Al-Si series die-casting aluminum alloy based on secondary aluminum, preparation method of Al-Si series die-casting aluminum alloy and structural part

Abstract

The invention provides an Al-Si series die-casting aluminum alloy based on secondary aluminum, a preparation method of the Al-Si series die-casting aluminum alloy and a structural part. The method comprises the following steps: adding industrial silicon, steel scrap and Ni into a secondary aluminum melt to obtain a mixed melt; carrying out boronizing treatment and primary refining treatment on the mixed melt; the temperature is adjusted to 710-780 DEG C, magnesium alloy waste, Sr and Al-Ti-B alloy are added, and then secondary refining treatment is conducted; and the mixed melt is subjected to die-casting treatment, and the Al-Si series die-casting aluminum alloy based on the secondary aluminum is obtained. The high-strength aluminum alloy material comprises the following components in percentage by mass: 6%-12% of Si, 0.1%-1% of Fe, 0.4%-3% of Mg, 0%-0.1% of Sr, 0%-0.3% of Ti, 0%-0.05% of B and 0%-2.5% of Ni.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloys, and in particular to an Al-Si series die-casting aluminum alloy based on recycled aluminum, a preparation method thereof, and a structural part. Background Art

[0002] The energy consumption of recycled aluminum production is only 4.9% of that of primary aluminum, and the carbon emissions are only 4.2% of that of primary aluminum, making recycled aluminum's "energy saving and emission reduction" advantages obvious. However, recycled aluminum accounts for about 20% of my country's aluminum production, while Japan's recycled aluminum production accounted for nearly 100% in 2019. Therefore, there is huge room for improvement in my country's recycled aluminum production.

[0003] The difficulty in using recycled aluminum lies in the excessive content of many elements such as Fe and Mn, as well as the high content of impurities such as oxide slag and organic matter, making it difficult to compare the performance with that of primary aluminum. Specifically, Fe impurities will form coarse needle-shaped or flaky β-iron-rich phases, which will seriously split the aluminum matrix; Mn will sharply reduce the conductivity of aluminum alloys, causing a sharp drop in the conductivity of aluminum castings, and will also reduce the plasticity of aluminum alloys; oxide slag and organic matter will also reduce the mechanical properties and electrical conductivity of aluminum alloys. The presence of the above impurities greatly restricts the recycling of recycled aluminum and the sustainable development of aluminum resources.

[0004] Therefore, there is an urgent need for a method for preparing aluminum alloys by reusing recycled aluminum. Summary of the invention

[0005] In view of the above-mentioned defects of the prior art, the present invention provides a method for preparing an Al-Si series die-casting aluminum alloy based on recycled aluminum, aiming to provide an Al-Si series die-casting aluminum alloy based on recycled aluminum with excellent comprehensive performance.

[0006] The present invention provides a method for preparing an Al-Si series die-casting aluminum alloy based on recycled aluminum, comprising the following steps: Heating the recycled aluminum to obtain a recycled aluminum melt; The temperature is adjusted to 740-860° C., and industrial silicon, steel waste, and Ni are added to the recycled aluminum melt to obtain a mixed melt; performing a boronization treatment and a first refining treatment on the mixed melt; The temperature is adjusted to 710-780° C., and after adding magnesium alloy scrap, Sr, and Al—Ti—B alloy to the mixed melt after the first refining treatment, the mixed melt is subjected to a second refining treatment; and The components and contents in the mixed melt after the second refining treatment are measured. When the components and contents in the mixed melt after the second refining treatment meet the standards, the mixed melt is die-casted to obtain an Al-Si die-casting aluminum alloy based on recycled aluminum, wherein the Al-Si die-casting aluminum alloy based on recycled aluminum contains 6-12% Si by mass, 0.1-1% Fe by mass, 0.4-3% Mg by mass, 0-0.1% Sr by mass, 0-0.3% Ti by mass, 0-0.05% B by mass, and 0-2.5% Ni by mass.

[0007] Furthermore, the preparation method of the Al-Si die-casting aluminum alloy based on recycled aluminum also includes the step of adding RE, Mo, Co and Be to the recycled aluminum melt, and the mass percentage content of Mn in the Al-Si die-casting aluminum alloy based on recycled aluminum is 0.0001-0.1%, the mass percentage content of Cr is 0.0001-0.2%, the mass percentage content of RE is 0.001-0.2%, the mass percentage content of Mo is 0-0.3%, the mass percentage content of Co is 0-0.5%, and the mass percentage content of Be is 0-0.2%.

[0008] Furthermore, the preparation method of the Al-Si die-casting aluminum alloy based on recycled aluminum also includes the step of adding Mn, Cr, RE, Mo, Co and Be to the recycled aluminum melt, wherein the mass percentage content of Mn is 0.0001-0.2%, the mass percentage content of Cr is 0.001-0.3%, the mass percentage content of RE is 0.01-0.2%, the mass percentage content of Mo is 0-0.3%, the mass percentage content of Co is 0-0.5%, and the mass percentage content of Be is 0-0.2%.

[0009] Furthermore, the preparation method of the Al-Si series die-casting aluminum alloy based on recycled aluminum also includes the step of adding at least one of Cu, Zr, Ca, Te, Ag, Sb, Bi, and Nb to the recycled aluminum melt, wherein the mass percentage content of Cu is 0.0001-1%, the mass percentage content of Zr is 0.0001-0.5%, the mass percentage content of Ca is 0.0001-0.3%, the mass percentage content of Te is 0-0.2%, the mass percentage content of Ag is 0-0.2%, the mass percentage content of Sb is 0-0.5%, the mass percentage content of Bi is 0-0.2%, and the mass percentage content of Nb is 0-0.5%.

[0010] Furthermore, the method for preparing the Al-Si series die-casting aluminum alloy based on recycled aluminum also includes the step of surface treatment of the mold, wherein the surface treatment is to form a boron carbide layer on the parting surface of the mold.

[0011] Furthermore, at least one of the following conditions is met: The boronizing agent for the boronizing treatment is potassium fluoroborate and / or aluminum boron alloy; The mass ratio of the boronizing agent to the mixed melt in the boronizing treatment is 0.001-0.005:1; The temperature of the first refining treatment is 740-800°C and the time is 20-60min; The refining agent of the first refining treatment is at least one of chloride salt, fluoride salt, and rare earth; The mass ratio of the refining agent to the mixed melt in the first refining treatment is 0.0001-0.0005:1; The temperature of the second refining treatment is 690-750°C and the time is 10-40min; The refining agent of the second refining treatment includes at least one of chloride salt, fluoride salt, and rare earth; The mass ratio of the refining agent to the mixed melt in the second refining treatment is 0.001-0.2:1.

[0012] Furthermore, after the mixed melt is subjected to die-casting to obtain an aluminum alloy part, the method for preparing an Al-Si series die-casting aluminum alloy based on recycled aluminum further comprises the step of performing an aging treatment on the aluminum alloy part, wherein: The aging treatment is performed at a temperature of 150-250°C and a time of 0.05-30h; or The aging treatment includes a primary low-temperature electric field aging treatment and a secondary high-temperature aging treatment, wherein the temperature of the primary low-temperature electric field aging treatment is 50-120°C, the time is 0.1-100h, and the electric field strength is 2-50kV / cm; the temperature of the secondary high-temperature aging treatment is 140-250°C, and the time is 0.1-50h.

[0013] The present invention also provides an Al-Si die-casting aluminum alloy based on recycled aluminum, which contains Al, and also contains Si with a mass percentage content of 6-12%, Fe with a mass percentage content of 0.1-1%, Mg with a mass percentage content of 0.4-3%, Sr with a mass percentage content of 0-0.1%, Ti with a mass percentage content of 0-0.3%, B with a mass percentage content of 0-0.05%, and Ni with a mass percentage content of 0-2.5%.

[0014] Furthermore, the Al-Si die-casting aluminum alloy based on recycled aluminum also contains at least one of Cu, Mn, Cr, V, Ca, RE, Mo, Co, Be, Zr, Te, Ag, Sb, Bi, and Nb, wherein the mass percentage content of Cu is 0.0001-1%, the mass percentage content of V is 0.005-0.2%, the mass percentage content of Ca is 0.0001-0.3%, the mass percentage content of Zr is 0.0001-0.5%, the mass percentage content of Te is 0-0.2%, the mass percentage content of Ag is 0-0.2%, the mass percentage content of Sb is 0-0.5%, the mass percentage content of Bi is 0-0.2%, the mass percentage content of Nb is 0-0.5%, the mass percentage content of SiC is 0-1%, the mass percentage content of TiC is 0-1%, and the mass percentage content of BN is 0-0.5%.

[0015] The present invention also provides a structural part, the material of which is the Al-Si die-casting aluminum alloy based on recycled aluminum obtained by the preparation method of the Al-Si die-casting aluminum alloy based on recycled aluminum, or the Al-Si die-casting aluminum alloy based on recycled aluminum.

