A method of reducing hydrogen content of a secondary aluminium melt

Abstract

This invention discloses a method for reducing the hydrogen content of molten recycled aluminum, relating to the field of recycled aluminum smelting technology, and includes the following steps: S1, Pretreatment of recycled aluminum raw materials: Prepare recycled aluminum raw materials by first crushing them into particles with a diameter of 5-10 mm, removing fine powder with a diameter less than 3 mm and coarse particles with a diameter greater than 12 mm using a vibrating grading screen, and then placing the remaining raw materials in a degreasing tank equipped with an ultrasonic generator for gradient degreasing and ultrasonic enhancement treatment. This method for reducing the hydrogen content of molten recycled aluminum, through refined pretreatment of recycled aluminum raw materials by crushing and grading, gradient degreasing and ultrasonic enhancement, and online moisture monitoring, can efficiently remove oil and moisture from the surface of the raw materials, cutting off the path of water decomposition and oil combustion to produce hydrogen from the source, and significantly reducing the burden on subsequent hydrogen removal processes. The synergistic effect of gradient degreasing and ultrasonic treatment significantly improves degreasing efficiency.

Description

Technical Field

[0001] This invention relates to the field of recycled aluminum smelting technology, and in particular to a method for reducing the hydrogen content of recycled aluminum melt. Background Technology

[0002] With the rapid development of the global aluminum industry, the demand for aluminum continues to grow. However, bauxite, as a non-renewable resource, is becoming increasingly scarce. The recycled aluminum industry, due to its advantages of low energy consumption, low pollution, and high resource utilization, has gained widespread attention and rapid development. Recycled aluminum is produced by remelting and refining scrap aluminum and aluminum alloy waste. However, during the smelting process, the molten aluminum easily absorbs hydrogen, resulting in excessively high hydrogen content. This leads to defects such as porosity and looseness in subsequent casting and processing, severely affecting the mechanical properties, corrosion resistance, and processing performance of the products, thus limiting the application of recycled aluminum in high-quality fields.

[0003] Currently, the mainstream methods for reducing the hydrogen content of molten aluminum have significant limitations: inert gas blowing is simple to operate and low in cost, but its hydrogen removal efficiency is low, and it is ineffective at removing fine hydrogen bubbles, especially when processing recycled aluminum melt with high impurity content, where the bubble dispersion is affected, leading to a further decrease in effectiveness; vacuum refining has a better hydrogen removal effect, but it suffers from high equipment investment, high energy consumption, and low production efficiency, and the aluminum melt is easily oxidized in a vacuum environment, requiring additional protection measures and increasing costs, which is not conducive to large-scale industrial application; traditional degassing agent methods often use single components such as magnesium chloride and calcium fluoride, which have limited hydrogen removal effects and easily introduce new impurities. Although existing technologies have composite degassing agents and combined processes, they generally suffer from problems such as insufficient raw material pretreatment, inaccurate control of process parameters, and lack of degassing agent integration, resulting in continuous hydrogen production from moisture and oil in the raw materials, making it difficult to control the hydrogen content at a low level.

[0004] Therefore, it is necessary to propose a method to reduce the hydrogen content of recycled aluminum melt to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a method for reducing the hydrogen content of recycled aluminum melt, in order to solve the problem that the inert gas blowing method is simple to operate and low in cost, but has low hydrogen removal efficiency and poor effect on removing fine hydrogen bubbles. In particular, when processing recycled aluminum melt with high impurity content, the bubble dispersion is affected, which leads to a further decrease in effect.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for reducing the hydrogen content of recycled aluminum melt, comprising the following steps:

[0007] S1. Pretreatment of recycled aluminum raw materials: Prepare recycled aluminum raw materials by first crushing them into particles with a diameter of 5-10mm. Remove fine powder with a diameter less than 3mm and coarse particles with a diameter greater than 12mm by using a vibrating grading screen. Then, place the remaining raw materials in a degreasing tank equipped with an ultrasonic generator for gradient degreasing and ultrasonic enhancement treatment. Afterward, rinse with deionized water until neutral and place them in a hot air circulating oven with online moisture monitoring function to dry until the moisture content is ≤0.1%.

[0008] S2. Melting and In-situ Dehydrogenation Triggering Treatment: Add the pretreated raw materials to the melting furnace and heat them at a rate of 10-15℃ / min. When the temperature reaches 600-650℃, hold it for 10-15 minutes. At the same time, introduce a nitrogen-water vapor mixed gas flow at a speed of 0.1-0.2 m³ / h for 5-8 minutes. Then, restore the pure nitrogen protective atmosphere and continue heating to 800-850℃ to completely melt the raw materials and form aluminum melt.

[0009] S3. Addition of composite degassing agent: Add the pre-made composite degassing agent to the aluminum melt at a rate of 0.8-1.2% of the mass of the aluminum melt, and stir to ensure that the degassing agent is fully mixed with the melt;

[0010] S4. Segmented refining: First, lower the melt temperature to 750-780℃, then introduce argon gas for blowing. After blowing, lower the temperature to 720-750℃ and evacuate to 50-80Pa for vacuum refining.

[0011] S5. Settling and Testing: After vacuum refining, let the melt stand for 10-15 minutes at a temperature of 720-750℃. Use the vacuum gas sampling method to sample the hydrogen content from the upper, middle and lower parts of the melt. If the average value is ≤0.12ml / 100gAl, the processing is complete. If it does not meet the standard, repeat the vacuum refining step.

[0012] Preferably, in step S1, during the gradient degreasing and ultrasonic enhancement treatment, a 3-4% sodium hydroxide solution is first used for pretreatment at a temperature of 40-45°C for 5-8 minutes. Then, the solution concentration is increased to 5-8%, the temperature is raised to 50-60°C, and ultrasonic treatment is performed at a frequency of 20-40kHz, a power of 500-800W, and a duration of 15-22 minutes.

[0013] Preferably, in step S1, the drying temperature is 120-150℃, the drying time is 1-1.5h, and the moisture content of the raw material is monitored in real time by an infrared moisture sensor.

[0014] Preferably, the melting furnace is a resistance melting furnace or an induction melting furnace.

[0015] Preferably, the composite degassing agent is composed of magnesium chloride, calcium fluoride, and silicon dioxide in a mass ratio of 3:2:1. Each component is pulverized to 100-200 mesh using a ball mill, dried at 300-350℃ for 2-3 hours, and then sealed for storage.

[0016] Preferably, in step S4, when argon gas is introduced for blowing, the nozzle used to deliver argon gas is inserted into the melt to a depth of 15-20 cm, the nozzle orifice diameter is 2-3 mm, the argon gas flow rate is 0.3-0.5 m³ / h, and the blowing time is 15-20 min.

[0017] Preferably, in step S4, the vacuum pumping rate is 5-8 Pa / s, the refining time is 25-30 min, and a stirring operation is performed every 5 min during the refining process.

[0018] Preferably, in step S5, each part is sampled 2-3 times, and the average value of all sample test results is taken as the final hydrogen content.

[0019] Preferably, in step S2, the nitrogen-water vapor mixed gas flow is introduced at the same time as the heat preservation stage, and is evenly dispersed in the melting furnace by a gas distributor.

[0020] Preferably, in step S1, one or more of the following are selected as recycled aluminum raw materials: waste aluminum alloy doors and windows, and waste aluminum profile processing waste.

[0021] The technical effects and advantages of this invention are as follows:

[0022] By implementing refined pretreatment of recycled aluminum raw materials through crushing and grading, gradient degreasing and ultrasonic strengthening, and online moisture monitoring, oil and moisture on the surface of the raw materials can be efficiently removed, cutting off the path of water decomposition and oil combustion to produce hydrogen from the source, and greatly reducing the burden on subsequent hydrogen removal processes. Among them, the synergistic effect of gradient degreasing and ultrasonic strengthening significantly improves degreasing efficiency and solves the problem of continuous hydrogen production caused by insufficient raw material pretreatment in existing technologies.

[0023] By triggering in-situ hydrogen removal during the smelting stage, an inert gas-water vapor mixed gas flow is introduced during the heat preservation period. This can catalyze the reaction of residual trace oil and water vapor to accelerate the escape of impurities, and also form a hydrogen escape channel on the oxide film surface. Combined with a nitrogen protective atmosphere throughout the process, it can reduce the oxidation and hydrogen absorption during the smelting process, while avoiding local overheating and oxidation of raw materials, and improving the purity of the melt.

[0024] By adding a composite degassing agent composed of magnesium chloride, calcium fluoride, and silicon dioxide in a specific ratio, a synergistic effect of "reaction-flotation-adsorption purification" is achieved: magnesium chloride reacts with hydrogen to generate escapeable gas, calcium fluoride reduces the surface tension of the melt and promotes the floating of bubbles, and silicon dioxide adsorbs harmful impurities, significantly improving the degassing effect and melt purity. Compared with traditional single degassing agents, the degassing capacity is greatly enhanced, and new impurities are avoided, solving the defects of limited effect and easy impurity introduction of single degassing agents.

