Method for avoiding oxide skin inclusion of regenerated aluminum alloy cast ingot

Abstract

The invention discloses a method for avoiding oxide skin inclusion of a secondary aluminum alloy cast ingot, which relates to the field of secondary aluminum alloy processing, and comprises the following steps of: 1, raw material pretreatment: crushing a secondary aluminum raw material by a jaw crusher, 2, atmosphere smelting: putting the pretreated raw material into a graphite crucible smelting furnace for smelting, and 3, two-stage purification: after a melt is completely molten, carrying out primary purification, and carrying out secondary purification. And 4, precise casting: transferring the purified melt to a vertical semi-continuous casting machine, and realizing full-process management and control of oxide skin from source inhibition, process removal to terminal interception through a full-process collaborative process of raw material grading pretreatment, inert gas atmosphere smelting, two-stage melt purification and precise casting control. The oxide skin inclusion amount of the regenerated aluminum alloy cast ingot is effectively reduced, the strict requirements of high-end fields such as automobile lightweight and electronic equipment shells on the purity of the cast ingot are met, and the machining defects caused by oxide skin inclusion are reduced.

Description

Technical Field

[0001] This invention relates to the field of recycled aluminum alloy processing, and in particular to a method for avoiding oxide scale inclusions in recycled aluminum alloy ingots. Background Technology

[0002] Driven by global "dual carbon" goals and resource recycling strategies, the recycled aluminum alloy industry has become one of the core directions for the development of the aluminum industry. Recycled aluminum alloys use waste aluminum products (such as scrapped automotive aluminum, waste building profiles, and decommissioned aerospace components) as raw materials. Compared to virgin aluminum alloys, they can save more than 95% of energy consumption and reduce carbon emissions by more than 90%, making them a typical green and low-carbon material.

[0003] However, the problem of oxide scale inclusions in its production has always constrained the quality of ingots. The surface of recycled aluminum raw materials is prone to forming multiple layers of oxide scale with large differences in composition. Existing pretreatment can only remove large impurities or cause element loss and environmental pollution due to acid washing. Melting is mostly done in an open mode with uneven gas distribution. Purification technology is difficult to balance efficiency and effectiveness. The casting parameter control precision is insufficient, resulting in high oxide scale inclusions and low pass rate in ingots, which cannot meet the needs of high-end fields.

[0004] Therefore, it is necessary to propose a method to avoid oxide scale inclusions in recycled aluminum alloy ingots to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a method to avoid oxide scale inclusions in recycled aluminum alloy ingots. This method addresses the problems of high oxide scale inclusions and low pass rates in ingots due to the easy formation of multiple oxide scales on the surface of recycled aluminum raw materials, the fact that existing pretreatment can only remove large impurities or cause element loss and environmental pollution due to acid washing, the fact that smelting is mostly done in an open manner with uneven gas distribution, the difficulty in balancing efficiency and effectiveness in purification technology, and the insufficient precision in controlling casting parameters. These issues fail to meet the needs of high-end fields.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for avoiding oxide scale inclusions in recycled aluminum alloy ingots, comprising the following steps: Step 1: Raw material pretreatment: The recycled aluminum raw material is crushed by a jaw crusher to control the particle size after crushing to 20-40mm. Metal and non-metal impurities with a diameter greater than 5mm are removed by a screening machine. Then the crushed raw material is placed in a hot air baking oven and baked at 380-420℃ for 1.5-2.5h in an atmosphere with an oxygen content of no more than 3%. The material is turned over every 40 minutes during the baking process. Step 2, Atmosphere melting: The pretreated raw materials are put into the graphite crucible melting furnace, and after the vacuum is drawn to a pressure not exceeding 40Pa, argon gas is introduced to maintain the pressure inside the melting furnace at 0.08-0.12MPa. Then the temperature is raised to 800-840℃ for melting to form a melt. During the melting process, the argon gas flow rate is controlled at 10-15L / min, and the slag is skimmed off every 25 minutes. The slag skimming temperature is controlled at 810-830℃. Step 3, Two-stage purification: After the melt is completely melted, it is first purified using a rotary jetting device. The jetting head is inserted into the melt to a depth of 250-350mm, the nitrogen pressure is 0.4-0.6MPa, the device speed is controlled at 180-220r / min, and the purification time is 18-22min. Then the melt is filtered through a ceramic filter plate with a pore size of 20-40μm, a filtration area of ​​0.6-0.9m², and a melt flow rate of 0.3-0.5m / s. Step 4, Precision Casting: After purification, the melt is transferred to a vertical semi-continuous casting machine. Before casting, the melt is treated by an online degassing device. The vacuum degree of the degassing device is controlled at 25-35 Pa, and the degassing time is 6-9 min. After degassing, casting is carried out. The casting temperature is controlled at 700-730℃, and the casting speed is 0.6-1.0 m / min. The cooling water temperature of the crystallizer of the vertical semi-continuous casting machine is controlled at 28-32℃, and the cooling water flow rate is controlled at 1.8-2.2 m / s. The ingot is demolded after cooling to below 300℃.

[0007] Preferably, in the raw material pretreatment step, the crushing gap of the jaw crusher is adjusted to 15-25mm, and compressed air of 0.25-0.35MPa is introduced for dust removal during crushing.

[0008] Preferably, the wall thickness of the graphite crucible in the atmosphere melting step is 20-30 mm, and the heating rate of the melting furnace is controlled at 15-20℃ / min.

[0009] Preferably, in the dual-stage purification step, the nozzle of the rotary jetting device has a porous structure with a pore diameter of 1.5-2.5 mm, and the nozzle material is a high-temperature resistant alloy.

[0010] Preferably, the ceramic filter plate in the dual-stage purification step has a composite structure, consisting of an upper layer, a middle layer, and a lower layer. The upper layer has a pore size of 40μm, the middle layer has a pore size of 30μm, and the lower layer has a pore size of 20μm. The filter plate is preheated at 400-450℃ for 30-40 minutes before use.

[0011] According to claim 5, a method for avoiding oxide scale inclusions in recycled aluminum alloy ingots is characterized in that: the online degassing device in the precision casting step adopts a rotor-type degassing machine with a rotor speed of 400-500 r / min, and the melt temperature fluctuation during the degassing process is controlled within ±5℃.

[0012] Preferably, in the precision casting step, the casting machine's pouring port is provided with a guide groove, and the inner wall of the guide groove is coated with a boron nitride coating with a coating thickness of 5-8 μm.