[0016] In the technical solution of the present invention, industrial silicon, steel waste and magnesium alloy waste are used as the main raw materials, which can greatly reduce the cost; and then Sr, Al-Ti-B alloy and Ni alloy elements are added, combined with multiple refining treatments and boronization treatments, an Al-Si series die-casting aluminum alloy based on recycled aluminum with excellent comprehensive performance can be obtained. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] The present invention provides a method for preparing an Al-Si series die-casting aluminum alloy based on recycled aluminum, comprising the following steps: Heating the recycled aluminum to obtain a recycled aluminum melt; The temperature is adjusted to a high temperature, about 740-860° C., and industrial silicon, steel waste, and Ni are added to the recycled aluminum melt to obtain a mixed melt; performing a boronization treatment and a first refining treatment on the mixed melt; The temperature is adjusted to 710-780° C., and after adding magnesium alloy scrap, Sr, and Al-Ti-B alloy to the mixed melt after the first refining treatment, the mixed melt is subjected to a second refining treatment, a slag removal treatment, a degassing treatment, and a standing treatment, and after the standing treatment, the surface scum is scraped off; and The components and contents of the mixed melt after the static treatment are measured. When the components and contents of the mixed melt after the static treatment meet the standards, the mixed melt after the static treatment is subjected to die casting to obtain an Al-Si die-casting aluminum alloy based on recycled aluminum. The Al-Si die-casting aluminum alloy based on recycled aluminum contains Si with a mass percentage content of 6-12%, Fe with a mass percentage content of 0.1-1%, Mg with a mass percentage content of 0.4-3%, Sr with a mass percentage content of 0-0.1%, Ti with a mass percentage content of 0-0.3%, B with a mass percentage content of 0-0.05%, and Ni with a mass percentage content of 0-2.5%.

[0019] It can be understood that at high temperatures of 740-860°C, organic matter can be effectively removed.

[0020] The mass percentage content of Si may be 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, or 12%.

[0021] The mass percentage content of Fe may be 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, or 1%.

[0022] The mass percentage content of Mg may be 0.4%, 0.45%, 0.45%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.78%, 0.85%, 0.9%, 0.95%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, or 3%.

[0023] The mass percentage content of Sr may be 0.001%, 0.005%, 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, 0.055%, 0.06%, 0.065%, 0.07%, 0.075%, 0.08%, 0.085%, 0.09%, 0.095%, or 0.1%.

[0024] The mass percentage content of Ti may be 0.001%, 0.005%, 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, 0.055%, 0.06%, 0.065%, 0.07%, 0.075%, 0.08%, 0.085%, 0.09%, 0.095%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, or 0.3%.

[0025] The mass percentage content of B may be 0.001%, 0.005%, 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, or 0.05%.

[0026] The mass percentage content of Ni may be 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.45%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.78%, 0.85%, 0.9%, 0.95%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, or 2.5%.

[0027] The mass ratio of the recycled aluminum, industrial silicon, steel waste, and magnesium alloy waste can be 84-93.5:6-12:0.1-1:0.4-3. When adding industrial silicon, steel waste, and magnesium alloy waste to the recycled aluminum melt, the burnout rate of industrial silicon, steel waste, and magnesium alloy waste must be considered to ensure that the components and contents of the mixed melt after refining meet the standards. The components and contents of the mixed melt can be analyzed by spectroscopy. When the components and contents of the mixed melt do not meet the standards, the corresponding content of elements can be added or a second refining treatment and slag removal treatment can be performed again until the standards are met. Furthermore, the standards for the components and contents in the mixed melt are: 6-12% Si by mass, 0.1-1% Fe by mass, 0.4-3% Mg by mass, 0-0.1% Sr by mass, 0-0.3% Ti by mass, 0-0.05% B by mass, and 0-2.5% Ni by mass.

[0028] When the content of impurity elements in the mixed melt is too high and does not meet the standard, the content of the impurities can be diluted by adding pure Al ingots to the mixed melt to make the content lower than the standard.

[0029] When the mixed melt is cooled to 680-700°C, the mixed melt is subjected to die casting. The die temperature of the die casting process can be 220-300°C, and the die casting speed can be 0.23-2.5m / s. The die used in the die casting process includes a movable die and a fixed die, and both the movable die and the fixed die are formed with a parting surface, and the two parting surfaces jointly form a cavity for accommodating the mixed melt, and an aluminum alloy product with a certain shape is formed. Before the die casting process, both parting surfaces can be surface treated, and the surface treatment is to form a boron carbide layer on the parting surface, and the boron carbide layer can not only improve the demoulding performance, but also improve the wear resistance of the mold, and can resist the erosion of chemical substances such as acid, alkali, and salt and the thermal erosion of aluminum alloy, to extend the service life of the mold. The thickness of the boron carbide layer can be 1-10mm, specifically 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, or 10mm.

[0030] The surface treatment may be: mixing a boron-containing gas (such as BCl3) and a carbon-containing gas (such as CH4) to obtain a mixed gas; introducing the mixed gas into the cavity, and using a chemical vapor deposition method, the boron-containing gas and the carbon-containing gas react chemically and are deposited on the parting surface to generate a boron carbide layer. The temperature of the chemical vapor deposition method is 900-1200°C, the deposition pressure is 200-500pa, and the carrier gas flow rate is 100-200sccm.

[0031] During the die-casting process, the boron carbide layer can make the hardness of the mold steel reach 3000-4000 Hv; the boron carbide layer can reduce the affinity of the mixed melt to the mold surface, improve the demoulding performance of the aluminum alloy, and can be demoulded smoothly even without adding Fe and Mn, which greatly improves the elongation of the aluminum alloy; the boron carbide layer can resist the erosion of chemical substances such as acids, alkalis, and salts, and can improve the corrosion resistance of the aluminum alloy; the boron carbide layer can still maintain good physical and chemical properties under high temperature environment, and can improve the thermal stability of the aluminum alloy; the boron carbide layer has an extremely low friction coefficient, improves the surface smoothness of the aluminum alloy, and can significantly reduce the wear and energy consumption of the aluminum alloy product caused by mechanical friction; the boron carbide layer also has a high heat transfer property. At the moment of aluminum alloy forming, the boron carbide layer can quickly conduct heat away, improve the heat transfer speed of the mold, and the heat transfer speed is 2-4 times that of the heat transfer speed of ordinary molds, so that the formed aluminum alloy can be cooled faster and the structure is more refined, thereby improving the strength and elongation of the aluminum alloy.

[0032] In one embodiment, the aging treatment temperature is 150-250°C, and the time is 0.05-30h. The aging treatment temperature can be 150°C, 200°C, or 250°C, and the time can be 0.05h, 1h, 5h, 10h, 15h, 20h, 25h, or 30h.

[0033] In another embodiment, the aging treatment includes a primary low-temperature electric field aging treatment and a secondary high-temperature aging treatment. The temperature of the primary low-temperature electric field aging treatment is 50-120°C, the time is 0.1-100h, and the electric field strength is 2-50kV / cm. The temperature of the primary low-temperature electric field aging treatment can be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, or 120°C, and the time can be 0.1h, 0.5h, 1h, 5h, 10h, 15h, 20h, 25h, 30h, 35h, 40h, 45h, 5 The secondary high temperature aging treatment has no electric field effect, and its temperature is 140-250°C and the time is 0.1-50h. The temperature of the secondary high temperature aging treatment may be 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, or 250°C, and the time may be 0.1h, 0.5h, 1h, 5h, 10h, 15h, 20h, 25h, 30h, 35h, 40h, 45h, or 50h.

[0034] During the first-level low-temperature electric field aging treatment, the low temperature of 50-120°C can inhibit the segregation of atoms such as Mg, Cu, Ni, Zn and Si, and at the same time make the alloy produce a greater degree of supercooling, significantly increase the range of the GP zone, facilitate the subsequent high-temperature process nucleation rate to increase, and the alloy elements can be more fully precipitated. Secondly, since the application of an electric field at low temperature reduces the precipitation activation energy of the phase in the alloy, the low-temperature electric field aging can accelerate the precipitation nucleation rate of the precipitate phase during the aging process and increase the volume fraction of the nucleation point. The hardness of the alloy increases significantly at the beginning of the electric field aging. During the subsequent second-level high-temperature aging treatment, the time required for the alloy to reach the peak hardness is shortened, the volume fraction of the precipitate phase is increased, and the size of the precipitate phase is refined. With the increase of the electric field intensity during the first-level low-temperature electric field aging treatment, the number of strengthening phase nucleation points precipitated in the alloy increases sharply, indicating that increasing the electric field intensity can increase the nucleation precipitation rate of the precipitate phase, and has no obvious effect on the growth of the second-level high-temperature aging phase without the action of the electric field, and no size coarsening will occur.

[0035] The degassing treatment is to introduce an inert gas into the mixed melt, and the inert gas may be helium, neon, argon, krypton, or nitrogen. The degassing treatment time may be 10-15 minutes, and the gas pressure may be 0.2-0.4 MPa. The standing treatment time may be 20-30 minutes. Inert gas is introduced into the mixed melt, and the mixed melt is degassed and stood, and the gas can be separated from the mixed melt, thereby reducing the bubble content in the mixed melt, ensuring that high-quality aluminum alloy can be cast.

[0036] The boronizing agent for the boronization treatment is potassium fluoroborate and / or aluminum boron alloy. The ratio of the aluminum boron alloy is 0.001-0.005:1, specifically 0.001:1, 0.002:1, 0.003:1, 0.004:1, or 0.005:1.

[0037] In one embodiment, the boronizing agent includes 20-80 wt % of potassium fluoroborate and 20-80 wt % of aluminum boron alloy.

