A process for purifying an aluminum alloy melt

Abstract

The application discloses an aluminum alloy melt purification treatment process and belongs to the technical field of aluminum alloy smelting and aluminum alloy melt purification. The purification treatment process comprises the following steps: aluminum inlet refining, alloy additive refining, smelting furnace refining, guide furnace refining, holding furnace refining, online melt purification treatment, ultrasonic and horizontal filtration and melt quality detection. The first, second and third remelting refining agents with different proportions of KCl and NaCl are used to form a gradient composition, and are matched with alloy additives, three rotors in series, a double-stage plate filter box, a deep bed filter box, an ultrasonic treatment area and a horizontal filtration area, so that the synergistic effect of chemical refining, multi-stage filtration and ultrasonic purification is realized. After the treatment, the hydrogen content of the aluminum alloy melt is less than or equal to 0.05 mL / 100gAl, the 70s slag passing quality is greater than or equal to 1.4 kg, the Na and K alkali metal contents are both less than or equal to 10 ppm, and the production requirements of high-end aluminum foil and cast-rolling stock can be met.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy smelting and aluminum alloy melt purification technology, specifically relating to an aluminum alloy melt purification process. Background Technology

[0002] Aluminum alloy molten metal faces a series of severe purification challenges during smelting and casting. First, aluminum alloy molten metal has extremely high chemical reactivity, readily reacting with oxygen in the air to form alumina inclusions. Simultaneously, when exposed to moisture, it reacts violently, absorbing hydrogen from the water and forming new oxide inclusions, leading to hydrogen absorption and slagging. Second, throughout the entire process from smelting to casting, aluminum alloy molten metal comes into contact with various refractory materials. These refractory materials are rich in complex alkali metal salts, which are subject to erosion and shedding during use, easily attracting and entraining inclusions into the melt. Due to the high interfacial energy and high viscosity of aluminum alloy molten metal, these inclusions, once inside the melt, are difficult to separate and remove, remaining stably within the melt and ultimately causing serious quality problems such as pinholes, loose structure, peeling, and decreased mechanical properties in aluminum foil.

[0003] To address the aforementioned issues, traditional aluminum alloy melt purification methods often employ single-stage powder spraying refining, rotary degassing, or single-layer filtration. However, these traditional solutions have significant drawbacks: firstly, insufficient degassing depth makes it difficult to stably control hydrogen content below 0.05 mL / 100gAl; secondly, low removal efficiency for micron- and submicron-sized inclusions, with residual large particles easily causing defects in the product; and thirdly, the high fluorine content of traditional fluxes easily leads to melt contamination, hydrogen absorption, and secondary oxidation. Furthermore, existing solutions suffer from fragmented processes and poor stability, failing to achieve synergistic purification effects of deep degassing, efficient impurity removal, in-situ alkali removal, and low-temperature, low-oxidation, thus failing to meet the stable and continuous production requirements of high-end aluminum foil manufacturing.

[0004] Therefore, developing an aluminum alloy melt processing technology that can achieve multi-level coupling, online continuous operation, and ultra-clean purification has become a technical challenge that urgently needs to be solved in this field. Summary of the Invention

[0005] To address the problems existing in the background technology, this invention discloses a multi-stage coupled, online continuous, ultra-clean aluminum alloy melt purification process. It uses alloy additives with refining effects, remelting refining agents in different proportions, high-purity argon, three-rotor series degassing, series two-stage plate filter box, deep bed filter box, ultrasonic purification, horizontal filtration, etc., to achieve multi-stage treatment and graded purification. The hydrogen content, alkali metal content, and slag content of the treated melt meet the technical requirements of high-end aluminum foil.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0007] A process for purifying aluminum alloy melt includes the following steps:

[0008] Step S1, Aluminum Inlet Refining: Place the first remelting refining agent at the aluminum inlet of the smelting furnace, and pour the electrolytic aluminum into the smelting furnace through the aluminum inlet. Together with the self-produced waste material at the bottom of the furnace and the remelted aluminum ingot, they form an aluminum alloy melt for preliminary refining.

[0009] Step S2, Alloy Additive Refining: Add an alloy additive with refining effect to the aluminum alloy melt in the melting furnace. The alloy additive includes elemental metal powder and a compound remelting refining agent as a flux to carry out alloying refining.

[0010] Step S3, Refining in a melting furnace: After the alloy composition is found to be qualified, a combination of automatic and manual refining is used. The second remelting refining agent is blown into the aluminum alloy melt through a rotor using high-purity argon as a carrier for refining. After refining, the mixture is allowed to stand and the slag is removed. The second remelting refining agent is in powder form.

[0011] Step S4, furnace refining: The aluminum alloy melt after refining, slag removal and settling in the smelting furnace is exported from the outlet of the smelting furnace and introduced into the holding furnace through the guide channel. During the introduction process, high-purity argon gas is introduced into the aluminum alloy melt through the porous refining pipe for furnace refining.

[0012] Step S5, Refining in a holding furnace: In the holding furnace, the third remelting refining agent is blown into the aluminum alloy melt through the refining tube using high-purity argon as a carrier for refining. After refining, the melt is allowed to stand, slag is removed, and high-purity argon is introduced into the holding furnace as a protective atmosphere.

[0013] Step S6, Online Melt Purification Treatment: The aluminum alloy melt, after refining, settling, and slag removal in the holding furnace, flows sequentially through a three-rotor series degassing box, a series two-stage plate filter box, and a deep bed filter box for degassing and multi-stage filtration. The three-rotor series degassing box uses high-purity argon gas as a carrier to blow the second remelting refining agent into the aluminum alloy melt for impurity removal and refining. The series two-stage plate filter box uses a four-stage gradient ceramic filter plate combination. The deep bed filter box is sequentially laid with filter grids, coarse alumina ceramic balls, medium alumina ceramic balls, fine alumina gravel, medium alumina ceramic balls, and coarse alumina ceramic balls, forming a symmetrical layered structure.

[0014] Step S7, Ultrasonic and Horizontal Filtration: The aluminum alloy melt after step S6 is sequentially passed through the ultrasonic treatment zone and the horizontal filtration zone. The ultrasonic treatment zone uses at least two sets of ultrasonic tool heads to apply an ultrasonic field to the melt. The resulting cavitation effect is used to disperse fine inclusion agglomerates and accelerate the rise of hydrogen bubbles. The horizontal filtration zone uses a plate-type horizontal filter plate for final filtration to trap residual fine inclusions.

[0015] Step S8, Melt quality inspection: Inspect the hydrogen content, slag content and alkali metal content of the treated aluminum alloy melt to confirm that it meets the preset quality standards;

[0016] In step S1, the first remelting refining agent (in granular form), in step S3, the second remelting refining agent (in powder form), and in step S5, the third remelting refining agent (in granular form) are respectively composed of different mass ratios of KCl and NaCl to form a gradient composition.

[0017] Further, by mass percentage, the specific components of each remelting refining agent are as follows: the first remelting refining agent in step S1 contains 30%-35% KCl and 65%-70% NaCl; the second remelting refining agent in step S3 contains 65%-70% KCl and 30%-35% NaCl; and the third remelting refining agent in step S5 contains 70%-75% KCl and 25%-30% NaCl.