[0025] A segmented refining process combining inert gas blowing and vacuum refining, coupled with precise parameter control, achieves deep hydrogen removal: the first stage of argon blowing forms uniform, fine bubbles to capture hydrogen, while the second stage of vacuum refining utilizes pressure difference to accelerate hydrogen escape. The two stages work together to stably control the hydrogen content within the target range. Compared to single inert gas blowing, hydrogen removal efficiency is significantly improved; compared to full vacuum refining, energy consumption is significantly reduced, and the total processing time is reasonable, meeting the needs of industrial production. Attached Figure Description

[0026] Figure 1 This is a flowchart of the method for reducing the hydrogen content of recycled aluminum melt according to the present invention. Detailed Implementation

[0027] This invention provides, for example Figure 1 The method shown is to reduce the hydrogen content of recycled aluminum melt. Through a series of interconnected operations, including raw material pretreatment, precision smelting, addition of composite degassing agent, segmented refining and static testing, a complete technical system is built from source hydrogen control to deep hydrogen removal and then to precision testing, so as to achieve efficient and stable removal of hydrogen.

[0028] In practice, the recycled aluminum raw materials are first pretreated by crushing, degreasing, cleaning and drying to lay a solid foundation for hydrogen removal in subsequent smelting. Then, the temperature, atmosphere and other parameters of the smelting process are precisely controlled to melt the raw materials and reduce oxidation and hydrogen absorption. Next, a special composite degassing agent is added and fully mixed to initially remove hydrogen through the synergistic effect of its components. Then, the hydrogen removal effect is further enhanced by a segmented refining method of inert gas blowing and vacuum refining. Finally, the treated aluminum melt is allowed to stand and the hydrogen content is tested to ensure that the target hydrogen content is achieved.

[0029] The specific implementation steps are as follows:

[0030] I. Pretreatment of recycled aluminum raw materials

[0031] Crushing and Grading: One or more types of waste aluminum alloy doors and windows, or waste aluminum profile processing waste, are selected as raw materials for recycled aluminum. Crushing equipment (such as a jaw crusher) is used to crush them into particles with a diameter of 5-10 mm. After crushing, the particles are graded using a vibrating grading screen to remove fine powder smaller than 3 mm and coarse particles larger than 12 mm. Fine powder is prone to loss and contamination during subsequent degreasing and smelting, while coarse particles are difficult to fully degrease and melt. Grading further optimizes the uniformity of the raw material particle size, laying the foundation for subsequent processes.

[0032] Gradient degreasing and ultrasonic enhancement treatment: The graded raw materials are placed in a degreasing tank equipped with an ultrasonic generator, and degreasing is performed using sodium hydroxide solutions of varying concentrations. Specifically: First, a 3-4% (w / w) sodium hydroxide solution is used for pretreatment at 40-45℃ for 5-8 minutes to initially remove surface oil; then, the solution concentration is increased to 5-8%, the temperature is raised to 50-60℃, and ultrasonic enhancement treatment (frequency 20-40kHz, power 500-800W) is activated for 15-22 minutes. The cavitation effect generated by the ultrasound can destroy the adhesion interface of oil on the surface of the raw materials. Combined with the gradient concentration degreasing agent, this avoids excessive corrosion of the aluminum raw materials by high-concentration solutions and achieves deep removal of oil, improving the degreasing efficiency by more than 30% compared to traditional single-concentration degreasing.

[0033] Cleaning, drying, and online moisture monitoring: After degreasing, the raw material is removed from the degreasing tank and repeatedly rinsed with deionized water until neutral (this can be determined by testing the pH value of the wastewater after rinsing with pH test paper). The rinsed raw material is then placed in a hot air circulating oven with online moisture monitoring and dried at 120-150℃ for 1-1.5 hours. During the drying process, the moisture content of the raw material is monitored in real time using an infrared moisture sensor. Drying is stopped when the moisture content drops below 0.1%, ensuring complete removal of moisture from the raw material and cutting off the hydrogen production pathway from water decomposition at the source.

[0034] II. Melting and In-situ Dehydrogenation Triggering Treatment

[0035] The pretreated recycled aluminum raw material is added to the smelting furnace (such as a resistance smelting furnace) through a feeding device. The smelting furnace heating system is started, and the temperature is increased at a rate of 10-15℃ / min. When the furnace temperature reaches 600-650℃, the heating is stopped and the temperature is held for 10-15 minutes. At the same time, a mixture of inert gas and water vapor (nitrogen with a purity ≥99.99%) with a volume fraction of 5-8% is introduced into the furnace at a flow rate of 0.1-0.2 m³ / h. The gas is continuously introduced for 5-8 minutes during the holding period.

[0036] This mixed airflow can trigger a catalytic reaction between the trace amounts of oil and water vapor remaining on the surface of the raw materials, accelerating the escape of volatile impurities. At the same time, the weak reaction between water vapor and the oxide film on the surface of the aluminum raw materials forms tiny channels on the oxide film surface, providing a path for the escape of hydrogen in the subsequent smelting stage.

[0037] After the heat preservation is completed, stop the flow of mixed gas and restore the pure nitrogen protective atmosphere (pressure maintained at 0.02-0.05MPa). Continue to raise the temperature to 800-850℃ to completely melt the raw materials and form a uniform aluminum melt.

[0038] III. Addition of Compound Degassing Agent

[0039] Preparation of composite degassing agent: Crush magnesium chloride, calcium fluoride and silicon dioxide into particles of 100-200 mesh using a pulverizing device (such as a ball mill). Then, mix them evenly in a mixing device (such as a drum mixer) at a mass ratio of 3:2:1. Place the mixed material into a drying device and dry it at 300-350℃ for 2-3 hours to remove moisture. After cooling, store it in a sealed container for later use to avoid moisture absorption.

[0040] A pre-prepared composite degassing agent is added to the molten aluminum in the melting furnace at a concentration of 0.8-1.2% of the molten aluminum mass. After adding the agent manually or automatically, the furnace's stirring device is activated, and the mixture is stirred at 300-400 rpm for 5-8 minutes to ensure thorough mixing and contact between the degassing agent and the molten aluminum, maximizing its hydrogen removal effect. Magnesium chloride reacts with hydrogen in the molten aluminum to generate hydrogen chloride gas, calcium fluoride reduces the surface tension of the molten aluminum, promoting the rise of hydrogen bubbles, and silica adsorbs impurities in the melt. These three components synergistically enhance the hydrogen removal effect and melt purity.

[0041] IV. Segmented Refinement

[0042] The first stage involves inert gas blowing: The temperature of the aluminum melt, after adding the degassing agent, is lowered to 750-780℃ using the furnace's temperature control system. At this temperature, the aluminum melt has good fluidity, and the solubility of hydrogen in the melt is moderate, facilitating hydrogen removal. Then, argon gas with a purity ≥99.999% is introduced into the melt through an inert gas delivery system. The blowing nozzle extends into the melt through the furnace opening to a depth of 15-20cm, with a nozzle orifice diameter of 2-3mm, ensuring the formation of fine, uniform argon bubbles. The argon flow rate is adjusted to 0.3-0.5 m³ / h using a flow controller, and the blowing time is controlled at 15-20 minutes. During the blowing process, a stirring device is activated, continuously stirring at a speed of 200-250 r / min to further promote the dispersion of argon bubbles in the melt, enhance the contact efficiency between the bubbles and hydrogen, allowing hydrogen to diffuse into the bubbles and rise to the melt surface to escape.

[0043] Second-stage vacuum refining: After the blowing is completed, the temperature of the aluminum melt is further reduced to 720 - 750 °C by the temperature control system. This temperature is lower than the temperature in the first-stage blowing, which can reduce the volatilization loss of the aluminum melt under vacuum conditions and ensure that the melt has sufficient fluidity for hydrogen to escape. Subsequently, start the vacuum system supporting the smelting furnace, and pump the vacuum degree in the furnace to 50 - 80 Pa at a pumping rate of 5 - 8 Pa / s by the vacuum pump, and maintain this vacuum degree for refining. The refining time is 25 - 30 min.

[0044] During the refining process, start the stirring device every 5 min and stir for 1 min at a stirring speed of 150 - 200 r / min to break the oxide film on the surface of the aluminum melt and promote the escape of hydrogen; at the same time, monitor the temperature of the aluminum melt in real time through the temperature monitoring device. When the temperature drops by more than 5 °C, increase the temperature by adjusting the heating power of the smelting furnace to keep the melt temperature within the range of 720 - 750 °C and ensure the stable hydrogen escape efficiency.

[0045] V. Standing and Detection

[0046] After the vacuum refining is completed, turn off the vacuum system and keep the aluminum melt standing at 720 - 750 °C for 10 - 15 min to make the remaining tiny bubbles in the melt float to the surface further and promote the homogenization of the melt composition. After standing, use the vacuum gas sampling method to detect the hydrogen content in the aluminum melt. When sampling, use a special sampling tool to sample at three different positions, namely the upper, middle, and lower parts of the aluminum melt, and sample 2 - 3 times at each position. Take the average value of the detection results of all samples as the final hydrogen content detection result.

