Die-casting aluminum alloy preparation method based on aluminum-containing waste, die-casting aluminum alloy and application of die-casting aluminum alloy

Abstract

The invention provides a die-casting aluminum alloy preparation method based on aluminum-containing waste, a die-casting aluminum alloy and application of the die-casting aluminum alloy. The preparation method comprises the following steps: S1, heating and melting the aluminum-containing waste at 760-820 DEG C to obtain a first melt; s2, raw materials are added into the first melt according to the components of the die-casting aluminum alloy to be prepared, and a second melt is prepared; s3, the second melt is cooled, and a third melt with the temperature ranging from 690 DEG C to 720 DEG C is obtained; and S4, the third melt is subjected to die-casting treatment, and the die-casting aluminum alloy is obtained. The die-casting aluminum alloy with high Fe tolerance and high Zn tolerance is prepared by taking the aluminum-containing waste as a main raw material. By accurately controlling the alloy components of the die-casting aluminum alloy and combining the smelting condition of the aluminum-containing waste raw material and the subsequent die-casting process, the die-casting aluminum alloy with high mechanical property is prepared under the condition of avoiding a heat treatment process.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloys, and in particular to a method for preparing a die-cast aluminum alloy based on aluminum-containing waste, a die-cast aluminum alloy and applications thereof. Background Art

[0002] Recently, the requirements for lightweighting of new energy vehicles have been continuously improved. The automobile body accounts for about 30% of the total weight of the vehicle, which is the part with the highest weight share of the vehicle and the field with the greatest potential for lightweighting. Integrated die-casting has become the focus of lightweight technology layout in the automotive industry. However, the large-scale die-casting parts caused by the integration of multiple parts have greatly increased the difficulty of subsequent correction and scrap rate of heat treatment. Therefore, the development of heat-free aluminum alloy materials suitable for large and thin-walled die-casting parts has become an inevitable choice for integrated die-casting. Although the strength and toughness of the alloys in the current heat-free patents can meet the requirements of integrated die-casting, the allowable upper limits of impurity elements such as iron and zinc are generally low. Electrolytic aluminum is often used as the main raw material in the preparation of the alloy, and it is difficult to increase the proportion of recycled waste aluminum, which is not conducive to reducing material costs and energy conservation and emission reduction. It is necessary to reduce material costs to increase the acceptance of integrated die-casting by OEMs.

[0003] Recycled aluminum has become a research hotspot due to its advantages such as extremely low damage during use, high recycling value, effective conservation of the natural environment and protection of the ecological environment. Due to its complex source and high content of impurity elements, especially Fe and Zn elements, recycled aluminum can generally only be downgraded or used in low-end casting alloys, resulting in insufficient economic benefits and market competitiveness of recycled aluminum. Therefore, it is urgent to increase the application of high-end alloys of recycled aluminum and the number of recycling uses at the same level, and ultimately improve the economic benefits of recycled aluminum. As aluminum alloy die-casting structural parts are increasingly used in the automotive field, die-casting aluminum alloys and their costs are increasingly limited by the performance constraints of low-Fe aluminum alloys. Therefore, aluminum alloy die-casting structural parts, especially heat-treatment-free die-casting structural parts, urgently need to break through the bottleneck of original aluminum.

[0004] Prior art CN 117448634 A discloses a heat-treatment-free die-cast aluminum alloy based on recycled aluminum, the mass percentage composition of the alloy is as follows: Si 8.0-10.5%, Fe≤0.2%, Cu≤0.20%, Mn 0.4-0.8%, Mg<0.20%, Ti≤0.15%, Zn<0.15%, Ca≤20ppm, P≤20ppm, Sr 0.01-0.04%, Zr 0.1-0.30%; the rest is Al and unavoidable impurities. It improves the alloy structure by Al-Sr and TCB to obtain a die-cast aluminum alloy with high strength, high toughness and excellent thermal stability, which can meet the performance requirements of die-cast structural parts of the vehicle body. However, the patent has strict restrictions on Fe, Cu and Zn, the proportion of recycled aluminum cannot be too high, and Sr is easily burned during the recycling process, requiring additional addition, which increases the process cost.

[0005] Prior art CN117512414 A discloses a renewable high-strength and tough heat-treatment-free aluminum alloy, whose mass percentage composition is as follows: Si 6.5% to 9.5%, Cu 0.8% to 1.2%, Mg 0.1% to 0.3%, Mn 0.2% to 0.4%, Fe 0.20% 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 is 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%. This patent significantly increases the allowable range of impurity elements such as Fe and Zn, and can greatly broaden the range of types of recycled scrap aluminum when preparing the alloy. However, the patent uses Sr to modify the silicon phase, which is easy to burn out during the recycling process, requires additional addition, increases process costs, and also leads to insufficient welding performance. In addition, the excessive Cu content in the alloy will significantly reduce the corrosion resistance of the alloy, thereby affecting the application range of castings.

[0006] Prior art CN116949306 A discloses a method for preparing a heat-treatment-free integrated die-casting aluminum alloy using recycled aluminum as raw material. The alloy has the following mass percentage composition: Al 87.0-92.5%, Si 6-10.0%, Cu 0.5-1.0%, Mg0.1-0.5%, Fe 0.5-0.8%, Mn 0.5-0.8%, La 0.05-0.3%. The patent changes the hard and brittle second phase particle morphology from needle-shaped to short rod-shaped by adding rare earth lanthanum, thereby improving the performance of the casting. However, the Fe and Mn content in the patent is too high, and a coarse phase has been formed, resulting in insufficient toughness of the alloy. In addition, if the Cu element content in the alloy is too high, the corrosion resistance of the alloy will be significantly reduced, thereby affecting the application range of the casting.

[0007] Based on this, how to provide a method for preparing a die-cast aluminum alloy with excellent mechanical properties based on aluminum-containing waste is one of the important technical problems that need to be solved in this field. Summary of the invention

[0008] The main purpose of the present invention is to provide a method for preparing a die-cast aluminum alloy based on aluminum-containing waste, a die-cast aluminum alloy and its application, so as to solve the problem that it is difficult to prepare a die-cast aluminum alloy with excellent mechanical properties based on aluminum-containing waste and its alloys in the prior art.

