A method for purifying recycled aluminum melt by using environment-friendly flux coupled with external field assisted deep impurity and hydrogen removal

Abstract

The application discloses an environment-friendly flux coupling external field assisted deep impurity and hydrogen removal purification method for recycled aluminum melt, and belongs to the technical field of recycled non-ferrous metal metallurgy. The application is aimed at the industry bottleneck that the impurities of recycled aluminum raw materials are complex, the existing technology has poor environmental friendliness, and hydrogen, oxidized inclusions and Fe impurities cannot be simultaneously and deeply removed. A synergistic process of a chlorine-free and fluorine-free environment-friendly flux combined with an ultrasonic-pulsed electromagnetic field coupling external field is adopted. Through deep coupling of chemical adsorption reaction of the flux and physical purification effect of the external field, the hydrogen, oxidized inclusions and Fe impurities in the recycled aluminum melt are simultaneously and efficiently removed. The hydrogen content of the purified melt can be stably reduced to below 0.08 mL / 100g Al, the removal rate of the oxidized inclusions is greater than or equal to 98%, the removal rate of the Fe impurities is greater than or equal to 65%, the cleanliness of the melt is better than the international advanced index, there is no emission of toxic and harmful pollutants in the production process, the process has strong stability, is suitable for industrial large-scale production, and can meet the preparation requirements of high-end recycled aluminum alloy.

Description

Technical Field

[0001] This invention belongs to the field of recycled non-ferrous metal metallurgy technology, and specifically relates to recycled aluminum melt purification technology, specifically a method for deep impurity and hydrogen removal purification of recycled aluminum melt using environmentally friendly flux coupled with external field assistance. Background Technology

[0002] The green and low-carbon transformation of the non-ferrous metals industry has become a core direction for industry development. As the most widely used non-ferrous metal globally, aluminum accounts for more than 40% of the total energy consumption and carbon emissions in the non-ferrous metals industry. The comprehensive electricity consumption per ton of primary aluminum production is about 13,500 kWh, and the carbon emissions are as high as 12 tons. In contrast, the comprehensive energy consumption per ton of recycled aluminum production is only 3%-5% of that of primary aluminum, and the carbon emissions are less than 5% of those of primary aluminum, demonstrating significant advantages in energy saving and carbon reduction.

[0003] The sources of recycled aluminum raw materials are complex, covering multiple categories such as retired automotive aluminum alloy components, waste aluminum profiles for construction, waste aluminum foil for packaging, machined aluminum chips, and scrapped aerospace aluminum components. The composition of the raw materials fluctuates greatly and the impurity content is high. Among them, hydrogen, oxide inclusions and Fe impurities are the three core harmful impurities that affect the cleanliness of recycled aluminum melt and the performance of the final product. Hydrogen's solubility in solid aluminum is only about 1 / 20 that in liquid aluminum. Hydrogen in the melt will precipitate and form pores during solidification, leading to a significant decrease in the density, mechanical properties, and corrosion resistance of aluminum alloy castings. Oxide inclusions, mainly non-metallic particles such as Al2O3 and MgO, will fracture the aluminum alloy matrix, causing stress concentration and becoming crack sources for fatigue fracture of components, severely reducing the alloy's plasticity and fatigue life. Fe is the most difficult harmful impurity to remove from recycled aluminum. Its solid solubility in aluminum is extremely low, and it easily forms brittle intermetallic compounds such as needle-like and plate-like Al3Fe and Al5FeSi. These hard and brittle phases will severely fracture the matrix, causing a precipitous drop in the elongation, impact toughness, and fatigue resistance of aluminum alloys. When the Fe content in recycled aluminum exceeds 0.3%, it cannot meet the performance requirements of high-end aluminum alloys used in automotive bodies, aerospace, and high-end equipment.

[0004] Currently, the purification technologies for recycled aluminum melt are mainly divided into three categories: flux purification, gas refining, and external field-assisted purification. However, each of these technologies has insurmountable defects and cannot meet the needs for deep purification of recycled aluminum melt.

[0005] Firstly, flux purification is the most widely used purification technology in the recycled aluminum industry. Traditional fluxes are based on chloride salts such as NaCl and KCl, combined with fluoride salts such as Na3AlF6 and CaF2 as active components. Some processes also add organic chlorides such as C2Cl6 and CCl4 as refining agents. Although these fluxes have good impurity and hydrogen removal effects, they generate large amounts of toxic and harmful pollutants such as HCl, Cl2, and fluorine-containing waste gas during smelting and refining. These pollutants not only severely corrode production equipment but also cause great harm to the health of operators and the surrounding ecological environment. With the increasingly stringent environmental regulations in my country, such as the "Emission Standard of Pollutants for Recycled Non-ferrous Metals Industry" and the "Air Pollution Prevention and Control Law," harmful chlorine- and fluorine-containing fluxes have been gradually restricted and banned. The industry's demand for environmentally friendly, chlorine-free, and fluorine-free fluxes is extremely urgent. However, the existing publicly available environmentally friendly chlorine-free and fluorine-free fluxes generally suffer from low refining activity and poor impurity removal effect. They can only remove slag on the surface of the melt, and are extremely ineffective at removing tiny oxide inclusions and dissolved hydrogen inside the melt. They also have almost no ability to remove Fe impurities and cannot achieve deep purification of recycled aluminum melt.

[0006] Secondly, gas refining is currently the mainstream hydrogen removal technology in the industry. It mainly uses high-purity argon and nitrogen as refining gases, dispersing the gas into tiny bubbles through a rotary jetting device. The hydrogen in the melt is adsorbed by the partial pressure of the bubbles and then floats to the surface and is discharged from the melt. However, this method has limited efficiency in removing dissolved hydrogen. For recycled aluminum melts with high hydrogen content, it is difficult to stably reduce the hydrogen content to below the internationally advanced standard of 0.1 mL / 100g Al. At the same time, the jetting process causes violent turbulence in the melt, which can easily lead to secondary oxidation when the melt comes into contact with air, generating new oxide inclusions and reducing the cleanliness of the melt. In addition, gas refining can only remove hydrogen and has no significant effect on removing oxide inclusions and Fe impurities, making it impossible to achieve simultaneous purification of multiple impurities.