[0018] Furthermore, the alloy additive in step S2 simultaneously includes iron, manganese, copper, and titanium agents; each of the iron, manganese, copper, and titanium agents independently comprises elemental metal powder and a compound remelting refining agent as a fluxing agent, and the weight percentage of elemental metal powder in each metal additive is 40%-45%, with the remainder being a compound remelting refining agent composed of 30%-35% KCl and 65%-70% NaCl.

[0019] Furthermore, in step S2, the melt temperature is controlled at 730-750℃ before adding the alloy additive.

[0020] Furthermore, in step S3, the rotor speed during automatic refining is 750±50 r / min, the pressure of the high-purity argon gas is 1.0±0.2 MPa, and the amount of the second remelting refining agent is 2.0±0.2 kg / min; the total time for automatic refining and manual refining is not less than 30 min, and after refining, the mixture is allowed to stand for not less than 15 min before slag removal; after slag removal, the surface of the melt is mirror-like, and there is no slag larger than 20 mm × 20 mm.

[0021] Furthermore, in step S4, the aluminum inlet of the heat preservation furnace adopts a U-shaped tube design and is 200-250mm away from the furnace bottom. The diameter of the porous refining tube does not exceed 5mm, and the pressure of the high-purity argon gas introduced is 4.0±0.3MPa.

[0022] Furthermore, in step S5, the pressure of the high-purity argon gas introduced is 0.5±0.1MPa, and the amount of the third remelting refining agent is 1.0±0.1kg per ton of aluminum alloy melt; after slag removal, the temperature of the melt is controlled to be 710-720℃.

[0023] Further, in step S6, the rotor speed of the three-rotor series degassing box is 300±10 r / min, the pressure of the high-purity argon gas is 0.6±0.2 MPa, and the dosage of the second remelting refining agent is 0.5 kg per minute; the series dual-stage plate filter box includes a pre-stage filter box and a post-stage filter box, wherein the pre-stage filter box is sequentially equipped with ceramic filter plates with mesh sizes of 30 ppi and 40 ppi, and the post-stage filter box is sequentially equipped with ceramic filter plates with mesh sizes of 50 ppi and 60 ppi, forming a two-stage four-gradient filtration combination.

[0024] Furthermore, in step S7, two sets of ultrasonic tool heads are set at a distance of 300-400mm from front to back along the melt flow direction. The ultrasonic tool heads are submerged in the melt and within 10mm from the bottom of the flow channel. The ultrasonic frequency is set to 30-40Hz, and the ultrasonic power of the two stages is set to 45-50kW and 30-35kW respectively. The insert-type horizontal filter plate is a 60ppi filter plate.

[0025] Furthermore, the preset quality standards in step S8 are: hydrogen content ≤ 0.05 mL / 100 g Al, slag analyzer test, melt mass passing through within 70 seconds ≥ 1.4 kg, and Na and K alkali metal content ≤ 10 ppm.

[0026] The beneficial effects of this invention are as follows:

[0027] (1) This invention organically couples three major technologies: chemical refining, plate filtration and deep bed filtration, and physical ultrasound, resulting in a significant synergistic effect. Its working principle is as follows: the first, second, and third remelting agents play their roles at different stages, removing most of the large particle inclusions and dissolved hydrogen from the melt, thus reducing the load on subsequent refining processes; the series-connected dual-stage plate filter box combined with the deep bed filter box constitutes the ultimate "physical barrier," capable of precisely trapping tiny inclusions smaller than 20μm; the ultrasonic field generated in the ultrasonic treatment zone serves as a "physical enhancement method," effectively removing tiny, dispersed inclusions that are difficult to remove using conventional chemical methods, thereby improving refining efficiency. This gradient purification mode of "chemical refining + multi-stage filtration + ultrasonic purification" can reduce the total amount of oxide inclusions in the aluminum alloy melt by more than 80%, completely solving the industry's technical bottleneck of difficulty in removing ultrafine inclusions using a single process.

[0028] (2) The present invention utilizes the synergistic effect of alloy additives and granular and powdered remelting agents. By configuring KCl and NaCl composite remelting agents with different mass ratios at different process stages, the efficient removal of hydrogen, oxide inclusions and alkali metals can be achieved. Specifically: In step S1, the first remelting refining agent (granular) contains 30%~35% KCl and 65%~70% NaCl by mass percentage. It spreads under the influence of high-temperature molten aluminum at the aluminum inlet, performing preliminary adsorption and removal of oxide inclusions and alkali metals. In steps S3 and S6, the second remelting refining agent contains 65%~70% KCl and 30%~35% NaCl by mass percentage. It is in powder form with a large specific surface area, allowing it to penetrate deep into the melt for degassing and impurity removal when combined with high-purity argon gas injection. In step S5, the third remelting refining agent (granular) contains 70%~75% KCl and 25%~30% NaCl by mass percentage, with the highest KCl content, enabling deep removal of alkali metals such as Na. Combined with staged addition of refining agents, high-purity argon gas degassing, ultrasonic purification, and multi-stage filtration, a synergistic purification mechanism of chemical refining, physical impurity removal, and micro-inclusion interception is formed. Compared with traditional processes, the hydrogen content of the aluminum alloy melt treated by this invention can be reduced to below 0.05 mL / 100gAl, and the alkali metal content is ≤10 ppm.

[0029] (3) In step S2, the alloy additive refining process of this invention involves the combined use of elemental metal powder and a compound remelting refining agent. The alloy additive simultaneously comprises iron, manganese, copper, and titanium agents; each of these agents independently comprises elemental metal powder and a compound remelting refining agent as a fluxing agent. The weight percentage of elemental metal powder in each metal additive is 40%-45%, with the remainder being a compound remelting refining agent composed of 30%-35% KCl and 65%-70% NaCl. The principle behind this design is that traditional alloy additives consist only of elemental metal powder, which is easily burned, scattered, and difficult to disperse evenly upon addition. This invention uses a compound remelting refining agent as a fluxing agent, which can break down the oxide film on the surface of the elemental metal powder, improving its wettability and dispersibility in the aluminum alloy melt, allowing alloying elements such as iron, manganese, copper, and titanium to dissolve quickly and uniformly in the aluminum alloy melt. Meanwhile, the compound remelting refining agent itself has a refining effect, which can simultaneously remove inclusions and gases in the melt during the alloying process, realizing the integrated operation of alloying and refining, simplifying the process flow and improving production efficiency.

[0030] (4) In step S4 of the present invention, a U-shaped aluminum inlet design is adopted in the aluminum inlet, which is 200-250mm away from the furnace bottom, so that the aluminum alloy melt enters the holding furnace smoothly from the bottom, reducing splashing and tumbling, thereby reducing oxidation and slag formation. At the same time, high-purity argon gas at a pressure of 4.0±0.3MPa is introduced into the melt through a porous refining pipe with a diameter ≤5mm, forming a dense bubble curtain. During the rising process, the bubbles adsorb and carry away the oxide inclusions and dissolved hydrogen in the melt, while the argon atmosphere isolates the air and prevents secondary oxidation.