[0009] In order to achieve the above-mentioned object, the first aspect of the present invention provides a method for preparing a die-casting aluminum alloy based on aluminum-containing waste, comprising: step S1, heating and melting the aluminum-containing waste at 760° C. to 820° C. to obtain a first melt; step S2, adding raw materials to the first melt according to the composition of the die-casting aluminum alloy to be prepared to prepare a second melt; in terms of weight percentage, the composition of the die-casting aluminum alloy includes 7.0% to 9.5% Si, 0.40% to 0.75% Mn, 0. 0.08% to 0.55% Fe, 0.05% to 0.35% Mg, 0.05% to 0.35% Cu, 0.05% to 0.65% Zn, 0.03% to 0.88% Sb, the remainder being Al and unavoidable impurity elements, and the composition of the die-casting aluminum alloy does not include Sr; step S3, cooling the second melt to obtain a third melt with a temperature of 690°C to 720°C; step S4, die-casting the third melt to obtain a die-casting aluminum alloy.

[0010] Furthermore, the composition of the die-casting aluminum alloy includes, by weight percentage, 8.0% to 9.5% Si, 0.45% to 0.75% Mn, 0.10% to 0.45% Fe, 0.15% to 0.30% Mg, 0.30% to 0.35% Cu, 0.05% to 0.65% Zn, 0.03% to 0.88% Sb, 0% to 0.5% impurity elements, and the remainder is Al, and the composition of the die-casting aluminum alloy does not include Sr.

[0011] Furthermore, in the composition of the die-cast aluminum alloy, the weight ratio of Cu and Mg is (0.3-3.0):1, preferably (1.2-2.7):1; and / or, the weight ratio of Mn and Fe is (1.2-5.5):1, preferably (2.9-5.5):1; and / or, (Fe+2Mn) is denoted as m, and in terms of weight percentage, m is 0.9%-1.7%, preferably 1.0%-1.5%.

[0012] Further, the aluminum-containing waste is selected from one or more of recycled aluminum ingots, A356 alloy castings, A356 alloy scraps, AlSi10MnMg alloy castings and AlSi10MnMg alloy scraps; and, in terms of weight percentage, the content of Al element in the recycled aluminum ingots, A356 alloy castings, A356 alloy scraps, AlSi10MnMg alloy castings and AlSi10MnMg alloy scraps is each independently 80% to 93%, and the content of Fe element is each independently 0.10% to 0.15%.

[0013] Furthermore, step S2 also includes: step S2-1, adding aluminum raw material, manganese raw material, copper raw material, antimony raw material and silicon raw material to the first melt according to the composition of the die-casting aluminum alloy, and obtaining an intermediate melt through a first smelting; step S2-2, adding magnesium raw material to the intermediate melt according to the composition of the die-casting aluminum alloy, and obtaining a second melt through a second smelting.

[0014] Further, the temperature of the first smelting is 750°C to 790°C; and / or the temperature of the second smelting is 740°C to 760°C.

[0015] Further, in step S4, the die-casting process includes a slow shot stage and a fast shot stage performed sequentially, and the switching point between the slow shot stage and the fast shot stage is 550mm to 650mm in front of the gate in the die-casting mold, and the injection speed in the slow shot stage is 0.18m / s to 0.55m / s; and / or, the injection speed in the fast shot stage is 2.5m / s to 6.0m / s.

[0016] A second aspect of the present invention provides a die-casting aluminum alloy, which is prepared by the above-mentioned method for preparing a die-casting aluminum alloy based on aluminum-containing waste.

[0017] Furthermore, the tensile strength of the die-cast aluminum alloy is 260MPa~310MPa, the yield strength is 100MPa~150MPa, and the elongation is 11.0%~16.0%; preferably, the die-cast aluminum alloy is subjected to three remelting die-castings to obtain a remelted die-cast aluminum alloy, and the tensile strength of the remelted die-cast aluminum alloy is 250MPa~305MPa, the yield strength is 100MPa~145MPa, and the elongation is 10.1%~14.0%; more preferably, each remelting die-casting includes a remelting step at a temperature of 750℃~770℃ and a vacuum die-casting step at a temperature of 690℃~700℃.

[0018] A third aspect of the present invention provides an application of the above die-cast aluminum alloy as an automobile body structural component in the field of new energy vehicles.

[0019] By applying the technical solution of the present invention, a die-cast aluminum alloy with high Fe tolerance and high Zn tolerance is prepared with aluminum-containing waste as the main raw material. By accurately controlling the alloy composition of the die-cast aluminum alloy, combining the smelting conditions of the aluminum-containing waste raw material and the subsequent die-casting process, a die-cast aluminum alloy with high mechanical properties is prepared without the need for a heat treatment process. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0021] Figure 1 This is a scanning electron microscope photograph of the die-cast aluminum alloy obtained in Example 1;

[0022] Figure 2 This is a metallographic photograph of the die-cast aluminum alloy obtained in Example 1. DETAILED DESCRIPTION

[0023] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0024] As described in the background technology, it is difficult to prepare die-cast aluminum alloys with excellent mechanical properties based on aluminum-containing waste and its alloys in the prior art. In order to solve the above technical problems, the first aspect of the present invention provides a method for preparing die-cast aluminum alloys based on aluminum-containing waste, comprising: step S1, heating and melting the aluminum-containing waste at 760°C to 820°C to obtain a first melt; step S2, adding raw materials to the first melt according to the composition of the die-cast aluminum alloy to be prepared to prepare a second melt; in terms of weight percentage, the composition of the die-cast aluminum alloy includes 7.0% to 9.5% Si, 0.40% to 0.75% Mn, 0. .08% to 0.55% Fe, 0.05% to 0.35% Mg, 0.05% to 0.35% Cu, 0.05% to 0.65% Zn, 0.03% to 0.88% Sb, the remainder being Al and unavoidable impurity elements, and the composition of the die-casting aluminum alloy does not include Sr; step S3, cooling the second melt to obtain a third melt with a temperature of 690°C to 720°C; step S4, die-casting the third melt to obtain a die-casting aluminum alloy.

