 1:(1.6-2.6):(0.4-1.0), and at the same time, the weight ratio of Cu and Mg is reduced and the weight ratio of Mn and Fe is increased, thereby ensuring that the alloy has excellent toughness while maintaining high strength, meeting the requirements of large-scale integrated die-cast battery packs.

[0031] 4. Ti element will form Al3Ti phase with Al, which is the main grain refinement element.

[0032] 5. Sr element is the main eutectic Si modifier, which transforms the lamellar eutectic Si into granular form 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 0.04~0.07%, the weight ratio of Ni, Ce and Sm is 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 the high strength of the aluminum alloy while also having good toughness, and the addition amount of recycled aluminum reaches more than 90%. The low-carbon and high-strength and toughness aluminum alloy of the present invention has an ultimate tensile strength of 270~320MPa, a yield strength of 140~170MPa, and an elongation after fracture of 8~14%.

[0034] The advantages of the material's toughness provide more space for part design, reduce part wall thickness and redundant reinforcement ribs, and play a positive role in reducing the weight of parts. Therefore, "recycling" + "lightweighting" further reduces part costs and increases the installed capacity of integrated structural parts in automobiles, which will actively promote and lead the development of large-scale integrated structural parts in my country. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0036] Figure 2 This is a composition diagram of the iron-rich phase in the low-carbon, high-strength and tough aluminum alloy prepared in Example 1. DETAILED DESCRIPTION

[0037] The present invention is further described in detail below through specific examples. The following examples are only illustrative and not restrictive, and the protection scope of the present invention cannot be limited thereto.

[0038] Example 1

[0039] A low-carbon, high-strength and tough aluminum alloy for a large integrated die-cast battery pack, comprising, relative to the total weight of the aluminum alloy, 8.72% Si, 0.35% Mg, 0.27% Cu, 0.45% Mn, 0.21% Fe, 0.12% Ti, 0.018% Ni, 0.011% Sm, 0.032% Ce, 0.031% Sr, ≤ 0.6% Zn, and the rest being 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 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:

[0041] 1) Electrolytic aluminum to prepare aluminum alloy liquid; 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 are put into a smelting furnace according to the above proportions, and the furnace is evenly heated to 780°C, stirred 3 times during the process, and stirred again for 2 minutes after the aluminum ingot is completely melted. After standing for 10-20 minutes, samples are taken to detect the composition to obtain aluminum alloy liquid.

[0042] 2) After the alloy composition test is qualified, adjust the aluminum liquid temperature to 710℃, weigh the STJ-A1 particle refining agent (weigh 0.15% of the total amount of molten aluminum liquid) and add it to the refining equipment, adjust the parameters of the refining equipment, control the speed of spraying the particle refining agent to 1.0kg / min, and after the refining equipment is connected to the argon gas with a pressure of 0.8MPa, spray the particle refining agent evenly into the aluminum alloy liquid, let it stand for 20 minutes, so that the particle refining agent fully reacts and floats, and remove the slag formed on the surface of the aluminum alloy liquid for the first time;

[0043] 3) adding 99.95% magnesium ingot, AlSr10 rod and AlTiCB refiner to the aluminum alloy liquid after slag removal, stirring, and performing modification and refinement treatment;

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

[0045] 5) After refining and degassing, let it stand for 20 minutes to remove the slag formed on the surface of the aluminum alloy liquid;

[0046] 6) The aluminum alloy liquid flows from the smelting furnace along the flow channel into the degassing box. The degassing box is equipped with a double-rotor rotary degasser for online degassing throughout the whole process. The speed of the degasser is set at 450r / min and the argon flow rate is 25L / min;

[0047] 7) After online degassing, the aluminum alloy liquid enters the filter tank for filtration and purification, with a ceramic filter plate of 40 mesh;

[0048] 8) The temperature of the aluminum alloy liquid is controlled at 680°C, and the aluminum alloy liquid enters the preheated ingot mold through the distributor. The flow control valve is adjusted to control the flow of the aluminum alloy liquid. The bottom of the ingot mold is cooled by rotating water spray to produce aluminum ingots to obtain a low-carbon, high-strength and tough aluminum alloy.

[0049] The low-carbon, high-strength and tough aluminum alloy prepared above was die-casted by a LK DCC500 die-casting machine, with a die-casting temperature of 720°C, a casting pressure of 1400 bar, a slow shot speed of 0.5 m / s, a fast shot speed of 6 m / s, a mold temperature and a barrel temperature of 200°C, a mold cavity vacuum of 40 mbar, and a release agent dilution ratio of 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 aluminum alloy prepared in Example 1 is as follows: Figure 1 As shown, Figure 2 This is a composition diagram of the iron-rich phase of the low-carbon, high-strength and tough aluminum alloy prepared in Example 1.

[0051] Embodiment 2~6

[0052] The preparation method and die-casting process are the same as those in Example 1, the only difference being the element content. The specific element content is shown in Table 1, and the performance parameters are shown in Table 3.