[0031] (5) This invention innovatively constructs a multi-stage coupled fine filtration system of a series-connected dual-stage plate filter box and a deep-bed filter box. Its working principle is as follows: through a step-by-step interception mechanism of coarse filtration-fine filtration-deep fine filtration, it achieves efficient removal of inclusions of different sizes in aluminum alloy melt. Specifically, the series-connected dual-stage plate filter box includes a pre-stage filter box and a post-stage filter box. The pre-stage filter box is sequentially equipped with ceramic filter plates with mesh sizes of 30ppi and 40ppi, and the post-stage filter box is sequentially equipped with ceramic filter plates with mesh sizes of 50ppi and 60ppi, forming a two-stage four-gradient filtration combination, which can quickly intercept larger-sized oxide inclusions, flux slag and non-metallic particles in the melt, and significantly reduce the load on the subsequent deep-bed filter box. The deep-bed filter box is sequentially lined with filter grids, coarse alumina ceramic balls (3 / 4 inch), medium alumina ceramic balls (1 / 2 inch), fine alumina gravel (3mm-5mm), medium alumina ceramic balls, and coarse alumina ceramic balls, forming a symmetrical, layered structure. As the melt flows through, the deep adsorption and sieving action of the tortuous channels precisely captures micron-sized and some submicron-sized fine inclusions that are difficult to remove with conventional filtration. Compared to traditional single-stage filtration processes, this invention's multi-stage filtration combination provides more thorough purification and higher melt cleanliness, significantly reducing defects such as pinholes, inclusions, and porosity in castings.

[0032] (6) In the online melt purification process of step S6 of this invention, a three-rotor series degassing box is used in conjunction with a second remelting refining agent. The three-rotor series degassing box uses high-purity argon as a carrier to disperse the second remelting refining agent in the aluminum alloy melt to achieve impurity removal and refining; the rotor speed is 300±10 r / min, the high-purity argon pressure is 0.6±0.2 MPa, and the dosage of the second remelting refining agent is 0.5 kg / min. The three rotors connected in series can form a multi-stage stirring and dispersion zone in the degassing box, breaking the argon into a large number of tiny bubbles; hydrogen atoms diffuse into the bubbles and float to the surface and are discharged, achieving deep degassing; the refining agent droplets adsorb fine inclusions in the melt, achieving synergistic degassing and impurity removal. The second remelting refining agent is in powder form with a large specific surface area, and can be uniformly dispersed throughout the melt under the carrying of high-purity argon, greatly improving the degassing and impurity removal efficiency.

[0033] (7) This invention employs the synergistic effect of an ultrasonic treatment zone and a horizontal filtration zone. The working principle is as follows: During the aluminum alloy melt treatment process, the ultrasonic field generates a strong cavitation effect and micro-jet action, which can effectively disperse and deagglomerate fine oxide inclusions within the melt, significantly accelerate the diffusion of hydrogen atoms into bubbles and promote bubble rise, enhance the end-filtering effect, and improve melt cleanliness. This invention uses two sets of ultrasonic toolheads spaced 300-400mm apart along the melt flow direction, with an ultrasonic frequency set to 30-40Hz. The two ultrasonic power levels are set to 45-50kW and 30-35kW respectively, forming a gradient ultrasonic field. The high-intensity ultrasound in the first stage mainly disperses and deagglomerates inclusions, while the medium-intensity ultrasound in the second stage promotes the rise and removal of small bubbles and fine inclusions. The horizontal filtration zone uses a 60ppi insert-type horizontal filter plate for final filtration to trap residual fine inclusions. Compared with conventional processes without ultrasonic purification, the present invention achieves more thorough degassing and slag removal from the melt, more complete removal of inclusions, higher melt purity, more uniform and dense as-cast structure, and a significant reduction in casting defects.

[0034] (8) In this invention, after refining in the holding furnace in step S5, high-purity argon gas is introduced into the holding furnace as an inert atmosphere to prevent oxidation and slag formation on the surface of the aluminum alloy melt. Simultaneously, after slag removal in step S5, the melt's settling temperature is controlled at 710-720℃. This temperature ensures good melt fluidity while preventing secondary oxidation and hydrogen absorption caused by excessively high temperatures. The high-pressure argon protection in the furnace refining process in step S4 and the argon protection after refining in the holding furnace in step S5 form a double anti-oxidation barrier, reducing secondary oxidation pollution of the melt from the source.

[0035] (9) This invention establishes a complete quality control closed loop through melt quality testing in step S8. A liquid hydrogen analyzer is used to detect hydrogen content online, requiring a hydrogen content ≤0.05mL / 100gAl; an ABB brand PZM0700D slag analyzer is used to detect slag content in the melt online, requiring a melt mass ≥1.4kg to pass through within 70s; samples are taken for composition testing, requiring both Na and K alkali metal contents ≤10ppm. This quantitative testing standard provides clear melt quality criteria for high-end aluminum foil production, ensuring product quality stability and traceability. Detailed Implementation

[0036] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0037] This invention provides a purification process for molten aluminum alloy, which achieves ultra-clean purification of molten aluminum alloy through a multi-stage coupled, online continuous processing method. The following details each step:

[0038] Step S1, Aluminum Inlet Refining: Add self-produced scrap and remelted aluminum ingots to the bottom of the smelting furnace. Place the first remelting refining agent at the aluminum inlet of the smelting furnace. Using 40 kg of the first remelting refining agent per bag of molten aluminum, pour the molten aluminum into the smelting furnace through the aluminum inlet. This molten aluminum, together with the self-produced scrap and remelted aluminum ingots at the bottom of the furnace, forms an aluminum alloy melt. After pouring out the molten aluminum, clean the aluminum slag from the aluminum inlet of the smelting furnace. The first remelting refining agent used in this step is granular and contains 30%-35% KCl and 65%-70% NaCl by mass percentage. The purpose of this step is to allow the high-temperature molten aluminum to wash over the granular first remelting refining agent at the aluminum inlet, causing it to spread rapidly on the surface of the molten aluminum. The chlorides in the refining agent capture oxide inclusions through wetting and adsorption, achieving preliminary purification. Furthermore, the formed molten salt film can isolate air and reduce secondary oxidation of the molten aluminum.

[0039] Step S2, Alloy Additive Refining: After pouring molten aluminum into the melting furnace, turn on the electromagnetic stirrer, ignite and heat to level the melt. After sampling and testing the initial composition, control the melt temperature to 730-750℃. According to the target alloy composition requirements, evenly sprinkle alloy additives with refining effects into the furnace. These alloy additives simultaneously include iron, manganese, copper, and titanium agents. Each of the iron, manganese, copper, and titanium agents independently contains elemental metal powder and a compound remelting refining agent as a flux. The weight percentage of elemental metal powder in each metal additive is 40%-45%, with the remainder being a compound remelting refining agent composed of 30%-35% KCl and 65%-70% NaCl. After adding the additives, close the furnace door and seal for at least 30 minutes. Use a slag remover to submerge the slag removal teeth at least 30cm into the melt and circulate and stir for at least 5 minutes. After stirring, take samples to test the alloy composition. The purpose of this step is as follows: Traditional alloy additives are simply metal elemental powders, which are easily burned off, scattered, and difficult to disperse evenly when added. The alloy additive used in this invention combines metal elemental powders with a compound remelting refining agent. The compound remelting refining agent acts as a flux, breaking down the oxide film on the surface of the metal elemental powders and improving their wettability and dispersibility in the aluminum alloy melt, allowing the alloying elements to dissolve quickly and evenly in the aluminum alloy melt. Simultaneously, the compound remelting refining agent itself has a refining effect, removing inclusions and gases from the melt during the alloying process, achieving integrated alloying and refining operations. It should be noted that the relative proportions of iron, manganese, copper, and titanium in the alloy additive of this invention are not fixed and can be adaptively adjusted according to the specific composition requirements of the target aluminum alloy grade. Therefore, this invention does not limit the proportions of each additive.