[0025] The above-mentioned preparation method can effectively utilize aluminum-containing waste, and the prepared die-cast aluminum alloy has a higher upper limit of elements such as Fe and Zn, and excellent mechanical properties. When the inventor carried out the composition design of the above-mentioned die-cast aluminum alloy, by combining the component characteristics of the aluminum-containing waste, the remaining alloying elements were selected to make a reasonable combination and optimize their addition amount, thereby significantly improving the mechanical properties of the final prepared die-cast aluminum alloy. Among them, in particular: silicon is the first main alloying element in the die-cast aluminum alloy provided by the present invention, and its weight percentage is controlled at 7.0% to 9.5%, which can ensure that the aluminum alloy has good filling ability while taking into account strength and toughness. When the silicon content is lower than 7.0%, the casting molding performance of the aluminum alloy is insufficient, especially after obtaining large and complex die-castings, its strength is poor; and when the silicon content is higher than 9.5%, not only the strength of the obtained alloy casting is limited, but also its elongation is significantly reduced, which is not conducive to its comprehensive performance improvement.

[0026] In particular, as mentioned in the background technology, regarding the aluminum alloy prepared from aluminum-containing waste, the Sr element is often used in the prior art to optimize the morphology and distribution of eutectic silicon, thereby improving the performance of the obtained aluminum alloy. The present invention uses the Sb element instead of the Sr element, which can not only cooperate with other element components to achieve the same above-mentioned effect, but also ensure that the silicon phase modification effect is not attenuated during the subsequent recycling process. More importantly, for the die-cast aluminum alloy obtained by the present invention, if it involves welding operations in subsequent application production, the Sr element will cause severe air inhalation during the welding process, thereby significantly reducing the welding performance of the casting.

[0027] The inevitable impurity elements in the composition of the obtained die-casting aluminum alloy are mainly one or more of Ni, V, P and Ca. Of course, although Sr is not included in the die-casting aluminum alloy provided in the present application, it may still exist in trace amounts as an inevitable impurity element, but it is not considered as one of the components of the die-casting aluminum alloy.

[0028] And, for the above-mentioned formula of die-casting aluminum alloy, the present invention has designed its preparation method accordingly, wherein the aluminum-containing waste is heated at 760℃~820℃. Within this temperature range, the aluminum-containing waste can be effectively melted, while avoiding excessive evaporation of effective alloy elements therein, ensuring the subsequent precise control of the composition of the die-casting aluminum alloy, thereby improving the comprehensive performance of the final aluminum alloy. As for the melt temperature during die-casting treatment, that is, the temperature of the third melt, the present invention strictly controls it to 690℃~720℃, so as to better match the content of each element in its components, ensure the fluidity of the melt during the die-casting process, control the generation of its impurity phase, and avoid defects such as cracks caused by excessively high temperature, and problems such as insufficient filling caused by too low temperature, and finally realize the preparation of die-casting aluminum alloy with high mechanical properties. In particular, through the perfect combination of the above-mentioned preparation method and the alloy composition, the obtained die-casting aluminum alloy exhibits excellent various properties after die-casting treatment, which can meet the application requirements of various fields. Therefore, the above-mentioned preparation method provided by the present invention does not involve any heat treatment of the die-cast aluminum alloy, thereby achieving a further reduction in its preparation cost.

[0029] In practical applications, in order to further reduce impurities in the obtained die-cast aluminum alloy and improve its purity, the above preparation method also includes refining, slagging, degassing and deslagging the second melt in sequence before the cooling treatment. The specific conditions are:

[0030] Refining and slag removal: add 0.1wt% to 0.3wt% of sodium-free refining agent to the second melt, control the melt temperature at 730°C to 750°C, stir for 10min to 15min and then perform slag removal.

[0031] Degassing and deslagging: Add sodium-free covering agent to the second melt after refining and slagging within 0 to 2 minutes, the amount added is 0.05wt% to 0.1wt% of the total amount of the alloy melt, and introduce argon gas with a pressure of 0.18MPa to 0.25MPa into the melt. Degassing and deslagging are carried out at a rotor speed of 300rad / min to 500rad / min, a degassing time of 5min to 20min, and a temperature of 720℃ to 730℃.

[0032] In summary, the present invention uses aluminum-containing waste as the main raw material to prepare a die-cast aluminum alloy with high Fe tolerance and high Zn tolerance. In particular, the alloy composition of the die-cast aluminum alloy is precisely controlled, and the smelting conditions of the aluminum-containing waste raw material and the subsequent die-casting process are combined to achieve the preparation of a die-cast aluminum alloy with high mechanical properties without the need for a heat treatment process.

[0033] Further, by weight percentage, the composition of the die-casting aluminum alloy includes 8.0% to 9.5% Si, 0.45% to 0.75% Mn, 0.10% to 0.45% Fe, 0.15% to 0.30% Mg, 0.30% to 0.35% Cu, 0.05% to 0.65% Zn, 0.03% to 0.88% Sb, and the balance is Al and unavoidable impurity elements, and the composition of the die-casting aluminum alloy does not include Sr. Based on the above alloy formula, the above range is preferably obtained again, and the various element components can better cooperate with each other, so as to obtain a die-casting aluminum alloy with better mechanical properties.

[0034] In several typical embodiments, the weight ratio of Cu to Mg in the composition of the die-cast aluminum alloy is (0.3-3.0): 1, preferably (1.2-2.7): 1. Copper and magnesium are both main strengthening elements in the aluminum alloy formula provided by the present invention, and the above preferred range of the copper-magnesium ratio, especially when it is (1.2-2.7): 1, can not only improve the strength-toughness balance of the obtained die-cast aluminum alloy, but also enhance its corrosion resistance.

[0035] In order to better achieve effective control of the precipitation of primary iron-rich phase, and then achieve more effective regulation of the morphology, size and distribution of the iron-rich phase, and ultimately reduce its damage to the toughness of the obtained die-cast aluminum alloy, the weight ratio of Mn and Fe is preferably (1.2-5.5):1, preferably (2.9-5.5):1. At the same time, (Fe+2Mn) is recorded as m, and m is 0.9%-1.7% by weight, preferably 1.0%-1.5%. The above-mentioned relationship between the content of manganese and iron is further limited to optimization, which can effectively improve the corrosion resistance and thermal stability of the obtained die-cast aluminum alloy, and can also cooperate with other components to further optimize the mechanical properties of the alloy.

