Aluminum alloy template processing waste closed-loop recycling process

Abstract

The application discloses an aluminum alloy template processing waste closed-loop recycling process and belongs to the technical field of solid waste resource disposal. Six core improvement links are as follows: fatigue damage degree is quantitatively detected and classified and separated in the pre-sorting stage, the local heating and stripping of the welded heterogeneous zone are carried out before crushing to separate the base material and the welding filler, the clean aluminum material is smelted at low superheat and low temperature, the harmful impurities are removed from the aluminum melt, the aluminum ash is in-situ harmless and fully recycled, and the multi-cycle component pre-compensation control of the purified aluminum liquid is carried out. The application solves the problems of low gradient utilization, high smelting loss and multi-cycle impurity accumulation of the existing process, reduces energy consumption and secondary pollution, and the performance of the recycled aluminum reaches the standard of the original template aluminum, so that the aluminum alloy template low-loss and low-carbon full-process closed-loop recycling is realized, and the application is suitable for industrial large-scale popularization.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization technology, specifically a closed-loop recycling process for aluminum alloy template processing waste. Background Technology

[0002] Currently, the industry generally adopts a common waste aluminum recycling process for the recycling of aluminum alloy template waste. The core process is "waste collection - manual pre-sorting - crushing - multi-stage sorting - smelting - refining - casting - profile extrusion", which can achieve basic recycling of aluminum alloys. However, the existing processes are all general waste aluminum recycling technologies and have not been specifically developed for the unique characteristics of aluminum alloy template waste (including welded heterogeneous areas, internal fatigue damage, stringent requirements for alloy composition and mechanical properties, and the need to achieve a closed-loop cycle from template to template). In practical applications, there are many technical bottlenecks and defects, making it impossible to achieve truly long-term stable closed-loop recycling.

[0003] The efficiency of waste recycling is extremely low, resulting in serious waste of resources at the source. Current pre-sorting technology relies solely on manual visual sorting, which can only remove completely damaged or severely deformed waste materials, failing to identify templates that appear intact but have internal cyclic fatigue damage. To avoid engineering safety risks, a large number of templates that could be directly refurbished or reused are directly crushed and melted, resulting in a direct reuse rate of only 10%-20%, causing significant waste of resources and energy. Furthermore, current processes do not treat the dissimilar welding areas of the templates. The stiffeners and joints of the aluminum alloy templates are welded using 4043 / 4047 aluminum-silicon welding wire, which has a significantly different composition from the base material 6061 / 6082 aluminum alloy. Direct mixing leads to large fluctuations in the silicon content of the melt, uncontrolled composition, and a severe decline in the weldability and fatigue resistance of the recycled aluminum alloy, even resulting in batch scrapping. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a closed-loop recycling process for aluminum alloy template processing waste.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a closed-loop recycling process for aluminum alloy template processing waste, comprising waste collection, pre-sorting, crushing, sorting and impurity removal, smelting, refining, casting, and template extrusion molding, and further comprising the following steps:

[0006] (1) In the pre-sorting stage, the fatigue damage degree of a single piece of waste is quantitatively tested, and the waste is graded and diverted to the corresponding recycling branch according to the test results;

[0007] (2) Before crushing, the welded heterogeneous areas of the waste are locally heated and peeled off to separate the base material from the weld filler;

[0008] (3) The clean aluminum material after sorting and impurity removal is smelted using a low superheat and low temperature process;

[0009] (4) The aluminum melt obtained from smelting is subjected to targeted removal of harmful impurities;

[0010] (5) The aluminum ash produced by smelting shall be treated in situ to render it harmless and to fully recover and reuse it as a resource;

[0011] (6) The refined purified aluminum liquid is pre-compensated and adjusted to match the aluminum alloy grade standard for templates.

[0012] Preferably, the quantitative detection of fatigue damage is carried out by combining eddy current conductivity detection with Brinell hardness testing; the graded and diverted recycling branches include direct refurbishment and reuse branches, modified reuse branches, and smelting regeneration branches.