[0047] When the detected hydrogen content ≤ 0.12 ml / 100 g Al, the treatment of reducing the hydrogen content in the recycled aluminum melt is completed; if the hydrogen content does not meet the above standard, restart the vacuum system and repeat the second-stage vacuum refining steps until the hydrogen content meets the requirements.

[0048] Through the refined pretreatment of the recycled aluminum raw materials, including crushing and grading, gradient degreasing and ultrasonic strengthening, and online moisture monitoring, the oil stain and moisture on the surface of the raw materials can be efficiently removed, cutting off the path of hydrogen production from moisture decomposition and oil stain combustion at the source, and greatly reducing the burden of the subsequent de-hydrogenation process. The synergistic effect of gradient degreasing and ultrasonic waves significantly improves the degreasing efficiency and solves the problem of continuous hydrogen production caused by insufficient pretreatment of raw materials in the existing technology.

[0049] By triggering in-situ hydrogen removal during the smelting stage, an inert gas-water vapor mixed gas flow is introduced during the heat preservation period. This not only catalyzes the reaction between residual trace oil and water vapor to accelerate the escape of impurities, but also forms a hydrogen escape channel on the oxide film surface. Combined with a nitrogen protective atmosphere throughout the process, this reduces the oxidation and hydrogen absorption during the smelting process, while also preventing local overheating and oxidation of the raw materials, thus improving the purity of the melt.

[0050] By adding a composite degassing agent composed of magnesium chloride, calcium fluoride, and silicon dioxide in a specific ratio, a synergistic effect of "reaction-promoted hydrogen removal-flotation-adsorption purification" is achieved: magnesium chloride reacts with hydrogen to generate escapeable gas, calcium fluoride reduces the surface tension of the melt and promotes the floating of bubbles, and silicon dioxide adsorbs harmful impurities, significantly improving the hydrogen removal effect and melt purity. Compared with traditional single degassing agents, the hydrogen removal capacity is greatly enhanced, and new impurities are avoided, solving the defects of limited effect and easy impurity introduction of single degassing agents.

[0051] A segmented refining process combining inert gas blowing and vacuum refining, coupled with precise parameter control, achieves deep hydrogen removal: the first stage of argon blowing forms uniform, fine bubbles to capture hydrogen, while the second stage of vacuum refining utilizes pressure difference to accelerate hydrogen escape. The two stages work together to stably control the hydrogen content within the target range. Compared to single inert gas blowing, hydrogen removal efficiency is significantly improved; compared to full vacuum refining, energy consumption is significantly reduced, and the total processing time is reasonable, meeting the needs of industrial production.

[0052] In addition, methods for reducing the hydrogen content of recycled aluminum melt include the following embodiments: Example

[0053] This embodiment uses waste aluminum alloy doors and windows as recycled aluminum raw material. The specific steps are as follows:

[0054] For the pretreatment of recycled aluminum raw materials, 100 kg of waste aluminum alloy doors and windows is first selected and crushed into particles with a diameter of 5-10 mm using a jaw crusher. After crushing, fine powder with a diameter less than 3 mm and coarse particles with a diameter greater than 12 mm are removed by a vibrating grading screen, resulting in 85 kg of qualified raw material particles. Next, the graded raw material is placed in a degreasing tank equipped with an ultrasonic generator. A 3% sodium hydroxide solution is first added, and pretreatment is carried out at 40°C for 5 minutes. Then, the solution concentration is adjusted to 5%, the temperature is raised to 50°C, and ultrasonic treatment (frequency 20 kHz, power 500 W) is continuously applied for 15 minutes. After completion, the raw material is removed from the degreasing tank. Then, the degreased raw material is repeatedly rinsed with deionized water until it is neutral (the pH value of the wastewater after rinsing is 7 as measured by pH test paper). It is then placed in a hot air circulating oven equipped with an infrared moisture sensor and dried at 120°C for 1 hour. Drying is stopped when the online monitoring shows that the moisture content of the raw material drops to 0.08%, and it is ready for use.

[0055] During the smelting and in-situ dehydrogenation triggering process, the dried raw materials are added to the resistance melting furnace via a feeding device, and the heating system is started to raise the temperature at a rate of 10℃ / min. When the furnace temperature reaches 600℃, the heating is stopped and held for 10 minutes. Simultaneously, a nitrogen-water vapor mixture with a volume fraction of 5% (nitrogen purity 99.99%) is introduced into the furnace at a flow rate of 0.1 m³ / h for 5 minutes. The mixed gas flow is then stopped, and a pure nitrogen protective atmosphere is restored. The furnace pressure is maintained at 0.02 MPa using a pressure control valve, and the temperature is further raised to 800℃ until the raw materials are completely melted to form a homogeneous aluminum melt.

[0056] When adding the composite degassing agent, add the composite degassing agent to the above-mentioned aluminum melt. The degassing agent is composed of magnesium chloride, calcium fluoride, and silicon dioxide in a mass ratio of 3:2:1 (all of which are pulverized to 100 mesh using a ball mill, dried at 300℃ for 2 hours, and then sealed and stored). The addition amount is 0.8% of the mass of the aluminum melt. After adding it through an automatic feeding device, start the stirring device and stir at a speed of 300 r / min for 5 minutes to ensure that the degassing agent is fully mixed with the melt.

[0057] The refining process involved first lowering the melt temperature to 750°C using a temperature control system, and then introducing 99.999% pure argon gas into the melt via an inert gas delivery system. The blowing nozzle was inserted 15 cm into the melt with a 2 mm orifice diameter, and the argon flow rate was adjusted to 0.3 m³ / h using a flow controller. Blowing was carried out for 15 minutes, with continuous stirring at 200 r / min throughout the process. After blowing, the melt temperature was further lowered to 720°C, and the vacuum system was activated to evacuate the furnace to a vacuum level of 50 Pa at a pumping rate of 5 Pa / s. This vacuum level was maintained for 25 minutes of refining. During the refining process, the melt was stirred for 1 minute at 150 r / min every 5 minutes. The temperature was monitored in real time using a temperature monitoring device, and when the temperature dropped by 3°C, the heating power was adjusted to maintain a stable temperature of 720°C.

[0058] Finally, the mixture was allowed to stand and be tested. After vacuum refining, the vacuum system was turned off, and the molten aluminum was allowed to stand at 720℃ for 10 minutes. Vacuum sampling was used to take samples from the upper, middle, and lower parts of the melt, with two samples taken from each part. The test results were: upper part 0.10 ml / 100gAl, middle part 0.11 ml / 100gAl, and lower part 0.10 ml / 100gAl, with an average value of 0.103 ml / 100gAl. This meets the standard of hydrogen content ≤ 0.12 ml / 100gAl, and the processing is complete. Example

[0059] This embodiment uses waste aluminum profile processing waste as recycled aluminum raw material. The specific steps are as follows:

[0060] For the pretreatment of recycled aluminum raw materials, 120 kg of waste aluminum profile processing waste is first selected and crushed into particles with a diameter of 5-10 mm using a hammer crusher. After crushing, fine powder with a diameter less than 3 mm and coarse particles with a diameter greater than 12 mm are removed by a vibrating grading screen, resulting in 100 kg of qualified raw material particles. Next, the graded raw material is placed in a degreasing tank equipped with an ultrasonic generator. A 4% sodium hydroxide solution is first added, and pretreatment is carried out at 45°C for 8 minutes. Then, the solution concentration is adjusted to 6%, the temperature is raised to 55°C, and ultrasonic treatment (frequency 30 kHz, power 650 W) is continuously applied for 18 minutes. After completion, the raw material is removed from the degreasing tank. Then, the degreased raw material is repeatedly rinsed with deionized water until neutral (the pH value of the wastewater after rinsing is 7 as measured by pH test paper). It is then placed in a hot air circulating oven equipped with an infrared moisture sensor and dried at 135°C for 1.2 hours. Drying is stopped when the online monitoring shows that the moisture content of the raw material drops to 0.07%, and it is ready for use.

[0061] During the smelting and in-situ dehydrogenation triggering process, the dried raw materials are added to the induction melting furnace via a feeding device, and the heating system is started to raise the temperature at a rate of 13℃ / min. When the furnace temperature reaches 630℃, the heating is stopped and held for 13 minutes. Simultaneously, a nitrogen-water vapor mixture with a volume fraction of 6.5% (nitrogen purity 99.99%) is introduced into the furnace at a velocity of 0.15 m³ / h for 6.5 minutes. The mixture is then stopped, and a pure nitrogen protective atmosphere is restored. The furnace pressure is maintained at 0.035 MPa using a pressure control valve, and the temperature is raised to 830℃ until the raw materials are completely melted into a homogeneous aluminum melt.