[0036] In several more typical embodiments, the composition of the die-casting aluminum alloy includes, by weight percentage, 8.13% Si, 0.55% Mn, 0.17% Fe, 0.21% Mg, 0.30% Cu, 0.34% Zn, 0.046% Sb, and the balance is Al and unavoidable impurity elements, and the composition of the die-casting aluminum alloy does not contain Sr; or, by weight percentage, the composition of the die-casting aluminum alloy includes 8.25% Si, 0.48% Mn, 0.09% Fe, 0.25% Mg, 0.32% Cu, 0.43% Zn, 0.055% Sb, the balance is Al and inevitable impurity elements, and the composition of the die-cast aluminum alloy does not contain Sr; or, by weight percentage, the composition of the die-cast aluminum alloy includes 9.45% Si, 0.62% Mn, 0.21% Fe, 0.15% Mg, 0.35% Cu, 0.09% Zn, 0.085% Sb, the balance is Al and inevitable impurity elements, and the composition of the die-cast aluminum alloy does not contain Sr. After a large number of experiments, the inventor optimized the content of each component in the die-cast aluminum alloy to obtain the above three formulas, and the die-cast aluminum alloys obtained by these three formulas show more excellent mechanical properties, with tensile strength higher than 290MPa, yield strength higher than 135MPa, and elongation higher than 13.0%.

[0037] Furthermore, in order to more effectively reduce the overall cost of die-casting aluminum alloys and at the same time improve the recovery rate of aluminum-containing waste, in the preparation process, the aluminum-containing waste is preferably selected from one or more of recycled aluminum ingots, A356 alloy castings, A356 alloy waste, AlSi10MnMg alloy castings and AlSi10MnMg alloy waste; and, in terms of weight percentage, the Al content of the recycled aluminum ingots, A356 alloy castings, A356 alloy waste, AlSi10MnMg alloy castings and AlSi10MnMg alloy waste is each independently 80% to 93%, and the Fe content is each independently 0.1% to 0.15%.

[0038] It should be noted in advance that the raw material of the recycled aluminum ingot used in the present invention refers to the aluminum ingot obtained by recycling waste aluminum materials and undergoing processes such as melting, purification, and recasting. A356 alloy castings and waste parts, as well as AlSi10MnMg alloy castings and waste parts, all refer to aluminum alloy products that have been used, are no longer suitable for their original purpose, and have not undergone any remelting or other recycling treatment.

[0039] Specifically, by weight percentage, the components of the recycled aluminum ingot include 89% to 91% Al, 0.12% to 0.14% Fe, 3% to 5% Si, 0.05% to 0.40% Mg, 0.1% to 0.5% Mn, and 0.05% to 0.35% Cu. The components of the A356 alloy casting include 89% to 93% Al, 0.1% to 0.15% Fe, 0.01% to 0.3% Mn, and 6.0% to 7.5% Si; the components of the A356 alloy scrap include 92.1% to 93.0% Al, 0.12% to 0.14% Fe, 5.0% to 7.5% Si, 0.1% to 0.7% Mg, and 0.001% to 0.03% Sr. The composition of AlSi10MnMg alloy castings includes 87% to 93% Al, 0.1% to 0.15% Fe, 8.5% to 12% Si, 0.1% to 0.6% Mg, 0.3% to 0.7% Mn, and 0.001% to 0.03% Sr. The composition of AlSi10MnMg alloy scraps includes 85% to 90% Al, 0.1% to 0.15% Fe, 7.5% to 12% Si, 0.1% to 0.6% Mg, 0.3% to 0.7% Mn, and 0.001% to 0.03% Sr.

[0040] In several typical embodiments, step S2 also includes: step S2-1, according to the composition of the die-cast aluminum alloy, adding aluminum raw material, manganese raw material, copper raw material, antimony raw material and silicon raw material to the first melt, and obtaining an intermediate melt through the first smelting; step S2-2, according to the composition of the die-cast aluminum alloy, adding magnesium raw material to the intermediate melt, and obtaining a second melt through the second smelting. The preparation method of the die-cast aluminum alloy provided by the present invention has comprehensively considered the synergistic effect of each alloy element within a specific content range from the perspective of the alloy component formula. On this basis, the raw materials involved are prepared into the second melt according to the above-mentioned feeding sequence and process conditions, so that each alloy element can form a more uniform metallographic structure in the obtained aluminum alloy, reduce the formation of coarse impurity second phase, and thus obtain a die-cast aluminum alloy with excellent comprehensive performance. At the same time, the above-mentioned step-by-step smelting can more accurately control the alloy composition, avoid the alloy composition fluctuation caused by adding multiple alloy elements at one time, thereby improving the uniformity and consistency of the final die-cast aluminum alloy, so that it exhibits higher mechanical properties.

[0041] Specifically, the aluminum raw material uses industrial pure aluminum (Al purity ≥ 99.0%) or electrolytic aluminum, the manganese raw material uses aluminum-manganese intermediate alloy or manganese agent, the copper raw material uses industrial pure copper (Cu purity ≥ 99.0%) or Al-Cu intermediate alloy, the antimony raw material uses Al-Sb intermediate alloy, the silicon raw material uses one or more of aluminum-silicon intermediate alloy, industrial silicon (Si purity ≥ 90.0%) and quick-dissolving silicon, and the magnesium raw material uses industrial pure magnesium ingot (Mg purity ≥ 99.0%).

[0042] In the above smelting process, further, the temperature of the first smelting is 750℃~790℃; and / or, the temperature of the second smelting is 740℃~760℃. That is, the types of element raw materials added in the first smelting and the second smelting are optimized. The selection of this temperature range can promote the full dissolution of each alloy element, while inhibiting the excessive evaporation of the alloy element at high temperature, thereby more significantly improving the composition accuracy and performance stability of the obtained die-cast aluminum alloy.

[0043] In several typical embodiments, in order to obtain a casting with a more uniform internal structure, the die-casting process in step S4 includes a slow shot stage and a fast shot stage performed in sequence, and the transition point between the slow shot stage and the fast shot stage is 550mm to 650mm in front of the gate in the die-casting mold. After a large number of experiments, the inventors preferably obtain an injection speed of 0.18m / s to 0.55m / s in the slow shot stage; and / or, an injection speed of 2.5m / s to 6.0m / s in the fast shot stage. The optimization of the die-casting speed in the above-mentioned different injection stages can promote the uniform filling of the aluminum alloy melt in the mold, effectively reducing the generation of pores and shrinkage cavities. At the same time, the above-mentioned die-casting process can cooperate with the temperature control of the third melt during die-casting, and synergistically improve the surface quality and the density of the internal structure of the obtained aluminum alloy die-casting from the perspective of kinetics and thermodynamics, thereby making it show better comprehensive performance.