[0053] Example 7

[0054] A low-carbon, high-strength and toughness aluminum alloy for a large integrated die-cast battery pack, comprising, relative to the total weight of the aluminum alloy, 8.89% Si, 0.28% Mg, 0.30% Cu, 0.50% Mn, 0.23% Fe, 0.13% Ti, 0.016% Ni, 0.012% Sm, 0.033% Ce, 0.033% Sr, ≤ 0.6% Zn, and the rest being 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 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 between the preparation method and Example 1 is step 1), specifically: 30% of the total weight of waste automobile wheels and 30% of 1 series waste aluminum wires are put into a smelting furnace, and the furnace is evenly heated to 780°C, stirred 5 times during the period, and the waste slag produced during the melting process is scraped out, and stirred again for 2 minutes after the waste is completely melted, and then sampled and tested for composition after standing for 20 minutes. If the composition detection of Si, Cu, Mn, Ni, and Fe is lower than the required range, the composition is fine-tuned to the qualified composition by using 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 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 toughness aluminum alloy for a large integrated die-cast battery pack, comprising, relative to the total weight of the aluminum alloy, 8.87% Si, 0.29% Mg, 0.30% Cu, 0.51% Mn, 0.23% Fe, 0.12% Ti, 0.017% Ni, 0.011% Sm, 0.035% Ce, 0.033% Sr, ≤ 0.6% Zn, and the rest being 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 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 between the preparation method and Example 1 is step 1), specifically: 35% of the total weight of waste automobile wheels, 30% of the waste aluminum wire, 25% of the waste A356 structural parts, and the remaining 2% of the waste cans are put into a smelting furnace, and the furnace is evenly heated to 780°C, stirred 5 times during the period, and the waste slag produced during the melting process is scraped out, and stirred again for 2 minutes after the waste is completely melted, and the composition is sampled and tested after standing for 20 minutes. If the composition detection Si, Cu, Mn, Ni, and Fe are lower than the required range, the composition is fine-tuned to the qualified composition by using 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 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 of 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 of 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 of Example 8, the only difference being 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 of Example 8, except that the weight ratio of Cu to 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 of Example 8, except that the weight ratio of Cu to 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 of Example 8, with the only difference being that the weight ratio of Mn to 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 of Example 8, with the only difference being that the weight ratio of Mn to 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] Ni, Ce and Sm are added to the formula disclosed in patent CN117448634A, and the formula is: 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 description is only a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several modifications and improvements without departing from the inventive concept, which 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: Relative to the total weight of the aluminum alloy, it contains: 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%, 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 and high strength and toughness aluminum alloy is 270~320MPa, the yield strength is 140~170MPa, and the elongation after fracture is 8~14%.

2. The low-carbon, high-strength and tough aluminum alloy according to claim 1, characterized in that: Relative to 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%, Fe0.15%~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%, and Zn≤0.6%.

3. The method for preparing a low-carbon, high-strength and tough aluminum alloy according to claim 1 or 2, characterized in that: The steps include: 1) preparing aluminum alloy liquid; 2) After the alloy composition is tested and qualified, adjust the temperature of the aluminum liquid to 710~730℃, add 0.15~0.25% of the total amount of aluminum alloy liquid into the refining equipment, adjust the parameters of the refining equipment, control the speed of spraying the particle refining agent to 0.8~1.2kg / min, and after the refining equipment is connected to the argon gas with a pressure of 0.6~0.8MPa, spray the particle refining agent evenly into the aluminum alloy liquid, let it stand for 10~20min, so that the particle refining agent fully reacts and floats, and remove the slag formed on the surface of the aluminum alloy liquid for the first time; 3) adding 99.95% magnesium ingot, AlSr10 rod and AlTiCB refiner to the aluminum alloy liquid after slag removal, stirring, and performing modification and refinement treatment; 4) Maintain the aluminum alloy liquid temperature at 710~730℃, use the rotary degasser in the melting furnace, connect the argon gas with a pressure of 0.3~0.5MPa, control the rotor speed at 380~400r / min, and the argon gas flow rate at 15~20m 3 / h; 5) After refining and degassing, let it stand for 10 to 20 minutes to remove the slag formed on the surface of the aluminum alloy liquid; 6) The aluminum alloy liquid flows from the smelting furnace along the flow channel into the degassing box. The degassing box is equipped with a double-rotor rotary degasser for online degassing throughout the whole process. The speed of the degasser is set at 430~450r / min, and the argon flow rate is 15~25L / min; 7) After online degassing, the aluminum alloy liquid enters the filter tank for filtration and purification, with a ceramic filter plate of 40 mesh; 8) The temperature of the aluminum alloy liquid is controlled at 660-680°C, and the aluminum alloy liquid enters the preheated ingot casting mold through a distributor for die casting. The flow control valve is adjusted to control the flow of the aluminum alloy liquid. The aluminum ingot is die-casted by a rotating water spray cooling method at the bottom of the ingot casting mold to obtain a low-carbon and high-strength aluminum alloy.

4. The preparation method according to claim 3, characterized in that: The preparation method of step 1) is as follows: 99.97% of 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 are put into a smelting furnace according to a proportion, and the temperature in the furnace is uniformly raised to 760-780° C. During the period, the furnace is stirred 1-3 times, and after the aluminum ingot is completely melted, the mixture is stirred again for 2 minutes, and after standing for 10-20 minutes, samples are taken to detect the composition to obtain aluminum alloy liquid.

5. The preparation method according to claim 3, characterized in that: The preparation method of step 1) is as follows: 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 cans are put into a smelting furnace, and the furnace is evenly heated to 760-780°C, stirred 3-5 times during the period, and the waste slag produced during the melting process is scraped out, and after the waste aluminum is completely melted, it is stirred again for 2 minutes, and the composition is sampled and tested after standing for 10-20 minutes; if the composition detection Si, Cu, Mn, Ni, Sm, and Ce are lower than the required range, the composition is fine-tuned to a qualified 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 to obtain aluminum alloy liquid.

6. A die-casting process suitable for the low-carbon high-strength and toughness aluminum alloy according to any one of claims 1 to 2, characterized in that: The die-casting temperature is 700~720℃, the casting pressure is 1400~1600bar, the slow shot speed is 0.2~0.5m / s, the fast shot speed is 4~6m / s, the mold temperature and barrel temperature are 150~200℃, the mold cavity vacuum is 20~40mbar, and the release agent dilution ratio is 1:60.

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