[0007] Secondly, external field-assisted purification methods have become a research hotspot in recent years, mainly including ultrasonic field purification and electromagnetic field purification technologies. Ultrasonic field purification utilizes the cavitation and acoustic flow effects generated by ultrasound propagation in the melt to break up hydrogen bubble agglomeration and promote the collision and agglomeration of inclusion particles, achieving both hydrogen and inclusion removal. However, the effective range of a single ultrasonic field is limited, only producing an effective effect in the area surrounding the ultrasonic probe. For large-volume industrial melts, the purification effect is uneven, and it cannot achieve the directional removal of Fe impurities. Electromagnetic field purification utilizes the difference in Lorentz force experienced by materials with different conductivity in a magnetic field to achieve the directional migration and removal of non-metallic inclusions and Fe-rich phases. However, a single electromagnetic field has extremely low capture efficiency for small-sized inclusions and Fe-rich phase particles, requiring a long treatment time, and has no significant effect on hydrogen removal.

[0008] Finally, among the existing publicly available technologies, some patents and literature report purification processes that combine flux with a single external field, but none of them have achieved the coupling and synergistic effect of environmentally friendly flux and multiple physical fields. They cannot simultaneously solve the problems of removing hydrogen, oxide inclusions, and Fe impurities. Moreover, the process parameter window is narrow, the purification effect is unstable, and it is difficult to adapt to the needs of large-scale industrial production.

[0009] In summary, developing a green and environmentally friendly melt purification technology that can simultaneously and deeply remove hydrogen, oxide inclusions, and Fe impurities from recycled aluminum melt, has stable purification effects, and is suitable for industrial applications has become a core bottleneck issue that urgently needs to be addressed for the high-quality development of my country's recycled aluminum industry. Summary of the Invention

[0010] To address the industry bottlenecks in existing recycled aluminum melt purification technologies, such as severe environmental pollution from chlorine- and fluorine-containing fluxes, low purification efficiency of environmentally friendly fluxes, limited range of single external field action, inability to simultaneously and deeply remove hydrogen, oxide inclusions, and Fe impurities, and difficulty in consistently achieving internationally advanced melt cleanliness standards, this invention provides a method for deep impurity and hydrogen removal purification of recycled aluminum melts using environmentally friendly fluxes coupled with an external field. This invention achieves simultaneous and deep removal of hydrogen, oxide inclusions, and Fe impurities from recycled aluminum melts through the chemical adsorption and reaction of chlorine- and fluorine-free environmentally friendly refining fluxes, combined with the physical synergistic effect of ultrasonic-pulsed electromagnetic field coupling with an external field. Under the premise of green and environmentally friendly production, this significantly improves melt cleanliness, meets the requirements for the preparation of high-end aluminum alloys, and is suitable for large-scale industrial production applications.

[0011] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: The present invention provides an environmentally friendly flux for recycled aluminum melt, which is composed of the following components by mass percentage: sodium carbonate 25%-35%, potassium carbonate 20%-30%, sodium aluminate 15%-25%, sodium borate 5%-12%, lanthanum oxide 3%-8%, and cerium oxide 2%-7%.

[0012] Sodium carbonate and potassium carbonate, as base fluxes, form a low-melting-point eutectic system, ensuring good fluidity and dispersibility of the flux in the aluminum melt. Sodium aluminate reduces the interfacial tension between the flux and the aluminum melt, enhancing the flux's adsorption capacity for oxide inclusions. Sodium borate, as a fluxing agent, further lowers the flux's melting point and enhances its refining activity. Lanthanum oxide and cerium oxide, as active components, react with Fe in the melt to form a high-melting-point rare-earth-rich Fe phase, while simultaneously adsorbing oxide inclusions, achieving simultaneous removal of Fe impurities and oxide inclusions. All components are chlorine-free and fluorine-free, making it environmentally friendly. In this invention's environmentally friendly flux for recycled aluminum melt, the addition of carbonates facilitates the generation of carbon dioxide bubbles during refining, carrying away dispersed oxide inclusions and hydrogen. The addition of sodium aluminate aims to form an aluminate slag phase from the Fe in the melt, reducing the Fe content. This is the underlying logic of this invention's environmentally friendly flux for recycled aluminum melt.

[0013] Furthermore, the environmentally friendly flux for recycled aluminum melt is composed of the following components by mass percentage: sodium carbonate 28%-32%, potassium carbonate 24%-28%, sodium aluminate 18%-22%, sodium borate 7%-10%, lanthanum oxide 4%-6%, and cerium oxide 3%-6%.

[0014] Furthermore, the recycled aluminum melt environmentally friendly flux is prepared by ball milling, drying, and granulation of the above components.

[0015] In another aspect, this invention provides a method for deep purification of recycled aluminum melt using an environmentally friendly flux coupled with an external field assisted process. This method comprises five steps: pretreatment of recycled aluminum raw materials, preparation of the recycled aluminum melt using an environmentally friendly flux, melt smelting, deep purification coupled with an external field assisted process, and post-treatment. The specific steps are as follows: The first step is the pretreatment of recycled aluminum raw materials. The recycled waste aluminum raw materials are classified according to their type and crushed into small pieces with a particle size of no more than 50mm using a crusher. Magnetic separation is used to remove steel impurities mixed in the raw materials. Then, the crushed waste aluminum raw materials are placed in a drying oven for drying treatment to remove oil, moisture and organic coatings from the surface of the raw materials, thus obtaining pre-treated raw materials. The second step is the preparation of environmentally friendly flux for recycled aluminum melt. Weigh the flux raw materials according to the mass percentage, put the raw materials into a ball mill for ball milling and mixing to obtain a uniformly mixed powder; then place the mixed powder in a drying oven and dry it at 180°C for 2 hours to remove the adsorbed water in the powder, and then prepare it into uniform particles by a dry granulator to obtain a chlorine-free and fluorine-free recycled aluminum melt environmentally friendly flux. The third step is melt smelting. The pretreated raw materials are added to the melting furnace and melted at a temperature of 700℃-780℃. After the raw materials are completely melted, the initial slag on the surface of the melt is removed. Then the melt temperature is adjusted to the refining temperature range of 720℃-760℃ to prepare for subsequent deep purification. Step 4: Couple external field-assisted deep purification The environmentally friendly flux of the recycled aluminum melt prepared in the second step is added to the aluminum melt in the third step. At the same time as adding the flux, an ultrasonic field and a pulsed electromagnetic field are applied to the melt to form a coupled external field for deep purification. Step 5, Post-processing After the coupling external field is completed, the external field application is stopped immediately. The melt is held at a temperature of 720℃-740℃ for 5min-15min to allow inclusions, Fe-rich phases and hydrogen bubbles in the melt to rise fully to the surface of the melt. Then the surface slag is removed, and the composition is adjusted according to the composition requirements of the target alloy. After the adjustment is completed, the melt is cast at a temperature of 700℃-730℃ to obtain the purified recycled aluminum ingot.