[0044] In addition, in order to obtain a die-cast aluminum alloy with better mechanical properties, with respect to other parameters in the die-casting process, it is preferred that: the die-casting temperature is 675°C to 710°C, the casting pressure is 1200bar to 1600bar, the mold temperature and the barrel temperature are each independently 140°C to 250°C, and the mold cavity vacuum is 80Pa to 95Pa.

[0045] The second aspect of the present invention provides a die-cast aluminum alloy, which is prepared by the above-mentioned die-cast aluminum alloy preparation method based on aluminum-containing waste. The obtained high-strength and tough heat-treatment-free die-cast aluminum alloy has a higher upper limit of the allowable impurity elements, which is conducive to adding a higher proportion of recycled waste aluminum and reducing material costs.

[0046] Furthermore, the tensile strength of the die-cast aluminum alloy is 260MPa-310MPa, the yield strength is 100MPa-150MPa, and the elongation is 11.0%-16.0%. That is, the obtained die-cast aluminum alloy has excellent comprehensive mechanical properties and can meet the use requirements of various fields.

[0047] Furthermore, the die-cast aluminum alloy is subjected to three remelting die-castings to obtain a remelted die-cast aluminum alloy, and the remelted die-cast aluminum alloy has a tensile strength of 250MPa to 305MPa, a yield strength of 100MPa to 145MPa, and an elongation of 10.1% to 14.0%. In other words, the die-cast aluminum alloy prepared by the present invention can effectively realize the same-level recycling, thereby further realizing energy conservation and emission reduction, and has significant technical significance and broad application prospects.

[0048] In several preferred embodiments, exemplarily, each remelting die-casting includes a remelting step at a temperature of 750° C. to 770° C. and a vacuum die-casting step at a temperature of 690° C. to 700° C.

[0049] The third aspect of the present invention provides an application of the above die-cast aluminum alloy as an automobile body structural part in the field of new energy vehicles. Since the above die-cast aluminum alloy prepared by the present invention has excellent mechanical properties and can also show a good state after cyclic remelting casting, it is particularly applicable to the production and application of large structural parts with large size requirements, complex structure requirements, high toughness requirements, and difficult heat treatment, such as automobile body structural parts.

[0050] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0051] Unless otherwise defined, all professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0052] Example 1

[0053] A method for preparing die-cast aluminum alloy based on aluminum-containing waste:

[0054] Step (1), using recycled aluminum ingot as raw material (by weight percentage, its components include 90% Al, 0.13% Fe, 4.8% Si, 0.12% Mg, 0.24% Mn, and 0.05% Cu), the raw material is put into an industrial smelting furnace, and heated to 790° C. to obtain a first melt.

[0055] Step (2), detecting the alloy element content in the first melt, and preparing the final die-casting aluminum alloy with a formula of Si 7.01%, Mn 0.42%, Fe 0.15%, Mg 0.06%, Cu 0.12%, Zn 0.06%, Sb 0.032%, and the balance being Al and impurity elements (by weight percentage).

[0056] Step (2-1), according to the above ingredients, adding aluminum raw material, manganese raw material, copper raw material, antimony raw material and silicon raw material into the first melt, and performing a first smelting at a temperature of 770° C. to obtain an intermediate melt;

[0057] Step (2-2), according to the above ingredients, continue to add magnesium raw material to the intermediate melt, and undergo a second smelting at a temperature of 750° C. to obtain a second melt.

[0058] Step (3), refining, deslagging, degassing, deslagging and standing for cooling the second melt in sequence to obtain a third melt.

[0059] Step (3-1), refining and deslagging: adding a sodium-free refining agent in an amount of 0.2 wt% of the total amount of the alloy melt to the second melt, controlling the melt temperature at 740° C., stirring for 10 min, and then performing deslagging treatment;

[0060] Step (3-2), degassing and deslagging: add a sodium-free covering agent within 1 minute, the amount added is 0.08wt% of the total amount of the alloy melt, and argon gas with a pressure of 0.20MPa is introduced into the melt. Degassing and deslagging are carried out at a rotor speed of 400rad / min, a degassing time of 10min, and a temperature of 720°C;

[0061] Step (3-3), standing and cooling: the second melt after degassing and deslagging is allowed to stand and cool until a third melt with a temperature of 700° C. is obtained.

[0062] Step (4), put the third melt into the aluminum melting furnace of the die casting machine, and use the die casting machine for vacuum high pressure casting to obtain a die casting aluminum alloy. Set the first 550mm of the gate in the die casting mold as the switching point between the slow injection stage and the fast injection stage, and the speed of the slow injection stage is 0.36m / s, and the speed of the fast injection stage is 4.2m / s. At the same time, set the die casting temperature to 690℃, the casting pressure to 1400bar, the mold temperature to 150℃, the barrel temperature to 250℃, and the mold cavity vacuum to 90Pa.

[0063] The SEM photos of the obtained die-cast aluminum alloy are shown in Figure 1 , metallographic photos see Figure 2 .

[0064] Example 2

[0065] A method for preparing die-cast aluminum alloy based on aluminum-containing waste:

[0066] Step (1), using A356 alloy scrap and recycled aluminum ingots in a weight ratio of 1:1 as raw materials (in terms of weight percentage, the components of the A356 alloy scrap include 92.3% Al, 0.13% Fe, 0.32% Mg, 7.1% Si, and 0.012% Sr; the components of the recycled aluminum ingots are consistent with those in Example 1), the raw materials are put into an industrial smelting furnace, and heated to 760° C. to obtain a first melt.

[0067] Step (2), detecting the alloy element content in the first melt, and preparing the final die-casting aluminum alloy with a formula of Si 7.32%, Mn 0.52%, Fe 0.44%, Mg 0.15%, Cu 0.06%, Zn 0.13%, Sb 0.048%, and the balance Al and impurity elements (by weight percentage).

[0068] Step (2-1), according to the above ingredients, adding aluminum raw material, manganese raw material, copper raw material, antimony raw material and silicon raw material into the first melt, and performing a first smelting at a temperature of 750° C. to obtain an intermediate melt;

[0069] Step (2-2), according to the above ingredients, continue to add magnesium raw material to the intermediate melt, and undergo a second smelting at a temperature of 740° C. to obtain a second melt.

[0070] Step (3), refining, deslagging, degassing, deslagging and standing for cooling the second melt in sequence to obtain a third melt.