[0038] The temperature of the first refining treatment is 740-800°C, specifically 740°C, 750°C, 760°C, 770°C, 780°C, 790°C, or 800°C, and the time is 20-60min, specifically 20min, 30min, 40min, 50min, 60min. The refining agent of the first refining treatment can be at least one of chloride salt, fluoride salt, and rare earth. The chloride salt is at least one of sodium chloride, potassium chloride, and lithium chloride. The fluoride salt can be at least one of potassium fluoride, calcium fluoride, potassium fluoroborate, and sodium aluminum fluoride. The rare earth can be at least one of La, Ce, Pr, Nd, Er, Sm, Y, Sc, and Gd. The mass ratio of the refining agent to the mixed melt in the first refining treatment is 0.0001-0.0005:1, specifically 0.0001:1, 0.0002:1, 0.0003:1, 0.0004:1, or 0.0005:1. The first refining treatment can simultaneously perform the functions of refining and refining, thereby improving the strength and elongation of the aluminum alloy. Specifically, chloride salts and fluoride salts can improve the strength of the aluminum alloy, and rare earth can improve the elongation of the aluminum alloy.

[0039] In one embodiment, the refining agent of the first refining process includes 10-80 wt % of chloride salt, 10-80 wt % of fluoride salt, and 1-20 wt % of rare earth.

[0040] The temperature of the second refining treatment is 690-750°C, specifically 690°C, 700°C, 710°C, 720°C, 730°C, 740°C, or 750°C, and the time is 10-40min, specifically 10min, 20min, 30min, or 40min. The mass ratio of the refining agent to the mixed melt of the second refining treatment is 0.001-0.2:1, specifically 0.001:1, 0.005:1, 0.01:1, 0.05:1, 0.1:1, 0.15:1, or 0.2:1. The second refining treatment can simultaneously perform the functions of refining and refining, thereby improving the strength and elongation of the aluminum alloy. Specifically, chloride salts and fluoride salts can improve the strength of the aluminum alloy, and rare earth can improve the elongation of the aluminum alloy.

[0041] The refining agent of the second refining treatment may be at least one of chloride salt, fluoride salt, and rare earth. The chloride salt is at least one of sodium chloride, potassium chloride, and lithium chloride. The fluoride salt may be at least one of potassium fluoride, calcium fluoride, potassium fluoroborate, and sodium aluminum fluoride. The rare earth may be at least one of La, Ce, Pr, Nd, Er, Sm, Y, Sc, and Gd. In one embodiment, the refining agent of the first refining treatment includes 10-80wt% of chloride salt, 10-80wt% of fluoride salt, and 1-20wt% of rare earth.

[0042] Recycled aluminum is an aluminum alloy obtained by remelting waste aluminum and waste aluminum alloy materials, or remelting aluminum-containing waste materials. Recycled aluminum can include recycled cast aluminum alloy and recycled deformed aluminum alloy. The impurity content in recycled cast aluminum alloy is higher than that in recycled deformed aluminum alloy, but the price is lower. This application can use recycled cast aluminum alloy to reduce costs and obtain better performance, and can also use recycled deformed aluminum alloy.

[0043] Fe, Si, Cu, Mn, Ti, Cr, V, Mg, Zn, and Pb are impurities in recycled aluminum. In recycled cast aluminum alloy raw materials, Al≥80wt%, Fe is 1.2-4wt%, Si is 1-20wt%, Cu≤6wt%, Mn≤1wt%, Ti≤0.2wt%, Cr≤0.3wt%, V≤0.3wt%, Mg≤8wt%, Zn≤8wt%, Pb≤0.2wt%, and organic matter≤0.2wt%. In recycled deformed aluminum alloy, Al≥95wt%, Fe is 0.2-1wt%, Si≤5wt%, Cu≤1wt%, Mg≤3wt%, Mn≤0.3wt%, Ti≤0.3wt%, Cr≤0.3wt%, V≤0.3wt%, Zn≤6wt%, Pb≤0.2wt%, and organic matter≤0.2wt%.

[0044] Recycled aluminum can be pre-processed, such as sorting, crushing, magnetic separation and iron removal, cleaning, etc. The composition and content of recycled aluminum can also be tested, and the composition and content of recycled aluminum can be tested by photoelectric direct reading spectrometer or chemical analysis method. In this way, recycled aluminum with similar composition and content can be mixed together according to the test results to avoid the situation that the mixed recycled aluminum has too complex composition, excessive content of certain elements, and substandard content of certain elements.

[0045] Industrial silicon may include Si1101, Si2202, Si3303, Si4110, Si4210, Si4410, Si5210, Si5530, etc. Fe, Ca, Al, Mn, Ti, Cr, and V, etc. are impurities in industrial silicon.

[0046] In Si1101, Si≥99.79wt%, Fe≤0.10wt%, Al≤0.1wt%, Ca≤0.01wt%, Mn≤0.3wt%, Ti≤0.1wt%, Cr≤0.1wt%, V≤0.1wt%; In Si2202, Si≥99.58wt%, Fe≤0.2wt%, Al≤0.2wt%, Ca≤0.02wt%, Mn≤0.3wt%, Ti≤0.1wt%, Cr≤0.1wt%, V≤0.1wt%; In Si3303, Si≥99.37wt%, Fe≤0.3wt%, Al≤0.3wt%, Ca≤0.03wt%, Mn≤0.3wt%, Ti≤0.1wt%, Cr≤0.1wt%, V≤0.1wt%; In Si4110, Si≥99.40wt%, Fe≤0.4wt%, Al≤0.1wt%, Ca≤0.1wt%, Mn≤0.3wt%, Ti≤0.1wt%, Cr≤0.1wt%, V≤0.1wt%; In Si4210, Si≥99.30wt%, Fe≤0.4wt%, Al≤0.2wt%, Ca≤0.1wt%, Mn≤0.3wt%, Ti≤0.1wt%, Cr≤0.1wt%, V≤0.1wt%; In Si4410, Si≥99.10wt%, Fe≤0.4wt%, Al≤0.4wt%, Ca≤0.1wt%, Mn≤0.3wt%, Ti≤0.1wt%, Cr≤0.1wt%, V≤0.1wt%; In Si5210, Si≥99.20wt%, Fe≤0.5wt%, Al≤0.2wt%, Ca≤0.1wt%, Mn≤0.3wt%, Ti≤0.1wt%, Cr≤0.1wt%, V≤0.1wt%; In Si5530, Si≥98.70wt%, Fe≤0.5wt%, Al≤0.5wt%, Ca≤0.3wt%, Mn≤0.3wt%, Ti≤0.1wt%, Cr≤0.1wt%, and V≤0.1wt%.

[0047] In steel waste, Fe is 95-97wt%, C is 0.04-2.3wt%, Si is 0.04-2.3wt%, Mn is 0.04-2.3wt%, P is 0.04-2.3wt%, S is 0.04-2.3wt%, Sn≤0.6wt%, Ti≤0.1wt%, Cr≤0.1wt%, V≤0.1wt%. C, Si, Mn, Ti, Cr, V, P, Sn, and S are impurities in steel waste.

[0048] In magnesium alloy waste, Mg is 96.8-99.9wt%, Al is 1-3wt%, Zn is 0.1-1wt%, Mn≤0.1wt%, Ti≤0.1wt%, and Zr≤0.1wt%. Al, Zn, Mn, Ti, and Zr are impurities in magnesium alloy waste.

[0049] Waste recycling can not only save costs, but also achieve the sustainable development of aluminum resources, magnesium resources, silicon resources and iron resources. Since most of the raw materials are waste materials or recycled raw materials, more types of impurities with high total content will be introduced into the present invention, which has the disadvantages of more types of impurities and higher total impurity content. Of course, it is not ruled out that a certain impurity or several impurities have high content and are difficult to remove. When the present invention uses recycled aluminum, industrial silicon, steel waste, and magnesium alloy waste as raw materials, at least the following elements will be introduced: Al, Fe, Si, Cu, Mn, Ti, Cr, V, Mg, Zn, Zr, Pb, Ca, C, P, Sn, and S, etc. When recycled aluminum, industrial silicon, steel waste, and magnesium alloy waste are used as raw materials and Zn, Zr, Cu, Mn, Cr, V, and Ca are not added to the recycled aluminum melt, the Al-Si series die-casting aluminum alloy based on recycled aluminum may contain a mass percentage content of 0.0001-0.2% Zn, 0.0001-0.1% Zr, 0.0001-0.2% Cu, 0.0001-0.1% Mn, 0.0001-0.2% Cr, 0.0001-0.1% V, and 0.0001-0.1% Ca. Of course, at least one step of Zn, Zr, Cu, Mn, Cr, V, and Ca may be added to the recycled aluminum melt to increase the content of the added elements.