[0013] Preferably, the raw material pretreatment step, atmosphere melting step, two-stage purification step, and precision casting step all adopt a PLC control system to monitor process parameters such as temperature, pressure, flow rate, and rotation speed in real time. When the parameter deviation exceeds ±3%, an alarm is automatically triggered and adjustments are made.

[0014] Preferably, in the raw material pretreatment step, the aluminum content of the recycled aluminum raw material is not less than 95%, the metallic impurities include iron and copper, and the non-metallic impurities include plastics and rubber.

[0015] Preferably, the purity of the argon gas introduced in the atmosphere melting step is not less than 99.995%, and the purity of the nitrogen gas introduced in the two-stage purification step is not less than 99.99%.

[0016] The technical effects and advantages of this invention are as follows: 1. Through a collaborative process of “raw material classification and pretreatment - inert gas atmosphere melting - dual-stage melt purification - precision casting control”, the entire process of oxide scale control is achieved from source suppression and process removal to terminal interception. This effectively reduces the amount of oxide scale inclusions in recycled aluminum alloy ingots, meets the stringent requirements for ingot purity in high-end fields such as automotive lightweighting and electronic device housings, and reduces processing defects caused by oxide scale inclusions.

[0017] 2. By precisely controlling the process parameters at each stage, optimizing the crushing, sorting and baking conditions of raw material pretreatment, improving the melting atmosphere and temperature control, enhancing the adsorption and filtration effects of the two-stage purification, and precisely controlling the casting temperature, speed and cooling system, the ingot qualification rate and mechanical properties are improved simultaneously, and the internal structure uniformity of the ingot is optimized, so that the ingot can be directly adapted to subsequent precision processing procedures such as extrusion and forging, reducing scrap loss.

[0018] 3. By replacing the traditional pickling process with hot air baking in the raw material pretreatment stage, the loss of alloying elements is avoided and the utilization rate of recycled aluminum raw materials is improved; in the smelting stage, inert gas protection is used instead of a large amount of flux, reducing flux consumption and waste slag generation, while reducing flux cost and waste slag treatment cost, thus comprehensively reducing the production cost of recycled aluminum alloy ingots.

[0019] 4. By using a raw material pretreatment process without acid washing, acidic wastewater is avoided, reducing wastewater treatment costs and environmental risks; no corrosive gases are released during the smelting stage, meeting workshop air quality standards; the entire process adopts a PLC automatic control system to reduce manual intervention, reduce the frequency of operators' contact with high-temperature and high-pressure equipment, reduce the risk of safety accidents, and has the advantages of both green environmental protection and safe production.

[0020] 5. Through flexible and adjustable process parameter design, key parameters such as pretreatment temperature and smelting gas flow rate can be adjusted according to the type of recycled aluminum raw material (such as automotive aluminum, architectural aluminum, and aluminum for electronic equipment) to ensure the control effect of oxide scale for different raw materials. At the same time, the process is compatible with existing large-scale production equipment, requiring only minor modifications to be put into use. The modification cycle is short and the investment is low, making it easy for enterprises to quickly promote and apply. It has good process adaptability and large-scale compatibility. Through the PLC control system, the key process parameters of the entire process are monitored and automatically adjusted in real time, and parameter deviations are corrected in a timely manner, which greatly improves the stability of the process, avoids parameter fluctuations caused by manual operation, ensures the consistency of ingot quality in long-term continuous production, and guarantees the stability and reliability of product quality. Attached Figure Description

[0021] Figure 1 This is a schematic diagram illustrating the steps of the method for avoiding oxide scale inclusions in recycled aluminum alloy ingots according to the present invention. Detailed Implementation

[0022] This invention provides, for example Figure 1 The method shown includes the following steps to avoid oxide scale inclusions in recycled aluminum alloy ingots: S1. Raw material pretreatment: The recycled aluminum raw material is crushed by a jaw crusher to control the particle size after crushing to 20-40mm. Metal and non-metal impurities with a diameter greater than 5mm are removed by a screening machine. Then the crushed raw material is placed in a hot air baking oven and baked at 380-420℃ for 1.5-2.5h in an atmosphere with an oxygen content of no more than 3%. The material is turned over every 40 minutes during the baking process. Specifically, to address the issues of uneven oxide scale distribution and high impurity content in recycled aluminum raw materials, a "crushing-sorting-baking" grading process is adopted. First, a jaw crusher (crushing gap 15-25mm) is used to crush the recycled aluminum raw materials (containing Al ≥ 95%) to 20-40mm. This particle size ensures uniform heating during subsequent smelting and reduces excessive oxidation of the raw materials during crushing (when the particle size is < 20mm, the specific surface area increases, and the oxidation rate increases by 20%–30%). Compressed air at 0.25-0.35MPa is introduced during crushing, and dust removal is achieved through a cyclone separator (efficiency ≥ 95%), preventing dust from adsorbing onto the raw material surface and introducing impurities. Second, a combination of manual and mechanical sorting is used to remove metallic impurities such as Fe and Cu with a diameter > 5mm (to prevent the formation of intermetallic compound inclusions during smelting) and non-metallic impurities such as plastics and rubber (to prevent the generation of gases from high-temperature decomposition, which would exacerbate melt oxidation).

[0023] Finally, the sorted raw materials are placed in a sealed hot air baking oven, with the oxygen content inside the oven controlled to be ≤3% (adjusted by introducing a small amount of nitrogen), and baked at 380-420℃ for 1.5-2.5 hours. This temperature can remove the surface moisture (water content reduced to below 0.1%) and oil stains (oil stain removal rate ≥98%) from the raw materials, and can also cause the loose oxide scale (thickness >5μm) on the surface to fall off due to heat. At the same time, it avoids the oxidation of the alloy elements inside the raw materials due to excessive temperature (such as controlling the oxidation rate of Mg element to within 1%). The raw materials are turned over every 40 minutes during the baking process to ensure that the raw materials are heated evenly and to prevent local overheating.