[0071] Step (3-1), refining and deslagging: adding a sodium-free refining agent in an amount of 0.1 wt% of the total amount of the alloy melt to the second melt, controlling the melt temperature at 730° C., stirring for 15 minutes and then performing deslagging treatment;

[0072] Step (3-2), degassing and deslagging: add a sodium-free covering agent within 1 minute, the amount added is 0.05wt% of the total amount of the alloy melt, and argon gas with a pressure of 0.18MPa is introduced into the melt. Degassing and deslagging are performed at a rotor speed of 300rad / min, a degassing time of 15min, and a temperature of 720°C;

[0073] Step (3-3), standing and cooling: the second melt after degassing and deslagging is allowed to stand and cool until a third melt with a temperature of 690° C. is obtained.

[0074] Step (4), put the third melt into the aluminum melting furnace of the die casting machine, and use the die casting machine for vacuum high pressure casting to obtain a die casting aluminum alloy. Set the first 650mm of the gate in the die casting mold as the switching point between the slow injection stage and the fast injection stage, and the speed of the slow injection stage is 0.18m / s, and the speed of the fast injection stage is 2.5m / s. At the same time, set the die casting temperature to 675℃, the casting pressure to 1200bar, the mold temperature to 150℃, the barrel temperature to 250℃, and the mold cavity vacuum to 80Pa.

[0075] Example 3

[0076] A method for preparing die-cast aluminum alloy based on aluminum-containing waste:

[0077] Step (1), using AlSi10MnMg alloy scrap and recycled aluminum ingots in a weight ratio of 1:1 as raw materials (in terms of weight percentage, the components of the AlSi10MnMg alloy scrap include 89.1% Al, 0.14% Fe, 0.38% Mg, 10.3% Si, 0.015% Sr, and 0.57% Mn; the components of the recycled aluminum ingots are consistent with those in Example 1), the raw materials are put into an industrial smelting furnace, heated to 820°C, and a first melt is obtained.

[0078] Step (2), detecting the alloy element content in the first melt, and preparing the final die-casting aluminum alloy with a formula of Si 7.58%, Mn 0.72%, Fe 0.21%, Mg 0.12%, Cu 0.23%, Zn 0.12%, Sb 0.086%, and the remainder Al and impurity elements (by weight percentage).

[0079] Step (2-1), according to the above ingredients, adding aluminum raw material, manganese raw material, copper raw material, antimony raw material and silicon raw material into the first melt, and performing a first smelting at a temperature of 790° C. to obtain an intermediate melt;

[0080] Step (2-2), according to the above ingredients, continue to add magnesium raw material to the intermediate melt, and undergo a second smelting at a temperature of 760° C. to obtain a second melt.

[0081] Step (3), refining, deslagging, degassing, deslagging and standing for cooling treatment are performed on the second melt in sequence to obtain a third melt.

[0082] Step (3-1), refining and deslagging: adding a sodium-free refining agent in an amount of 0.3 wt% of the total amount of the alloy melt to the second melt, controlling the melt temperature at 750° C., stirring for 5 minutes, and then performing deslagging treatment;

[0083] Step (3-2), degassing and deslagging: add a sodium-free covering agent within 2 minutes, the amount added is 0.1wt% of the total amount of the alloy melt, and argon gas with a pressure of 0.25MPa is introduced into the melt. Degassing and deslagging are carried out at a rotor speed of 500rad / min, a degassing time of 20min, and a temperature of 730°C;

[0084] Step (3-3), standing and cooling: the second melt after degassing and deslagging is allowed to stand and cool until a third melt with a temperature of 720° C. is obtained.

[0085] Step (4), put the third melt into the aluminum melting furnace of the die casting machine, and use the die casting machine for vacuum high pressure casting to obtain a die casting aluminum alloy. Set the first 600mm of the gate in the die casting mold as the switching point between the slow injection stage and the fast injection stage, and the speed of the slow injection stage is 0.18m / s, and the speed of the fast injection stage is 6.0m / s. At the same time, set the die casting temperature to 710℃, the casting pressure to 1600bar, the mold temperature to 150℃, the barrel temperature to 250℃, and the mold cavity vacuum to 95Pa.

[0086] The only difference between Examples 4 to 9 and Example 1 is that the composition of the die-cast aluminum alloy finally obtained is different, as shown in Table 1 for details.

[0087] Example 10

[0088] A method for preparing die-cast aluminum alloy based on aluminum-containing waste:

[0089] The difference between this embodiment and embodiment 1 is only in step (2-1) and step (2-2), specifically:

[0090] Step (1) is consistent with that in Example 1.

[0091] Step (2), detecting the alloy element content in the first melt, and preparing the final die-casting aluminum alloy with a formula of Si 7.01%, Mn 0.42%, Fe 0.15%, Mg 0.06%, Cu 0.12%, Zn 0.06%, Sb 0.032%, and the balance being Al and impurity elements (by weight percentage).

[0092] Step (2-1), according to the above ingredients, adding aluminum raw material, manganese raw material, copper raw material, antimony raw material and silicon raw material into the first melt, and performing a first smelting at a temperature of 720° C. to obtain an intermediate melt;

[0093] Step (2-2), according to the above ingredients, continue to add magnesium raw material to the intermediate melt, and perform a second smelting at a temperature of 700° C. to obtain a second melt.

[0094] Step (3) and step (4) are consistent with those in Example 1.

[0095] Embodiment 11

[0096] A method for preparing die-cast aluminum alloy based on aluminum-containing waste:

[0097] The difference between this embodiment and embodiment 1 is only in step (2-1) and step (2-2), specifically:

[0098] Step (1) is consistent with that in Example 1.

[0099] Step (2), detecting the alloy element content in the first melt, and preparing the final die-casting aluminum alloy with a formula of Si 7.01%, Mn 0.42%, Fe 0.15%, Mg 0.06%, Cu 0.12%, Zn 0.06%, Sb 0.032%, and the balance being Al and impurity elements (by weight percentage).

[0100] Step (2-1), according to the above ingredients, adding aluminum raw material, manganese raw material, copper raw material, antimony raw material and silicon raw material into the first melt, and performing a first smelting at a temperature of 800° C. to obtain an intermediate melt;

[0101] Step (2-2), according to the above ingredients, continue to add magnesium raw material to the intermediate melt, and undergo a second smelting at a temperature of 780° C. to obtain a second melt.