[0013] Preferably, the local heating and peeling of the welded heterogeneous area is carried out by high-frequency induction local heating; the heating range only covers the weld and welding accessory area, and after heating, the base material and welding filler are separated by mechanical peeling; the separated base material and welding filler enter independent recycling branches respectively.

[0014] Preferably, the waste material after separation of the heterogeneous welding zone is subjected to integrated cleaning and removal treatment before crushing; the integrated cleaning and removal treatment is carried out by supercritical CO2 coupled ultrasonic field; the organic coating, oil stains, release agent residue and concrete adhesive on the surface of the waste material are removed simultaneously during the treatment process.

[0015] Preferably, in the low-superheat low-temperature smelting process, the smelting temperature is controlled between 665°C and 680°C; inert gas is introduced throughout the smelting process to maintain a slight positive pressure protection inside the furnace; strong convection stirring is applied simultaneously during the smelting process to ensure that the aluminum material is completely melted.

[0016] Preferably, the directional removal of harmful impurities adopts a two-stage directional solidification segregation process; in the first stage, the aluminum melt is cooled to 5°C to 10°C above the alloy liquidus line and kept at this temperature to allow the iron-rich phase to settle; in the second stage, gradient cooling is used to achieve directional solidification, so that harmful impurities are enriched at the end of the ingot, and after the enriched section is removed, low-impurity aluminum liquid is obtained.

[0017] Preferably, when refining and removing impurities from the aluminum melt, a pulsed electric field and a steady magnetic field are applied simultaneously; driven by the Lorentz force, oxide inclusions and hydrogen bubbles in the melt migrate directionally to the surface of the melt, thereby achieving pure physical deep purification of the melt.

[0018] Preferably, the in-situ harmless treatment and full resource recovery of aluminum ash is carried out by in-situ inert atmosphere hydrolysis of hot aluminum ash; the treatment process causes aluminum nitride to be converted in a directional manner and recovers the ammonia gas generated in the conversion process; the treated aluminum ash is screened, the metallic aluminum is directly smelted in the furnace, and the alumina powder is reused as a smelting covering agent.

[0019] Preferably, the composition pre-compensation control is implemented based on the element burn-off database of multi-cycle regeneration of aluminum alloy templates; the burn-off rate of core alloy elements and the accumulation rate of harmful elements are predicted according to the number of cycles of waste materials; in the smelting and batching stage, the core alloy elements are pre-compensated in advance, and the harmful impurities are removed in a targeted manner simultaneously.

[0020] Preferably, the refined purified aluminum liquid is directly used to prepare aluminum alloy template profiles using a short-process continuous casting and extrusion process; the concrete waste residue removed during the pre-sorting and pre-treatment process is crushed, ground, and surface modified to prepare a template release agent, which is then reused in the template production and turnover process.

[0021] Compared with the prior art, the present invention provides a closed-loop recycling process for aluminum alloy template processing waste, which has the following beneficial effects:

[0022] By employing a quantitative fatigue damage detection and grading process, this technology overcomes the limitations of existing methods that rely solely on appearance to determine reusability. It can accurately identify templates that appear intact but have internal fatigue damage, prioritizing the diversion of templates with no or minor damage to branches for direct refurbishment and reuse. This avoids the waste of resources caused by ineffective crushing and melting of intact templates, increasing the direct reuse rate of templates from 10%-20% in existing technologies to over 35%. Simultaneously, through a local heating and peeling process in the welding heterogeneous zone, precise separation of the template base material and welding filler is achieved, avoiding the problems of uncontrolled melt composition and high scrap rates caused by the mixing of heterogeneous materials. This improves raw material utilization from the source and reduces the amount of ineffective processing in the melting process.