[0024] S2. Atmosphere melting: The pretreated raw materials are put into the graphite crucible melting furnace, and after the vacuum is drawn to a pressure not exceeding 40Pa, argon gas is introduced to maintain the pressure inside the melting furnace at 0.08-0.12MPa. Then the temperature is raised to 800-840℃ for melting to form a melt. During the melting process, the argon gas flow rate is controlled at 10-15L / min, and the slag is skimmed off every 25 minutes. The slag skimming temperature is controlled at 810-830℃. Specifically, to reduce melt oxidation during the smelting process, a "vacuum-argon protective" atmosphere is used for smelting. A graphite crucible with a wall thickness of 20-30mm is selected (high temperature resistance, good chemical stability, and to prevent reaction with the melt). After the pretreated raw materials are added to the crucible, a vacuum is first drawn to ≤40Pa to remove air from the furnace (oxygen content reduced to below 0.1%). Then, argon gas with a purity ≥99.995% is introduced to maintain the furnace pressure at 0.08-0.12MPa, forming an inert protective zone. The heating rate of the smelting furnace is controlled at 15-20℃ / min to avoid local overheating (when the local temperature is >860℃, the melt oxidation rate increases significantly). Finally, the temperature is raised to 800-840℃—this temperature range ensures complete melting of the raw materials (melting rate >2kg / min) while inhibiting the selective oxidation of alloying elements (such as Si and Mg) (Mg oxidation rate ≤0.5%). During the smelting process, argon gas is uniformly introduced through a porous distributor (1-2 mm in diameter) at the bottom of the furnace, with a flow rate controlled at 10-15 L / min. As the argon bubbles rise, they carry some oxide scale to the surface of the melt. Every 25 minutes, slag is skimmed off at 810-830℃ (at this temperature, the slag has good fluidity and is easy to separate from the melt). The slag skimming tool is made of high-temperature resistant alloy material to avoid tool damage and the introduction of impurities.

[0025] S3. Two-stage purification: After the melt is completely melted, it is first purified by a rotary jetting device. The jetting head is inserted into the melt to a depth of 250-350mm, the nitrogen pressure is 0.4-0.6MPa, the device speed is controlled at 180-220r / min, and the purification time is 18-22min. Then the melt is filtered by a ceramic filter plate with a pore size of 20-40μm, a filtration area of ​​0.6-0.9m², and a melt flow rate of 0.3-0.5m / s. Specifically, to efficiently remove residual oxide scale (especially fine particles with a diameter ≤10μm) from the melt, a two-stage purification process of "rotary jetting + ceramic filtration" is adopted. The first stage of rotary jetting purification: After the raw material is completely melted, the nozzle of the rotary jetting device (made of Cr25Ni20 high-temperature resistant alloy, with an orifice diameter of 1.5-2.5mm) is inserted into the melt to a depth of 250-350mm. Nitrogen gas with a purity ≥99.99% (pressure 0.4-0.6MPa) is introduced, and the device speed is controlled at 180-220r / min—the high-speed rotation causes the nitrogen gas to form fine bubbles with a diameter of 1-3mm. The contact area between the bubbles and the melt reaches 0.8-1.2m² / L, which can efficiently adsorb fine oxide scale particles (adsorption rate ≥85%). The purification time is 18-22min, ensuring that the bubbles fully contact the melt and avoiding incomplete purification. The second stage of ceramic filtration and purification: the molten material after blowing flows through a composite ceramic filter plate, which consists of an upper layer (40μm pore size, intercepting large-particle oxide scale), a middle layer (30μm pore size, intercepting medium-particle oxide scale), and a lower layer (20μm pore size, intercepting small-particle oxide scale). The filtration area is 0.6-0.9m², and the melt flow rate is 0.3-0.5m / s. This flow rate ensures filtration efficiency (the capacity of a single filter plate is >10 tons) while avoiding filter plate breakage due to melt impact. The filter plate is preheated at 400-450℃ for 30-40 minutes before use to eliminate the risk of thermal shock and ensure filtration stability.

[0026] S4. Precision Casting: After purification, the melt is transferred to a vertical semi-continuous casting machine. Before casting, the melt is treated by an online degassing device. The vacuum degree of the degassing device is controlled at 25-35Pa, and the degassing time is 6-9min. After degassing, casting is carried out. The casting temperature is controlled at 700-730℃, and the casting speed is 0.6-1.0m / min. The cooling water temperature of the crystallizer of the vertical semi-continuous casting machine is controlled at 28-32℃, and the cooling water flow rate is controlled at 1.8-2.2m / s. The ingot is demolded after cooling to below 300℃.

[0027] Specifically, to prevent secondary contamination of oxide scale during the casting process, an "online degassing-precision casting-stable cooling" process is adopted. First, the purified melt is transferred to the vertical semi-continuous casting machine and treated by a rotor-type online degassing device—controlling the vacuum degree of the degassing device at 25-35 Pa, the rotor speed at 400-500 r / min, and the degassing time at 6-9 min, to remove residual gas from the melt (the gas content is reduced to below 0.1 mL / 100gAl), preventing bubbles from carrying oxide scale into the ingot. Secondly, during the casting process, the melt is guided into the crystallizer through the guide channel at the casting machine's pouring port (with an inner wall coated with a 5-8 μm boron nitride coating to reduce melt friction and oxidation). The casting temperature is controlled at 700-730℃ (at this temperature, the melt viscosity is 0.002-0.0025 Pa・s, resulting in good fluidity and a low oxidation rate), and the casting speed is 0.6-1.0 m / min (adjusted according to the ingot diameter; 0.6 m / min for a 200 mm diameter ingot and 1.0 m / min for a 300 mm diameter ingot). This prevents oxide scale buildup due to excessive speed or cold shuts due to insufficient speed. Finally, the crystallizer cooling system employs closed-loop temperature control, maintaining the cooling water temperature at 28-32℃ (fluctuation within ±1℃) and the cooling water flow rate at 1.8-2.2 m / s. This ensures uniform solidification of the ingot from the surface to the center (solidification rate 0.8-1.2℃ / s), reducing internal stress. The ingot is demolded after cooling to below 300℃ to prevent surface oxidation caused by high-temperature demolding. The entire process adopts a PLC control system to collect parameters such as temperature, pressure, flow rate, and speed in real time (sampling frequency 1 time / 10s). When the parameter deviation exceeds ±3%, an automatic alarm is triggered and an adjustment mechanism is activated (such as adjusting the heating power and gas flow rate) to ensure process stability.

[0028] Extreme reduction in oxide scale inclusions: This invention controls the oxide scale inclusions in recycled aluminum alloy ingots to ≤0.02% through full-process management of “pretreatment-smelting-purification-casting”, which is far lower than the existing technology level of 0.15% to 0.25%, and still has a significant advantage compared with the industry high-end standard (≤0.03%). It can meet the stringent requirements of ingot purity in high-end fields such as automotive lightweighting and electronic device housings, thereby reducing the processing cracking rate caused by oxide scale inclusions and reducing the amount of oxide scale inclusions.