[0102] Step (3) and step (4) are consistent with those in Example 1.

[0103] Example 12

[0104] A method for preparing die-cast aluminum alloy based on aluminum-containing waste:

[0105] The difference between this embodiment and embodiment 1 is only in step (4), specifically:

[0106] Step (1), step (2) and step (3) are all consistent with Example 1.

[0107] Step (4), put the third melt into the aluminum melting furnace of the die casting machine, and use the die casting machine for vacuum high pressure casting to obtain a die casting aluminum alloy. Set the first 500mm of the gate in the die casting mold as the switching point between the slow injection stage and the fast injection stage, and the speed of the slow injection stage is 0.12m / s, and the speed of the fast injection stage is 2.0m / s. At the same time, set the die casting temperature to 710℃, the casting pressure to 1600bar, the mold temperature to 150℃, the barrel temperature to 250℃, and the mold cavity vacuum to 95Pa.

[0108] Example 13

[0109] A method for preparing die-cast aluminum alloy based on aluminum-containing waste:

[0110] The difference between this embodiment and embodiment 1 is only in step (4), specifically:

[0111] Step (1), step (2) and step (3) are all consistent with Example 1.

[0112] Step (4), put the third melt into the aluminum melting furnace of the die casting machine, and use the die casting machine for vacuum high pressure casting to obtain a die casting aluminum alloy. Set the first 700mm of the gate in the die casting mold as the switching point between the slow injection stage and the fast injection stage, and the speed of the slow injection stage is 0.60m / s, and the speed of the fast injection stage is 7.0m / s. At the same time, set the die casting temperature to 710℃, the casting pressure to 1600bar, the mold temperature to 150℃, the barrel temperature to 250℃, and the mold cavity vacuum to 95Pa.

[0113] Embodiment 14

[0114] A method for preparing die-cast aluminum alloy based on aluminum-containing waste:

[0115] The only difference between this embodiment and embodiment 1 is that the recycled aluminum ingot raw material used in step (1) is changed so that its component content satisfies: in terms of weight percentage, its components include 94.7% Al, 0.19% Fe, 9.8% Si, 0.38% Mg, 0.15% Mn, and 0.34% Cu.

[0116] Embodiment 15

[0117] A method for preparing die-cast aluminum alloy based on aluminum-containing waste:

[0118] The only difference between this embodiment and embodiment 1 is that the recycled aluminum ingot raw material used in step (1) is changed so that its component content satisfies: in terms of weight percentage, its components include 75.1% Al, 0.07% Fe, 3.8% Si, 0.06% Mg, 0.1% Mn, and 0.07% Cu.

[0119] The difference between Comparative Examples 1 to Comparative Examples 5 and Example 1 is only that the composition of the die-cast aluminum alloy finally obtained is different, as shown in Table 1 for details.

[0120] Comparative Example 6

[0121] A method for preparing die-cast aluminum alloy based on aluminum-containing waste:

[0122] The difference between this comparative example and Example 1 is only in step (1) and step (3-3), specifically:

[0123] Step (1), using the recycled aluminum ingot used in Example 1 as a raw material, the raw material is put into an industrial smelting furnace and heated to 720° C. to obtain a first melt.

[0124] Step (2) is consistent with that in Example 1.

[0125] Step (3), refining, deslagging, degassing, deslagging and standing for cooling treatment are performed on the second melt in sequence to obtain a third melt.

[0126] Step (3-1) and step (3-2) are consistent with Example 1.

[0127] Step (3-3), standing and cooling: the second melt after degassing and deslagging is allowed to stand and cool until a third melt with a temperature of 650° C. is obtained.

[0128] Step (4) is consistent with that in Example 1.

[0129] Comparative Example 7

[0130] A method for preparing die-cast aluminum alloy based on aluminum-containing waste:

[0131] The difference between this comparative example and Example 1 is only in step (1) and step (3-3), specifically:

[0132] Step (1), using the recycled aluminum ingot used in Example 1 as a raw material, the raw material is put into an industrial smelting furnace, heated to 850° C., and a first melt is obtained.

[0133] Step (2) is consistent with that in Example 1.

[0134] Step (3), refining, deslagging, degassing, deslagging and standing for cooling treatment are performed on the second melt in sequence to obtain a third melt.

[0135] Step (3-1) and step (3-2) are consistent with Example 1.

[0136] Step (3-3), standing and cooling: the second melt after degassing and deslagging is allowed to stand and cool until a third melt with a temperature of 750° C. is obtained.

[0137] Step (4) is consistent with that in Example 1.

[0138] The element contents in the die-cast aluminum alloys obtained in the above-mentioned embodiments and comparative examples are shown in Table 1.

[0139] Table 1

[0140]

[0141] And, in Comparative Example 1, 0.02 wt% of Sr was further added; in Comparative Example 2, 0.016 wt% of Sr was further added; and in Comparative Example 3, 0.023 wt% of Sr was further added.

[0142] Test Method

[0143] Mechanical properties testing of die-cast aluminum alloys: including tensile strength, yield strength and elongation, are all carried out in accordance with GB228.1-2021.

[0144] Preparation and mechanical property testing of remelted die-cast aluminum alloy: The die-cast aluminum alloys obtained in each embodiment and comparative example were melted at 750°C to obtain a melt, and then vacuum die-casted at 700°C to complete a remelting die-casting. Repeat this remelting die-casting step 3 times to obtain each remelted die-cast aluminum alloy sample. The mechanical properties of each obtained remelted die-cast aluminum alloy sample were also tested according to GB228.1-2021.

[0145] The above test results are shown in Table 2.

[0146] Table 2

[0147]

[0148] From the above description, it can be seen that the above-mentioned embodiment of the present invention uses aluminum-containing waste as raw material to prepare die-cast aluminum alloy. The obtained die-cast aluminum alloy not only has high tensile strength, high yield strength and high elongation, but also can maintain excellent comprehensive mechanical properties, especially after multiple remelting and die-casting. At the same time, the method provided by the present invention has a high tolerance for impurity elements in aluminum-containing waste, which is beneficial to increase the number of recycling times to reduce the material preparation cost. In addition, there is no need to make an additional distribution ratio during the remelting process, which is beneficial to reduce production costs and energy consumption.