[0040] Step S3, Refining in the Melting Furnace: After the alloy composition is found to be qualified, the HD2000 automatic refining machine is turned on to begin refining. The rotor speed of the refining machine is set to 750±50 r / min. High-purity argon gas is introduced into the rotor, along with a second remelting refining agent. The high-purity argon gas pressure for refining is 1.0±0.2 MPa, and the dosage of the second remelting refining agent is set to 2.0±0.2 kg / min. During automatic refining, manual refining is performed simultaneously using high-purity argon gas at a pressure of 0.8±0.2 MPa. During manual refining, the tool head of the refining tube must be immersed in the molten material for more than 100 mm, and the height of the molten material churning should not exceed 100 mm. The combined time for automatic and manual refining should be at least 30 minutes. After refining, the mixture should be allowed to stand for at least 15 minutes before slag removal. After slag removal, the surface of the melt must be mirror-like, and no slag larger than 20mm x 20mm is allowed. The aluminum alloy melt after slag removal should be allowed to stand for at least 30 minutes before being introduced into the furnace. The second remelting refining agent used in this step is in powder form, containing 65%-70% KCl and 30%-35% NaCl by mass percentage. The purpose of this step is that the powdered second remelting refining agent has a large specific surface area, and under the carrying of high-purity argon gas, it is dispersed by the rotor and evenly distributed into the melt. Through adsorption and dissolution, it removes oxide inclusions. At the same time, the chlorides in it react with alkali metals (Na, K) to form chloride salts, which float to the surface and are then removed. High-purity argon gas serves as the carrier gas, on the one hand, sending the refining agent deep into the melt, and on the other hand, the bubbles in the melt provide a low hydrogen partial pressure environment, allowing dissolved hydrogen to diffuse into the bubbles and float to the surface and be discharged. The combination of automatic and manual refining can cover different areas within the furnace, ensuring uniform and thorough refining.

[0041] Step S4, Furnace Refining: After refining, slag removal, and settling in the smelting furnace, the melt is discharged from the furnace outlet and enters the holding furnace via a guide channel. During the furnace guiding process, the melt flow rate is strictly controlled to prevent tumbling and slagging in the guide channel. The aluminum inlet of the holding furnace adopts a U-shaped pipe design, positioned 200-250mm above the furnace bottom. After the furnace guiding is completed, the melt completely submerges the inlet. During furnace guiding, a porous refining pipe with a perforation diameter of less than 5mm is placed at the aluminum inlet of the holding furnace. High-purity argon gas at a pressure of 4.0±0.3MPa is introduced into the porous refining pipe for furnace guiding refining. The furnace guiding refining begins 2 minutes before furnace guiding and ends 10 minutes after the flow guide. The furnace door must be closed during the furnace guiding refining period to prevent melt splashing. The purpose of this step is as follows: During the process of molten aluminum alloy being drawn from the melting furnace and flowing through the guide channel into the holding furnace, changes in flow velocity and drop height can easily cause tumbling and turbulence, thus entraining air and forming new oxide inclusions. This step involves installing a porous refining tube at the aluminum inlet of the holding furnace. High-pressure argon gas forms a dense bubble curtain. As the melt flows through, the high-pressure argon bubbles violently agitate and wash away the melt. This not only removes newly generated oxide inclusions and bubbles during the guiding process but also isolates the air from the surrounding environment, reducing secondary oxidation. The U-shaped inlet design allows the melt to enter the holding furnace from the bottom, avoiding splashing and tumbling, further reducing oxidation and slagging.

[0042] Step S5, Refining in the Holding Furnace: After the furnace is opened, manual refining begins immediately inside the holding furnace. Refining is first performed in the furnace door area on the molten metal outlet side, followed by refining in the area on the other furnace door side. High-purity argon gas is introduced into the refining tube, along with a third remelting agent. The high-purity argon gas pressure is 0.5±0.1 MPa, and the amount of the third remelting agent is set at 1.0±0.1 kg per ton of aluminum alloy melt. During refining, the tool head of the refining tube must be immersed in the molten metal for more than 100 mm, and the height of the melt churning during refining must not exceed 100 mm. The refining time in the holding furnace must be at least 30 minutes. After refining, the furnace should be allowed to stand for at least 15 minutes before slag removal. After slag removal, the surface of the melt must be mirror-like, and no slag larger than 20mm x 20mm is allowed. High-purity argon is introduced into the holding furnace after slag removal as an inert atmosphere to prevent oxidation and slagging of the aluminum alloy melt surface. The holding temperature of the melt after slag removal is controlled at 710-720℃. The third remelting refining agent used in this step is granular and contains 70%-75% KCl and 25%-30% NaCl by mass percentage. The purpose of this step is: holding furnace refining is the final in-furnace treatment before casting. A high-KCl content third remelting refining agent (70%-75%) is used, where KCl can deeply remove alkali metals such as Na. High-purity argon acts as a carrier to blow the refining agent deep into the melt, while argon bubbles absorb and dissolve hydrogen during their ascent. After refining, the furnace is allowed to stand, allowing inclusions and bubbles to fully float to the surface, resulting in a mirror-like surface after slag removal. Finally, high-purity argon gas is introduced as a protective atmosphere to isolate the melt from air and prevent secondary oxidation.