[0023] This invention employs an integrated cleaning and removal process using supercritical CO2 coupled with an ultrasonic field, replacing existing pretreatment methods such as high-temperature roasting, acid and alkali washing, and sandblasting. It can simultaneously remove organic coatings, oil stains, release agents, and concrete binders from waste surfaces under low-temperature, non-corrosive conditions. The entire process generates no acid or alkali wastewater, no sandblasting solid waste, and no organic fumes. The CO2 medium can be recycled, completely solving the secondary pollution problem of traditional pretreatment processes. Simultaneously, it avoids aluminum oxidation and burn-off caused by high-temperature roasting and aluminum substrate corrosion caused by acid and alkali washing. The aluminum loss rate in the pretreatment stage is reduced to less than 0.1%, far lower than the 1%-2% loss level of existing technologies.

[0024] By employing a low-superheat, low-temperature smelting process, the smelting temperature is reduced from the existing 720-750℃ to the near-liquidity range of 665-680℃. Combined with full-process inert gas micro-positive pressure protection and strong convection stirring, the oxidation and burn-off of aluminum and the volatilization of core alloying elements such as Mg and Si are fundamentally suppressed. The aluminum burn-off rate in the smelting process is reduced from 3%-5% in the existing technology to less than 0.5%. At the same time, low-temperature smelting can reduce the overall energy consumption of the smelting process by more than 30%. Combined with the continuous casting and extrusion short-process technology, high-energy-consuming steps such as billet sawing, homogenization, and secondary remelting can be omitted. The overall energy consumption of the entire process is reduced by more than 60% compared with traditional recycling processes and by more than 95% compared with primary aluminum production. The carbon emissions of the entire process are significantly reduced, meeting the dual carbon target requirements.

[0025] Employing a two-stage directional solidification segregation process, this technology can deeply remove harmful impurities such as Fe and Cu that accumulate repeatedly in molten aluminum. This addresses the industry pain point that existing technologies can only remove slag and gas but cannot remove dissolved harmful impurities. It can stably control the Fe content in recycled aluminum to below 0.15%, meeting the impurity standards for aluminum used in primary aluminum templates. Combined with a multi-cycle composition pre-compensation and control process, it can predict the burn-off rate of core alloying elements and the accumulation rate of harmful elements in advance, achieving precise pre-compensation before smelting. This ensures that the alloy composition remains consistently up to standard, allowing aluminum alloy templates to complete more than 10 closed-loop cycles with a mechanical property decay rate of ≤5%. This completely solves the problem of closed-loop chain breakage in existing technologies, where impurities exceed standards after 3-5 cycles, rendering the templates unusable for template production.

[0026] A purely physical refining process coupled with a pulsed electric field and a steady magnetic field replaces the existing sodium / fluoride chemical refining technology. Driven by Lorentz force, it achieves efficient removal of micron-level oxide inclusions and hydrogen bubbles, with an inclusion removal rate of ≥99% and the hydrogen content of the melt can be stably controlled within 0.1mL / 100g. No chemical refining agents are added throughout the process, completely avoiding the problems of sodium embrittlement and reduced toughness of the aluminum matrix caused by sodium and fluoride residues. This enables the tensile strength, yield strength, elongation, weldability, and fatigue resistance of recycled aluminum to reach the level of virgin 6061 / 6082-T6 aluminum alloy, solving the problems of easy cracking, poor welding, and short turnover life of traditional recycled aluminum templates.

[0027] A hot-state aluminum ash in-situ inert atmosphere hydrolysis process is adopted to treat aluminum ash generated from smelting online in a harmless and fully resource-based manner. No cooling or transfer is required, enabling the directional harmless conversion of aluminum nitride, recovering ammonia to prepare byproducts, and directly remelting the metallic aluminum in the ash. High-purity alumina powder is reused as a smelting covering agent. 100% of the aluminum ash is disposed of within a closed-loop system, completely resolving the environmental risks and cost pressures of outsourcing the disposal of aluminum ash as hazardous waste under existing technologies. Simultaneously, the concrete waste residue removed during pretreatment is prepared in-situ into a special release agent for formwork, which is reused in the formwork production cycle, achieving closed-loop reuse of byproducts. The entire process has no solid waste discharge, significantly improving environmental compliance.