[0149] By comparing the embodiments with the comparative examples, it can be seen that by precisely controlling the alloy composition of the die-cast aluminum alloy, combining the smelting conditions of the aluminum-containing waste raw materials and the parameter control of the subsequent die-casting process, a die-cast aluminum alloy with high mechanical properties can be prepared without the need for a heat treatment process.

[0150] By comparing Examples 1 to 9 with Examples 10 to 15, it can be seen that by further optimizing the process steps of the aluminum-containing waste and optimizing the component content of the raw materials, the various properties of the obtained die-cast aluminum alloy can be further improved.

[0151] Among them, especially in Examples 5, 6, and 9, the tensile strength of the die-cast aluminum alloy obtained is greater than 290MPa, the yield strength is greater than 135MPa, and the elongation at break is greater than 13.0%, showing excellent comprehensive mechanical properties. After these three are remelted and die-casted for many times, the remelted die-cast aluminum alloy samples obtained also show excellent comprehensive properties, that is, the tensile strength is greater than 280MPa, the yield strength is still greater than 135MPa, and the elongation at break is still greater than 13.0%. It can be shown that on the basis of the overall process provided by the present invention, it is preferred that Cu / Mg is (1.2-2.7): 1, Mn / Fe is (2.9-5.5): 1, and (Fe+2Mn) is 1.0%-1.5%, which can promote the formation of a die-cast aluminum alloy with better comprehensive mechanical properties.

[0152] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those described herein, for example.

[0153] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing die-cast aluminum alloy based on aluminum-containing waste, characterized in that: include: Step S1, heating and melting the aluminum-containing waste at 760° C. to 820° C. to obtain a first melt; Step S2, adding raw materials to the first melt according to the composition of the die-casting aluminum alloy to be prepared, to prepare a second melt; in terms of weight percentage, the composition of the die-casting aluminum alloy includes 7.0% to 9.5% Si, 0.40% to 0.75% Mn, 0.08% to 0.55% Fe, 0.05% to 0.35% Mg, 0.05% to 0.35% Cu, 0.05% to 0.65% Zn, 0.03% to 0.88% Sb, and the remainder is Al and unavoidable impurity elements, and the composition of the die-casting aluminum alloy does not contain Sr; Step S3, cooling the second melt to obtain a third melt with a temperature of 690° C. to 720° C.; Step S4, performing die-casting on the third melt to obtain the die-cast aluminum alloy.

2. The method for preparing die-cast aluminum alloy based on aluminum-containing waste according to claim 1, characterized in that: In terms of weight percentage, the composition of the die-casting aluminum alloy includes 8.0% to 9.5% Si, 0.45% to 0.75% Mn, 0.10% to 0.45% Fe, 0.15% to 0.30% Mg, 0.30% to 0.35% Cu, 0.05% to 0.65% Zn, 0.03% to 0.88% Sb, and the remainder is Al and unavoidable impurity elements, and the composition of the die-casting aluminum alloy does not contain Sr.

3. The method for preparing die-cast aluminum alloy based on aluminum-containing waste according to claim 1 or 2, characterized in that: The composition of the die-casting aluminum alloy is: The weight ratio of the Cu to the Mg is (0.3-3.0):1, preferably (1.2-2.7):1; and / or, The weight ratio of the Mn to the Fe is (1.2-5.5):1, preferably (2.9-5.5):1; and / or, (Fe+2Mn) is denoted as m, and in terms of weight percentage, the m is 0.9%-1.7%, preferably 1.0%-1.5%.

4. The method for preparing a die-casting aluminum alloy based on aluminum-containing waste according to any one of claims 1 to 3, characterized in that: The aluminum-containing waste is selected from one or more of recycled aluminum ingots, A356 alloy castings, A356 alloy scraps, AlSi10MnMg alloy castings, and AlSi10MnMg alloy scraps; and, Measured by weight percentage, in the recycled aluminum ingot, the A356 alloy casting, the A356 alloy scrap, the AlSi10MnMg alloy casting and the AlSi10MnMg alloy scrap, the Al content of the element is independently 80% to 93%, and the Fe content is independently 0.10% to 0.15%.

5. The method for preparing a die-casting aluminum alloy based on aluminum-containing waste according to any one of claims 1 to 4, characterized in that: Step S2 also includes: Step S2-1, adding aluminum raw material, manganese raw material, copper raw material, antimony raw material and silicon raw material into the first melt according to the composition of the die-casting aluminum alloy, and performing a first smelting to obtain an intermediate melt; Step S2-2, adding magnesium raw material to the intermediate melt according to the composition of the die-casting aluminum alloy, and performing a second smelting to obtain the second melt.

6. The method for preparing die-cast aluminum alloy based on aluminum-containing waste according to claim 5, characterized in that: The temperature of the first smelting is 750°C to 790°C; and / or the temperature of the second smelting is 740°C to 760°C.

7. The method for preparing a die-casting aluminum alloy based on aluminum-containing waste according to any one of claims 1 to 6, characterized in that: In step S4, the die-casting process includes a slow shot phase and a fast shot phase performed sequentially, and the switching point between the slow shot phase and the fast shot phase is 550 mm to 650 mm in front of the gate in the die-casting mold; and, The injection speed in the slow injection stage is 0.18 m / s to 0.55 m / s; and / or the injection speed in the fast injection stage is 2.5 m / s to 6.0 m / s.

8. A die-cast aluminum alloy, characterized in that: The die-casting aluminum alloy is prepared by the die-casting aluminum alloy preparation method based on aluminum-containing waste according to any one of claims 1 to 7.

9. The die-cast aluminum alloy according to claim 8, characterized in that: The die-cast aluminum alloy has a tensile strength of 260 MPa to 310 MPa, a yield strength of 100 MPa to 150 MPa, and an elongation of 11.0% to 16.0%; Preferably, the die-cast aluminum alloy is subjected to three remelting and die-casting to obtain a remelted die-cast aluminum alloy, wherein the remelted die-cast aluminum alloy has a tensile strength of 250 MPa to 305 MPa, a yield strength of 100 MPa to 145 MPa, and an elongation of 10.1% to 14.0%; More preferably, each remelting die-casting comprises a remelting step at a temperature of 750°C to 770°C and a vacuum die-casting step at a temperature of 690°C to 700°C.

10. Use of the die-cast aluminum alloy according to claim 8 or 9 as an automobile body structural part in the field of new energy automobiles.

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