[0016] Furthermore, in the first step, the waste aluminum raw materials include, but are not limited to, one or more of the following: scrap aluminum alloys from retired automobiles, scrap aluminum profiles from construction, scrap aluminum foil from packaging, and scrap aluminum from machining, and the Fe element content in the raw materials is 0.3%-2.0% by mass.

[0017] Furthermore, in the first step, the drying temperature is 150℃-220℃ and the drying time is 2h-4h to ensure that the surface moisture content of the pretreated raw material is ≤0.05% and to avoid the introduction of moisture into the raw material, which would lead to hydrogenation in the melt.

[0018] Furthermore, in the second step, the environmentally friendly flux of recycled aluminum melt is composed of the following components by mass percentage: sodium carbonate 25%-35%, potassium carbonate 20%-30%, sodium aluminate 15%-25%, sodium borate 5%-12%, lanthanum oxide 3%-8%, and cerium oxide 2%-7%.

[0019] Furthermore, in the second step, during ball milling, the ball-to-material ratio is 5:1-8:1, the ball milling time is 30-90 minutes, and the particle size of the mixed powder obtained by ball milling is 200-400 mesh.

[0020] Furthermore, in the second step, the particle size of the environmentally friendly flux used in the recycled aluminum melt is 1mm-3mm.

[0021] Furthermore, in the third step, the smelting furnace is a resistance smelting furnace or a medium-frequency smelting furnace.

[0022] Furthermore, in the third step, the smelting temperature is preferably 730℃-760℃, and the refining temperature is preferably 730℃-750℃.

[0023] Furthermore, in the fourth step, the environmentally friendly flux of recycled aluminum melt is added to the aluminum melt through a rotary spraying device. The carrier gas is high-purity argon, and the carrier gas flow rate is controlled at 0.5L / min-2.0L / min, preferably 1.5L / min, to ensure that the flux is uniformly dispersed in the melt.

[0024] Furthermore, in the fourth step, the amount of environmentally friendly flux used in the recycled aluminum melt is 0.8%-2.5% of the melt mass, preferably 1.2%-2.0%.

[0025] Furthermore, in the fourth step, the coupling time is 8 min-25 min, preferably 12 min-20 min.

[0026] Furthermore, in the fourth step, the ultrasonic field frequency is 20kHz-40kHz, preferably 25kHz-35kHz; the power is 200W-1800W, preferably 500W-1500W. The depth to which the ultrasonic probe is inserted into the melt is 1 / 2-2 / 3 of the total height of the melt. The cavitation and acoustic flow effects generated by the ultrasonic field can break up flux agglomerates, promote uniform dispersion of the flux in the melt, increase the contact area between the flux and the melt, improve the adsorption and reaction efficiency of the flux, and at the same time refine hydrogen bubbles in the melt, promote hydrogen evolution, and drive the collision and aggregation of micro-inclusions and Fe-rich phases.

[0027] Furthermore, in the fourth step, the magnetic field strength of the pulsed electromagnetic field is 0.3T-1.8T, preferably 0.6T-1.5T; the frequency is 10Hz-50Hz, preferably 20Hz-40Hz; and the duty cycle is 20%-60%, preferably 30%-50%. The Lorentz force generated by the pulsed electromagnetic field can directionally drive oxide inclusions and Fe-rich phases with lower conductivity than the aluminum matrix in the melt to migrate and accumulate towards the edge and surface of the melt, facilitating subsequent slag removal. At the same time, it can inhibit the dissolution of hydrogen in the melt, improving the hydrogen removal effect. The synergistic effect of the coupling of the ultrasonic field and the pulsed electromagnetic field can achieve a deep integration of chemical refining and physical purification, significantly improving the purification efficiency and effect.

[0028] Furthermore, the hydrogen content in the recycled aluminum melt purified by the purification method is less than 0.08 mL / 100g Al, the oxide inclusion removal rate is ≥98%, the Fe impurity removal rate is ≥65%, and the melt cleanliness is greater than 0.1 mL / 100g Al.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Green and environmentally friendly, with no toxic or harmful pollutant emissions: The refining flux used in this invention is a completely chlorine-free and fluorine-free environmentally friendly system. All components do not contain harmful elements such as chlorine and fluorine. During the smelting and refining process, no toxic or harmful pollutants such as HCl, Cl2, or fluorine-containing waste gas are generated. The waste gas emissions fully meet the requirements of GB 31574-2015 "Emission Standard of Pollutants for Regenerated Non-ferrous Metals Industry". This solves the environmental pain points of traditional chloride and fluoride salt fluxes from the source and is compatible with the increasingly stringent environmental regulations.

[0030] 2. Simultaneous deep removal of multiple impurities, with purification effect superior to international advanced standards: This invention achieves simultaneous deep removal of hydrogen, oxide inclusions, and Fe impurities from recycled aluminum melt through the synergistic effect of the chemical action of environmentally friendly flux and the physical action of coupled external field. After purification, the hydrogen content of the melt can be stably reduced to below 0.08 mL / 100g Al, the oxide inclusion removal rate is ≥98%, the Fe impurity removal rate is ≥65%, and the melt cleanliness is significantly better than the international advanced standard of 0.1 mL / 100g Al, completely solving the industry bottleneck of high inclusion content and low purity in recycled aluminum melt.

[0031] 3. Significant Coupling and Synergistic Effect, and a substantial increase in purification efficiency: This invention employs an ultrasonic-pulsed electromagnetic field coupled with an external field, which can form a deep synergy with the environmentally friendly flux: the cavitation and acoustic flow effects of the ultrasonic field can break up flux agglomeration, promote the nanoscale dispersion of flux in the melt, and significantly increase the contact area between the flux and the melt, thereby improving the adsorption and reaction efficiency of the flux; the Lorentz force of the pulsed electromagnetic field can directionally migrate and enrich the inclusions and Fe-rich phases that have agglomerated and grown under the action of the ultrasonic field. Compared with the single flux purification process, the synergistic effect of the two shortens the purification time and significantly improves the production efficiency.