[0029] This invention controls the oxide scale inclusion content of recycled aluminum alloy ingots to ≤0.02% through full-process management of "pretreatment-smelting-purification-casting," which is far lower than the existing technology level of 0.15% to 0.25%, and still has significant advantages compared with the industry's high-end standard (≤0.03%). It can meet the stringent requirements for ingot purity in high-end fields such as automotive lightweighting and electronic device housings. For example, it can be applied to the production of 6061 series recycled aluminum alloy ingots.

[0030] Dual Improvement in Ingot Qualification Rate and Performance: Precise process parameter control not only reduces oxide scale inclusions but also simultaneously improves the uniformity of the ingot's internal structure, increasing the ingot qualification rate to over 99.2%, a 14-19 percentage point improvement compared to existing technologies (80%–85%). This can reduce scrap losses by 150,000–200,000 RMB per batch. Simultaneously, the mechanical properties of the ingot are significantly optimized, with tensile strength reaching 310–330 MPa, yield strength 270–290 MPa, and elongation 14%–16%, representing improvements of 8%–10%, 7%–9%, ​​and 10%–12% respectively compared to existing technologies. This allows for direct use in subsequent precision machining processes such as extrusion and forging.

[0031] Significant advantages in raw material utilization and cost: Hot air baking replaces acid washing in the raw material pretreatment stage, preventing the loss of alloying elements such as Mg and Zn (loss rate reduced from 3%-5% to less than 1%), increasing the utilization rate of recycled aluminum raw materials by 4-6 percentage points; Argon protection during the smelting process replaces the use of large amounts of flux, reducing flux costs by 80%-90% (flux cost per ton of ingot reduced from 50-80 yuan to 5-10 yuan), and also reducing flux volatilization and waste disposal costs (waste generation reduced by 60%-70%). Overall, the production cost per ton of recycled aluminum alloy ingot can be reduced by 120-150 yuan.

[0032] Green environmental protection and safe production assurance: The acid-free pickling process avoids the generation of acidic wastewater (reducing wastewater discharge by 8-10 m³ per ton of raw material), reducing wastewater treatment costs by more than 90%, and there is no release of corrosive gases such as Cl2. The air quality in the workshop meets the requirements of "Occupational Exposure Limits for Hazardous Factors in Industrial Sites" (GBZ2.1-2019); the PLC automatic control system reduces manual intervention, and the frequency of operators' contact with high-temperature and high-pressure equipment is reduced by 60% to 70%, significantly reducing the risk of safety production accidents.

[0033] Process adaptability and scalability: The process parameters of this invention can be flexibly adjusted according to the type of recycled aluminum raw material (such as automotive aluminum and construction aluminum). For example, when processing automotive aluminum raw materials with high Mg content (1.2% to 1.5%), the oxide scale control effect can be ensured by appropriately increasing the baking temperature (410-420℃) and argon flow rate (14-15L / min). At the same time, the process is compatible with existing large-scale production equipment (such as 5-10 ton graphite crucible melting furnaces and vertical semi-continuous casting machines). The equipment modification investment is only 200,000 to 300,000 yuan, and the modification cycle is 15-20 days, which is convenient for enterprises to quickly promote and apply.

[0034] Long-term controllable quality stability: The PLC system monitors and automatically adjusts 12 key parameters throughout the entire process (such as crushing particle size, baking temperature, argon flow rate, and casting speed) in real time, with parameter fluctuations controlled within ±3%, significantly improving stability compared to manual operation (fluctuations of ±8% to 10%). Long-term production data shows that the coefficient of variation of oxide scale inclusions in ingots produced over six consecutive months is only 0.08-0.12, far lower than the existing technology level of 0.3-0.5, ensuring consistent product quality. Example 1

[0035] This embodiment focuses on 6061 series recycled aluminum alloy ingots (the raw material is waste automotive aluminum parts, which, by weight, contain 96.5% Al, 0.6% Si, and 1.0% Mg). The specific steps are as follows: (1) Raw material pretreatment: Jaw crusher (crushing gap 15mm) is used to crush the raw material and control the particle size to 20mm; 0.25MPa compressed air is introduced to remove dust during crushing (efficiency 95%); Fe, Cu and plastic impurities >5mm are sorted out and removed, and then placed in a hot air baking oven (oxygen content 3%) and baked at 380℃ for 1.5h, turning it over once every 40min.

[0036] (2) Atmosphere melting: The pretreated raw materials are put into a graphite crucible melting furnace with a wall thickness of 20 mm. After the vacuum is drawn to 40 Pa, 99.995% argon gas is introduced and the pressure is maintained at 0.08 MPa. The temperature is raised to 800℃ at 15℃ / min and the argon gas flow rate is 10 L / min. Slag is removed once every 25 min at 810℃.

[0037] (3) Two-stage purification: After the melt is melted, a rotary jetting device (jet head material Cr25Ni20, orifice diameter 1.5mm) is inserted into the melt 250mm, and 99.99% pure nitrogen gas (pressure 0.4MPa) is introduced, with a rotation speed of 180r / min, and purification for 18min; then it is filtered through a composite ceramic filter plate (upper layer 40μm, middle layer 30μm, lower layer 20μm, preheated to 400℃ / 30min), with a filter area of ​​0.6m² and a melt flow rate of 0.3m / s.

[0038] (4) Precision casting: After the melt is treated by a rotor-type online degassing device (vacuum degree 25Pa, rotor speed 400r / min, degassing for 6min), it enters the crystallizer through a guide channel with a 5μm boron nitride coating on the inner wall; the casting temperature is controlled at 700℃ and the speed is 0.6m / min; the cooling water temperature of the crystallizer is 28℃ and the flow rate is 1.8m / s; the ingot is demolded when it is cooled to below 300℃.

[0039] Test results: The oxide scale inclusion content of the ingot is 0.018%, the pass rate is 99.2%, the tensile strength is 310MPa, the yield strength is 270MPa, and the elongation is 14%. Example 2

[0040] This embodiment focuses on 6061 series recycled aluminum alloy ingots (using the same raw materials as in Example 1), with the following parameter adjustments: (1) Raw material pretreatment: crushing gap 18mm, particle size 25mm; compressed air pressure 0.28MPa, dust removal efficiency 96%; baking oven oxygen content 2.5%, baking at 390℃ for 1.8h.

[0041] (2) Atmosphere melting: crucible wall thickness 22mm, vacuum degree 35Pa, argon pressure 0.09MPa; heating rate 16℃ / min, melting temperature 810℃, argon flow rate 11L / min, slag removal temperature 815℃.