[0043] Step S6, Online Melt Purification Treatment: The aluminum alloy melt, after refining, settling, and slag removal in the holding furnace, flows into the degassing box through a flow channel. The degassing box is set with a three-rotor series layout. The rotor speed of the three-rotor series degassing box is set to 300±10 r / min. High-purity argon gas is introduced into the rotor, and a powdered second remelting refining agent (the same as the second remelting refining agent in step S3) is used. The high-purity argon gas blows the second remelting refining agent into the melt. The high-purity argon gas pressure is set to 0.6±0.2 MPa, and the amount of the second remelting refining agent is set to 0.5 kg per minute. The three-rotor series degassing box needs to remove slag once per hour, and each slag removal must be clean. The melt, degassed by the three-rotor series degassing box, flows through a series two-stage plate filter box. The series two-stage plate filter box contains ceramic filter plates, and the installation of the ceramic filter plates must ensure a seamless fit between the ceramic filter plates and the filter box body. The series two-stage plate filter box includes a pre-stage filter box and a post-stage filter box. The pre-stage filter box contains ceramic filter plates with mesh sizes of 30ppi and 40ppi, while the post-stage filter box contains ceramic filter plates with mesh sizes of 50ppi and 60ppi, forming a two-stage, four-gradient filtration combination. After filtration by the series two-stage plate filter box, the filter flows through a deep bed filter box. The deep bed filter box uses filter grids, alumina ceramic balls, and alumina gravel as the filter media. Specifically, it is laid out in sequence as filter grids, 3 / 4-inch coarse alumina ceramic balls, 1 / 2-inch medium alumina ceramic balls, 3mm-5mm fine alumina gravel, 1 / 2-inch medium alumina ceramic balls, and 3 / 4-inch coarse alumina ceramic balls, forming a symmetrical, layered structure. The purpose of this step is as follows: Online melt purification is the final refining process before casting, directly determining the quality of the melt entering the crystallizer. The three-rotor series degassing box uses three medium-speed rotating rotors to break high-purity argon gas into numerous tiny bubbles, which are then evenly dispersed throughout the melt. Hydrogen atoms diffuse into the argon bubbles to form hydrogen molecules, which rise and are expelled with the bubbles, achieving deep degassing. Simultaneously, the rotors drive the second remelting refining agent to disperse evenly, adsorbing fine inclusions in the melt, achieving synergistic degassing and impurity removal. The series dual-stage plate filter box uses four-stage gradient ceramic filter plates (30ppi, 40ppi, 50ppi, 60ppi), with progressively decreasing porosity. This allows for a gradual transition from coarse to fine filtration. Large inclusions are intercepted by the preceding ceramic filter plates, while small and medium-sized inclusions are intercepted by the subsequent ceramic filter plates, avoiding the problems of easy clogging and short filter life of single ceramic filter plates. The deep bed filter box uses a filter medium with a symmetrical layered structure (3 / 4 inch coarse particles → 1 / 2 inch medium particles → 3mm-5mm fine particles → 1 / 2 inch medium particles → 3 / 4 inch coarse particles). When the melt flows through the tortuous channel, submicron-sized fine inclusions are captured through deep adsorption and sieving, achieving efficient removal of ultrafine inclusions that cannot be removed by conventional filtration.

[0044] Step S7, Ultrasonic and Horizontal Filtration: At the deep-bed filter outlet, place two sets of ultrasonic toolheads, one behind the other, spaced 300-400mm apart. The ultrasonic toolheads should be submerged in the melt, within 10mm of the bottom of the flow channel. Set the ultrasonic frequency to 30-40Hz, and the ultrasonic power for the two stages to 45-50kW and 30-35kW respectively. Install a horizontal filter plate (ceramic filter plate) 200-300mm downstream of the ultrasonic treatment zone in the flow channel. The filter plate should have a mesh size of 60ppi. The purpose of this step is to generate cavitation and microjets in the aluminum melt using the ultrasonic field. The shock waves generated by the collapse of cavitation bubbles break up fine inclusions and agglomerates. The microjets promote microscopic flow in the melt, accelerate bubble coalescence and buoyancy, and enhance the contact between inclusions and the filter medium. Two-stage ultrasound creates a gradient field: the initial high-intensity ultrasound (45-50kW) primarily disperses inclusions and agglomerates, while the subsequent medium-intensity ultrasound (30-35kW) promotes the flotation of small bubbles and fine inclusions. Subsequently, a 60ppi horizontal filter plate traps residual fine inclusions, ensuring ultra-clean melt.

[0045] Step S8, Melt Quality Inspection: After online treatment, the hydrogen content of the aluminum alloy melt is detected online using a liquid hydrogen analyzer, and the slag content is detected online using an ABB brand PZM0700D slag analyzer. Samples are taken for composition analysis. The purpose of this step is to quantitatively evaluate the quality of the treated melt through online detection and sampling, ensuring that the melt meets the technical requirements for high-end aluminum foil production. The preset quality standards are: hydrogen content ≤ 0.05 mL / 100g Al, melt mass passing through within 70 seconds using a slag analyzer ≥ 1.4 kg, and alkali metal content of Na and K both ≤ 10 ppm. Only melts meeting the above standards can enter the casting process, thereby guaranteeing the quality of the final product.

[0046] The technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0047] Example 1

[0048] This embodiment provides a process for purifying aluminum alloy melts, the specific steps of which are as follows:

[0049] Step S1, Aluminum Inlet Refining: Add self-produced waste and remelted aluminum ingots to the smelting furnace and place them at the bottom of the furnace. Place the first remelting refining agent at the aluminum inlet of the smelting furnace. The composition of the first remelting refining agent is 35% KCl + 65% NaCl (mass percentage). Use 40 kg of the first remelting refining agent per bag of electrolytic aluminum. Pour the electrolytic aluminum into the smelting furnace from the aluminum inlet. After the electrolytic aluminum is poured out, clean the aluminum slag at the aluminum inlet of the smelting furnace.

[0050] Step S2, Alloy Additive Refining: After pouring molten aluminum into the melting furnace, turn on the electromagnetic stirrer, ignite and heat to level the mixture. After sampling and testing the initial composition, measure the melt temperature at 742℃. Evenly sprinkle alloy additives into the furnace according to the target alloy composition requirements. The alloy additives include iron, manganese, copper, and titanium. Specifically, the iron additive contains 41.4% by weight of elemental metal powder, with the remainder being a compound remelting refining agent composed of 31% KCl and 69% NaCl; the manganese additive contains 43.2% by weight of elemental metal powder, with the remainder being a compound remelting refining agent composed of 31% KCl and 69% NaCl; the copper additive contains 44.6% by weight of elemental metal powder, with the remainder being a compound remelting refining agent composed of 31% KCl and 69% NaCl; and the titanium additive contains 40.9% by weight of elemental metal powder, with the remainder being a compound remelting refining agent composed of 31% KCl and 69% NaCl. After the alloy additives were added, the furnace door was closed and sealed for 37 minutes. The slag removal cart was used to submerge the slag removal teeth into the melt to 31 cm. The mixture was circulated and stirred for 7 minutes. After stirring, samples were taken to test the alloy composition.

[0051] Step S3, Refining in the Melting Furnace: After the alloy composition is found to be qualified, the HD2000 automatic refining machine is turned on to begin refining. The rotor speed of the refining machine is set to 745 r / min, and high-purity argon gas is introduced into the rotor along with a second remelting refining agent. The second remelting refining agent has a composition of 69% KCl + 31% NaCl (mass percentage) and is in powder form. The high-purity argon gas blows the second remelting refining agent into the melt. The high-purity argon gas pressure for refining is 1.0 MPa, and the dosage of the second remelting refining agent is set to 2.0 kg / min. During automatic refining, manual refining is performed using high-purity argon gas at a pressure of 0.9 MPa. During manual refining, the tool head of the refining tube must be immersed 110 mm into the melt surface, and the melt tumbling height must be 80 mm. The combined automatic and manual refining time is 33 minutes. After refining, the mixture is allowed to stand for 16 minutes for slag removal. After slag removal, the surface of the melt is mirror-like, with no slag larger than 20mm×20mm. The aluminum alloy melt after slag removal is allowed to stand for 32 minutes before being introduced into the furnace.