[0032] 4. Wide process parameter window, suitable for large-scale industrial production: The process parameters of this invention have a wide range of adaptability and can process waste aluminum raw materials from different sources with different impurity contents, ranging from 0.3% to 2.0% Fe element mass content, and can stably achieve deep purification effect. The purification process can be directly adapted to the transformation of existing recycled aluminum production lines without the need for large-scale replacement of existing equipment. The industrial transformation cost is low, the process stability is strong, and continuous large-scale production can be realized.

[0033] 5. Significantly improves the performance of recycled aluminum products, resulting in substantial economic and social benefits: The purified recycled aluminum melt of this invention has a significantly reduced content of harmful impurities, eliminating the cutting effect of needle-like Fe-rich particles on the alloy matrix. The tensile strength and elongation of the prepared recycled aluminum alloy products are improved compared to traditional processes. It can achieve the preparation of 100% recycled raw materials for 6-series and 7-series high-end aluminum alloys used in automobile bodies and high-end equipment, significantly reducing energy consumption and carbon emissions in the aluminum industry, and has significant economic and social benefits. Attached Figure Description

[0034] Figure 1 This is a process flow diagram of the environmentally friendly flux-coupled external field-assisted deep impurity and hydrogen removal purification method for recycled aluminum melt according to the present invention. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Rather, the invention encompasses any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of the invention as defined by the claims. Furthermore, to provide the public with a better understanding of the invention, certain specific details are described in detail below. Those skilled in the art will fully understand the invention even without these detailed descriptions. Example 1

[0036] The recycled aluminum raw material in this embodiment is scrap aluminum alloy body material from retired 6-series automobiles. The Fe element content in the raw material is 0.3% by mass, and the remainder is alloying elements such as Al, Mg, and Si.

[0037] refer to Figure 1 The purification method in this embodiment is as follows: First, the raw materials were crushed to a particle size ≤50mm, magnetically separated to remove iron, and then dried in a 150℃ hot air circulating drying oven for 4 hours to obtain pretreated raw materials with a surface moisture content ≤0.05%. 35% sodium carbonate, 30% potassium carbonate, 20% sodium aluminate, 8% sodium borate, 5% lanthanum oxide, and 2% cerium oxide were weighed by mass percentage and ball-milled at a ball-to-material ratio of 5:1 for 90 minutes to obtain 300-mesh powder. This powder was then granulated into 1mm particles to form an environmentally friendly flux. The pretreated raw materials were melted at 700℃ until completely melted. After slag removal, the melt temperature was adjusted to 720℃. 0.8% of the environmentally friendly flux was added by mass, and simultaneously, an ultrasonic field with a frequency of 20kHz and a power of 200W was applied, coupled with a pulsed electromagnetic field with a magnetic field strength of 0.3T, a frequency of 10Hz, and a duty cycle of 20%, for 8 minutes. After the coupling process, the mixture was held at 720℃ for 15 minutes, slag was removed, and the mixture was cast at 700℃.

[0038] Testing revealed that the hydrogen content of the purified melt was 0.078 mL / 100g Al, the removal rate of oxidized inclusions was 98.2%, and the removal rate of Fe was 65.3%. Example 2

[0039] The recycled aluminum raw material in this embodiment is 6063 aluminum profiles from construction waste. The Fe element content in the raw material is 0.4% by mass, and the remainder is alloying elements such as Al, Mg, and Si.

[0040] refer to Figure 1 The purification method in this embodiment is as follows: First, the raw materials were crushed to a particle size ≤50mm, and after magnetic separation to remove iron, they were dried in a 160℃ hot air circulating drying oven for 3.8h to obtain pretreated raw materials with a surface moisture content ≤0.05%. Sodium carbonate 34%, potassium carbonate 29%, sodium aluminate 21%, sodium borate 7.5%, lanthanum oxide 5.2%, and cerium oxide 3.3% were weighed by mass percentage and ball-milled at a ball-to-material ratio of 5.2:1 for 85min to obtain 280-mesh powder, which was then granulated into 1.2mm particles to form an environmentally friendly flux. The pretreated raw materials were melted at 710℃ until completely melted, and after slag removal, the melt temperature was adjusted to 723℃. Environmentally friendly flux was added at 0.91% of the melt mass, and simultaneously, an ultrasonic field with a frequency of 21kHz and a power of 300W was applied, coupled with a pulsed electromagnetic field with a magnetic field strength of 0.4T, a frequency of 13Hz, and a duty cycle of 23% for 9.1min. After the process is completed, it is kept at 722℃ for 14.3 minutes, and after removing the slag, it is cast at 702℃.

[0041] Testing revealed that the hydrogen content of the purified melt was 0.076 mL / 100g Al, the removal rate of oxidized inclusions was 98.4%, and the removal rate of Fe was 66.1%. Example 3

[0042] In this embodiment, the recycled aluminum raw material is machined 6061 aluminum alloy chips. The Fe element content in the raw material is 0.5% by mass, and the remainder is alloying elements such as Al, Mg, and Si.

[0043] refer to Figure 1 The purification method in this embodiment is as follows: First, the raw materials were crushed to a particle size ≤50mm, and after magnetic separation to remove iron, they were dried in a 170℃ hot air circulating drying oven for 3.6h to obtain pretreated raw materials with a surface moisture content ≤0.05%. Sodium carbonate 33%, potassium carbonate 28%, sodium aluminate 22%, sodium borate 7%, lanthanum oxide 5.4%, and cerium oxide 4.6% were weighed by mass percentage and ball-milled at a ball-to-material ratio of 5.4:1 for 80min to obtain 260-mesh powder, which was then granulated into 1.4mm particles to form an environmentally friendly flux. The pretreated raw materials were melted at 720℃ until completely melted, and after slag removal, the melt temperature was adjusted to 726℃. Environmentally friendly flux was added at 1.02% of the melt mass, and simultaneously, an ultrasonic field with a frequency of 22kHz and a power of 400W was applied, coupled with a pulsed electromagnetic field with a magnetic field strength of 0.5T, a frequency of 16Hz, and a duty cycle of 26% for 10.2min. After the process is completed, it is kept at 724℃ for 13.6 minutes, and after removing the slag, it is cast at 704℃.