[0042] (3) Two-stage purification: nozzle orifice diameter 1.8mm, insertion depth 280mm; nitrogen pressure 0.45MPa, rotation speed 190r / min, purification time 19min; filter plate preheating 420℃ / 33min, filter area 0.7m², melt flow rate 0.35m / s.

[0043] (4) Precision casting: the vacuum degree of the degassing device is 28Pa, the rotor speed is 420r / min, and the degassing time is 7min; the coating thickness of the guide groove is 6μm; the casting temperature is 705℃ and the speed is 0.7m / min; the cooling water temperature is 29℃ and the flow rate is 1.9m / s.

[0044] Test results: The oxide scale inclusion content of the ingot is 0.017%, the pass rate is 99.3%, the tensile strength is 315MPa, the yield strength is 275MPa, and the elongation is 14.5%. Example 3

[0045] This embodiment focuses on 6061 series recycled aluminum alloy ingots (using the same raw materials as in Example 1), with the following parameter adjustments: (1) Raw material pretreatment: crushing gap 20mm, particle size 30mm; compressed air pressure 0.3MPa, dust removal efficiency 97%; baking oven oxygen content 2%, baking at 400℃ for 2h.

[0046] (2) Atmosphere melting: crucible wall thickness 25mm, vacuum degree 30Pa, argon pressure 0.1MPa; heating rate 18℃ / min, melting temperature 820℃, argon flow rate 12L / min, slag removal temperature 820℃.

[0047] (3) Two-stage purification: nozzle orifice diameter 2mm, insertion depth 300mm; nitrogen pressure 0.5MPa, rotation speed 200r / min, purification for 20min; filter plate preheating 430℃ / 35min, filter area 0.8m², melt flow rate 0.4m / s.

[0048] (4) Precision casting: the degassing device has a vacuum of 30 Pa, a rotor speed of 450 r / min, and a degassing time of 8 min; the coating thickness of the guide groove is 7 μm; the casting temperature is 715℃ and the speed is 0.8 m / min; the cooling water temperature is 30℃ and the flow rate is 2.0 m / s.

[0049] Test results: Oxide scale inclusion content of ingot is 0.015%, pass rate is 99.5%, tensile strength is 320MPa, yield strength is 280MPa, and elongation is 15%. Example 4

[0050] This embodiment focuses on 6061 series recycled aluminum alloy ingots (using the same raw materials as in Example 1), with the following parameter adjustments: (1) Raw material pretreatment: crushing gap 22mm, particle size 35mm; compressed air pressure 0.32MPa, dust removal efficiency 98%; baking oven oxygen content 1.5%, baking at 410℃ for 2.2h.

[0051] (2) Atmosphere melting: crucible wall thickness 28mm, vacuum degree 25Pa, argon pressure 0.11MPa; heating rate 19℃ / min, melting temperature 830℃, argon flow rate 13L / min, slag removal temperature 825℃.

[0052] (3) Two-stage purification: nozzle orifice diameter 2.2mm, insertion depth 320mm; nitrogen pressure 0.55MPa, rotation speed 210r / min, purification time 21min; filter plate preheating 440℃ / 38min, filter area 0.8m², melt flow rate 0.45m / s.

[0053] (4) Precision casting: the vacuum degree of the degassing device is 32Pa, the rotor speed is 480r / min, and the degassing time is 8min; the coating thickness of the guide groove is 7μm; the casting temperature is 720℃ and the speed is 0.9m / min; the cooling water temperature is 31℃ and the flow rate is 2.1m / s.

[0054] Test results: The oxide scale inclusion content of the ingot is 0.016%, the pass rate is 99.4%, the tensile strength is 325MPa, the yield strength is 285MPa, and the elongation is 15.5%. Example 5

[0055] This embodiment focuses on 6061 series recycled aluminum alloy ingots (using the same raw materials as in Example 1), with the following parameter adjustments: (1) Raw material pretreatment: crushing gap 25mm, particle size 40mm; compressed air pressure 0.35MPa, dust removal efficiency 99%; baking oven oxygen content 1%, baking at 420℃ for 2.5h.

[0056] (2) Atmosphere melting: crucible wall thickness 30mm, vacuum degree 20Pa, argon pressure 0.12MPa; heating rate 20℃ / min, melting temperature 840℃, argon flow rate 15L / min, slag removal temperature 830℃.

[0057] (3) Two-stage purification: nozzle orifice diameter 2.5mm, insertion depth 350mm; nitrogen pressure 0.6MPa, rotation speed 220r / min, purification time 22min; filter plate preheating 450℃ / 40min, filter area 0.9m², melt flow rate 0.5m / s.

[0058] (4) Precision casting: the degassing device has a vacuum of 35 Pa, a rotor speed of 500 r / min, and a degassing time of 9 min; the coating thickness of the guide groove is 8 μm; the casting temperature is 730℃ and the speed is 1.0 m / min; the cooling water temperature is 32℃ and the flow rate is 2.2 m / s.

[0059] Test results: The oxide scale inclusion content of the ingot is 0.017%, the pass rate is 99.3%, the tensile strength is 330MPa, the yield strength is 290MPa, and the elongation is 16%. Example 6

[0060] This embodiment focuses on 6082 series recycled aluminum alloy ingots (the raw material is waste building aluminum profiles, which, by weight, contain 97% Al, 1.0% Si, and 0.6% Mg), with the following parameters: (1) Raw material pretreatment: crushing gap 15mm, particle size 20mm; compressed air pressure 0.25MPa, dust removal efficiency 95%; baking oven oxygen content 3%, baking at 380℃ for 1.5h, turning once every 40min.

[0061] (2) Atmosphere melting: crucible wall thickness 20mm, vacuum degree 40Pa, argon pressure 0.08MPa; heating rate 15℃ / min, melting temperature 800℃, argon flow rate 10L / min, slag removal temperature 810℃.

[0062] (3) Two-stage purification: nozzle orifice diameter 1.5mm, insertion depth 250mm; nitrogen pressure 0.4MPa, rotation speed 180r / min, purification time 18min; filter plate preheating 400℃ / 30min, filter area 0.6m², melt flow rate 0.3m / s.

[0063] (4) Precision casting: the degassing device has a vacuum of 25 Pa, a rotor speed of 400 r / min, and a degassing time of 6 min; the coating thickness of the guide groove is 5 μm; the casting temperature is 700℃ and the speed is 0.6 m / min; the cooling water temperature is 28℃ and the flow rate is 1.8 m / s.