[0028] It can be directly adapted to the upgrading and transformation of existing recycled aluminum production lines without the need for large-scale replacement of core equipment. The steps of graded diversion, heterogeneous separation, cleaning and removal, low-loss smelting, impurity removal, and full recycling can be flexibly combined to adapt to the treatment of aluminum alloy template waste of different batches, different pollution levels, and different cycles. At the same time, the invention achieves an overall aluminum metal recycling rate of ≥98%, which is 3-5 percentage points higher than the traditional process. The production cost of recycled templates is reduced by more than 40% compared with virgin aluminum templates and by more than 20% compared with the traditional recycling process. It has both environmental and economic benefits and is suitable for large-scale industrial promotion and application.

[0029] A complete carbon footprint accounting and management system can be established, from waste recycling to template reuse. Through green electricity substitution, waste heat cascade utilization, and by-product energy reuse, net-zero carbon emission recycled template production can be achieved. The recycled aluminum templates produced can be used as zero-carbon building materials, meeting the mandatory requirements of ultra-low energy consumption buildings and near-zero carbon buildings, and satisfying the standards for green building material certification and low-carbon product certification. It has a strong differentiated competitiveness in the green building market. Detailed Implementation

[0030] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0031] A closed-loop recycling process for aluminum alloy formwork processing waste involves the unified collection of cutting scraps, punching waste, deformed and scrapped formwork, decommissioned formwork, residual aluminum shavings after demolding, and aluminum-containing waste slag generated during the aluminum alloy formwork processing. The waste is then initially sorted manually according to the 6061 and 6082 aluminum alloy grades to remove large foreign objects such as steel bars, timber, and plastic blocks.

[0032] In the pre-sorting stage, the fatigue damage of individual complete decommissioned / scrapped templates is quantitatively tested. An eddy current conductivity meter is used to perform a full-area scan of the template substrate, while a Brinell hardness tester is used to perform multi-point hardness tests on the template's faceplate and ribs. Based on a pre-defined database of conductivity-hardness-fatigue damage correlation, the internal fatigue damage of individual templates is quantitatively graded.

[0033] The tiered and triaged criteria are as follows:

[0034] Fatigue-free damage grade: conductivity deviation ≤2%, hardness deviation ≤3%, diverted to direct refurbishment and reuse branch, and directly returned to the template rental / use system after straightening, hole repair and surface cleaning;

[0035] Mild fatigue damage level: conductivity deviation 2%-5%, hardness deviation 3%-8%, diverted to the modified and reused branch, cut into small standard templates, internal and external corner accessories, etc., and reused after further processing;

[0036] Severe fatigue damage level: conductivity deviation > 5%, hardness deviation > 8%, diverted to the smelting and regeneration branch, entering the subsequent pretreatment and smelting stages.

[0037] For waste entering the smelting and recycling branch, localized heating and stripping treatment is performed on the welded heterogeneous areas before crushing. High-frequency induction heating equipment is used to locally heat the welded heterogeneous areas such as the splicing welds, stiffener welds, and rivet fixing positions of the template. The heating power is controlled at 15-30kW, the heating temperature at 280-350℃, and the heating range only covers the weld and welding accessories area, without heating the base material itself. After holding at this temperature for 30-60 seconds, a mechanical stripping device is used to peel off the weld stiffeners and weld filler layer, achieving 100% separation of the 6061 / 6082 base material from the 4043 / 4047 aluminum-silicon welding filler. The separated base material enters the subsequent cleaning and removal stage, while the welding filler is collected separately and enters a separate recycling and smelting branch.

[0038] After the separation of heterogeneous welding zones, the waste material from the parent material undergoes an integrated cleaning and removal process before crushing. The waste is placed in a sealed supercritical reactor, and CO2 is introduced. The temperature inside the reactor is controlled at 35-55℃ and the pressure at 8-18MPa to bring the CO2 to a supercritical state. Simultaneously, the reactor's built-in low-frequency ultrasonic generator is activated, with the ultrasonic frequency controlled at 20-40kHz and the power density at 0.5-1.5W / cm², and the process is maintained at the same temperature and pressure for 20-40 minutes. After treatment, the pressure is reduced and released, and the CO2 is condensed, compressed, and recycled. The treated waste material simultaneously undergoes the removal of surface organic coatings, oil stains, release agent residue, and adhesive residue from concrete joints.