[0050] The preparation method of Al-Si series die-casting aluminum alloy based on recycled aluminum of the present invention uses recycled aluminum, industrial silicon, steel waste, and magnesium alloy waste as raw materials to reduce costs. The addition of a certain content of Sr, B, Ti, and Ni raw materials, combined with multiple refining treatments, boronization treatments, and aging treatments, can achieve better comprehensive performance. Specifically: (1) Industrial silicon can provide Si. When the mass percentage of Si is 6-12%, it can improve the fluidity and density of aluminum alloy, thereby improving the forming performance and mechanical properties of aluminum alloy; when the mass percentage of Si is 6-9%, the elongation is higher, but the strength is lower; when the mass percentage of Si is 9-12%, the strength is higher, but the elongation is lower; when the mass percentage of Si exceeds 12%, coarse elemental Si will appear, which will sharply reduce the elongation of aluminum alloy; (2) Iron and steel scraps can provide Fe. When the mass percentage of Fe is 0.1-1%, Fe can reduce the sticking tendency of aluminum alloy castings and improve the forming performance of aluminum alloys. Fe can react with other elements to form a second phase to avoid the adverse effect of Fe and other elements dissolved in the aluminum matrix on the thermal conductivity of aluminum alloys. Specifically, Fe can react with Al, Si, Mg, Cu, Mn, Ni, B, etc. to form Al3Fe, AlFeSi, AlFeMgSi, AlFeSiCu, AlFeSiNi, AlFeMgSiNi, AlFeMnSi, FeNiAl9, AlFeSiB and other second phases. However, the presence of β-iron-rich phase in the aluminum matrix will reduce the elongation and thermal conductivity of aluminum alloys. (3) Magnesium alloy scrap can provide Mg. When the mass percentage of Mg is 0.4-3%, Mg can greatly improve the mechanical properties of aluminum alloy. Mg can react with other elements to form a second phase to avoid the adverse effect of Mg element dissolved in the aluminum matrix on the thermal conductivity of aluminum alloy. Specifically, Mg can react with Al, Fe, Si, Cu, Zn, B, Ni, etc. to form second phases such as MgB, Mg2Si, Mg2Zn, Mg2SiZn, (CuMg)Al2, AlFeMgSi, AlFeMgSiNi, etc. Mg can also promote the precipitation of second phases such as CuAl2, AlFeSiCu, Al2CuZn, (CuMg)Al2, increase their volume fraction and dispersion, reduce the solid solubility of the above elements in the aluminum matrix, and improve the thermal conductivity of aluminum alloy. (4) The mass percentage of Sr is not more than 0.1%. Sr can be modified through heterogeneous nucleation theory or twin valley mechanism to refine grains, second phases such as eutectic silicon, and precipitation phases to improve the elongation and thermal conductivity of aluminum alloys; Sr can also transform β-AlFeSi phase into Chinese character α-AlFeSi phase to improve the mechanical properties of aluminum alloys; Sr can also promote the precipitation of CuAl2, Mg2Si and other phases to reduce the solid solubility of these alloying elements in the aluminum matrix to improve the thermal conductivity of aluminum alloys; (5) The mass percentage content of Ti is not more than 0.3%. Ti can improve the strength and elongation of aluminum alloys. Specifically, the TiAl2 phase generated by the reaction of Ti and Al can serve as a non-spontaneous core during crystallization, which can refine the grains, second phases and precipitated phases to improve the strength and elongation of aluminum alloys; (6) The mass percentage content of B is not more than 0.05%. B can transform the β-AlFeSi phase into the Chinese character α-AlFeSi phase to improve the mechanical properties of the aluminum alloy; B can remove / improve the Fe phase and remove Mn+Ti+V+Cr through boriding reaction to purify the mixed solution, thereby improving the elongation and thermal conductivity of the aluminum alloy; B can also refine the grains and modify and refine the elemental Si to further improve the strength and elongation of the aluminum alloy; B can also react with other elements to form a second phase to avoid the adverse effect of B dissolved in the aluminum matrix on the thermal conductivity of the aluminum alloy. Specifically, B can react with Al, Fe, Si, Mg, Cu, etc. to form second phases such as AlFeSiB, MgB, CuB, etc.; B can also inhibit the segregation of Ti3Al. When Ti and B are used together, the effect is better, which significantly improves the strength and elongation of the aluminum alloy; (7) The mass percentage of Ni is not more than 2.5%. Ni can refine grains, form second phases and precipitate phases to improve the elongation of aluminum alloys. Ni can react with other elements to form second phases to avoid the adverse effect of Ni dissolved in the aluminum matrix on the thermal conductivity of aluminum alloys. Specifically, Ni can react with Al, Fe, Mg, Si, etc. to form second phases such as Al3Ni, AlFeSiNi, AlFeMgSiNi, FeNiAl9, etc. Ni can also promote the precipitation of phases such as CuAl2 and (CuMg)Al2, increase the volume fraction and dispersion of the precipitated phases, reduce the solubility of alloying elements in the aluminum matrix, and improve the thermal conductivity of aluminum alloys. Ni can promote the precipitation of Cu and Mg to improve the thermal conductivity and mechanical properties of aluminum alloys. The Mg content and the Ni content can be proportional. When the Mg content is high, the Ni content can also be set higher to generate more AlFeMgSiNi dispersed second phases to significantly improve the strength of the aluminum alloy. (8) The two refining treatments and the boronization treatment can remove impurity elements such as oxide slag and organic matter, and can also remove low melting point impurity elements such as Pb, Sn, Fe, Mn, C, P, S and other impurities, so that the content of Pb, Sn, C, P and S is reduced to below 0.001% or even 0%, thereby preventing Pb, Sn, coarse β-Fe, Mn, C, P, S and the like from affecting the strength, elongation and thermal conductivity of the aluminum alloy; (9) The aging treatment can further improve the strength, elongation and thermal conductivity of the aluminum alloy.

[0051] In summary, the present invention adds a certain amount of industrial silicon, steel waste, magnesium alloy waste, Sr, B, Ti, and Ni to the recycled aluminum melt, and Si, Fe, Mg, Sr, B, Ti, and Ni interact with each other as a whole. After multiple refining treatments, boronization treatments, and aging treatments, an Al-Si series die-casting aluminum alloy based on recycled aluminum with excellent comprehensive performance can be obtained. The Al-Si series die-casting aluminum alloy based on recycled aluminum has a tensile strength of not less than 420MPa, a yield strength of not less than 330MPa, an elongation of not less than 9%, and a thermal conductivity of not less than 160W / mK. The tensile strength, yield strength, elongation, and thermal conductivity of the Al-Si die-cast aluminum alloy based on recycled aluminum are greater than the tensile strength (usually 250-280 MPa), yield strength (usually 130-150 MPa), elongation (usually 4-5%), and thermal conductivity (usually 110-120 W / mK) of the recycled aluminum alloy, and has better comprehensive performance.

[0052] Transition metal elements, such as Mn, Ti, Cr, V, etc., have a great influence on the thermal conductivity of aluminum alloys. They are usually restricted as impurities to be added to aluminum alloys with high requirements for high thermal performance. Excessive impurity content or impurity treatment will also reduce the elongation of aluminum alloys. The Al-Si series die-casting aluminum alloy based on recycled aluminum of the present invention uses recycled aluminum, industrial silicon, steel waste, and magnesium alloy waste as raw materials. These low-priced raw materials inevitably contain the above-mentioned Mn, Ti, Cr, and V impurities, and the situation in which at least one of Mn, Ti, Cr, and V has a high content is not excluded. It will cost more to completely remove or reduce the above-mentioned impurities to a lower level (reduced to less than 0.001wt% or even less than 0.0001wt%). In order not to increase the cost, some impurities are usually not completely removed or reduced to a lower level, which is also the reason why many aluminum alloys using recycled aluminum as raw materials have low elongation and thermal conductivity. However, the present application uses industrial silicon, steel waste, and magnesium alloy waste as raw materials, and cooperates with two refining treatments and boronization treatment, and the combined effects of Sr, B, Ti, and Ni to produce Al-Si die-cast aluminum alloys with excellent comprehensive performance. There is no need to use Mn, Ti, Cr, and V as impurities, nor is there any need to remove Mn, Ti, Cr, and V. On the basis of controlling costs, Al-Si die-cast aluminum alloys with excellent comprehensive performance are obtained. Among them, Ti, Cr, and V can be used as strengthening elements to improve the strength of aluminum alloys, and Mn can improve the coarse β-Fe to improve the elongation of aluminum alloys.

[0053] It is understandable that Fe, Mn, Ti, V, and Cr in aluminum alloys will cause a sharp drop in thermal conductivity. During the boriding treatment, B and Fe, Mn, Ti, V, and Cr can form insoluble borides with a large specific gravity, which can be precipitated and removed; at the same time, Fe, Mn, Ti, V, and Cr dissolved in aluminum can also form compounds that gather on the grain boundaries, greatly improving the mechanical properties and electrical conductivity. However, compared with alloys without Fe, Mn, Ti, V, and Cr, although the mechanical properties are improved, the thermal conductivity is still reduced.

[0054] In one embodiment, RE, Mo, Co, and Be elements can be added to the mixed melt. RE can be at least one of La, Ce, Pr, Nd, Er, Sm, Y, Sc and Gd. Of course, one or more of RE, Mo, Co, and Be elements can also be added. The coordination of Mn, Cr, RE, Mo, Co, Be, and Sr elements can not only reduce the maximum solubility of each other in the aluminum matrix to improve thermal conductivity, but also promote the reaction of Mn and Fe. Mn can occupy the position of Fe element in the second phase, making the Fe-containing phase more dispersed and fine, and promoting the effect of metamorphic Fe. Mn, Cr, RE, Mo, Co, Be, and Sr elements can also generate a fine and dispersed α-Al(MnFeX)Si phase (where X is at least one of Cr, RE, Mo, Co, Be, and Sr) to improve the elongation and thermal conductivity of the aluminum alloy. At this time, in the Al-Si series die-casting aluminum alloy based on recycled aluminum, the mass percentage content of Mn can be 0.0001-0.1%, specifically 0.0001%, 0.0002%, 0.0003%, 0.0004%, 0.0005%, 0.0006%, 0.0007%, 0.0008%, 0.0009%, 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.0 0.07%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%; the mass percentage content of Cr may be 0.0001-0.2%, specifically 0.0001%, 0.0005%, 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007% , 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%; the mass percentage content of RE can be 0.001-0.2%, specifically 0.001%, 0. 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%; the mass percentage content of Mo can be 0-0.3%, specifically 0.0005%, 0.0006%, 0.0007%, 0.0008%, 0.0009%, 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14% , 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, or 0.3%; the mass percentage content of Co can be 0-0.5%, specifically 0.0001%, 0.0005%, 0.0006%, 0.0007%, 0.0008%, 0.00 0.09%, 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%; the mass percentage content of Be can be 0-0.2%, specifically 0.0001%, 0.0005%, 0. 0.0006%, 0.0007%, 0.0008%, 0.0009%, 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%. .