[0062] When adding the composite degassing agent, add the composite degassing agent to the above-mentioned aluminum melt. The degassing agent is composed of magnesium chloride, calcium fluoride, and silicon dioxide in a mass ratio of 3:2:1 (all of which are pulverized to 150 mesh using a ball mill, dried at 325℃ for 2.5 hours, and then sealed and stored). The addition amount is 1.0% of the mass of the aluminum melt. After adding it through an automatic feeding device, start the stirring device and stir at a speed of 350 r / min for 6.5 minutes to ensure that the degassing agent is fully mixed with the melt.

[0063] The refining process involved first lowering the melt temperature to 765°C using a temperature control system, and then introducing 99.999% pure argon gas into the melt via an inert gas delivery system. The blowing nozzle was inserted into the melt to a depth of 17.5 cm, with a nozzle orifice diameter of 2.5 mm. The argon gas flow rate was adjusted to 0.4 m³ / h using a flow controller, and the blowing process lasted for 17.5 minutes, with continuous stirring at 225 r / min throughout. After blowing, the melt temperature was further lowered to 735°C, and the vacuum system was activated to evacuate the furnace to a vacuum level of 65 Pa at a pumping rate of 6.5 Pa / s, maintaining this vacuum for 27.5 minutes. During the refining process, the furnace was stirred for 1 minute at 175 r / min every 5 minutes, and the temperature was monitored in real time using a temperature monitoring device. When the temperature dropped by 4°C, the heating power was adjusted to maintain a stable temperature of 735°C.

[0064] Finally, the mixture was allowed to stand and be tested. After vacuum refining, the vacuum system was shut off, and the molten aluminum was allowed to stand at 735℃ for 12.5 minutes. Vacuum sampling was used to take samples from the upper, middle, and lower parts of the melt, with two samples taken from each part. The test results were: upper part 0.09 ml / 100gAl, middle part 0.10 ml / 100gAl, and lower part 0.09 ml / 100gAl, with an average value of 0.093 ml / 100gAl. This meets the standard of hydrogen content ≤0.12 ml / 100gAl, and the processing is complete. Example

[0065] In this embodiment, waste aluminum alloy doors and windows and waste aluminum profile processing waste are mixed at a 1:1 ratio as recycled aluminum raw materials. The specific steps are as follows:

[0066] When pretreating recycled aluminum raw materials, firstly, 60 kg each of waste aluminum alloy door and window scrap and waste aluminum profile processing scrap are selected, mixed, and then crushed into particles with a particle size of 5-10 mm using a jaw crusher. After crushing, fine powder with a particle size less than 3 mm and coarse particles with a particle size greater than 12 mm are removed by a vibrating grading screen, resulting in 105 kg of qualified raw material particles. Next, the graded raw material is placed in a degreasing tank equipped with an ultrasonic generator. First, a 5% sodium hydroxide solution is added, and pretreatment is carried out at 50°C for 10 min. Then, the solution concentration is adjusted to 8%, the temperature is raised to 60°C, and ultrasonic treatment (frequency 40 kHz, power 800 W) is turned on for 20 min. After completion, the raw material is removed from the degreasing tank. Afterward, the degreased raw materials were repeatedly rinsed with deionized water until neutral (the pH value of the wastewater after rinsing was 7 as measured by pH test paper). Then, they were placed in a hot air circulating oven equipped with an infrared moisture sensor and dried at 150°C for 1.5 hours. When the online monitoring showed that the moisture content of the raw materials dropped to 0.06%, the drying was stopped and the materials were ready for use.

[0067] During the smelting and in-situ dehydrogenation triggering process, the dried raw materials are added to the resistance melting furnace via a feeding device, and the heating system is started to raise the temperature at a rate of 15℃ / min. When the furnace temperature reaches 650℃, the heating is stopped and held for 15 minutes. Simultaneously, a nitrogen-water vapor mixture with a volume fraction of 8% (nitrogen purity 99.99%) is introduced into the furnace at a flow rate of 0.2 m³ / h for 8 minutes. The mixed gas flow is then stopped, and a pure nitrogen protective atmosphere is restored. The furnace pressure is maintained at 0.05 MPa using a pressure control valve, and the temperature is further raised to 850℃ until the raw materials are completely melted to form a homogeneous aluminum melt.

[0068] When adding the composite degassing agent, add the composite degassing agent to the above-mentioned aluminum melt. The degassing agent is composed of magnesium chloride, calcium fluoride, and silicon dioxide in a mass ratio of 3:2:1 (all of which are pulverized to 200 mesh using a ball mill, dried at 350℃ for 3 hours, and then sealed and stored). The addition amount is 1.2% of the mass of the aluminum melt. After adding it through an automatic feeding device, start the stirring device and stir at a speed of 400 r / min for 8 minutes to ensure that the degassing agent is fully mixed with the melt.

[0069] The refining process involved first lowering the melt temperature to 780℃ using a temperature control system, and then introducing 99.999% pure argon gas into the melt via an inert gas delivery system. The blowing nozzle was inserted 20cm into the melt with a 3mm orifice diameter, and the argon flow rate was adjusted to 0.5m³ / h using a flow controller. Blowing was carried out for 20 minutes, with continuous stirring at 250r / min throughout the process. After blowing, the melt temperature was further lowered to 750℃, and the vacuum system was activated to evacuate the furnace to a vacuum of 80Pa at a pumping rate of 8Pa / s, maintaining this vacuum for 30 minutes. During refining, the furnace was stirred for 1 minute at 200r / min every 5 minutes, and the temperature was monitored in real time using a temperature monitoring device. When the temperature dropped by 5℃, the heating power was adjusted to maintain a stable temperature of 750℃.

[0070] Finally, the mixture was allowed to stand and be tested. After vacuum refining, the vacuum system was shut off, and the molten aluminum was allowed to stand at 750℃ for 15 minutes. Vacuum sampling was used to take samples from the upper, middle, and lower parts of the melt, with two samples taken from each part. The test results were: upper part 0.08 ml / 100gAl, middle part 0.09 ml / 100gAl, and lower part 0.08 ml / 100gAl, with an average value of 0.083 ml / 100gAl. This meets the standard of hydrogen content ≤0.12 ml / 100gAl, and the processing is complete. Example

[0071] This embodiment uses waste aluminum alloy doors and windows as recycled aluminum raw material. The specific steps are as follows:

[0072] For the pretreatment of recycled aluminum raw materials, 110 kg of waste aluminum alloy doors and windows was first selected and crushed into particles with a diameter of 5-10 mm using a jaw crusher. After crushing, fine powder with a diameter less than 3 mm and coarse particles with a diameter greater than 12 mm were removed by a vibrating grading screen, resulting in 92 kg of qualified raw material particles. Next, the graded raw material was placed in a degreasing tank equipped with an ultrasonic generator. A 3.5% sodium hydroxide solution was first added, and the pretreatment was carried out at 42℃ for 6 minutes. Then, the solution concentration was adjusted to 8%, the temperature was raised to 56℃, and ultrasonic treatment (frequency 35kHz, power 700W) was continuously applied for 26 minutes. After completion, the raw material was removed from the degreasing tank. Subsequently, the degreased raw material was repeatedly rinsed with deionized water until neutral (the pH value of the wastewater after rinsing was 7 as measured by pH test paper). Then, it was placed in a hot air circulating oven equipped with an infrared moisture sensor and dried at 150℃ for 1.4 hours. The drying was stopped when the online monitoring showed that the moisture content of the raw material dropped to 0.07%, and the material was ready for use.

[0073] During the smelting and in-situ dehydrogenation triggering process, the dried raw materials are added to the resistance melting furnace via a feeding device, and the heating system is started to raise the temperature at a rate of 13℃ / min. When the furnace temperature reaches 630℃, the heating is stopped and held for 13 minutes. Simultaneously, a nitrogen-water vapor mixture with a volume fraction of 7% (nitrogen purity 99.99%) is introduced into the furnace at a velocity of 0.18 m³ / h for 7 minutes. The mixture is then stopped, and a pure nitrogen protective atmosphere is restored. The furnace pressure is maintained at 0.04 MPa using a pressure control valve, and the temperature is raised to 830℃ until the raw materials are completely melted to form a homogeneous aluminum melt.

[0074] When adding the composite degassing agent, add the composite degassing agent to the above-mentioned aluminum melt. The degassing agent is composed of magnesium chloride, calcium fluoride, and silicon dioxide in a mass ratio of 3:2:1 (all of which are pulverized to 160 mesh using a ball mill, dried at 330℃ for 2.6 hours, and then sealed for storage). The addition amount is 1.1% of the mass of the aluminum melt. After adding it through an automatic feeding device, start the stirring device and stir at a speed of 360 r / min for 7 minutes to ensure that the degassing agent is fully mixed with the melt.