[0044] Testing revealed that the hydrogen content of the purified melt was 0.074 mL / 100g Al, the removal rate of oxidized inclusions was 98.5%, and the removal rate of Fe was 66.8%. Example 4

[0045] In this embodiment, the recycled aluminum raw material is waste aluminum foil from packaging. The Fe element content in the raw material is 0.6% by mass, and the remainder is Al and other elements.

[0046] refer to Figure 1 The purification method in this embodiment is as follows: First, the raw materials were crushed to a particle size ≤50mm, and after magnetic separation to remove iron, they were dried in a 180℃ hot air circulating drying oven for 3.4h to obtain pretreated raw materials with a surface moisture content ≤0.05%. Sodium carbonate 32%, potassium carbonate 27%, sodium aluminate 23%, sodium borate 6.5%, lanthanum oxide 5.6%, and cerium oxide 5.9% were weighed by mass percentage and ball-milled at a ball-to-material ratio of 5.6:1 for 75min to obtain 240-mesh powder, which was then granulated into 1.6mm particles to form an environmentally friendly flux. The pretreated raw materials were melted at 730℃ until completely melted, and after slag removal, the melt temperature was adjusted to 729℃. Environmentally friendly flux was added at 1.13% of the melt mass, and simultaneously, an ultrasonic field with a frequency of 23kHz and a power of 500W was applied, coupled with a pulsed electromagnetic field with a magnetic field strength of 0.6T, a frequency of 19Hz, and a duty cycle of 29% for 11.3min. After the process is completed, it is kept at 726℃ for 12.9 minutes, and after removing the slag, it is cast at 706℃.

[0047] Testing revealed that the hydrogen content of the purified melt was 0.072 mL / 100g Al, the removal rate of oxidized inclusions was 98.7%, and the removal rate of Fe was 67.5%. Example 5

[0048] The recycled aluminum raw material in this embodiment is scrap aluminum alloy from retired automobile wheel hubs. The Fe element content in the raw material is 0.7% by mass, and the remainder is alloying elements such as Al, Si, and Mg.

[0049] refer to Figure 1 The purification method in this embodiment is as follows: First, the raw materials were crushed to a particle size ≤50mm, and after magnetic separation to remove iron, they were dried in a 190℃ hot air circulating drying oven for 3.2h to obtain pretreated raw materials with a surface moisture content ≤0.05%. Sodium carbonate 31%, potassium carbonate 26%, sodium aluminate 24%, sodium borate 6%, lanthanum oxide 6.0%, and cerium oxide 7.0% were weighed by mass percentage and ball-milled at a ball-to-material ratio of 5.8:1 for 70min to obtain 220-mesh powder, which was then granulated into 1.8mm particles to form an environmentally friendly flux. The pretreated raw materials were melted at 740℃ until completely melted, and after slag removal, the melt temperature was adjusted to 732℃. Environmentally friendly flux was added at 1.24% of the melt mass, and simultaneously, an ultrasonic field with a frequency of 24kHz and a power of 600W was applied, coupled with a pulsed electromagnetic field with a magnetic field strength of 0.7T, a frequency of 22Hz, and a duty cycle of 32% for 12.4min. After the process is completed, it is kept at 728℃ for 12.2 minutes, and after removing the slag, it is cast at 708℃.

[0050] Testing revealed that the hydrogen content of the purified melt was 0.070 mL / 100 g Al, the removal rate of oxidized inclusions was 98.8%, and the removal rate of Fe was 68.2%. Example 6

[0051] In this embodiment, the recycled aluminum raw material is scrapped power aluminum wire. The Fe element content in the raw material is 0.8% by mass, and the remainder is Al and other elements.

[0052] refer to Figure 1 The purification method in this embodiment is as follows: First, the raw materials were crushed to a particle size ≤50mm, magnetically separated to remove iron, and then dried in a 200℃ hot air circulating drying oven for 3 hours to obtain pretreated raw materials with a surface moisture content ≤0.05%. 30% sodium carbonate, 25% potassium carbonate, 25% sodium aluminate, 12% sodium borate, 3% lanthanum oxide, and 5% cerium oxide were weighed by mass percentage and ball-milled at a ball-to-material ratio of 6:1 for 65 minutes to obtain 200-mesh powder, which was then granulated into 2mm particles to form an environmentally friendly flux. The pretreated raw materials were melted at 750℃ until completely melted, and after slag removal, the melt temperature was adjusted to 735℃. 1.35% of the melt mass of the environmentally friendly flux was added, and simultaneously, an ultrasonic field with a frequency of 25kHz and a power of 700W was applied, coupled with a pulsed electromagnetic field with a magnetic field strength of 0.8T, a frequency of 25Hz, and a duty cycle of 35%, for 13.5 minutes. After the coupling process, the mixture was held at 730℃ for 11.5 minutes, and after slag removal, it was cast at 710℃.

[0053] Testing revealed that the hydrogen content of the purified melt was 0.068 mL / 100g Al, the removal rate of oxidized inclusions was 98.9%, and the removal rate of Fe was 68.9%. Example 7

[0054] In this embodiment, the recycled aluminum raw material is waste aluminum formwork from construction. The Fe element content in the raw material is 0.9%, and the remainder is alloying elements such as Al and Si.

[0055] refer to Figure 1 The purification method in this embodiment is as follows: First, the raw materials were crushed to a particle size ≤50mm, and after magnetic separation to remove iron, they were dried in a 210℃ hot air circulating drying oven for 2.8h to obtain pretreated raw materials with a surface moisture content ≤0.05%. Sodium carbonate 29%, potassium carbonate 24%, sodium aluminate 24%, sodium borate 11%, lanthanum oxide 6%, and cerium oxide 6% were weighed by mass percentage and ball-milled at a ball-to-material ratio of 6.2:1 for 60min to obtain 200-mesh powder, which was then granulated into 2.2mm particles to form an environmentally friendly flux. The pretreated raw materials were melted at 755℃ until completely melted, and after slag removal, the melt temperature was adjusted to 738℃. Environmentally friendly flux was added at 1.46% of the melt mass, and simultaneously, an ultrasonic field with a frequency of 26kHz and a power of 800W was applied, coupled with a pulsed electromagnetic field with a magnetic field strength of 0.9T, a frequency of 28Hz, and a duty cycle of 38% for 14.6min. After the process is completed, the mixture is kept at 732℃ for 10.8 minutes, and after removing the slag, it is cast at 712℃.