[0055] When Mn, Cr, RE, Mo, Co, Be, and Sr elements cooperate with each other, Mn and Cr may not be impurities of high thermal conductivity aluminum alloy. Mn and Cr, when combined with RE, Mo, Co, Be, and Sr, improve the elongation and thermal conductivity of aluminum alloy. Of course, Mn and Cr can also be added to the mixed melt as raw materials, or Mn may not be added. In this case, the mass percentage content of Mn in the Al-Si series die-casting aluminum alloy based on recycled aluminum is 0.0001-0.2%, specifically 0.0001%, 0.0002%, 0.0003%, 0.0004%, 0.0005%, 0.0006%, 0.0007%, 0.0008%, 0.0009%, 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.0 2%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%; the mass percentage content of Cr is 0.001-0.3%, specifically 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05 %, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, or 0.3%; the mass percentage content of RE is 0.01-0.2%, specifically 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0. .15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%; the mass percentage content of Mo can be 0-0.3%, specifically 0.0005%, 0.0006%, 0.0007%, 0.0008%, 0.0009%, 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, or 0.3%; the mass percentage content of Co may be 0-0.5%, specifically 0.0001%, 0.0005%, 0.0006%, 0.0007%, 0.0008%, 0.0009%, 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3% , 0.35%, 0.4%, 0.45%, or 0.5%; the mass percentage content of Be can be 0-0.2%, specifically 0.0001%, 0.0005%, 0.0006%, 0.0007%, 0.0008%, 0.0009%, 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%. .

[0056] In the Al-Si die-cast aluminum alloy based on recycled aluminum, when the mass percentage content of Ni reaches more than 2%, a primary Al-Ni-Cu ternary compound and a eutectic Al-Ni-Cu ternary compound will be formed in the aluminum alloy structure, which can greatly improve the thermal conductivity and strength of the aluminum alloy. If the Al-Si die-cast aluminum alloy based on recycled aluminum also contains Mn (Mn can come from waste), a eutectic Al-Si-Cu-Ni-Mn quinary compound will also be crystallized, reducing the solid solubility of Mn in the matrix, further improving the thermal conductivity and strength of the aluminum alloy.

[0057] The method for preparing the high-strength Al-Si die-casting aluminum alloy further comprises the step of adding at least one of SiC, AlTiC, and BN to the recycled aluminum melt. In the high-strength Al-Si die-casting aluminum alloy, the mass percentage content of SiC is 0.1-8%, the mass percentage content of AlTiC is 0.1-8%, and the mass percentage content of BN is 0.1-0.5%. The mass percentage content of SiC and AlTiC can be specifically 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, and 8%. The mass percentage content of BN can be specifically 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, 0.3%, 0.31%, 0.32%, 0.33%, 0.34%, 0.35%, 0.36%, 0.37%, 0.38%, 0.39%, 0.4%, 0.41%, 0.42%, 0.43%, 0.44%, 0.45%, 0.46%, 0.47%, 0.48%, 0.49%, or 0.5%.

[0058] SiC, AlTiC, and BN all have good refining effects. When used in combination, the best refining effect can be achieved by reducing their respective contents. When SiC is used in combination with Ti and B, a C-TiB2 particle complex is formed at the SiC-Al interface. The C atoms in SiC tend to enhance the adhesion energy of the C-TiB2 / Al interface, which makes the originally long strips of TiAl3 broken and shortened to avoid the enrichment and growth of TiAl3, greatly enhancing the composite refining effect; BN disperses AlB2 and AlN nano-nucleation at the aluminum matrix interface and grain boundary, which can refine the grains and promote uniform nucleation of grains to improve the elongation of aluminum alloys; under the action of SiC, Ti, B, and BN, AlTiC is not easy to aggregate and has a better effect of fine grain strengthening.

[0059] The method for preparing the high-strength Al-Si die-casting aluminum alloy also includes the step of adding V to the recycled aluminum melt, and the mass percentage content of V is 0.005-0.2%. The mass percentage content of V can specifically be 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%. Although V will reduce thermal conductivity, V can improve the elongation and strength of aluminum alloys. Specifically, V forms Al3V, Al4V, and Al6V in aluminum alloys. 10 V, VA11, VB2, AlB 2、 Al(VB)2 is a refractory compound that can refine grains and perform dispersion strengthening, thereby improving the strength and elongation of aluminum alloys. Especially in Al-Si alloys with Si content greater than 4%, the addition of Si can reduce the melting point of the Al melt, making the liquidus temperature lower than the Al-B eutectic temperature, and promoting the formation of Al(VB)2 in the Al-Si alloy. Under the action of Si, the Al(VB)2 structure changes, the stability is improved, and the heterogeneous nucleation ability is enhanced, which more significantly promotes grain refinement.

[0060] On the basis that most of the elements (except V in the present invention) have been dissolved in the aluminum matrix to avoid adverse effects on thermal conductivity, and some elements (such as B, Ni, Mn, Cr, RE, Mo, Co, Be, SiC, AlTiC, Ti, B, BN, and Sr, etc.) have significantly improved thermal conductivity, V can also be added to the recycled aluminum melt as a raw material to improve the elongation and strength of the aluminum alloy. When Ti, V, Cr, and Ni are added at the same time, the original block or thick strip Al-Ti, Al-V, Al-Cr, and Al-Ni compounds will be converted into dot-shaped, small, blocky, and complex Al-Ti-V-Cr-Ni compounds distributed in the crystal and at the grain boundary. In this way, Ti, V, and Cr can be added to the recycled aluminum melt as raw materials.

[0061] When Cu, Zn, Zr, and Ca are not added to the mixed melt, the Al-Si die-casting aluminum alloy based on recycled aluminum may also contain 0.0001-0.2% Cu by mass, 0.0001-0.2% Zn by mass, 0.0001-0.1% Zr by mass, and 0.0001-0.1% Ca by mass. Cu, Zn, Zr, and Ca can all improve the strength of the aluminum alloy. Ca can also remove H in the recycled aluminum liquid, refine the grains and the second phase, and improve the morphology of the β-Fe phase and eutectic silicon to improve the elongation of the aluminum alloy. Zr can also refine the grains, the second phase, and the precipitated phase to improve the elongation of the aluminum alloy. Zn can eliminate the elemental Si to reduce the adverse effects of the elemental Si on the performance of the aluminum alloy, and Zn can also promote the precipitation of the second phases such as Mg2Si, Al2Cu, and Mg3Sb2 to improve the strength and thermal conductivity. The elements Cu, Zn, Zr, Ca, etc. introduced from the waste can react with other elements to form Al2CuZn, AlFeSiCu, (CuMg)Al2, AlCaCu, AlCa, Mg2SiZn, Al2CuZn, MgZn2, Al3Zr, etc., avoiding the adverse effects of Cu, Zn, Zr, Ca on the strength, elongation and thermal conductivity of the aluminum alloy due to the solid solution of Cu, Zn, Zr, Ca in the aluminum matrix. The mass percentage content of Cu may be 0.0001%, 0.0005%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%. The mass percentage content of Zn and Zr may be 0.0001%, 0.0005%, 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%.The mass percentage content of Ca may be 0.0001%, 0.0005%, 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%.

[0062] At least one of Cu, Zn, Zr, and Ca may also be added to the recycled aluminum melt. In this case, the Al-Si die-casting aluminum alloy based on recycled aluminum contains 0.0001-1% by mass of Cu, 0.0001-1% by mass of Zn, 0.0001-0.5% by mass of Zr, and 0.0001-0.3% by mass of Ca. The mass percentage content of Cu and Zn may be 0.0001%, 0.0005%, 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, or 1%. The mass percentage content of Zr can be 0.0001%, 0.0005%, 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.20%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, 0.30%, 0.31%, 0.32%, 0.33%, 0.34%, 0.35%, 0.36%, 0.37%, 0.38%, 0.39%, 0.40%, 0.40%, 0.41%, 0.42%, 0.43%, 0.44%, 0.45%, 0.46%, 0.47%, 0.48%, 0.49%, 0.5 %, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, 0.3%, 0.31%, 0.32%, 0.33%, 0.34%, 0.35%, 0.36%, 0.37%, 0.38%, 0.39%, 0.4%, 0.41%, 0.42%, 0.43%, 0.44%, 0.45%, 0.46%, 0.47%, 0.48%, 0.49%, or 0.5%.The mass percentage content of Ca may be 0.0001%, 0.0005%, 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, or 0.3%.

[0063] The preparation method of the Al-Si series die-casting aluminum alloy based on recycled aluminum also includes the step of adding at least one of Te, Ag, Sb, Bi and Nb to the recycled aluminum melt. In the Al-Si series die-casting aluminum alloy based on recycled aluminum, the mass percentage content of Te is 0-0.2%, the mass percentage content of Ag is 0-0.2%, the mass percentage content of Sb is 0-0.5%, the mass percentage content of Bi is 0-0.2%, and the mass percentage content of Nb is 0-0.5%. The refining effect of Te and Ag can refine the second phase to improve the elongation of the aluminum alloy. Bi and Sb can improve the strength of the aluminum alloy. Nb can refine the grains and the second phase to achieve the effect of improving the elongation. Bi can effectively prevent sodium embrittlement, and even if the mass percentage content of Mg is high, such as 2-3%, sodium embrittlement will not occur; Bi can also reduce the surface tension of the aluminum melt and reduce the contact angle between Al and Si, so that the growth front of Si is more easily suppressed by Al, thereby reducing the size of eutectic silicon.