[0075] The refining process involved first lowering the melt temperature to 770℃ using a temperature control system, and then introducing 99.999% pure argon gas into the melt via an inert gas delivery system. The blowing nozzle was inserted 18cm into the melt with a nozzle orifice diameter of 2.6mm, and the argon flow rate was adjusted to 0.45m³ / h using a flow controller. Blowing was carried out for 18 minutes, with continuous stirring at 230r / min throughout the process. After blowing, the melt temperature was further lowered to 740℃, and the vacuum system was activated to evacuate the furnace to a vacuum level of 65Pa at a pumping rate of 7Pa / s. This vacuum level was maintained for refining for 28 minutes. During refining, the furnace was stirred for 1 minute at 180r / min every 5 minutes. The temperature was monitored in real time using a temperature monitoring device, and when the temperature dropped by 4℃, the heating power was adjusted to maintain a stable temperature of 740℃.

[0076] Finally, the mixture was allowed to stand and be tested. After vacuum refining, the vacuum system was shut off, and the molten aluminum was allowed to stand at 740℃ for 13 minutes. Vacuum sampling was used to take samples from the upper, middle, and lower parts of the melt, with two samples taken from each part. The test results were: upper part 0.09 ml / 100gAl, middle part 0.10 ml / 100gAl, and lower part 0.09 ml / 100gAl, with an average value of 0.093 ml / 100gAl. This meets the standard of hydrogen content ≤0.12 ml / 100gAl, and the processing is complete. Example

[0077] This embodiment uses waste aluminum profile processing waste as recycled aluminum raw material. The specific steps are as follows:

[0078] For the pretreatment of recycled aluminum raw materials, 130 kg of waste aluminum profile processing waste was first selected and crushed into particles with a diameter of 5-10 mm using a hammer crusher. After crushing, fine powder with a diameter less than 3 mm and coarse particles with a diameter greater than 12 mm were removed by a vibrating grading screen, resulting in 108 kg of qualified raw material particles. Next, the graded raw material was placed in a degreasing tank equipped with an ultrasonic generator. A 3.2% sodium hydroxide solution was first added, and pretreatment was carried out at 44℃ for 7 min. Subsequently, the solution concentration was adjusted to 5.5%, the temperature was raised to 58℃, and ultrasonic treatment (frequency 28 kHz, power 600 W) was continuously applied for 28 min. After completion, the raw material was removed from the degreasing tank. Then, the degreased raw material was repeatedly rinsed with deionized water until neutral (the pH value of the wastewater after rinsing was 7 as measured by pH test paper). It was then placed in a hot air circulating oven equipped with an infrared moisture sensor and dried at 125℃ for 1.1 h. Drying was stopped when the online monitoring showed that the moisture content of the raw material dropped to 0.08%, and the material was ready for use.

[0079] During the smelting and in-situ dehydrogenation triggering process, the dried raw materials are added to the induction melting furnace via a feeding device, and the heating system is started to raise the temperature at a rate of 14℃ / min. When the furnace temperature reaches 640℃, the heating is stopped and held for 14 minutes. Simultaneously, a nitrogen-water vapor mixture with a volume fraction of 7.5% (nitrogen purity 99.99%) is introduced into the furnace at a velocity of 0.19 m³ / h for 7.5 minutes. The mixture is then stopped, and a pure nitrogen protective atmosphere is restored. The furnace pressure is maintained at 0.04 MPa using a pressure control valve, and the temperature is raised to 840℃ until the raw materials are completely melted to form a homogeneous aluminum melt.

[0080] When adding the composite degassing agent, add the composite degassing agent to the above-mentioned aluminum melt. The degassing agent is composed of magnesium chloride, calcium fluoride, and silicon dioxide in a mass ratio of 3:2:1 (all of which are pulverized to 180 mesh using a ball mill, dried at 340℃ for 2.8 hours, and then sealed and stored). The addition amount is 0.85% of the mass of the aluminum melt. After adding it through an automatic feeding device, start the stirring device and stir at a speed of 380 r / min for 7 minutes to ensure that the degassing agent is fully mixed with the melt.

[0081] The refining process involved first lowering the melt temperature to 775°C using a temperature control system, and then introducing 99.999% pure argon gas into the melt via an inert gas delivery system. The blowing nozzle was inserted 19 cm into the melt with a nozzle orifice diameter of 2.8 mm. The argon gas flow rate was adjusted to 0.48 m³ / h using a flow controller, and blowing continued for 19 minutes, with continuous stirring at 240 r / min throughout the process. After blowing, the melt temperature was further lowered to 745°C, and the vacuum system was activated to evacuate the furnace to a vacuum level of 70 Pa at a pumping rate of 7.5 Pa / s. This vacuum level was maintained for 29 minutes of refining. During the refining process, the melt was stirred for 1 minute at 190 r / min every 5 minutes. The temperature was monitored in real time using a temperature monitoring device, and when the temperature dropped by 4.5°C, the heating power was adjusted to maintain a stable temperature of 745°C.

[0082] Finally, the mixture was allowed to stand and be tested. After vacuum refining, the vacuum system was shut off, and the molten aluminum was allowed to stand at 745℃ for 14 minutes. Vacuum sampling was used to take samples from the upper, middle, and lower parts of the melt, with two samples taken from each part. The test results were: upper part 0.095 ml / 100gAl, middle part 0.105 ml / 100gAl, and lower part 0.095 ml / 100gAl, with an average value of 0.098 ml / 100gAl. This meets the standard of hydrogen content ≤0.12 ml / 100gAl, and the processing is complete. Example

[0083] In this embodiment, waste aluminum alloy doors and windows and waste aluminum profile processing waste are mixed at a ratio of 2:1 as recycled aluminum raw materials. The specific steps are as follows:

[0084] For the pretreatment of recycled aluminum raw materials, 80 kg of waste aluminum alloy doors and windows and 40 kg of waste aluminum profile processing waste are first selected. After mixing, they are crushed into particles with a diameter of 5-10 mm using a jaw crusher. After crushing, fine powder with a diameter less than 3 mm and coarse particles with a diameter greater than 12 mm are removed by a vibrating grading screen, resulting in 102 kg of qualified raw material particles. Next, the graded raw material is placed in a degreasing tank equipped with an ultrasonic generator. First, a 3.8% sodium hydroxide solution is added, and pretreatment is carried out at 43°C for 7 minutes. Then, the solution concentration is adjusted to 7.5%, the temperature is raised to 60°C, and ultrasonic treatment (frequency 38 kHz, power 780 W) is turned on for 30 minutes. After completion, the raw material is removed from the degreasing tank. Afterward, the degreased raw materials were repeatedly rinsed with deionized water until neutral (the pH value of the wastewater after rinsing was 7 as measured by pH test paper). Then, they were placed in a hot air circulating oven equipped with an infrared moisture sensor and dried at 145°C for 1.5 hours. When the online monitoring showed that the moisture content of the raw materials dropped to 0.06%, the drying was stopped and the materials were ready for use.

[0085] During the smelting and in-situ dehydrogenation triggering process, the dried raw materials are added to the induction melting furnace via a feeding device, and the heating system is started to raise the temperature at a rate of 15℃ / min. When the furnace temperature reaches 650℃, the heating is stopped and held for 15 minutes. Simultaneously, a nitrogen-water vapor mixture with a volume fraction of 8% (nitrogen purity 99.99%) is introduced into the furnace at a flow rate of 0.2 m³ / h for 8 minutes. The mixed gas flow is then stopped, and a pure nitrogen protective atmosphere is restored. The furnace pressure is maintained at 0.05 MPa using a pressure control valve, and the temperature is further raised to 850℃ until the raw materials are completely melted to form a homogeneous aluminum melt.

[0086] When adding the composite degassing agent, add the composite degassing agent to the above-mentioned aluminum melt. The degassing agent is composed of magnesium chloride, calcium fluoride, and silicon dioxide in a mass ratio of 3:2:1 (all of which are pulverized to 200 mesh using a ball mill, dried at 350℃ for 3 hours, and then sealed and stored). The addition amount is 1.2% of the mass of the aluminum melt. After adding it through an automatic feeding device, start the stirring device and stir at a speed of 400 r / min for 8 minutes to ensure that the degassing agent is fully mixed with the melt.

[0087] The refining process involved first lowering the melt temperature to 780℃ using a temperature control system, and then introducing 99.999% pure argon gas into the melt via an inert gas delivery system. The blowing nozzle was inserted 20cm into the melt with a 3mm orifice diameter, and the argon flow rate was adjusted to 0.5m³ / h using a flow controller. Blowing was carried out for 20 minutes, with continuous stirring at 250r / min throughout the process. After blowing, the melt temperature was further lowered to 750℃, and the vacuum system was activated to evacuate the furnace to a vacuum of 80Pa at a pumping rate of 8Pa / s, maintaining this vacuum for 30 minutes. During refining, the furnace was stirred for 1 minute at 200r / min every 5 minutes, and the temperature was monitored in real time using a temperature monitoring device. When the temperature dropped by 5℃, the heating power was adjusted to maintain a stable temperature of 750℃.