[0052] Step S4, Furnace Refining: After refining, slag removal, and settling in the smelting furnace, the melt is discharged from the furnace outlet and enters the holding furnace via a guide channel. The aluminum inlet of the holding furnace adopts a U-shaped pipe design, located 210mm above the furnace bottom. After the furnace is guided, the melt completely submerges the inlet. During the furnace guiding process, the melt flow rate is strictly controlled to prevent the melt from tumbling and forming slag in the guide channel. During furnace guiding, a porous refining tube with a 4mm orifice is placed at the aluminum inlet of the holding furnace. High-purity argon gas at a pressure of 3.9MPa is introduced into the porous refining tube for furnace guiding refining. The furnace guiding refining begins 2 minutes before furnace guiding and ends 10 minutes after the flow guide. The furnace door must be closed during the furnace guiding refining period to prevent melt splashing.

[0053] Step S5, Refining in the Holding Furnace: After the furnace is opened, manual refining begins immediately inside the holding furnace. Refining is first performed in the furnace door area on the melt outlet side, followed by refining in the area on the other furnace door side. High-purity argon gas is introduced into the refining tube, along with a third remelting agent. The third remelting agent consists of 75% KCl + 25% NaCl (mass percentage) and is in granular form. The high-purity argon gas is used to blow the third remelting agent into the melt at a pressure of 0.5 MPa. The amount of the third remelting agent is set at 1.1 kg per ton of aluminum alloy melt. During refining, the tool head of the refining tube must be immersed 130 mm into the melt surface, and the melt should churn to a height of 90 mm during the refining process. The refining time in the holding furnace is 33 minutes. After refining, the furnace is allowed to stand for 19 minutes before slag removal. After slag removal, the surface of the melt is mirror-like, with no slag larger than 20mm×20mm. After slag removal, high-purity argon is introduced into the holding furnace as an inert atmosphere to prevent metal oxidation and slag formation on the surface of the aluminum alloy melt. The holding furnace melt static temperature is set at 718℃.

[0054] Step S6, Online Melt Purification Treatment: The aluminum alloy melt, after refining, settling, and slag removal in the holding furnace, flows into the degassing box through a flow channel. The degassing box is set with a three-rotor series layout. The rotor speed in the three-rotor series degassing box is set to 305 r / min. High-purity argon gas is introduced into the rotor, and a second remelting refining agent (the same as the second remelting refining agent in step S3) is used. The high-purity argon gas blows the second remelting refining agent into the melt. The high-purity argon gas pressure is set to 0.5 MPa, and the dosage of the second remelting refining agent is set to 0.5 kg per minute. The three-rotor series degassing box needs to remove slag once per hour, and each slag removal must be clean. The melt, degassed by the three-rotor series degassing box, flows through a series two-stage plate filter box. This box consists of a pre-stage filter box and a post-stage filter box. The pre-stage filter box contains ceramic filter plates with mesh sizes of 30ppi and 40ppi, while the post-stage filter box contains ceramic filter plates with mesh sizes of 50ppi and 60ppi, forming a two-stage, four-gradient filtration system. The ceramic filter plates must be installed seamlessly between themselves and the filter box housing. After the series two-stage filtration, the filter passes through a deep-bed filter box. This deep-bed filter box contains filter grids, 3 / 4-inch coarse alumina ceramic balls, 1 / 2-inch medium alumina ceramic balls, 3mm-5mm fine alumina gravel, 1 / 2-inch medium alumina ceramic balls, and 3 / 4-inch coarse alumina ceramic balls, forming a symmetrical, layered structure.

[0055] Step S7, Ultrasonic and Horizontal Filtration: At the deep bed filter outlet, place two sets of ultrasonic tool heads, one after the other, 350mm apart. The ultrasonic tool heads are submerged in the melt, 10mm from the bottom of the flow channel. The ultrasonic frequency is set to 33Hz, and the ultrasonic power for the two stages is set to 45kW and 30kW respectively. A horizontal filter plate with a ceramic mesh size of 60ppi is installed in the flow channel 230mm downstream of the ultrasonic treatment zone.

[0056] Step S8, Melt Quality Inspection: The hydrogen content of the aluminum alloy melt after online treatment was detected online using a liquid hydrogen analyzer, and the hydrogen content was 0.042 mL / 100gAl; the slag content of the melt was detected online using an ABB brand PZM0700D slag analyzer, and the melt mass after 70 seconds was 1.56 kg; samples were taken for composition testing, and the contents of alkali metals such as Na and K were all ≤10ppm.

[0057] Example 2

[0058] This embodiment provides a process for purifying aluminum alloy melts, the specific steps of which are as follows:

[0059] Step S1, Aluminum Inlet Refining: Add self-produced waste and remelted aluminum ingots to the bottom of the smelting furnace. Place the first remelting refining agent at the aluminum inlet of the smelting furnace. The composition of the first remelting refining agent is 30% KCl + 70% NaCl (mass percentage). Use 40 kg of the first remelting refining agent per bag of electrolytic aluminum. Pour the electrolytic aluminum into the smelting furnace from the aluminum inlet. After the electrolytic aluminum is poured out, clean the aluminum slag at the aluminum inlet of the smelting furnace.

[0060] Step S2, Alloy Additive Refining: After pouring molten aluminum into the melting furnace, turn on the electromagnetic stirrer, ignite and heat to level the mixture. After sampling and testing the initial composition, measure the melt temperature at 735℃. Evenly sprinkle alloy additives into the furnace according to the target alloy composition requirements. The alloy additives include iron, manganese, copper, and titanium. Specifically, the iron additive contains 43.2% by weight of elemental metal powder, with the remainder being a compound remelting refining agent composed of 33% KCl and 67% NaCl; the manganese additive contains 40.8% by weight of elemental metal powder, with the remainder being a compound remelting refining agent composed of 33% KCl and 67% NaCl; the copper additive contains 41.7% by weight of elemental metal powder, with the remainder being a compound remelting refining agent composed of 33% KCl and 67% NaCl; and the titanium additive contains 44.9% by weight of elemental metal powder, with the remainder being a compound remelting refining agent composed of 33% KCl and 67% NaCl. After adding the alloy additive, the furnace door was closed and sealed for 32 minutes. The slag removal car was used to submerge the slag removal teeth into the melt to 35 cm. The mixture was circulated and stirred for 6 minutes. After stirring, a sample was taken to test the alloy composition.

[0061] Step S3, Refining in the Melting Furnace: After the alloy composition is found to be qualified, the HD2000 automatic refining machine is turned on to begin refining. The rotor speed of the refining machine is set to 760 r / min, and high-purity argon gas is introduced into the rotor along with a second remelting refining agent. The second remelting refining agent has a composition of 65% KCl + 35% NaCl (mass percentage) and is in powder form. The high-purity argon gas blows the second remelting refining agent into the melt. The pressure of the high-purity argon gas used for refining is 1.1 MPa, and the dosage of the second remelting refining agent is set to 2.2 kg / min. During automatic refining, manual refining is performed using high-purity argon gas at a pressure of 1.0 MPa. During manual refining, the tool head of the refining tube must be immersed 110 mm into the melt surface, and the melt tumbling height must be 90 mm. The combined time for automatic and manual refining is 35 minutes. After refining, the mixture is allowed to stand for 18 minutes for slag removal. After slag removal, the surface of the melt is mirror-like, with no slag larger than 20mm×20mm. The aluminum alloy melt after slag removal is allowed to stand for 33 minutes before being introduced into the furnace.