[0039] After cleaning and removal, the waste material is first fed into a twin-shaft shredder to be crushed into 3-5cm pieces, and then fed into a hammer crusher to be further crushed into 1-3cm particles. The finely crushed particles undergo multi-stage sorting and impurity removal. First, a permanent magnet drum separator removes ferrous impurities, then an eddy current separator removes non-ferrous metal impurities such as copper and zinc, and finally a vibrating screen and gradient air classifier remove non-metallic impurities such as concrete debris and dust, ultimately yielding clean aluminum material.

[0040] After sorting and impurity removal, the clean aluminum material is fed into a double-chamber melting furnace for low-temperature melting with low superheat. The furnace is preheated to 200°C, and the clean aluminum material is then introduced. High-purity argon gas is circulated throughout the process as a protective gas to maintain a slight positive pressure inside the furnace, 50-100 Pa higher than the external atmospheric pressure. The melting temperature is controlled and stabilized at 665-680°C. During melting, the electromagnetic stirring device inside the furnace is activated to apply strong convection stirring at a frequency of 10-20 Hz until the aluminum material is completely melted. After melting, the initial surface dross is removed to obtain molten aluminum.

[0041] The molten aluminum obtained from smelting undergoes a two-stage directional solidification and segregation process to remove harmful impurities. In the first stage, the molten aluminum is transferred to a holding furnace and cooled to 5-10°C above the liquidus line of the corresponding aluminum alloy grade. It is then held at this temperature for 20-30 minutes, allowing harmful intermetallic phases such as iron-rich and copper-rich phases to initially settle to the bottom of the furnace. In the second stage, the settled molten aluminum is fed into a semi-continuous casting machine, where gradient cooling is used to achieve directional solidification. The casting speed is controlled at 80-120 mm / min, the temperature of the upper part of the ingot is maintained at 645-655°C, and the cooling intensity of the lower part of the ingot gradually increases, causing harmful impurities such as Fe and Cu to directionally accumulate at the end of the ingot. After casting, 10%-15% of the impurity-rich section at the end of the ingot is removed, resulting in a low-impurity aluminum ingot.

[0042] After removing harmful impurities, the molten aluminum undergoes refining and deep purification. The molten aluminum is heated to 700-720℃, and high-purity argon micron-sized bubbles are injected into the melt through a bottom-blowing device for degassing and slag removal. During the blowing process, a pulsed electric field and a steady magnetic field are simultaneously applied to the melt. The frequency of the pulsed electric field is controlled at 50-100Hz, the field strength at 10-20V / cm, and the magnetic induction intensity of the steady magnetic field is controlled at 0.3-0.8T. Driven by Lorentz force, micron-sized oxide inclusions and hydrogen bubbles in the melt migrate directionally to the melt surface. After removing the slag, the melt undergoes online filtration through a 20-30ppi ceramic foam filter, completing the pure physical deep purification of the melt.

[0043] Hot aluminum ash collected during smelting and refining is directly fed into a sealed, inert atmosphere reactor without cooling for in-situ harmless treatment and full resource recovery. High-purity argon is continuously introduced into the reactor to maintain an inert atmosphere, while a small amount of atomized water vapor is introduced into the hot aluminum ash. The reaction temperature is controlled at 200-300℃, and the reaction is maintained at this temperature for 30-60 minutes, causing the aluminum nitride in the aluminum ash to be directionally converted into alumina and ammonia. The ammonia generated during the reaction is collected and used to prepare ammonium salt byproducts. After the reaction, the aluminum ash is vibrated and sieved. The sieved aluminum particles are directly returned to the smelting furnace for remelting, while the high-purity alumina powder that passes through the sieve is ground and reused as a smelting covering agent or as a raw material for micro-arc oxidation on template surfaces.