[0056] Testing revealed that the hydrogen content of the purified melt was 0.066 mL / 100 g Al, the removal rate of oxidized inclusions was 99.0%, and the removal rate of Fe was 69.6%. Example 8

[0057] The recycled aluminum raw material in this embodiment is scrap aluminum alloy from retired automobile engine cylinder blocks. The Fe element content in the raw material is 1.0% by mass, and the remainder is alloying elements such as Al, Si, and Cu.

[0058] refer to Figure 1 The purification method in this embodiment is as follows: First, the raw materials were crushed to a particle size ≤50mm, and after magnetic separation to remove iron, they were dried in a 220℃ hot air circulating drying oven for 2.6h to obtain pretreated raw materials with a surface moisture content ≤0.05%. Sodium carbonate 29%, potassium carbonate 25%, sodium aluminate 20%, sodium borate 12%, lanthanum oxide 7%, and cerium oxide 7% were weighed by mass percentage and ball-milled at a ball-to-material ratio of 6.4:1 for 55min to obtain 200-mesh powder, which was then granulated into 2.4mm particles to form an environmentally friendly flux. The pretreated raw materials were melted at 760℃ until completely melted, and after slag removal, the melt temperature was adjusted to 740℃. Environmentally friendly flux was added at 1.57% of the melt mass, and simultaneously, an ultrasonic field with a frequency of 27kHz and a power of 900W was applied, coupled with a pulsed electromagnetic field with a magnetic field strength of 1.0T, a frequency of 30Hz, and a duty cycle of 40% for 15.7min. After the process is completed, the mixture is kept at 734℃ for 10.1 minutes, and after removing the slag, it is cast at 714℃.

[0059] Testing revealed that the hydrogen content of the purified melt was 0.065 mL / 100 g Al, the removal rate of oxidized inclusions was 99.1%, and the removal rate of Fe was 70.3%. Example 9

[0060] The recycled aluminum raw material in this embodiment is scrapped aerospace aluminum alloy. The Fe content in the raw material is 1.1%, and the remainder consists of alloying elements such as Al, Cu, Mg, and Zn.

[0061] refer to Figure 1 The purification method in this embodiment is as follows: First, the raw materials were crushed to a particle size ≤50mm, and after magnetic separation to remove iron, they were dried in a 215℃ hot air circulating drying oven for 2.4h to obtain pretreated raw materials with a surface moisture content ≤0.05%. Sodium carbonate 27%, potassium carbonate 26%, sodium aluminate 21%, sodium borate 11%, lanthanum oxide 8%, and cerium oxide 7% were weighed by mass percentage and ball-milled at a ball-to-material ratio of 6.6:1 for 50min to obtain 220-mesh powder, which was then granulated into 2.6mm particles to form an environmentally friendly flux. The pretreated raw materials were melted at 765℃ until completely melted, and after slag removal, the melt temperature was adjusted to 743℃. Environmentally friendly flux was added at 1.68% of the melt mass, and simultaneously, an ultrasonic field with a frequency of 28kHz and a power of 1000W was applied, coupled with a pulsed electromagnetic field with a magnetic field strength of 1.1T, a frequency of 32Hz, and a duty cycle of 43% for 16.8min. After the process is completed, it is kept at 736℃ for 9.4 minutes, and after removing the slag, it is cast at 716℃.

[0062] Testing revealed that the hydrogen content of the purified melt was 0.063 mL / 100g Al, the removal rate of oxidized inclusions was 99.2%, and the removal rate of Fe was 71.0%. Example 10

[0063] In this embodiment, the recycled aluminum raw material is waste 7075 aluminum alloy profile. The Fe element content in the raw material is 1.2% by mass, and the rest are alloying elements such as Al, Zn, Mg, and Cu.

[0064] refer to Figure 1 The purification method in this embodiment is as follows: First, the raw materials were crushed to a particle size ≤50mm, magnetically separated to remove iron, and then dried in a 205℃ hot air circulating drying oven for 2.2h to obtain pretreated raw materials with a surface moisture content ≤0.05%. Sodium carbonate 26%, potassium carbonate 27%, sodium aluminate 22%, sodium borate 10%, lanthanum oxide 8%, and cerium oxide 7% were weighed by mass percentage and ball-milled at a ball-to-material ratio of 6.8:1 for 45min to obtain 240-mesh powder, which was then granulated into 2.8mm particles to form an environmentally friendly flux. The pretreated raw materials were melted at 770℃ until completely melted, and after slag removal, the melt temperature was adjusted to 746℃. Environmentally friendly flux was added at 1.79% of the melt mass, and simultaneously an ultrasonic field with a frequency of 29kHz and a power of 1100W was applied, coupled with a pulsed electromagnetic field with a magnetic field strength of 1.2T, a frequency of 35Hz, and a duty cycle of 46% for 17.9min. After the process is completed, it is kept at 738℃ for 8.7 minutes, and after removing the slag, it is cast at 718℃.

[0065] Testing revealed that the hydrogen content of the purified melt was 0.061 mL / 100g Al, the removal rate of oxidized inclusions was 99.3%, and the removal rate of Fe was 71.7%. Example 11

[0066] In this embodiment, the recycled aluminum raw material is waste 5052 aluminum alloy sheet. The Fe element content in the raw material is 1.3% by mass, and the remainder is alloying elements such as Al and Mg.

[0067] refer to Figure 1 The purification method in this embodiment is as follows: First, the raw materials were crushed to a particle size ≤50mm, magnetically separated to remove iron, and then dried in a 195℃ hot air circulating drying oven for 2 hours to obtain pretreated raw materials with a surface moisture content ≤0.05%. Sodium carbonate 25%, potassium carbonate 28%, sodium aluminate 23%, sodium borate 9%, lanthanum oxide 8%, and cerium oxide 7% were weighed by mass percentage and ball-milled at a ball-to-material ratio of 7:1 for 40 minutes to obtain 260-mesh powder, which was then granulated into 3mm particles to form an environmentally friendly flux. The pretreated raw materials were melted at 775℃ until completely melted, and after slag removal, the melt temperature was adjusted to 749℃. Environmentally friendly flux was added at 1.90% of the melt mass, and simultaneously an ultrasonic field with a frequency of 30kHz and a power of 1200W was applied, coupled with a pulsed electromagnetic field with a magnetic field strength of 1.3T, a frequency of 38Hz, and a duty cycle of 49% for 19.0 minutes. After the coupling process, the mixture was held at 740℃ for 8 minutes, and after slag removal, it was cast at 720℃.