[0062] Step S4, Furnace Refining: After refining, slag removal, and settling in the smelting furnace, the melt is discharged from the furnace outlet and enters the holding furnace via a guide channel. The aluminum inlet of the holding furnace adopts a U-shaped pipe design, located 250mm above the furnace bottom. After the furnace is guided, the melt completely submerges the inlet. During the furnace guiding process, the melt flow rate is strictly controlled to prevent the melt from tumbling and forming slag in the guide channel. During furnace guiding, a porous refining tube with a 4mm orifice is placed at the aluminum inlet of the holding furnace. High-purity argon gas at a pressure of 4.0MPa is introduced into the porous refining tube for furnace guiding refining. The furnace guiding refining begins 2 minutes before furnace guiding and ends 10 minutes after the flow is guided. The furnace door must be closed during the furnace guiding refining period to prevent melt splashing.

[0063] Step S5, Refining in the Holding Furnace: After the furnace is opened, manual refining begins immediately inside the holding furnace. Refining is first performed in the furnace door area on the melt outlet side, followed by refining in the area on the other furnace door side. High-purity argon gas is introduced into the refining tube, along with a third remelting agent. The third remelting agent consists of 70% KCl + 30% NaCl (mass percentage) and is in granular form. The high-purity argon gas is used to blow the third remelting agent into the melt at a pressure of 0.6 MPa. The amount of the third remelting agent is set at 1.0 kg per ton of aluminum alloy melt. During refining, the tool head of the refining tube must be immersed 120 mm into the melt surface, and the melt should churn to a height of 80 mm during the refining process. The refining time in the holding furnace is 36 minutes. After refining, the furnace is allowed to stand for 17 minutes before slag removal. After slag removal, the surface of the melt is mirror-like, with no slag larger than 20mm×20mm. After slag removal, high-purity argon is introduced into the holding furnace as an inert atmosphere to prevent metal oxidation and slag formation on the surface of the aluminum alloy melt. The holding furnace melt static temperature is set at 713℃.

[0064] Step S6, Online Melt Purification Treatment: The aluminum alloy melt, after refining, settling, and slag removal in the holding furnace, flows into the degassing box through a flow channel. The degassing box is set with a three-rotor series layout. The rotor speed of the three-rotor series degassing box is set to 295 r / min. High-purity argon gas is introduced into the rotor, and a second remelting refining agent (the same as the second remelting refining agent in step S3) is used. The high-purity argon gas blows the second remelting refining agent into the melt. The high-purity argon gas pressure is set to 0.55 MPa, and the dosage of the second remelting refining agent is set to 0.5 kg per minute. The three-rotor series degassing box needs to remove slag once per hour, and each slag removal must be clean. The melt, degassed by the three-rotor series degassing box, flows through a series two-stage plate filter box, which includes a pre-stage filter box and a post-stage filter box. The pre-stage filter box contains ceramic filter plates with mesh sizes of 30ppi and 40ppi, while the post-stage filter box contains ceramic filter plates with mesh sizes of 50ppi and 60ppi, forming a two-stage, four-gradient filtration system. After the series two-stage filtration, the filtration proceeds to a deep-bed filter box. The deep-bed filter box contains filter grids, 3 / 4-inch coarse alumina ceramic balls, 1 / 2-inch medium alumina ceramic balls, 3mm-5mm fine alumina gravel, 1 / 2-inch medium alumina ceramic balls, and 3 / 4-inch coarse alumina ceramic balls, forming a symmetrical, layered structure.

[0065] Step S7, Ultrasonic and Horizontal Filtration: At the deep bed filter outlet, place two sets of ultrasonic tool heads, one after the other, spaced 340mm apart. The ultrasonic tool heads are submerged in the melt, 7mm from the bottom of the flow channel. The ultrasonic frequency is set to 35Hz, and the ultrasonic power for the two stages is set to 50kW and 33kW respectively. A horizontal filter plate with a ceramic mesh size of 60ppi is installed in the flow channel 250mm downstream of the ultrasonic treatment zone.

[0066] Step S8, Melt Quality Inspection: The hydrogen content of the aluminum alloy melt after online treatment was detected online using a liquid hydrogen analyzer, and the hydrogen content was 0.048 mL / 100gAl; the slag content of the melt was detected online using an ABB brand PZM0700D slag analyzer, and the melt mass after 70 seconds was 1.74 kg; samples were taken for composition testing, and the contents of alkali metals such as Na and K were all ≤10ppm.

[0067] Comparative Example 1

[0068] The difference between this comparative example and Example 1 is that it does not include steps S6 and S7.

[0069] The aluminum alloy melt treated in this comparative example was tested online using a liquid hydrogen analyzer, and the hydrogen content was 0.119 mL / 100 g Al. The slag content of the melt was tested online using an ABB PZM0700D slag analyzer, and the melt mass was 0.821 kg after 70 seconds. Samples were taken for composition analysis, and the Na content was 15 ppm and the K content was 21 ppm.

[0070] Comparative Example 2

[0071] The difference between this comparative example and Example 1 is that step S6 is not included.

[0072] The aluminum alloy melt treated in this comparative example was tested online using a liquid hydrogen analyzer, and the hydrogen content was 0.095 mL / 100 g Al. The slag content of the melt was tested online using an ABB brand PZM0700D slag analyzer, and the melt mass was 1.105 kg after 70 seconds. Samples were taken for composition analysis, and the Na content was 12 ppm and the K content was 16 ppm.

[0073] Comparative Example 3

[0074] The difference between this comparative example and Example 1 is that step S7 is not included.

[0075] The aluminum alloy melt treated in this comparative example was tested online using a liquid hydrogen analyzer, and the hydrogen content was 0.082 mL / 100 g Al. The slag content of the melt was tested online using an ABB PZM0700D slag analyzer, and the melt mass was 1.211 kg after 70 seconds. Samples were taken for composition analysis, and the Na content was 14 ppm and the K content was 13 ppm.

[0076] Comparative Example 4

[0077] The difference between this comparative example and Example 1 is that the first remelting refining agent is not added in step S1.

[0078] The aluminum alloy melt treated in this comparative example was tested online using a liquid hydrogen analyzer, and the hydrogen content was 0.105 mL / 100 g Al. The slag content of the melt was tested online using an ABB PZM0700D slag analyzer, and the melt mass was 0.522 kg after 70 seconds. Samples were taken for composition analysis, and the Na content was 22 ppm and the K content was 28 ppm.

[0079] A comparison of the test results of Examples 1-2 and Comparative Examples 1-4 shows that the examples employing the complete technical solution of this invention exhibit significantly better hydrogen content, slag content, and alkali metal content in the treated melt compared to the comparative examples. Comparative Examples 1-3, by omitting core steps such as online melt purification (step S6) or ultrasonic and horizontal filtration (step S7), resulted in a significant increase in hydrogen and slag content, failing to meet the preset quality standards. Comparative Example 4, by not adding the first remelting refining agent at the aluminum inlet, showed a substantial increase in alkali metal content. These comparative results fully verify the synergistic effect between the steps in the multi-stage coupled process of "chemical refining + multi-stage filtration + ultrasonic purification" constructed by this invention, and the cleanliness of the treated melt fully meets the production requirements of high-end aluminum foil and cast-rolled billets.