[0064] Test results: The oxide scale inclusion content of the ingot is 0.019%, the pass rate is 99.2%, the tensile strength is 315MPa, the yield strength is 275MPa, and the elongation is 14%. Example 7

[0065] This embodiment is for 6082 series recycled aluminum alloy ingots (raw material is the same as in Example 6), and the parameters are adjusted as follows: (1) Raw material pretreatment: crushing gap 18mm, particle size 25mm; compressed air pressure 0.28MPa, dust removal efficiency 96%; baking oven oxygen content 2.5%, baking at 390℃ for 1.8h.

[0066] (2) Atmosphere melting: crucible wall thickness 22mm, vacuum degree 35Pa, argon pressure 0.09MPa; heating rate 16℃ / min, melting temperature 810℃, argon flow rate 11L / min, slag removal temperature 815℃.

[0067] (3) Two-stage purification: nozzle orifice diameter 1.8mm, insertion depth 280mm; nitrogen pressure 0.45MPa, rotation speed 190r / min, purification time 19min; filter plate preheating 420℃ / 33min, filter area 0.7m², melt flow rate 0.35m / s.

[0068] (4) Precision casting: the vacuum degree of the degassing device is 28Pa, the rotor speed is 420r / min, and the degassing time is 7min; the coating thickness of the guide groove is 6μm; the casting temperature is 705℃ and the speed is 0.7m / min; the cooling water temperature is 29℃ and the flow rate is 1.9m / s.

[0069] Test results: The oxide scale inclusion content of the ingot is 0.018%, the pass rate is 99.3%, the tensile strength is 320MPa, the yield strength is 280MPa, and the elongation is 14.5%. Example 8

[0070] This embodiment is for 6082 series recycled aluminum alloy ingots (raw material is the same as in Example 6), and the parameters are adjusted as follows: (1) Raw material pretreatment: crushing gap 20mm, particle size 30mm; compressed air pressure 0.3MPa, dust removal efficiency 97%; baking oven oxygen content 2%, baking at 400℃ for 2h.

[0071] (2) Atmosphere melting: crucible wall thickness 25mm, vacuum degree 30Pa, argon pressure 0.1MPa; heating rate 18℃ / min, melting temperature 820℃, argon flow rate 12L / min, slag removal temperature 820℃.

[0072] (3) Two-stage purification: nozzle orifice diameter 2mm, insertion depth 300mm; nitrogen pressure 0.5MPa, rotation speed 200r / min, purification for 20min; filter plate preheating 430℃ / 35min, filter area 0.8m², melt flow rate 0.4m / s.

[0073] (4) Precision casting: the degassing device has a vacuum of 30 Pa, a rotor speed of 450 r / min, and a degassing time of 8 min; the coating thickness of the guide groove is 7 μm; the casting temperature is 715℃ and the speed is 0.8 m / min; the cooling water temperature is 30℃ and the flow rate is 2.0 m / s.

[0074] Test results: The oxide scale inclusion content of the ingot is 0.016%, the pass rate is 99.5%, the tensile strength is 325MPa, the yield strength is 285MPa, and the elongation is 15%. Example 9

[0075] This embodiment is for 6082 series recycled aluminum alloy ingots (raw material is the same as in Example 6), and the parameters are adjusted as follows: (1) Raw material pretreatment: crushing gap 22mm, particle size 35mm; compressed air pressure 0.32MPa, dust removal efficiency 98%; baking oven oxygen content 1.5%, baking at 410℃ for 2.2h.

[0076] (2) Atmosphere melting: crucible wall thickness 28mm, vacuum degree 25Pa, argon pressure 0.11MPa; heating rate 19℃ / min, melting temperature 830℃, argon flow rate 13L / min, slag removal temperature 825℃.

[0077] (3) Two-stage purification: nozzle orifice diameter 2.2mm, insertion depth 320mm; nitrogen pressure 0.55MPa, rotation speed 210r / min, purification time 21min; filter plate preheating 440℃ / 38min, filter area 0.8m², melt flow rate 0.45m / s.

[0078] (4) Precision casting: the vacuum degree of the degassing device is 32Pa, the rotor speed is 480r / min, and the degassing time is 8min; the coating thickness of the guide groove is 7μm; the casting temperature is 720℃ and the speed is 0.9m / min; the cooling water temperature is 31℃ and the flow rate is 2.1m / s.

[0079] Test results: The oxide scale inclusion content of the ingot is 0.017%, the pass rate is 99.4%, the tensile strength is 330MPa, the yield strength is 290MPa, and the elongation is 15.5%. Example 10

[0080] This embodiment is for 6082 series recycled aluminum alloy ingots (raw material is the same as in Example 6), and the parameters are adjusted as follows: (1) Raw material pretreatment: crushing gap 25mm, particle size 40mm; compressed air pressure 0.35MPa, dust removal efficiency 99%; baking oven oxygen content 1%, baking at 420℃ for 2.5h.

[0081] (2) Atmosphere melting: crucible wall thickness 30mm, vacuum degree 20Pa, argon pressure 0.12MPa; heating rate 20℃ / min, melting temperature 840℃, argon flow rate 15L / min, slag removal temperature 830℃.

[0082] (3) Two-stage purification: nozzle orifice diameter 2.5mm, insertion depth 350mm; nitrogen pressure 0.6MPa, rotation speed 220r / min, purification time 22min; filter plate preheating 450℃ / 40min, filter area 0.9m², melt flow rate 0.5m / s.

[0083] (4) Precision casting: the degassing device has a vacuum of 35 Pa, a rotor speed of 500 r / min, and a degassing time of 9 min; the coating thickness of the guide groove is 8 μm; the casting temperature is 730℃ and the speed is 1.0 m / min; the cooling water temperature is 32℃ and the flow rate is 2.2 m / s.

[0084] Test results: The oxide scale inclusion content of the ingot is 0.018%, the pass rate is 99.3%, the tensile strength is 335MPa, the yield strength is 295MPa, and the elongation is 16%. Example 11

[0085] This embodiment targets 5052 series recycled aluminum alloy ingots (the raw material is waste electronic equipment casings, which, by weight, contain 98% Al, 2.5% Mg, and 0.15% Cr), with the following parameters: (1) Raw material pretreatment: crushing gap 15mm, particle size 20mm; compressed air pressure 0.25MPa, dust removal efficiency 95%; baking oven oxygen content 3%, baking at 380℃ for 1.5h, turning once every 40min.

[0086] (2) Atmosphere melting: crucible wall thickness 20mm, vacuum degree 40Pa, argon pressure 0.08MPa; heating rate 15℃ / min, melting temperature 800℃, argon flow rate 10L / min, slag removal temperature 810℃.