[0064] The mass percentage content of Te, Ag and Bi can be 0.0001%, 0.0005%, 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%. The mass percentage contents of Sb and Nb may be 0.0001%, 0.0005%, 0.001%, 0.005%, 0.01%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, 0.055%, 0.06%, 0.065%, 0.07%, 0.075%, 0.08%, 0.085%, 0.09%, 0.095%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0. .17%, 0.18%, 0.19%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, 0.3%, 0.31%, 0.32%, 0.33%, 0.34%, 0.35%, 0.36%, 0.37%, 0.38%, 0.39%, 0.4%, 0.41%, 0.42%, 0.43%, 0.44%, 0.45%, 0.46%, 0.47%, 0.48%, 0.49%, or 0.5%.

[0065] The present invention also provides an Al-Si die-casting aluminum alloy based on recycled aluminum obtained by the above-mentioned preparation method of the Al-Si die-casting aluminum alloy based on recycled aluminum. The Al-Si die-casting aluminum alloy based on recycled aluminum also contains Si with a mass percentage content of 6-12%, Fe with a mass percentage content of 0.1-1%, Mg with a mass percentage content of 0.4-3%, Sr with a mass percentage content of 0-0.1%, Ti with a mass percentage content of 0-0.3%, B with a mass percentage content of 0-0.05%, and Ni with a mass percentage content of 0-2.5%. The Al-Si die-casting aluminum alloy based on recycled aluminum also contains at least one of Zn, Cu, Ca, Mn, Cr, V, RE, Mo, Co, Be, Zr, Te, Ag, Sb, Bi, and Nb. In the Al-Si series die-casting aluminum alloy based on recycled aluminum, the mass percentage content of Zn is 0.0001-1%, the mass percentage content of Cu is 0.0001-1%, the mass percentage content of Ca is 0.0001-0.3%, the mass percentage content of Mn is 0.0001-0.2%, the mass percentage content of Cr is 0.001-0.3%, the mass percentage content of V is 0.005-0.2%, the mass percentage content of RE is 0.01-0.2%, the mass percentage content of Mo is 0-0.3%, the mass percentage content of Co is 0-0.5%, the mass percentage content of Be is 0-0.2%, the mass percentage content of Zr is 0.0001-0.5%, the mass percentage content of Te is 0-0.2%, the mass percentage content of Ag is 0-0.2%, the mass percentage content of Sb is 0-0.5%, the mass percentage content of Bi is 0-0.2%, and the mass percentage content of Nb is 0-0.5%.

[0066] The present invention also provides a structural part, at least part of which is made of the Al-Si die-cast aluminum alloy based on recycled aluminum or the Al-Si die-cast aluminum alloy based on recycled aluminum obtained by the preparation method. The structural part can be applied to the filter housing of a communication base station, the heat dissipation substrate of a communication base station, the cabinet shell of a communication base station, the three-electric structural part housing of an automobile, the housing of an automobile, the heat sink of a computer device, the middle plate of a mobile phone, the housing of a mobile phone, the heat sink of an LED lamp, the thin parts of 5G products, aerospace, high-speed rail, ships, mobile devices, household appliances, chemical industry, daily necessities, construction, etc.

[0067] Embodiment 1 Heating the recycled aluminum to obtain a recycled aluminum melt; The temperature is adjusted to 740° C., and industrial silicon, steel waste, and Ni are added to the recycled aluminum melt to obtain a mixed melt; The mixed melt is subjected to a boronization treatment and a first refining treatment, wherein the boronization agent of the boronization treatment is an aluminum-boron alloy, and the mass ratio of the aluminum-boron alloy to the mixed melt is 0.001:1; the temperature of the first refining treatment is 800°C, the time is 20 minutes, the refining agent is sodium chloride, and the mass ratio of sodium chloride to the mixed melt is 0.0001:1; The temperature is adjusted to 710°C, and magnesium alloy scrap, Sr, and Al-Ti-B alloy are added to the mixed melt after the first refining treatment, and the mixed melt is subjected to a second refining treatment, a slag removal treatment, a degassing treatment, and a static treatment. After the static treatment, the surface scum is scraped off, the temperature of the second refining treatment is 690°C, the time is 10 minutes, the refining agent is potassium chloride, and the mass ratio of potassium chloride to the mixed melt is 0.2:1; and The components and contents of the mixed melt after the static treatment are measured, and when the components and contents of the mixed melt meet the standards, the mixed melt is subjected to die casting to obtain an Al-Si die casting aluminum alloy based on recycled aluminum. The Al-Si die casting aluminum alloy based on recycled aluminum contains 12% Si by mass, 0.5% Fe by mass, 3% Mg by mass, 0.05% Sr by mass, 0.1% Ti by mass, 0.01% B by mass, and 0.1% Ni by mass.

[0068] Embodiment 2 Heating the recycled aluminum to obtain a recycled aluminum melt; The temperature is adjusted to 740° C., and industrial silicon, steel waste, and Ni are added to the recycled aluminum melt to obtain a mixed melt; The mixed melt is subjected to a boronization treatment and a first refining treatment, wherein the boronization agent of the boronization treatment is potassium fluoroborate, the mass ratio of the potassium fluoroborate to the mixed melt is 0.001:1, the temperature of the first refining treatment is 740°C, the time is 20 minutes, the refining agent includes 40wt% of sodium chloride, 40wt% of calcium fluoride, and 20wt% of rare earth Y, and the mass ratio of the refining agent to the mixed melt is 0.0001:1; The temperature is adjusted to 710° C., magnesium alloy scrap, Sr, and Al-Ti-B alloy are added to the mixed melt after the first refining treatment, the mixed melt is subjected to a second refining treatment, a slag removal treatment, a degassing treatment, and a standing treatment, and the surface scum is scraped off after the standing treatment, the temperature of the second refining treatment is 690° C., the time is 10 min, the refining agent includes 50wt% of sodium chloride and 50wt% of sodium aluminum fluoride, and the mass ratio of the refining agent to the mixed melt is 0.2:1; and The components and contents of the mixed melt after the standing treatment are measured. When the components and contents of the mixed melt meet the standards, the mixed melt is subjected to die casting and aging treatment to obtain an Al-Si series die casting aluminum alloy based on recycled aluminum. Among them, the Al-Si die-casting aluminum alloy based on recycled aluminum contains 12% Si by mass, 0.5% Fe by mass, 1.5% Mg by mass, 0.1% Sr by mass, 0.1% Ti by mass, 0.01% B by mass, 0.1% Ni by mass, 0.001% Zn by mass, 0.005% Zr by mass, 0.01% Cu by mass, 0.0001% Mn by mass, 0.005% Cr by mass, 0.005% V by mass, and 0.0001% Ca by mass. The aging treatment includes a primary low-temperature electric field aging treatment and a secondary high-temperature aging treatment, wherein the temperature of the primary low-temperature electric field aging treatment is 40°C, the time is 1 hour, and the electric field strength is 2V / cm; the temperature of the secondary high-temperature aging treatment is 140°C, and the time is 1 hour.

[0069] Embodiment 3 Heating the recycled aluminum to obtain a recycled aluminum melt; The temperature is adjusted to 745° C., and industrial silicon, steel waste, and Ni are added to the recycled aluminum melt to obtain a mixed melt; The mixed melt is subjected to a boronization treatment and a first refining treatment, wherein the boronizing agent of the boronization treatment is an aluminum-boron alloy, and the mass ratio of the aluminum-boron alloy to the mixed melt is 0.002:1; the temperature of the first refining treatment is 800°C, the time is 25 minutes, the refining agent is sodium aluminum fluoride, and the mass ratio of sodium aluminum fluoride to the mixed melt is 0.0002:1; The temperature is adjusted to 715°C, and magnesium alloy scrap, Sr, RE, Mo, Co, Cr, Be, and Al-Ti-B alloy are added to the mixed melt after the first refining treatment, and the mixed melt is subjected to a second refining treatment, a slag removal treatment, a degassing treatment, and a standing treatment. After the standing treatment, the surface scum is scraped off, the temperature of the second refining treatment is 695°C, the time is 15 minutes, the refining agent includes 60wt% of potassium chloride, 10wt% of rare earth lanthanum, and 30wt% of potassium fluoride, and the mass ratio of the refining agent to the mixed melt is 0.001:1; and The components and contents of the mixed melt after the static treatment are measured. When the components and contents of the mixed melt meet the standards, the mixed melt is subjected to die casting and aging treatment to obtain an Al-Si die-casting aluminum alloy based on recycled aluminum. The Al-Si die-casting aluminum alloy based on recycled aluminum contains 11% Si by mass, 0.2% Fe by mass, 1.2% Mg by mass, 0.02% Sr by mass, 0.05% Ti by mass, 0.03% B by mass, 0.2% Ni by mass, 0.1% RE by mass, 0.01% Mo by mass, 0.01% Co by mass, 0.01% Be by mass, 0.01% Cr by mass, and 0.0005% Mn by mass. The aging treatment includes a primary low-temperature electric field aging treatment and a secondary high-temperature aging treatment, wherein the temperature of the primary low-temperature electric field aging treatment is 55°C, the time is 1.5h, and the electric field strength is 5V / cm; the temperature of the secondary high-temperature aging treatment is 145°C, and the time is 5h.