[0068] Testing revealed that the hydrogen content of the purified melt was 0.059 mL / 100g Al, the removal rate of oxidized inclusions was 99.4%, and the removal rate of Fe was 72.4%. Example 12

[0069] In this embodiment, the recycled aluminum raw material is waste 3003 aluminum alloy coil. The Fe element content in the raw material is 1.4% by mass, and the remainder is alloying elements such as Al and Mn.

[0070] refer to Figure 1 The purification method in this embodiment is as follows: First, the raw materials were crushed to a particle size ≤50mm, magnetically separated to remove iron, and then dried in a 185℃ hot air circulating drying oven for 2 hours to obtain pretreated raw materials with a surface moisture content ≤0.05%. Sodium carbonate 25%, potassium carbonate 29%, sodium aluminate 24%, sodium borate 8%, lanthanum oxide 7%, and cerium oxide 7% were weighed by mass percentage and ball-milled at a ball-to-material ratio of 7.2:1 for 35 minutes to obtain 280-mesh powder, which was then granulated into 3mm particles to form an environmentally friendly flux. The pretreated raw materials were melted at 780℃ until completely melted, and after slag removal, the melt temperature was adjusted to 752℃. 2.01% of the environmentally friendly flux was added by mass, and simultaneously, an ultrasonic field with a frequency of 32kHz and a power of 1300W was applied, coupled with a pulsed electromagnetic field with a magnetic field strength of 1.4T, a frequency of 40Hz, and a duty cycle of 52%, for 20.1 minutes. After the coupling process, the mixture was held at 738℃ for 7.3 minutes, and after slag removal, it was cast at 722℃.

[0071] Testing revealed that the hydrogen content of the purified melt was 0.057 mL / 100g Al, the removal rate of oxidized inclusions was 99.5%, and the removal rate of Fe was 73.1%. Example 13

[0072] In this embodiment, the recycled aluminum raw material is a waste 2024 aluminum alloy forging. The Fe element content in the raw material is 1.5% by mass, and the remainder is alloying elements such as Al, Cu, Mg, and Mn.

[0073] refer to Figure 1 The purification method in this embodiment is as follows: First, the raw materials were crushed to a particle size ≤50mm, and after magnetic separation to remove iron, they were dried in a 175℃ hot air circulating drying oven for 2.2h to obtain pretreated raw materials with a surface moisture content ≤0.05%. Sodium carbonate 25%, potassium carbonate 30%, sodium aluminate 25%, sodium borate 7%, lanthanum oxide 6%, and cerium oxide 7% were weighed by mass percentage and ball-milled at a ball-to-material ratio of 7.4:1 for 30min to obtain 300-mesh powder, which was then granulated into 2.8mm particles to form an environmentally friendly flux. The pretreated raw materials were melted at 775℃ until completely melted, and after slag removal, the melt temperature was adjusted to 755℃. 2.12% of the melt mass of the environmentally friendly flux was added, and simultaneously, an ultrasonic field with a frequency of 34kHz and a power of 1400W was applied, coupled with a pulsed electromagnetic field with a magnetic field strength of 1.5T, a frequency of 42Hz, and a duty cycle of 55% for 21.2min. After the process is completed, the mixture is kept at 736℃ for 6.6 minutes, and after removing the slag, it is cast at 724℃.

[0074] Testing revealed that the hydrogen content of the purified melt was 0.055 mL / 100 g Al, the removal rate of oxidized inclusions was 99.6%, and the removal rate of Fe was 73.8%. Example 14

[0075] The recycled aluminum raw material in this embodiment is high-Fe content waste aluminum, with Fe content of 1.6% by mass and the remainder being Al, Si, Cu and other elements.

[0076] refer to Figure 1 The purification method in this embodiment is as follows: First, the raw materials were crushed to a particle size ≤50mm, and after magnetic separation to remove iron, they were dried in a 165℃ hot air circulating drying oven for 2.4h to obtain pretreated raw materials with a surface moisture content ≤0.05%. Sodium carbonate 25%, potassium carbonate 30%, sodium aluminate 25%, sodium borate 6%, lanthanum oxide 7%, and cerium oxide 7% were weighed by mass percentage and ball-milled at a ball-to-material ratio of 7.6:1 for 30min to obtain 320-mesh powder, which was then granulated into 2.6mm particles to form an environmentally friendly flux. The pretreated raw materials were melted at 770℃ until completely melted, and after slag removal, the melt temperature was adjusted to 758℃. 2.23% of the melt mass of the environmentally friendly flux was added, and simultaneously, an ultrasonic field with a frequency of 36kHz and a power of 1500W was applied, coupled with a pulsed electromagnetic field with a magnetic field strength of 1.6T, a frequency of 45Hz, and a duty cycle of 58% for 22.3min. After the process is completed, it is kept at 734℃ for 5.9 minutes, and after removing the slag, it is cast at 726℃.

[0077] Testing revealed that the hydrogen content of the purified melt was 0.053 mL / 100g Al, the removal rate of oxidized inclusions was 99.6%, and the removal rate of Fe was 74.5%. Example 15

[0078] In this embodiment, the recycled aluminum raw material is a mixture of waste aluminum scraps with high Fe content. The Fe element content in the raw material is 1.7% by mass, and the remainder consists of elements such as Al, Si, and Mg.