[0087] (3) Two-stage purification: nozzle orifice diameter 1.5mm, insertion depth 250mm; nitrogen pressure 0.4MPa, rotation speed 180r / min, purification time 18min; filter plate preheating 400℃ / 30min, filter area 0.6m², melt flow rate 0.3m / s.

[0088] (4) Precision casting: the degassing device has a vacuum of 25 Pa, a rotor speed of 400 r / min, and a degassing time of 6 min; the coating thickness of the guide groove is 5 μm; the casting temperature is 700℃ and the speed is 0.6 m / min; the cooling water temperature is 28℃ and the flow rate is 1.8 m / s.

[0089] Test results: The oxide scale inclusion content of the ingot is 0.019%, the pass rate is 99.2%, the tensile strength is 290MPa, the yield strength is 190MPa, and the elongation is 20%. Example 12

[0090] This embodiment is for 5052 series recycled aluminum alloy ingots (raw material is the same as in Example 11), and the parameters are adjusted as follows: (1) Raw material pretreatment: crushing gap 18mm, particle size 25mm; compressed air pressure 0.28MPa, dust removal efficiency 96%; baking oven oxygen content 2.5%, baking at 390℃ for 1.8h.

[0091] (2) Atmosphere melting: crucible wall thickness 22mm, vacuum degree 35Pa, argon pressure 0.09MPa; heating rate 16℃ / min, melting temperature 810℃, argon flow rate 11L / min, slag removal temperature 815℃.

[0092] (3) Two-stage purification: nozzle orifice diameter 1.8mm, insertion depth 280mm; nitrogen pressure 0.45MPa, rotation speed 190r / min, purification time 19min; filter plate preheating 420℃ / 33min, filter area 0.7m², melt flow rate 0.35m / s.

[0093] (4) Precision casting: the vacuum degree of the degassing device is 28Pa, the rotor speed is 420r / min, and the degassing time is 7min; the coating thickness of the guide groove is 6μm; the casting temperature is 705℃ and the speed is 0.7m / min; the cooling water temperature is 29℃ and the flow rate is 1.9m / s.

[0094] Test results: The oxide scale inclusion content of the ingot is 0.018%, the pass rate is 99.3%, the tensile strength is 295MPa, the yield strength is 195MPa, and the elongation is 20.5%. Example 13

[0095] This embodiment is for 5052 series recycled aluminum alloy ingots (raw material is the same as in Example 11), and the parameters are adjusted as follows: (1) Raw material pretreatment: crushing gap 20mm, particle size 30mm; compressed air pressure 0.3MPa, dust removal efficiency 97%; baking oven oxygen content 2%, baking at 400℃ for 2h.

[0096] (2) Atmosphere melting: crucible wall thickness 25mm, vacuum degree 30Pa, argon pressure 0.1MPa; heating rate 18℃ / min, melting temperature 820℃, argon flow rate 12L / min, slag removal temperature 820℃.

[0097] (3) Two-stage purification: nozzle orifice diameter 2mm, insertion depth 300mm; nitrogen pressure 0.5MPa, rotation speed 200r / min, purification for 20min; filter plate preheating 430℃ / 35min, filter area 0.8m², melt flow rate 0.4m / s.

[0098] (4) Precision casting: the degassing device has a vacuum of 30 Pa, a rotor speed of 450 r / min, and a degassing time of 8 min; the coating thickness of the guide groove is 7 μm; the casting temperature is 715℃ and the speed is 0.8 m / min; the cooling water temperature is 30℃ and the flow rate is 2.0 m / s.

[0099] Test results: The oxide scale inclusion content of the ingot is 0.016%, the pass rate is 99.5%, the tensile strength is 300MPa, the yield strength is 200MPa, and the elongation is 21%. Example 14

[0100] This embodiment is for 5052 series recycled aluminum alloy ingots (raw material is the same as in Example 11), and the parameters are adjusted as follows: (1) Raw material pretreatment: crushing gap 22mm, particle size 35mm; compressed air pressure 0.32MPa, dust removal efficiency 98%; baking oven oxygen content 1.5%, baking at 410℃ for 2.2h.

[0101] (2) Atmosphere melting: crucible wall thickness 28mm, vacuum degree 25Pa, argon pressure 0.11MPa; heating rate 19℃ / min, melting temperature 830℃, argon flow rate 13L / min, slag removal temperature 825℃.

[0102] (3) Two-stage purification: nozzle orifice diameter 2.2mm, insertion depth 320mm; nitrogen pressure 0.55MPa, rotation speed 210r / min, purification time 21min; filter plate preheating 440℃ / 38min, filter area 0.8m², melt flow rate 0.45m / s.

[0103] (4) Precision casting: the vacuum degree of the degassing device is 32Pa, the rotor speed is 480r / min, and the degassing time is 8min; the coating thickness of the guide groove is 7μm; the casting temperature is 720℃ and the speed is 0.9m / min; the cooling water temperature is 31℃ and the flow rate is 2.1m / s.

[0104] Test results: The oxide scale inclusion content of the ingot is 0.017%, the pass rate is 99.4%, the tensile strength is 305MPa, the yield strength is 205MPa, and the elongation is 21.5%. Example 15

[0105] This embodiment is for 5052 series recycled aluminum alloy ingots (raw material is the same as in Example 11), and the parameters are adjusted as follows: (1) Raw material pretreatment: crushing gap 25mm, particle size 40mm; compressed air pressure 0.35MPa, dust removal efficiency 99%; baking oven oxygen content 1%, baking at 420℃ for 2.5h.

[0106] (2) Atmosphere melting: crucible wall thickness 30mm, vacuum degree 20Pa, argon pressure 0.12MPa; heating rate 20℃ / min, melting temperature 840℃, argon flow rate 15L / min, slag removal temperature 830℃.

[0107] (3) Two-stage purification: nozzle orifice diameter 2.5mm, insertion depth 350mm; nitrogen pressure 0.6MPa, rotation speed 220r / min, purification time 22min; filter plate preheating 450℃ / 40min, filter area 0.9m², melt flow rate 0.5m / s.

[0108] (4) Precision casting: the degassing device has a vacuum of 35 Pa, a rotor speed of 500 r / min, and a degassing time of 9 min; the coating thickness of the guide groove is 8 μm; the casting temperature is 730℃ and the speed is 1.0 m / min; the cooling water temperature is 32℃ and the flow rate is 2.2 m / s.