[0044] After refining and purification, the molten aluminum undergoes pre-compensation and adjustment of its composition. Based on a pre-established database of element burn-off from multi-cycle regeneration of aluminum alloy templates, the burn-off rates of core alloying elements such as Mg, Si, and Ti, as well as the accumulation rates of harmful elements such as Fe and Cu, are predicted according to the number of cycles of the waste to be processed. During the smelting and batching stage, the corresponding amounts of core alloying elements are added to the molten aluminum in advance according to the predicted values, simultaneously with the aforementioned targeted removal process for harmful impurities. After the addition is completed, a direct-reading spectrometer is used for pre-furnace detection, and the composition is fine-tuned to fully match the corresponding aluminum alloy grade standard in GB / T3190, resulting in an alloy aluminum molten aluminum that meets the requirements for template production.

[0045] After the purified aluminum liquid meets the composition standards, a closed-loop process is completed using two forming paths:

[0046] Path 1: Conventional closed-loop path. Aluminum alloy round castings are prepared by a semi-continuous casting machine. After homogenization treatment at 560-580℃ for 6-12 hours, the castings are sent to a 1000-2500T extrusion press to be extruded into aluminum alloy template profiles. After online quenching, pre-stretching, and aging treatment, they are cut, punched, and welded for deep processing to prepare brand new aluminum alloy templates, which are then returned to the system.

[0047] Path 2: Short-process closed-loop path, using integrated continuous casting and extrusion equipment. The refined purified aluminum liquid is directly fed into the horizontal continuous casting machine to form billets after online heat preservation. After online induction heating, it is directly fed into the continuous extrusion press to extrude special profiles for aluminum alloy templates. There is no secondary remelting of aluminum liquid throughout the entire process.

[0048] The concrete waste residue removed during pre-sorting and pre-treatment is crushed and ground to 200-400 mesh, then surface modified with silane coupling agent, and then compounded with water-based emulsion and additives to prepare a water-based release agent for aluminum alloy formwork, which is then reused in formwork production and recycling.

[0049] Example 1

[0050] The materials to be processed are 6061 aluminum alloy construction formwork waste that has been decommissioned and reused.

[0051] Ten tons of decommissioned 6061 aluminum alloy formwork were collected. Large foreign objects such as reinforcing bars and timber were initially removed through sorting. Eddy current conductivity and Brinell hardness tests were performed on individual formwork pieces to classify fatigue damage. Of these, 1.2 tons of formwork without fatigue damage were diverted to the direct refurbishment and reuse branch, 2.5 tons of formwork with slight fatigue damage were diverted to the remanufacturing and reuse branch, and the remaining 6.3 tons of formwork with severe fatigue damage entered the smelting and regeneration branch.

[0052] Separation of heterogeneous areas in welding: For 6.3t of waste material to be smelted, a 20kW high-frequency induction heating device is used to locally heat the weld area to 320℃. After holding at the temperature for 45s, the welding stiffener and weld filler are mechanically peeled off, and 6.0t of base material and 0.3t of welding filler are obtained. The two are then sent to independent recycling branches.

[0053] 6.0t of parent material waste is fed into a supercritical reactor, with the temperature controlled at 45℃ and the pressure at 12MPa. An ultrasonic field of 30kHz and 1.0W / cm² is coupled in and the process is carried out for 30 minutes. The surface coating, oil stains, and concrete adhesives are removed simultaneously. The CO2 is condensed and recycled.

[0054] After cleaning, the waste material is shredded and finely crushed into 1-3cm particles, and then subjected to magnetic separation, eddy current separation, and air separation sieving to obtain 5.85t of clean aluminum material with a cleanliness of 98.8%.

[0055] Clean aluminum material is fed into a double-chamber melting furnace. High-purity argon gas is circulated throughout the process to maintain a slight positive pressure of 80Pa inside the furnace. The melting temperature is controlled at 670℃, and electromagnetic stirring at 15Hz is used to ensure that the aluminum material is completely melted. Initial slag is then removed.