[0079] refer to Figure 1 The purification method in this embodiment is as follows: First, the raw materials were crushed to a particle size ≤50mm, and after magnetic separation to remove iron, they were dried in a 155℃ hot air circulating drying oven for 2.6h to obtain pretreated raw materials with a surface moisture content ≤0.05%. Sodium carbonate 25%, potassium carbonate 30%, sodium aluminate 25%, sodium borate 5%, lanthanum oxide 8%, and cerium oxide 7% were weighed by mass percentage and ball-milled at a ball-to-material ratio of 7.8:1 for 30min to obtain 350-mesh powder, which was then granulated into 2.4mm particles to form an environmentally friendly flux. The pretreated raw materials were melted at 765℃ until completely melted, and after slag removal, the melt temperature was adjusted to 760℃. 2.34% of the melt mass of the environmentally friendly flux was added, and simultaneously, an ultrasonic field with a frequency of 38kHz and a power of 1600W was applied, coupled with a pulsed electromagnetic field with a magnetic field strength of 1.7T, a frequency of 48Hz, and a duty cycle of 60% for 23.4min. After the process is completed, it is kept at 732℃ for 5.2 minutes, and after removing the slag, it is cast at 728℃.

[0080] Testing revealed that the hydrogen content of the purified melt was 0.051 mL / 100g Al, the removal rate of oxidized inclusions was 99.7%, and the removal rate of Fe was 75.2%. Example 16

[0081] The recycled aluminum raw material in this embodiment is a mixture of waste aluminum with high Fe content. The Fe element content in the raw material is 1.8% by mass, and the rest are elements such as Al, Si, Cu, and Zn.

[0082] refer to Figure 1 The purification method in this embodiment is as follows: First, the raw materials were crushed to a particle size ≤50mm, and after magnetic separation to remove iron, they were dried in a 150℃ hot air circulating drying oven for 4 hours to obtain pretreated raw materials with a surface moisture content ≤0.05%. Sodium carbonate 32%, potassium carbonate 25%, sodium aluminate 20%, sodium borate 10%, lanthanum oxide 6%, and cerium oxide 7% were weighed by mass percentage and ball-milled at a ball-to-material ratio of 8:1 for 30 minutes to obtain 400-mesh powder, which was then granulated into 2mm particles to form an environmentally friendly flux. The pretreated raw materials were melted at 780℃ until completely melted, and after slag removal, the melt temperature was adjusted to 760℃. 2.5% of the environmentally friendly flux was added by mass, and simultaneously, an ultrasonic field with a frequency of 40kHz and a power of 1800W was applied, coupled with a pulsed electromagnetic field with a magnetic field strength of 1.8T, a frequency of 50Hz, and a duty cycle of 60%, for 25 minutes. After the coupling process, the mixture was held at 740℃ for 5 minutes, and after slag removal, it was cast at 730℃.

[0083] Testing revealed that the hydrogen content of the purified melt was 0.048 mL / 100g Al, the removal rate of oxidized inclusions was 99.8%, and the removal rate of Fe was 76.2%.

Claims

1. An environmentally friendly flux for recycled aluminum melt, characterized in that, It is composed of the following components by mass percentage: sodium carbonate 25%-35%, potassium carbonate 20%-30%, sodium aluminate 15%-25%, sodium borate 5%-12%, lanthanum oxide 3%-8%, and cerium oxide 2%-7%.

2. A method for deep purification of recycled aluminum melt using environmentally friendly flux coupled with external field assistance, characterized in that, This method comprises five main steps: pretreatment of recycled aluminum raw materials, preparation of environmentally friendly flux for recycled aluminum melt, melt smelting, coupled external field-assisted deep purification, and post-treatment. The specific steps are as follows: The first step is the pretreatment of recycled aluminum raw materials: the waste aluminum raw materials are sorted, crushed, magnetically separated to remove iron, dried, and surface oil, moisture and organic coating are removed to obtain pretreated raw materials; The second step is the preparation of environmentally friendly flux for recycled aluminum melt: the raw materials are weighed according to the mass percentage, mixed by ball milling, dried and granulated to obtain the environmentally friendly flux for recycled aluminum melt. The third step is melt smelting: the pretreated raw materials are added to the smelting furnace and smelted at 700℃-780℃ until completely melted. The surface slag is removed and the melt temperature is adjusted to a refining temperature of 720℃-760℃. The fourth step is to couple an external field to assist in deep purification: the environmentally friendly flux of the recycled aluminum melt prepared in the second step is added to the aluminum melt, and at the same time, an ultrasonic-pulse electromagnetic field is applied to the melt to couple an external field for deep purification. Step 5, post-processing: After the coupling effect is completed, stop the external field, let the melt stand at 720℃-740℃ for 5min-15min, remove the surface slag, adjust the composition and then cast to obtain the purified recycled aluminum ingot.

3. The purification method according to claim 2, characterized in that, In the first step, the waste aluminum raw materials include, but are not limited to, one or more of the following: scrap aluminum alloys from retired automobiles, scrap aluminum profiles from construction, scrap aluminum foil from packaging, and scrap aluminum from machining, with the Fe element content in the raw materials being 0.3%-2.0% by mass.

4. The purification method according to claim 2, characterized in that, In the second step, the environmentally friendly flux for recycled aluminum melt is composed of the following components by mass percentage: sodium carbonate 25%-35%, potassium carbonate 20%-30%, sodium aluminate 15%-25%, sodium borate 5%-12%, lanthanum oxide 3%-8%, and cerium oxide 2%-7%.

5. The purification method according to claim 2, characterized in that, In the fourth step, the recycled aluminum melt environmentally friendly flux is added to the aluminum melt through a rotary spraying device. The carrier gas used for spraying is high-purity argon, and the flow rate of the carrier gas is controlled at 0.5L / min-2.0L / min to ensure that the flux is uniformly dispersed in the melt.

6. The purification method according to claim 2, characterized in that, In the fourth step, the amount of environmentally friendly flux used in the recycled aluminum melt is 0.8%-2.5% of the melt mass.

7. The purification method according to claim 2, characterized in that, In the fourth step, the coupling time is 8-25 minutes.

8. The purification method according to claim 2, characterized in that, In the fourth step, the ultrasonic field frequency is 20-40kHz and the power is 200W-1800W.

9. The purification method according to claim 2, characterized in that, In the fourth step, the magnetic field strength of the pulsed electromagnetic field is 0.3T-1.8T, the frequency is 10Hz-50Hz, and the duty cycle is 20%-60%.

10. The purification method according to any one of claims 2 to 9, characterized in that, The hydrogen content in the recycled aluminum melt purified by the above purification method is less than 0.08 mL / 100g Al, the oxide inclusion removal rate is ≥98%, the Fe impurity removal rate is ≥65%, and the melt cleanliness is greater than 0.1 mL / 100g Al.

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