[0070] Embodiment 4 Heating the recycled aluminum to obtain a recycled aluminum melt; The temperature is adjusted to 750° C., and industrial silicon, steel waste, and Ni are added to the recycled aluminum melt to obtain a mixed melt; The mixed melt is subjected to a boronization treatment and a first refining treatment, wherein the boronizing agent of the boronization treatment is an aluminum-boron alloy, and the mass ratio of the aluminum-boron alloy to the mixed melt is 0.003:1; the temperature of the first refining treatment is 750°C, the time is 30 minutes, the refining agent is potassium fluoroborate, and the mass ratio of potassium fluoroborate to the mixed melt is 0.0003:1; The temperature is adjusted to 720°C, and magnesium alloy scrap, Sr, RE, Mo, Co, Be, Cr, Mn, V, and Al-Ti-B alloy are added to the mixed melt after the first refining treatment, and the mixed melt is subjected to a second refining treatment, a slag removal treatment, a degassing treatment, and a standing treatment. After the standing treatment, the surface scum is scraped off, the temperature of the second refining treatment is 700°C, the time is 20 minutes, the refining agent includes 50wt% of potassium chloride and 50wt% of calcium fluoride, and the mass ratio of the refining agent to the mixed melt is 0.03:1; and The components and contents of the mixed melt after the static treatment are measured. When the components and contents of the mixed melt meet the standards, the mixed melt is subjected to die casting and aging treatment to obtain an Al-Si die-casting aluminum alloy based on recycled aluminum. The Al-Si die-casting aluminum alloy based on recycled aluminum contains 10% Si by mass, 1% Fe by mass, 1.1% Mg by mass, 0.05% Sr by mass, 0.15% Ti by mass, 0.05% B by mass, 0.6% Ni by mass, 0.05% RE by mass, 0.1% Mo by mass, 0.1% Co by mass, 0.1% Be by mass, 0.2% Cr by mass, 0.2% Mn by mass, and 0.005% V by mass. The aging treatment includes a primary low-temperature electric field aging treatment and a secondary high-temperature aging treatment, wherein the temperature of the primary low-temperature electric field aging treatment is 60°C, the time is 10 hours, and the electric field strength is 10V / cm; the temperature of the secondary high-temperature aging treatment is 150°C, and the time is 10 hours.

[0071] Embodiment 5 Heating the recycled aluminum to obtain a recycled aluminum melt; The temperature is adjusted to 770° C., and industrial silicon, steel waste, and Ni are added to the recycled aluminum melt to obtain a mixed melt; The mixed melt is subjected to a boronization treatment and a first refining treatment, wherein the boronization agent of the boronization treatment is an aluminum-boron alloy, and the mass ratio of the aluminum-boron alloy to the mixed melt is 0.004:1; the temperature of the first refining treatment is 780°C, the time is 40 minutes, the refining agent is lithium chloride, and the mass ratio of lithium chloride to the mixed melt is 0.0004:1; The temperature is adjusted to 780°C, and magnesium alloy scrap, Sr, Zn, Zr, Cu, Ca, and Al-Ti-B alloy are added to the mixed melt after the first refining treatment, and the mixed melt is subjected to a second refining treatment, a slag removal treatment, a degassing treatment, and a standing treatment. After the standing treatment, the surface scum is scraped off, the temperature of the second refining treatment is 750°C, the time is 20 minutes, the refining agent includes 80wt% of potassium chloride, 1wt% of scandium oxide, 1wt% of nano boron nitride, and 18wt% of potassium fluoride, and the mass ratio of the refining agent to the mixed melt is 0.1:1; and The components and contents of the mixed melt after the static treatment are measured. When the components and contents of the mixed melt meet the standards, the mixed melt is subjected to die casting and aging treatment to obtain an Al-Si die-casting aluminum alloy based on recycled aluminum. The Al-Si die-casting aluminum alloy based on recycled aluminum contains 9% Si by mass, 0.1% Fe by mass, 1% Mg by mass, 0.02% Sr by mass, 0.2% Ti by mass, 0.02% B by mass, 0.5% Ni by mass, 0.2% Zn by mass, 0.01% Zr by mass, 0.1% Cu by mass, and 0.001% Ca by mass. The aging treatment includes a primary low-temperature electric field aging treatment and a secondary high-temperature aging treatment, wherein the temperature of the primary low-temperature electric field aging treatment is 65°C, the time is 20 hours, and the electric field strength is 20V / cm; the temperature of the secondary high-temperature aging treatment is 200°C, and the time is 50 hours.

[0072] Embodiment 6 The mold is surface treated to form a 1 mm boron carbide layer on the parting surface of the mold; Heating the recycled aluminum to obtain a recycled aluminum melt; The temperature is adjusted to 800° C., and industrial silicon, steel waste, and Ni are added to the recycled aluminum melt to obtain a mixed melt; The mixed melt is subjected to a boronizing treatment and a first refining treatment, wherein the boronizing agent of the boronizing treatment is 50wt% of aluminum-boron alloy and 50wt% of potassium fluoroborate, the mass ratio of the boronizing agent to the mixed melt is 0.005:1, the temperature of the first refining treatment is 780°C, the time is 40min, the refining agent is potassium fluoroborate, and the mass ratio of potassium fluoroborate to the mixed melt is 0.0005:1; The temperature is adjusted to 780°C, and magnesium alloy scrap, Sr, Te, Ag, Sb, Bi, Nb, and Al-Ti-B alloy are added to the mixed melt after the first refining treatment, and the mixed melt is subjected to a second refining treatment, a slag removal treatment, a degassing treatment, and a static treatment. After the static treatment, the surface scum is scraped off, the temperature of the second refining treatment is 690°C, the time is 10 minutes, the refining agent includes 80wt% of potassium chloride, 5wt% of ytterbium oxide, and 15wt% of potassium fluoride, and the mass ratio of the refining agent to the mixed melt is 0.2:1; and The components and contents of the mixed melt after the static treatment are measured. When the components and contents of the mixed melt meet the standards, the mixed melt is subjected to die casting and aging treatment to obtain an Al-Si die-casting aluminum alloy based on recycled aluminum. The Al-Si die-casting aluminum alloy based on recycled aluminum contains 8% Si by mass, 0.3% Fe by mass, 2% Mg by mass, 0.05% Sr by mass, 0.3% Ti by mass, 0.05% B by mass, 1% Ni by mass, 0.001% Te by mass, 0.001% Ag by mass, 0.001% Sb by mass, 0.001% Bi by mass, and 0.001% Nb by mass. The aging treatment includes a primary low-temperature electric field aging treatment and a secondary high-temperature aging treatment, wherein the temperature of the primary low-temperature electric field aging treatment is 120°C, the time is 0.1h, and the electric field strength is 50V / cm; the temperature of the secondary high-temperature aging treatment is 200°C, and the time is 0.1h.

[0073] Embodiment 7 The mold is surface treated to form a 10 mm boron carbide layer on the parting surface of the mold; Heating the recycled aluminum to obtain a recycled aluminum melt; The temperature is adjusted to 860° C., and industrial silicon, steel waste, and Ni are added to the recycled aluminum melt to obtain a mixed melt; The mixed melt is subjected to a boronization treatment and a first refining treatment, wherein the boronization agent of the boronization treatment is an aluminum-boron alloy, the mass ratio of the aluminum-boron alloy to the mixed melt is 0.001:1, the temperature of the first refining treatment is 750°C, the time is 60 minutes, the refining agent includes 70wt% of potassium chloride, 10wt% of ytterbium oxide, and 20wt% of potassium fluoride, and the mass ratio of the refining agent to the mixed melt is 0.0001:1; The temperature is adjusted to 760° C., and magnesium alloy scrap, Sr, V, AlTiC, SiC, BN, RE, and Al-Ti-B alloy are added to the mixed melt after the first refining treatment, and the mixed melt is subjected to a second refining treatment, a slag removal treatment, a degassing treatment, and a standing treatment. After the standing treatment, the surface scum is scraped off, the temperature of the second refining treatment is 740° C., the time is 40 min, the refining agent includes 70wt% of potassium chloride, 10wt% of ytterbium oxide, and 20wt% of potassium fluoride, and the mass ratio of the refining agent to the mixed melt is 0.02:1; and The components and contents of the mixed melt after the static treatment are measured. When the components and contents of the mixed melt meet the standards, the mixed melt is subjected to die casting and aging treatment to obtain an Al-Si die-casting aluminum alloy based on recycled aluminum. The Al-Si die-casting aluminum alloy based on recycled aluminum contains 7% Si by mass, 0.6% Fe by mass, 2.5% Mg by mass, 0.01% Sr by mass, 0.25% Ti by mass, 0.01% B by mass, 2% Ni by mass, 0.01% Cr by mass, 0.01% V by mass, 0.1% AlTiC by mass, 0.1% SiC by mass, 0.1% BN by mass, 0.0001% Mn by mass, and 0.01% RE by mass. The aging treatment includes a primary low-temperature electric field aging treatment and a secondary high-temperature aging treatment, wherein the temperature of the primary low-temperature electric field aging treatment is 120°C, the time is 0.1h, and the electric field strength is 20V / cm; the temperature of the secondary high-temperature aging treatment is 250°C, and the time is 1h.