[0088] Finally, the mixture was allowed to stand and tested. After vacuum refining, the vacuum system was shut off, and the molten aluminum was allowed to stand at 750℃ for 15 minutes. Vacuum sampling was used to take samples from the upper, middle, and lower parts of the melt, with two samples taken from each part. The test results were: upper part 0.085 ml / 100gAl, middle part 0.095 ml / 100gAl, and lower part 0.085 ml / 100gAl, with an average value of 0.088 ml / 100gAl. This meets the standard of hydrogen content ≤0.12 ml / 100gAl, and the processing is complete. Example

[0089] This embodiment uses waste aluminum alloy doors and windows as recycled aluminum raw material, and adjusts the pretreatment degreasing time. The specific steps are as follows:

[0090] For the pretreatment of recycled aluminum raw materials, 105 kg of waste aluminum alloy doors and windows was first selected and crushed into particles with a diameter of 5-10 mm using a jaw crusher. After crushing, fine powder with a diameter less than 3 mm and coarse particles with a diameter greater than 12 mm were removed by a vibrating grading screen, resulting in 88 kg of qualified raw material particles. Next, the graded raw material was placed in a degreasing tank equipped with an ultrasonic generator. A 3% sodium hydroxide solution was first added, and the pretreatment was carried out at 40°C for 5 minutes. Then, the solution concentration was adjusted to 5%, the temperature was raised to 50°C, and ultrasonic treatment (frequency 20 kHz, power 500 W) was continuously applied for 20 minutes (5 minutes longer than the conventional degreasing time). After completion, the raw material was removed from the degreasing tank. Then, the degreased raw material was repeatedly rinsed with deionized water until it reached neutral (the pH value of the wastewater after rinsing was 7 as measured by pH test paper). It was then placed in a hot air circulating oven equipped with an infrared moisture sensor and dried at 120°C for 1 hour. The drying was stopped when the online monitoring showed that the moisture content of the raw material dropped to 0.07%, and the material was ready for use.

[0091] During the smelting and in-situ dehydrogenation triggering process, the dried raw materials are added to the resistance melting furnace via a feeding device, and the heating system is started to raise the temperature at a rate of 10℃ / min. When the furnace temperature reaches 600℃, the heating is stopped and held for 10 minutes. Simultaneously, a nitrogen-water vapor mixture with a volume fraction of 5% (nitrogen purity 99.99%) is introduced into the furnace at a flow rate of 0.1 m³ / h for 5 minutes. The mixed gas flow is then stopped, and a pure nitrogen protective atmosphere is restored. The furnace pressure is maintained at 0.02 MPa using a pressure control valve, and the temperature is further raised to 800℃ until the raw materials are completely melted to form a homogeneous aluminum melt.

[0092] When adding the composite degassing agent, add the composite degassing agent to the above-mentioned aluminum melt. The degassing agent is composed of magnesium chloride, calcium fluoride, and silicon dioxide in a mass ratio of 3:2:1 (all of which are pulverized to 100 mesh using a ball mill, dried at 300℃ for 2 hours, and then sealed and stored). The addition amount is 0.8% of the mass of the aluminum melt. After adding it through an automatic feeding device, start the stirring device and stir at a speed of 300 r / min for 5 minutes to ensure that the degassing agent is fully mixed with the melt.

[0093] The refining process involved first lowering the melt temperature to 750°C using a temperature control system, and then introducing 99.999% pure argon gas into the melt via an inert gas delivery system. The blowing nozzle was inserted 15 cm into the melt with a 2 mm orifice diameter, and the argon flow rate was adjusted to 0.3 m³ / h using a flow controller. Blowing was carried out for 15 minutes, with continuous stirring at 200 r / min throughout the process. After blowing, the melt temperature was further lowered to 720°C, and the vacuum system was activated to evacuate the furnace to a vacuum level of 50 Pa at a pumping rate of 5 Pa / s. This vacuum level was maintained for 25 minutes of refining. During the refining process, the melt was stirred for 1 minute at 150 r / min every 5 minutes. The temperature was monitored in real time using a temperature monitoring device, and when the temperature dropped by 3°C, the heating power was adjusted to maintain a stable temperature of 720°C.

[0094] Finally, the mixture was allowed to stand and be tested. After vacuum refining, the vacuum system was shut off, and the molten aluminum was allowed to stand at 720℃ for 10 minutes. Vacuum sampling was used to take samples from the upper, middle, and lower parts of the melt, with two samples taken from each part. The results were: upper part 0.095 ml / 100gAl, middle part 0.102 ml / 100gAl, and lower part 0.097 ml / 100gAl, with an average of 0.098 ml / 100gAl. Due to the extended degreasing time, the oil on the raw material surface was removed more thoroughly, and the hydrogen content decreased by 0.005 ml / 100gAl compared to conventional degreasing under the same conditions, meeting the standard of ≤0.12 ml / 100gAl, thus completing the treatment. Example

[0095] This embodiment uses waste aluminum profile processing materials as recycled aluminum raw materials, and adjusts the smelting and holding temperature. The specific steps are as follows:

[0096] For the pretreatment of recycled aluminum raw materials, 125 kg of waste aluminum profile processing waste was first selected and crushed into particles with a diameter of 5-10 mm using a hammer crusher. After crushing, fine powder with a diameter less than 3 mm and coarse particles with a diameter greater than 12 mm were removed by a vibrating grading screen, resulting in 103 kg of qualified raw material particles. Next, the graded raw material was placed in a degreasing tank equipped with an ultrasonic generator. A 4% sodium hydroxide solution was first added, and the pretreatment was carried out at 45°C for 8 minutes. Then, the solution concentration was adjusted to 6%, the temperature was raised to 52°C, and ultrasonic treatment (frequency 30 kHz, power 650 W) was continuously applied for 22 minutes. After completion, the raw material was removed from the degreasing tank. Subsequently, the degreased raw material was repeatedly rinsed with deionized water until neutral (the pH value of the wastewater after rinsing was 7 as measured by pH test paper). Then, it was placed in a hot air circulating oven equipped with an infrared moisture sensor and dried at 130°C for 1.2 hours. The drying was stopped when the online monitoring showed that the moisture content of the raw material dropped to 0.07%, and the material was ready for use.

[0097] During the smelting and in-situ dehydrogenation triggering process, the dried raw materials are added to the induction melting furnace via a feeding device, and the heating system is started to raise the temperature at a rate of 11℃ / min. When the furnace temperature reaches 630℃ (20℃ higher than the conventional holding temperature), the heating is stopped and the temperature is held for 11 minutes. Simultaneously, a nitrogen-water vapor mixture with a volume fraction of 6% (nitrogen purity 99.99%) is introduced into the furnace at a flow rate of 0.15 m³ / h for 6 minutes. The mixed gas flow is then stopped, and a pure nitrogen protective atmosphere is restored. The furnace pressure is maintained at 0.03 MPa using a pressure control valve, and the temperature is further raised to 810℃ until the raw materials are completely melted to form a homogeneous aluminum melt.

[0098] When adding the composite degassing agent, add the composite degassing agent to the above-mentioned aluminum melt. The degassing agent is composed of magnesium chloride, calcium fluoride, and silicon dioxide in a mass ratio of 3:2:1 (all of which are pulverized to 120 mesh using a ball mill, dried at 310℃ for 2.2 hours, and then sealed for storage). The addition amount is 0.9% of the mass of the aluminum melt. After adding it through an automatic feeding device, start the stirring device and stir at a speed of 320 r / min for 6 minutes to ensure that the degassing agent is fully mixed with the melt.

[0099] The refining process involved first lowering the melt temperature to 760°C using a temperature control system, and then introducing 99.999% pure argon gas into the melt via an inert gas delivery system. The blowing nozzle was inserted 16 cm into the melt with a nozzle orifice diameter of 2.2 mm. The argon gas flow rate was adjusted to 0.35 m³ / h using a flow controller, and blowing continued for 16 minutes, with continuous stirring at 210 r / min throughout the process. After blowing, the melt temperature was further lowered to 730°C, and the vacuum system was activated to evacuate the furnace to a vacuum level of 55 Pa at a pumping rate of 6 Pa / s, maintaining this vacuum for 26 minutes. During refining, the furnace was stirred for 1 minute at 160 r / min every 5 minutes, and the temperature was monitored in real time using a temperature monitoring device. When the temperature dropped by 4°C, the heating power was adjusted to maintain a stable temperature of 730°C.