[0056] The molten aluminum was transferred to a holding furnace and cooled to 658°C. It was held at this temperature for 25 minutes to allow the iron-rich phase to settle. Then, it was fed into a semi-continuous casting machine and subjected to gradient cooling and directional solidification at a casting speed of 100 mm / min. After casting, 12% of the impurity-rich section at the end of the ingot was removed to obtain a low-impurity molten aluminum with a Fe content of 0.12% in the main aluminum liquid.

[0057] The aluminum melt was heated to 710℃, and high-purity argon gas was sprayed from the bottom to remove gas. Simultaneously, an 80Hz pulsed electric field with a voltage of 15V / cm and a constant magnetic field of 0.5T were applied. After treatment for 15 minutes, the slag was removed and the mixture was filtered through a 25ppi ceramic filter to obtain purified aluminum liquid with a hydrogen content of 0.08mL / 100g.

[0058] The hot aluminum slag produced from smelting and refining is directly fed into an inert atmosphere reactor. Atomized steam is introduced at 250°C and reacted for 45 minutes. Ammonia is recovered to prepare ammonium salts. After sieving, the metallic aluminum is returned to the furnace, and the alumina powder is reused as a smelting covering agent.

[0059] Based on the multi-cycle element burn-off database, it was predicted that this waste material was from the 5th cycle, with a Mg burn-off rate of 4.2% and a Si burn-off rate of 2.8%. The corresponding amounts of Mg and Si elements were added in advance, and after fine-tuning by spectral detection, the composition fully met the national standard requirements for 6061-T6 aluminum alloy.

[0060] The purified aluminum liquid is semi-continuously cast into φ178mm round casting rods, which are then homogenized at 570℃ for 8 hours before being fed into an 1800T extruder to extrude special template profiles. After online quenching and aging at 175℃ for 8 hours, the profiles are further processed into brand-new aluminum alloy templates and returned to the recycling system. The concrete waste generated during pretreatment is ground and modified to prepare water-based release agents for reuse, completing a closed loop.

[0061] Example 2

[0062] The materials to be processed are 6082 aluminum alloy scraps and punching waste generated from the processing of aluminum alloy templates.

[0063] Eight tons of 6082 aluminum alloy processing waste were collected. Large foreign objects were initially sorted out and removed. Since the waste was new material with no fatigue damage, it was directly sent to the smelting and regeneration branch.

[0064] The waste material was fed into a supercritical reactor, and the temperature was controlled at 40℃ and the pressure at 10MPa. An ultrasonic field of 25kHz and 0.8W / cm² was coupled in and the material was treated for 25 minutes to remove surface oil and mold release agent residue.

[0065] The cleaned waste material was crushed into 1-2cm particles and then subjected to magnetic separation, eddy current separation, and air separation sieving to obtain 7.9t of clean aluminum material with a cleanliness of 99.2%.

[0066] Clean aluminum material is fed into a double-chamber melting furnace, and high-purity argon gas is introduced to maintain a slight positive pressure of 60Pa. The melting temperature is controlled at 675℃, and 12Hz electromagnetic stirring is used to completely melt the material.

[0067] The aluminum melt was cooled to 658℃ and held at that temperature for 20 minutes. After the iron-rich phase settled, it was directionally solidified by gradient cooling. The impurity-rich section at the end of the ingot was removed to obtain a low-impurity aluminum liquid with an Fe content of 0.10%.

[0068] The aluminum melt was heated to 715℃, high-purity argon gas was injected, and a 60Hz, 12V / cm pulsed electric field and a 0.4T steady magnetic field were applied simultaneously. After treatment for 12 minutes, the purified aluminum liquid was obtained after filtration.

[0069] Based on the element burn-off database, the predicted Mg burn-off rate of 3.5% and Si burn-off rate of 2.2% for a single smelting of processing waste were used to replenish alloying elements in advance, matching the composition to the national standard requirements for 6082 aluminum alloy.