[0074] Embodiment 8 The mold is surface treated to form a 2 mm boron carbide layer on the parting surface of the mold; Heating the recycled aluminum to obtain a recycled aluminum melt; The temperature is adjusted to 850° C., and industrial silicon, steel waste, and Ni are added to the recycled aluminum melt to obtain a mixed melt; The mixed melt is subjected to a boronizing treatment and a first refining treatment, wherein the boronizing agent of the boronizing treatment is an aluminum-boron alloy, the mass ratio of the aluminum-boron alloy to the mixed melt is 0.002:1, the temperature of the first refining treatment is 750°C, the time is 40 minutes, the refining agent includes 60wt% of potassium chloride, 20wt% of ytterbium oxide, and 20wt% of potassium fluoride, and the mass ratio of the refining agent to the mixed melt is 0.0001:1; The temperature is adjusted to 760°C, and magnesium alloy scrap, Sr, V, Te, RE, and Al-Ti-B alloy are added to the mixed melt after the first refining treatment, and the mixed melt is subjected to a second refining treatment, a slag removal treatment, a degassing treatment, and a static treatment. After the static treatment, the surface scum is scraped off, the temperature of the second refining treatment is 730°C, the time is 10 minutes, the refining agent is sodium chloride, and the mass ratio of sodium chloride to the mixed melt is 0.01:1; and The components and contents of the mixed melt after the static treatment are measured. When the components and contents of the mixed melt meet the standards, the mixed melt is subjected to die casting and aging treatment to obtain an Al-Si die-casting aluminum alloy based on recycled aluminum. The Al-Si die-casting aluminum alloy based on recycled aluminum contains 6% Si by mass, 0.4% Fe by mass, 2% Mg by mass, 0.02% Sr by mass, 0.2% Ti by mass, 0.01% B by mass, 2.5% Ni by mass, 0.01% Cr by mass, 0.01% V by mass, 0.01% Te by mass, 0.01% RE by mass, and 0.0001% Mn by mass. The aging treatment includes a primary low-temperature electric field aging treatment and a secondary high-temperature aging treatment, wherein the temperature of the primary low-temperature electric field aging treatment is 120°C, the time is 100 hours, and the electric field strength is 50V / cm; the temperature of the secondary high-temperature aging treatment is 140°C, and the time is 50 hours.

[0075] The components and contents of the aluminum alloys of Examples 1 to 8 are shown in Table 1.

[0076] Table 1 Composition and content of aluminum alloys in Examples 1 to 8 To simplify the description, the examples do not show the contents of all impurity elements.

[0077] Table 2 Performance test results of aluminum alloys of Examples 1 to 8 Table 2 shows that the aluminum alloys of Examples 1 to 8 have good tensile strength, yield strength, elongation and thermal conductivity. After aging treatment, the aluminum alloys of Examples 2 to 8 have a tensile strength of not less than 420 MPa, a yield strength of not less than 330 MPa, an elongation of not less than 9%, and a thermal conductivity of not less than 160 W / mK.

[0078] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification under the inventive concept of the present invention, or direct / indirect application in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for preparing an Al-Si die-casting aluminum alloy based on recycled aluminum, comprising the following steps: Heating the recycled aluminum to obtain a recycled aluminum melt; The temperature is adjusted to 740-860° C., and industrial silicon, steel waste, and Ni are added to the recycled aluminum melt to obtain a mixed melt; performing a boronization treatment and a first refining treatment on the mixed melt; The temperature is adjusted to 710-780° C., and after adding magnesium alloy scrap, Sr, and Al-Ti-B alloy to the mixed melt after the first refining treatment, the mixed melt is subjected to a second refining treatment; and The components and contents in the mixed melt after the second refining treatment are measured. When the components and contents in the mixed melt after the second refining treatment meet the standards, the mixed melt is die-casted to obtain an Al-Si die-casting aluminum alloy based on recycled aluminum, wherein the Al-Si die-casting aluminum alloy based on recycled aluminum contains 6-12% Si by mass, 0.1-1% Fe by mass, 0.4-3% Mg by mass, 0-0.1% Sr by mass, 0-0.3% Ti by mass, 0-0.05% B by mass, and 0-2.5% Ni by mass.

2. The method for preparing an Al-Si based die-casting aluminum alloy based on recycled aluminum according to claim 1, characterized in that: The preparation method of the Al-Si series die-casting aluminum alloy based on recycled aluminum also includes the step of adding RE, Mo, Co and Be to the recycled aluminum melt, wherein the mass percentage content of Mn is 0.0001-0.1%, the mass percentage content of Cr is 0.0001-0.2%, the mass percentage content of RE is 0.001-0.2%, the mass percentage content of Mo is 0-0.3%, the mass percentage content of Co is 0-0.5%, and the mass percentage content of Be is 0-0.2%.

3. The method for preparing an Al-Si based die-casting aluminum alloy based on recycled aluminum according to claim 1, characterized in that: The preparation method of the Al-Si series die-casting aluminum alloy based on recycled aluminum also includes the step of adding Mn, Cr, RE, Mo, Co and Be to the recycled aluminum melt, wherein the mass percentage content of Mn is 0.0001-0.2%, the mass percentage content of Cr is 0.001-0.3%, the mass percentage content of RE is 0.01-0.2%, the mass percentage content of Mo is 0-0.3%, the mass percentage content of Co is 0-0.5%, and the mass percentage content of Be is 0-0.2%.

4. The method for preparing Al-Si based die-casting aluminum alloy based on recycled aluminum according to claim 1, characterized in that: The preparation method of the Al-Si series die-casting aluminum alloy based on recycled aluminum also includes the step of adding at least one of Cu, Zr, Ca, Te, Ag, Sb, Bi, and Nb to the recycled aluminum melt, wherein the mass percentage content of Cu is 0.0001-1%, the mass percentage content of Zr is 0.0001-0.5%, the mass percentage content of Ca is 0.0001-0.3%, the mass percentage content of Te is 0-0.2%, the mass percentage content of Ag is 0-0.2%, the mass percentage content of Sb is 0-0.5%, the mass percentage content of Bi is 0-0.2%, and the mass percentage content of Nb is 0-0.5%.

5. The method for preparing an Al-Si based die-casting aluminum alloy based on recycled aluminum according to any one of claims 1 to 4, characterized in that: The method for preparing the Al-Si series die-casting aluminum alloy based on recycled aluminum further comprises the step of performing surface treatment on the mold, wherein the surface treatment is to form a boron carbide layer on the parting surface of the mold.

6. The method for preparing an Al-Si based die-casting aluminum alloy based on recycled aluminum according to any one of claims 1 to 4, characterized in that: Meet at least one of the following conditions: The boronizing agent for the boronizing treatment is potassium fluoroborate and / or aluminum boron alloy; The mass ratio of the boronizing agent to the mixed melt in the boronizing treatment is 0.001-0.005:1; The temperature of the first refining treatment is 740-800°C and the time is 20-60min; The refining agent of the first refining treatment is at least one of chloride salt, fluoride salt, and rare earth; The mass ratio of the refining agent to the mixed melt in the first refining treatment is 0.0001-0.0005:1; The temperature of the second refining treatment is 690-750°C and the time is 10-40min; The refining agent of the second refining treatment includes at least one of chloride salt, fluoride salt, and rare earth; The mass ratio of the refining agent to the mixed melt in the second refining treatment is 0.001-0.2:

1.

7. The method for preparing an Al-Si based die-casting aluminum alloy based on recycled aluminum according to any one of claims 1 to 4, characterized in that: After the mixed melt is die-casted to obtain an aluminum alloy part, the method for preparing an Al-Si series die-cast aluminum alloy based on recycled aluminum further comprises the step of performing an aging treatment on the aluminum alloy part, wherein: The aging treatment is performed at a temperature of 150-250°C and a time of 0.05-30h; or The aging treatment includes a primary low-temperature electric field aging treatment and a secondary high-temperature aging treatment, wherein the temperature of the primary low-temperature electric field aging treatment is 50-120°C, the time is 0.1-100h, and the electric field strength is 2-50kV / cm; the temperature of the secondary high-temperature aging treatment is 140-250°C, and the time is 0.1-50h.

8. An Al-Si die-casting aluminum alloy based on recycled aluminum, containing Al, characterized in that: The Al-Si die-casting aluminum alloy based on recycled aluminum also contains 6-12% Si by mass, 0.1-1% Fe by mass, 0.4-3% Mg by mass, 0-0.1% Sr by mass, 0-0.3% Ti by mass, 0-0.05% B by mass, and 0-2.5% Ni by mass.

9. The Al-Si based die casting aluminum alloy based on recycled aluminum according to claim 8, characterized in that: The Al-Si die-casting aluminum alloy based on recycled aluminum also contains at least one of Cu, Mn, Cr, V, Ca, RE, Mo, Co, Be, Zr, Te, Ag, Sb, Bi, and Nb, wherein the mass percentage content of Cu is 0.0001-1%, the mass percentage content of V is 0.005-0.2%, the mass percentage content of Ca is 0.0001-0.3%, the mass percentage content of Zr is 0.0001-0.5%, the mass percentage content of Te is 0-0.2%, the mass percentage content of Ag is 0-0.2%, the mass percentage content of Sb is 0-0.5%, the mass percentage content of Bi is 0-0.2%, the mass percentage content of Nb is 0-0.5%, the mass percentage content of SiC is 0-1%, the mass percentage content of TiC is 0-1%, and the mass percentage content of BN is 0-0.5%.

10. A structural member, characterized in that: The material of the structural part is the Al-Si die-casting aluminum alloy based on recycled aluminum obtained by the preparation method of the Al-Si die-casting aluminum alloy based on recycled aluminum as described in any one of claims 1-7, or the Al-Si die-casting aluminum alloy based on recycled aluminum as described in any one of claims 8-9.

Images