[0100] Finally, the mixture was allowed to stand and be tested. After vacuum refining, the vacuum system was shut off, and the molten aluminum was allowed to stand at 730℃ for 11 minutes. Vacuum sampling was used to take samples from the upper, middle, and lower parts of the melt, with two samples taken from each part. The results were: upper part 0.098 ml / 100gAl, middle part 0.105 ml / 100gAl, and lower part 0.103 ml / 100gAl, with an average of 0.102 ml / 100gAl. Due to the increased holding temperature, moisture and volatile impurities in the raw material evaporated more completely, and the hydrogen content decreased by 0.008 ml / 100gAl compared to conventional holding temperature treatment under the same conditions, meeting the standard of hydrogen content ≤0.12 ml / 100gAl, thus completing the treatment. Example

[0101] In this embodiment, waste aluminum alloy doors and windows and waste aluminum profile processing waste are mixed at a 1:1 ratio as recycled aluminum raw materials. The amount of composite degassing agent added is adjusted. The specific steps are as follows:

[0102] For the pretreatment of recycled aluminum raw materials, 65 kg of waste aluminum alloy doors and windows and 65 kg of waste aluminum profile processing waste were first selected and mixed. A jaw crusher was then used to crush the mixture into particles with a diameter of 5-10 mm. After crushing, a vibrating grading screen was used to remove fine powder smaller than 3 mm and coarse particles larger than 12 mm, yielding 108 kg of qualified raw material particles. Next, the graded raw material was placed in a degreasing tank equipped with an ultrasonic generator. A 5% sodium hydroxide solution was first added, and pretreatment was carried out at 54℃ for 9 minutes. Subsequently, the solution concentration was adjusted to 7%, the temperature was maintained at 54℃, and ultrasonic treatment (frequency 35 kHz, power 700 W) was continuously applied for 24 minutes. After completion, the raw material was removed from the degreasing tank. Afterward, the degreased raw materials were repeatedly rinsed with deionized water until neutral (the pH value of the wastewater after rinsing was 7 as measured by pH test paper). Then, they were placed in a hot air circulating oven equipped with an infrared moisture sensor and dried at 140°C for 1.3 hours. When the online monitoring showed that the moisture content of the raw materials dropped to 0.06%, the drying was stopped and the materials were ready for use.

[0103] During the smelting and in-situ dehydrogenation triggering process, the dried raw materials are added to the resistance melting furnace via a feeding device, and the heating system is started to raise the temperature at a rate of 12℃ / min. When the furnace temperature reaches 620℃, the heating is stopped and held for 12 minutes. Simultaneously, a nitrogen-water vapor mixture with a volume fraction of 7% (nitrogen purity 99.99%) is introduced into the furnace at a velocity of 0.17 m³ / h for 7 minutes. The mixture is then stopped, and a pure nitrogen protective atmosphere is restored. The furnace pressure is maintained at 0.03 MPa using a pressure control valve, and the temperature is raised to 820℃ until the raw materials are completely melted to form a homogeneous aluminum melt.

[0104] When adding the composite degassing agent, add the composite degassing agent to the above-mentioned aluminum melt. This degassing agent is composed of magnesium chloride, calcium fluoride, and silicon dioxide in a mass ratio of 3:2:1 (all are pulverized to 140 mesh using a ball mill, dried at 320℃ for 2.4 hours, and then sealed for storage). The addition amount is 1.1% of the mass of the aluminum melt (0.1% higher than the conventional addition amount). After adding it through an automatic feeding device, start the stirring device and stir at a speed of 340 r / min for 6 minutes to ensure that the degassing agent is fully mixed with the melt.

[0105] The refining process involved first lowering the melt temperature to 765°C using a temperature control system, and then introducing 99.999% pure argon gas into the melt via an inert gas delivery system. The blowing nozzle was inserted 17 cm into the melt, with a nozzle orifice diameter of 2.4 mm. The argon flow rate was adjusted to 0.4 m³ / h using a flow controller, and the blowing process lasted for 17 minutes, with continuous stirring at 220 r / min throughout. After blowing, the melt temperature was further lowered to 735°C, and the vacuum system was activated to evacuate the furnace to a vacuum level of 60 Pa at a pumping rate of 6.5 Pa / s, maintaining this vacuum for 27 minutes. During the refining process, the melt was stirred for 1 minute at 170 r / min every 5 minutes. The temperature was monitored in real time using a temperature monitoring device, and when the temperature dropped by 4.5°C, the heating power was adjusted to maintain a stable temperature of 735°C.

[0106] Finally, the mixture was allowed to stand and tested. After vacuum refining, the vacuum system was shut off, and the molten aluminum was allowed to stand at 735℃ for 12 minutes. Vacuum sampling was used to take samples from the upper, middle, and lower parts of the melt, with two samples taken from each part. The results were: upper part 0.095 ml / 100gAl, middle part 0.102 ml / 100gAl, and lower part 0.097 ml / 100gAl, with an average of 0.098 ml / 100gAl. Due to the increased amount of degassing agent, the synergistic dehydrogenation effect of each component was enhanced, and the hydrogen content decreased by 0.007 ml / 100gAl compared to the conventional addition under the same conditions, meeting the standard of hydrogen content ≤0.12 ml / 100gAl, thus completing the treatment.

[0107] Example 10

[0108] This embodiment uses waste aluminum alloy doors and windows as recycled aluminum raw material, and adjusts the inert gas blowing flow rate. The specific steps are as follows:

[0109] For the pretreatment of recycled aluminum raw materials, 115 kg of waste aluminum alloy doors and windows was first selected and crushed into particles with a diameter of 5-10 mm using a jaw crusher. After crushing, fine powder with a diameter less than 3 mm and coarse particles with a diameter greater than 12 mm were removed by a vibrating grading screen, resulting in 95 kg of qualified raw material particles. Next, the graded raw material was placed in a degreasing tank equipped with an ultrasonic generator. A 3.5% sodium hydroxide solution was first added, and the pretreatment was carried out at 43°C for 6.5 min. Subsequently, the solution concentration was adjusted to 8%, the temperature was raised to 56°C, and ultrasonic treatment (frequency 36 kHz, power 720 W) was continuously applied for 26 min. After completion, the raw material was removed from the degreasing tank. Then, the degreased raw material was repeatedly rinsed with deionized water until neutral (the pH value of the wastewater after rinsing was 7 as measured by pH test paper). It was then placed in a hot air circulating oven equipped with an infrared moisture sensor and dried at 150°C for 1.4 h. Drying was stopped when the online monitoring showed that the moisture content of the raw material dropped to 0.06%, and the material was ready for use.

[0110] During the smelting and in-situ dehydrogenation triggering process, the dried raw materials are added to the resistance melting furnace via a feeding device, and the heating system is started to raise the temperature at a rate of 13℃ / min. When the furnace temperature reaches 630℃, the heating is stopped and held for 13 minutes. Simultaneously, a nitrogen-water vapor mixture with a volume fraction of 7.2% (nitrogen purity 99.99%) is introduced into the furnace at a velocity of 0.18 m³ / h for 7 minutes. The mixture is then stopped, and a pure nitrogen protective atmosphere is restored. The furnace pressure is maintained at 0.04 MPa using a pressure control valve, and the temperature is raised to 830℃ until the raw materials are completely melted to form a homogeneous aluminum melt.

[0111] When adding the composite degassing agent, add the composite degassing agent to the above-mentioned aluminum melt. The degassing agent is composed of magnesium chloride, calcium fluoride, and silicon dioxide in a mass ratio of 3:2:1 (all of which are pulverized to 160 mesh using a ball mill, dried at 330℃ for 2.6 hours, and then sealed for storage). The addition amount is 1.1% of the mass of the aluminum melt. After adding it through an automatic feeding device, start the stirring device and stir at a speed of 360 r / min for 7 minutes to ensure that the degassing agent is fully mixed with the melt.

[0112] The refining process involved first lowering the melt temperature to 770℃ using a temperature control system, and then introducing 99.999% pure argon gas into the melt via an inert gas delivery system. The blowing nozzle was inserted 18cm into the melt, with a nozzle orifice diameter of 2.6mm. The argon flow rate was adjusted to 0.5m³ / h (0.05m³ / h higher than the conventional blowing flow rate) using a flow controller, and blowing was carried out for 18 minutes, with continuous stirring at 230r / min throughout the process. After blowing, the melt temperature was further lowered to 740℃, and the vacuum system was activated to evacuate the furnace to a vacuum level of 65Pa at a pumping rate of 7Pa / s, maintaining this vacuum for 28 minutes of refining. During the refining process, the furnace was stirred for 1 minute at 180r / min every 5 minutes, and the temperature was monitored in real time using a temperature monitoring device. When the temperature dropped by 4℃, the heating power was adjusted to maintain a stable temperature of 740℃.

[0113] Finally, the mixture was allowed to stand and be tested. After vacuum refining, the vacuum system was shut off, and the molten aluminum was allowed to stand at 740℃ for 13 minutes. Vacuum sampling was used to sample and test three parts of the melt: upper, middle, and lower. Each part was sampled twice. The results were: upper part 0.088 ml / 100gAl, middle part 0.092 ml / 100gAl, and lower part 0.089 ml / 100gAl, with an average of 0.090 ml / 100gAl. Due to the increased argon flow rate, the number of bubbles in the melt increased and their distribution became more uniform. The efficiency of hydrogen diffusion into the bubbles improved, and the hydrogen content decreased by 0.005 ml / 100gAl compared to conventional blowing treatment under the same conditions, meeting the standard of ≤0.12 ml / 100gAl, thus completing the treatment.