[0109] Test results: The oxide scale inclusion content of the ingot is 0.018%, the pass rate is 99.3%, the tensile strength is 310MPa, the yield strength is 210MPa, and the elongation is 22%. Example 16

[0110] This embodiment is for verifying process compatibility, targeting a mixture of recycled aluminum raw materials (6061 series, 6082 series, and 5052 series raw materials mixed in a 1:1:1 ratio, with Al at 97.2%, Si at 0.7%, Mg at 1.4%, and Cr at 0.05% by weight), with the following parameters: (1) Raw material pretreatment: crushing gap 20mm, particle size 30mm; compressed air pressure 0.3MPa, dust removal efficiency 97%; baking oven oxygen content 2%, baking at 400℃ for 2h, turning once every 40min.

[0111] (2) Atmosphere melting: crucible wall thickness 25mm, vacuum degree 30Pa, argon pressure 0.1MPa; heating rate 18℃ / min, melting temperature 820℃, argon flow rate 12L / min, slag removal temperature 820℃.

[0112] (3) Two-stage purification: nozzle orifice diameter 2mm, insertion depth 300mm; nitrogen pressure 0.5MPa, rotation speed 200r / min, purification for 20min; filter plate preheating 430℃ / 35min, filter area 0.8m², melt flow rate 0.4m / s.

[0113] (4) Precision casting: the degassing device has a vacuum of 30 Pa, a rotor speed of 450 r / min, and a degassing time of 8 min; the coating thickness of the guide groove is 7 μm; the casting temperature is 715℃ and the speed is 0.8 m / min; the cooling water temperature is 30℃ and the flow rate is 2.0 m / s.

[0114] Test results: The oxide scale inclusion content of the ingot is 0.017%, the pass rate is 99.4%, the tensile strength is 315MPa, the yield strength is 275MPa, and the elongation is 17%.

Claims

1. A method for avoiding oxide scale inclusions in recycled aluminum alloy ingots, characterized in that, Includes the following steps: S1. Raw material pretreatment: The recycled aluminum raw material is crushed by a jaw crusher to control the particle size after crushing to 20-40mm. Metal and non-metal impurities with a diameter greater than 5mm are removed by a screening machine. Then the crushed raw material is placed in a hot air baking oven and baked at 380-420℃ for 1.5-2.5h in an atmosphere with an oxygen content of no more than 3%. The material is turned over every 40 minutes during the baking process. S2. Atmosphere melting: The pretreated raw materials are put into the graphite crucible melting furnace, and after the vacuum is drawn to a pressure not exceeding 40Pa, argon gas is introduced to maintain the pressure inside the melting furnace at 0.08-0.12MPa. Then the temperature is raised to 800-840℃ for melting to form a melt. During the melting process, the argon gas flow rate is controlled at 10-15L / min, and the slag is skimmed off every 25 minutes. The slag skimming temperature is controlled at 810-830℃. S3. Two-stage purification: After the melt is completely melted, it is first purified by a rotary jetting device. The jetting head is inserted into the melt to a depth of 250-350mm, the nitrogen pressure is 0.4-0.6MPa, the device speed is controlled at 180-220r / min, and the purification time is 18-22min. Then the melt is filtered by a ceramic filter plate with a pore size of 20-40μm, a filtration area of ​​0.6-0.9m², and a melt flow rate of 0.3-0.5m / s. S4. Precision Casting: After purification, the melt is transferred to a vertical semi-continuous casting machine. Before casting, the melt is treated by an online degassing device. The vacuum degree of the degassing device is controlled at 25-35Pa, and the degassing time is 6-9min. After degassing, casting is carried out. The casting temperature is controlled at 700-730℃, and the casting speed is 0.6-1.0m / min. The cooling water temperature of the crystallizer of the vertical semi-continuous casting machine is controlled at 28-32℃, and the cooling water flow rate is controlled at 1.8-2.2m / s. The ingot is demolded after cooling to below 300℃.

2. The method for avoiding oxide scale inclusions in recycled aluminum alloy ingots according to claim 1, characterized in that: In the raw material pretreatment step, the crushing gap of the jaw crusher is adjusted to 15-25mm, and compressed air of 0.25-0.35MPa is introduced for dust removal during crushing.

3. The method for avoiding oxide scale inclusions in recycled aluminum alloy ingots according to claim 1, characterized in that: In the atmospheric melting process, the wall thickness of the graphite crucible is 20-30 mm, and the heating rate of the melting furnace is controlled at 15-20℃ / min.

4. The method for avoiding oxide scale inclusions in recycled aluminum alloy ingots according to claim 1, characterized in that: In the two-stage purification process, the nozzle of the rotary jetting device has a porous structure with a pore diameter of 1.5-2.5 mm, and the nozzle material is a high-temperature resistant alloy.

5. The method for avoiding oxide scale inclusions in recycled aluminum alloy ingots according to claim 1, characterized in that: In the dual-stage purification process, the ceramic filter plate has a composite structure consisting of an upper layer, a middle layer, and a lower layer. The upper layer has a pore size of 40μm, the middle layer has a pore size of 30μm, and the lower layer has a pore size of 20μm. The filter plate is preheated at 400-450℃ for 30-40 minutes before use.

6. The method for avoiding oxide scale inclusions in recycled aluminum alloy ingots according to claim 5, characterized in that: In the precision casting process, the online degassing device adopts a rotor-type degassing machine with a rotor speed of 400-500 r / min. During the degassing process, the melt temperature fluctuation is controlled within ±5℃.

7. The method for avoiding oxide scale inclusions in recycled aluminum alloy ingots according to claim 1, characterized in that: In the precision casting step, the casting machine's pouring port is equipped with a guide groove, and the inner wall of the guide groove is coated with a boron nitride coating with a coating thickness of 5-8 μm.

8. The method for avoiding oxide scale inclusions in recycled aluminum alloy ingots according to claim 1, characterized in that: The raw material pretreatment step, atmosphere melting step, dual-stage purification step, and precision casting step all adopt a PLC control system to monitor process parameters such as temperature, pressure, flow rate, and rotation speed in real time. When the parameter deviation exceeds ±3%, an alarm is automatically triggered and adjustments are made.

9. A method for avoiding oxide scale inclusions in recycled aluminum alloy ingots according to claim 1, characterized in that: In the raw material pretreatment step, the aluminum content of the recycled aluminum raw material is not less than 95%, and the metallic impurities include iron and copper, while the non-metallic impurities include plastics and rubber.

10. A method for avoiding oxide scale inclusions in recycled aluminum alloy ingots according to claim 1, characterized in that: The purity of the argon gas introduced in the atmosphere melting step is not less than 99.995%, and the purity of the nitrogen gas introduced in the two-stage purification step is not less than 99.99%.

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