[0080] In summary, this invention organically couples three technologies—chemical refining, multi-stage filtration, and ultrasonic purification—to form a gradient purification mode of "chemical refining + multi-stage filtration + ultrasonic purification," achieving deep removal of hydrogen, micron- and submicron-sized inclusions, and alkali metals from aluminum alloy melts. The data from Examples 1 and 2 fully verify the stability and reliability of the technical solution of this invention. The quality of the treated aluminum alloy melt fully meets the stringent requirements for melt quality in high-end products such as high-purity aluminum, lithium battery aluminum foil, double-zero aluminum foil, electronic aluminum foil, and high-end cast-rolled billets, demonstrating promising prospects for industrial application.

[0081] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A purification process for aluminum alloy melt, characterized in that, Includes the following steps: Step S1, Aluminum Inlet Refining: Place the first remelting refining agent at the aluminum inlet of the smelting furnace, and pour the electrolytic aluminum into the smelting furnace through the aluminum inlet. Together with the self-produced waste material at the bottom of the furnace and the remelted aluminum ingot, they form an aluminum alloy melt for preliminary refining. Step S2, Alloy Additive Refining: Add an alloy additive with refining effect to the aluminum alloy melt in the melting furnace. The alloy additive includes elemental metal powder and a compound remelting refining agent as a flux to carry out alloying refining. Step S3, Refining in a melting furnace: After the alloy composition is found to be qualified, a combination of automatic and manual refining is used. The second remelting refining agent is blown into the aluminum alloy melt through a rotor using high-purity argon as a carrier for refining. After refining, the mixture is allowed to stand and the slag is removed. The second remelting refining agent is in powder form. Step S4, furnace refining: The aluminum alloy melt after refining, slag removal and settling in the smelting furnace is exported from the outlet of the smelting furnace and introduced into the holding furnace through the guide channel. During the introduction process, high-purity argon gas is introduced into the aluminum alloy melt through the porous refining pipe for furnace refining. Step S5, Refining in a holding furnace: In the holding furnace, the third remelting refining agent is blown into the aluminum alloy melt through the refining tube using high-purity argon as a carrier for refining. After refining, the melt is allowed to stand, slag is removed, and high-purity argon is introduced into the holding furnace as a protective atmosphere. Step S6, Online Melt Purification Treatment: The aluminum alloy melt, after refining, settling, and slag removal in the holding furnace, flows sequentially through a three-rotor series degassing box, a series two-stage plate filter box, and a deep bed filter box for degassing and multi-stage filtration. The three-rotor series degassing box uses high-purity argon gas as a carrier to blow the second remelting refining agent into the aluminum alloy melt for impurity removal and refining. The series two-stage plate filter box uses a four-stage gradient ceramic filter plate combination. The deep bed filter box is sequentially laid with filter grids, coarse alumina ceramic balls, medium alumina ceramic balls, fine alumina gravel, medium alumina ceramic balls, and coarse alumina ceramic balls, forming a symmetrical layered structure. Step S7, Ultrasonic and Horizontal Filtration: The aluminum alloy melt after step S6 is sequentially passed through the ultrasonic treatment zone and the horizontal filtration zone. The ultrasonic treatment zone uses at least two sets of ultrasonic tool heads to apply an ultrasonic field to the melt. The resulting cavitation effect is used to disperse fine inclusion agglomerates and accelerate the rise of hydrogen bubbles. The horizontal filtration zone uses a plate-type horizontal filter plate for final filtration to trap residual fine inclusions. Step S8, Melt quality inspection: Inspect the hydrogen content, slag content and alkali metal content of the treated aluminum alloy melt to confirm that it meets the preset quality standards; In step S1, the first remelting refining agent, in step S3, the second remelting refining agent, and in step S5, the third remelting refining agent are respectively composed of different mass ratios of KCl and NaCl to form a gradient composition; in step S1, the first remelting refining agent contains 30%-35% KCl and 65%-70% NaCl; in step S3, the second remelting refining agent contains 65%-70% KCl and 30%-35% NaCl; and in step S5, the third remelting refining agent contains 70%-75% KCl and 25%-30% NaCl. The alloy additives mentioned in step S2 simultaneously include iron, manganese, copper, and titanium additives; each of the iron, manganese, copper, and titanium additives independently contains elemental metal powder and a compound remelting refining agent as a flux, and the weight percentage of elemental metal powder in each metal additive is 40%-45%, with the remainder being a compound remelting refining agent composed of 30%-35% KCl and 65%-70% NaCl.

2. The aluminum alloy melt purification process according to claim 1, characterized in that: In step S3, the rotor speed during automatic refining is 750±50 r / min, the pressure of the high-purity argon gas is 1.0±0.2 MPa, and the amount of the second remelting refining agent is 2.0±0.2 kg / min. In step S5, the pressure of the high-purity argon gas introduced is 0.5±0.1MPa, and the amount of the third remelting refining agent is 1.0±0.1kg per ton of aluminum alloy melt.

3. The aluminum alloy melt purification process according to claim 1, characterized in that: In step S4, the aluminum inlet of the heat preservation furnace adopts a U-shaped tube design and is 200-250mm away from the furnace bottom. The diameter of the porous refining tube does not exceed 5mm, and the pressure of the high-purity argon gas introduced is 4.0±0.3MPa.

4. The aluminum alloy melt purification process according to claim 1, characterized in that: In step S6, the rotor speed of the three-rotor series degassing box is 300±10 r / min, the pressure of the high-purity argon gas is 0.6±0.2 MPa, and the amount of the second remelting refining agent is 0.5 kg per minute; the series dual-stage plate filter box includes a pre-stage filter box and a post-stage filter box, wherein the pre-stage filter box is sequentially equipped with ceramic filter plates with a mesh size of 30 ppi and 40 ppi, and the post-stage filter box is sequentially equipped with ceramic filter plates with a mesh size of 50 ppi and 60 ppi, forming a two-stage four-gradient filtration combination.

5. The aluminum alloy melt purification process according to claim 1, characterized in that: In step S7, two sets of ultrasonic tool heads are set at a distance of 300-400mm from front to back along the melt flow direction. The ultrasonic tool heads are submerged in the melt and within 10mm from the bottom of the flow channel. The ultrasonic frequency is set to 30-40Hz, and the ultrasonic power of the two stages is set to 45-50kW and 30-35kW respectively. The insert-type horizontal filter plate is a 60ppi ceramic filter plate.

6. The aluminum alloy melt purification process according to claim 1, characterized in that: The preset quality standards mentioned in step S8 are: hydrogen content ≤ 0.05 mL / 100 g Al, slag analyzer test, melt mass passing through within 70 s ≥ 1.4 kg, and Na and K alkali metal content ≤ 10 ppm.

7. The aluminum alloy melt purification process according to claim 1, characterized in that: In step S3, the surface of the melt after slag removal is mirror-like and there is no slag larger than 20mm×20mm; the total time for automatic refining and manual refining is not less than 30 minutes, and the melt is left to stand for not less than 15 minutes after refining before slag removal.

8. The aluminum alloy melt purification process according to claim 1, characterized in that: In step S2, the melt temperature is controlled at 730-750℃ before adding alloy additives; in step S5, the melt temperature is controlled at 710-720℃ after slag removal.