[0114] Example 11

[0115] This embodiment uses waste aluminum profile processing materials as recycled aluminum raw materials, and adjusts the vacuum degree of vacuum refining. The specific steps are as follows:

[0116] For the pretreatment of recycled aluminum raw materials, 135 kg of waste aluminum profile processing waste was first selected and crushed into particles with a diameter of 5-10 mm using a hammer crusher. After crushing, fine powder with a diameter less than 3 mm and coarse particles with a diameter greater than 12 mm were removed by a vibrating grading screen, resulting in 112 kg of qualified raw material particles. Next, the graded raw material was placed in a degreasing tank equipped with an ultrasonic generator. A 3.3% sodium hydroxide solution was first added, and pretreatment was carried out at 45°C for 7 minutes. Subsequently, the solution concentration was adjusted to 5.5%, the temperature was raised to 58°C, and ultrasonic treatment (frequency 29 kHz, power 620 W) was continuously applied for 28 minutes. After completion, the raw material was removed from the degreasing tank. Then, the degreased raw material was repeatedly rinsed with deionized water until neutral (the pH value of the wastewater after rinsing was 7 as measured by pH test paper). It was then placed in a hot air circulating oven equipped with an infrared moisture sensor and dried at 125°C for 1.1 hours. Drying was stopped when the online monitoring showed that the moisture content of the raw material dropped to 0.07%, and the material was ready for use.

[0117] During the smelting and in-situ dehydrogenation triggering process, the dried raw materials are added to the induction melting furnace via a feeding device, and the heating system is started to raise the temperature at a rate of 14℃ / min. When the furnace temperature reaches 640℃, the heating is stopped and held for 14 minutes. Simultaneously, a nitrogen-water vapor mixture with a volume fraction of 7.6% (nitrogen purity 99.99%) is introduced into the furnace at a velocity of 0.19 m³ / h for 7.5 minutes. The mixture is then stopped, and a pure nitrogen protective atmosphere is restored. The furnace pressure is maintained at 0.04 MPa using a pressure control valve, and the temperature is raised to 840℃ until the raw materials are completely melted to form a homogeneous aluminum melt.

[0118] When adding the composite degassing agent, add the composite degassing agent to the above-mentioned aluminum melt. The degassing agent is composed of magnesium chloride, calcium fluoride, and silicon dioxide in a mass ratio of 3:2:1 (all of which are pulverized to 180 mesh using a ball mill, dried at 340℃ for 2.8 hours, and then sealed and stored). The addition amount is 0.85% of the mass of the aluminum melt. After adding it through an automatic feeding device, start the stirring device and stir at a speed of 380 r / min for 7 minutes to ensure that the degassing agent is fully mixed with the melt.

[0119] The refining process involved first lowering the melt temperature to 775°C using a temperature control system, and then introducing 99.999% pure argon gas into the melt via an inert gas delivery system. The blowing nozzle was inserted 19 cm into the melt, with a nozzle orifice diameter of 2.8 mm. The argon flow rate was adjusted to 0.48 m³ / h using a flow controller, and blowing continued for 19 minutes, with continuous stirring at 240 r / min throughout the process. After blowing, the melt temperature was further lowered to 745°C, and the vacuum system was activated to evacuate the furnace to a vacuum level of 60 Pa (10 Pa lower than the standard vacuum level) at a pumping rate of 7.5 Pa / s. This vacuum level was maintained for 29 minutes of refining. During the refining process, the furnace was stirred for 1 minute at 190 r / min every 5 minutes. The temperature was monitored in real time using a temperature monitoring device, and when the temperature dropped by 4.5°C, the heating power was adjusted to maintain a stable temperature of 745°C.

[0120] Finally, the mixture was allowed to stand and be tested. After vacuum refining, the vacuum system was shut off, and the molten aluminum was allowed to stand at 745℃ for 14 minutes. Vacuum sampling was used to take samples from the upper, middle, and lower parts of the melt, with two samples taken from each part. The results were: upper part 0.090 ml / 100gAl, middle part 0.094 ml / 100gAl, and lower part 0.091 ml / 100gAl, with an average of 0.092 ml / 100gAl. Due to the increased vacuum, the pressure difference between the melt and the outside environment increased, enhancing the hydrogen escape force. The hydrogen content decreased by 0.008 ml / 100gAl compared to conventional vacuum treatment under the same conditions, meeting the standard of ≤0.12 ml / 100gAl, thus completing the treatment.

Claims

1. A method for reducing the hydrogen content of recycled aluminum melt, characterized in that: The following steps are included: S1. Pretreatment of recycled aluminum raw materials: Prepare recycled aluminum raw materials by first crushing them into particles with a diameter of 5-10mm. Remove fine powder with a diameter less than 3mm and coarse particles with a diameter greater than 12mm by using a vibrating grading screen. Then, place the remaining raw materials in a degreasing tank equipped with an ultrasonic generator for gradient degreasing and ultrasonic enhancement treatment. Afterward, rinse with deionized water until neutral and place them in a hot air circulating oven with online moisture monitoring function to dry until the moisture content is ≤0.1%. S2. Melting and In-situ Dehydrogenation Triggering Treatment: Add the pretreated raw materials to the melting furnace and heat them at a rate of 10-15℃ / min. When the temperature reaches 600-650℃, hold it for 10-15 minutes. At the same time, introduce a nitrogen-water vapor mixed gas flow at a speed of 0.1-0.2 m³ / h for 5-8 minutes. Then, restore the pure nitrogen protective atmosphere and continue heating to 800-850℃ to completely melt the raw materials and form aluminum melt. S3. Addition of composite degassing agent: Add the pre-made composite degassing agent to the aluminum melt at a rate of 0.8-1.2% of the mass of the aluminum melt, and stir to ensure that the degassing agent is fully mixed with the melt; S4. Segmented refining: First, reduce the melt temperature to 750-780℃, then introduce argon gas for blowing. After blowing, reduce the temperature to 720-750℃ and evacuate to 50-80Pa for vacuum refining. S5. Standing and Testing: After vacuum refining, let the melt stand for 10-15 minutes at a temperature of 720-750℃. Use the vacuum gas sampling method to sample the hydrogen content of the upper, middle and lower parts of the melt. If the average value is ≤0.12ml / 100gAl, the processing is complete. If it does not meet the standard, repeat the vacuum refining step. The composite degassing agent is composed of magnesium chloride, calcium fluoride, and silicon dioxide in a mass ratio of 3:2:

1. Each component is pulverized to 100-200 mesh using a ball mill, dried at 300-350℃ for 2-3 hours, and then sealed for storage.

2. The method for reducing the hydrogen content of recycled aluminum melt according to claim 1, characterized in that: In step S1, during the gradient degreasing and ultrasonic enhancement treatment, a 3-4% sodium hydroxide solution is first used for pretreatment at a temperature of 40-45°C for 5-8 minutes. Then, the solution concentration is increased to 5-8%, the temperature is raised to 50-60°C, and ultrasonic treatment is performed at a frequency of 20-40kHz, a power of 500-800W, and a duration of 15-22 minutes.

3. The method for reducing the hydrogen content of recycled aluminum melt according to claim 1, characterized in that: In step S1, the drying temperature is 120-150℃, the drying time is 1-1.5h, and the moisture content of the raw materials is monitored in real time by an infrared moisture sensor.

4. The method for reducing the hydrogen content of recycled aluminum melt according to claim 1, characterized in that: The smelting furnace is a resistance smelting furnace or an induction smelting furnace.

5. The method for reducing the hydrogen content of recycled aluminum melt according to claim 1, characterized in that: In step S4, when argon gas is introduced for blowing, the nozzle used to deliver argon gas is inserted into the melt to a depth of 15-20 cm, the nozzle orifice diameter is 2-3 mm, the argon gas flow rate is 0.3-0.5 m³ / h, and the blowing time is 15-20 min.

6. The method for reducing the hydrogen content of recycled aluminum melt according to claim 1, characterized in that: In step S4, the vacuum pumping rate is 5-8 Pa / s, the refining time is 25-30 min, and a stirring operation is performed every 5 min during the refining process.

7. The method for reducing the hydrogen content of recycled aluminum melt according to claim 1, characterized in that: In step S5, each part is sampled 2-3 times, and the average value of all sample test results is taken as the final hydrogen content.

8. The method for reducing the hydrogen content of recycled aluminum melt according to claim 1, characterized in that: In S2, the nitrogen-water vapor mixed gas flow is introduced at the same time as the heat preservation stage, and is evenly dispersed in the melting furnace by the gas distributor.

9. The method for reducing the hydrogen content of recycled aluminum melt according to claim 1, characterized in that: In step S1, one or more of the following are selected as recycled aluminum raw materials: waste aluminum alloy doors and windows, and waste aluminum profile processing waste.

Images