[0070] The purified aluminum liquid is produced using an integrated continuous casting and extrusion system. After online insulation, horizontal continuous casting, and online induction heating, it is directly and continuously extruded into special template profiles, which are then processed to produce brand-new aluminum alloy templates. All aluminum ash is recycled, and concrete waste is used to prepare a reused release agent, completing a closed loop.

[0071] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A closed-loop recycling process for aluminum alloy template processing waste, comprising the following steps: waste collection, pre-sorting, crushing, separation and impurity removal, smelting, refining, casting, and template extrusion molding, characterized in that... It also includes the following steps: (1) In the pre-sorting stage, the fatigue damage degree of a single piece of waste is quantitatively tested, and the waste is graded and diverted to the corresponding recycling branch according to the test results; (2) Before crushing, the welded heterogeneous areas of the waste are locally heated and peeled off to separate the base material from the weld filler; (3) The clean aluminum material after sorting and impurity removal is smelted using a low superheat and low temperature process; (4) The aluminum melt obtained from smelting is subjected to targeted removal of harmful impurities; (5) The aluminum ash produced by smelting shall be treated in situ to render it harmless and to fully recover and reuse it as a resource; (6) The refined purified aluminum liquid is pre-compensated and adjusted to match the aluminum alloy grade standard for templates.

2. The closed-loop recycling process for aluminum alloy template processing waste according to claim 1, characterized in that, The quantitative detection of fatigue damage is carried out by combining eddy current conductivity detection with Brinell hardness testing; the graded and diverted recycling branches include direct refurbishment and reuse branches, modified reuse branches, and smelting and regeneration branches.

3. The closed-loop recycling process for aluminum alloy template processing waste according to claim 1, characterized in that, The localized heating and peeling of the heterogeneous welding area is carried out using high-frequency induction localized heating. The heating range only covers the weld and welding accessory area. After heating, the base material and welding filler are separated by mechanical peeling. The separated base material and welding filler enter independent recycling branches.

4. The closed-loop recycling process for aluminum alloy template processing waste according to claim 1, characterized in that, The waste material after separation of the heterogeneous welding zone is subjected to integrated cleaning and removal treatment before crushing; the integrated cleaning and removal treatment is carried out by supercritical CO2 coupled ultrasonic field; the organic coating, oil stains, release agent residue and concrete adhesive on the surface of the waste material are removed simultaneously during the treatment process.

5. The closed-loop recycling process for aluminum alloy template processing waste according to claim 1, characterized in that, The low-superheat low-temperature smelting process controls the smelting temperature between 665°C and 680°C; inert gas is introduced throughout the smelting process to maintain a slight positive pressure protection inside the furnace; strong convection stirring is applied simultaneously during the smelting process to ensure that the aluminum material is completely melted.

6. The closed-loop recycling process for aluminum alloy template processing waste according to claim 1, characterized in that, The directional removal of harmful impurities adopts a two-stage directional solidification segregation process. In the first stage, the aluminum melt is cooled to 5°C to 10°C above the alloy liquidus line and kept at that temperature to allow the iron-rich phase to settle. In the second stage, gradient cooling is used to achieve directional solidification, which enriches harmful impurities at the end of the ingot. After the enriched section is removed, low-impurity aluminum liquid is obtained.

7. The closed-loop recycling process for aluminum alloy template processing waste according to claim 1, characterized in that, When refining and removing impurities from aluminum melt, a pulsed electric field and a steady magnetic field are applied simultaneously. Driven by the Lorentz force, oxide inclusions and hydrogen bubbles in the melt migrate directionally to the surface of the melt, achieving pure physical deep purification of the melt.

8. The closed-loop recycling process for aluminum alloy template processing waste according to claim 1, characterized in that, The in-situ harmless treatment and full resource recovery of aluminum ash is carried out by in-situ inert atmosphere hydrolysis of hot aluminum ash; the treatment process enables the directional conversion of aluminum nitride and recovers the ammonia gas generated in the conversion process; the treated aluminum ash is screened, the metallic aluminum is directly smelted in the furnace, and the alumina powder is reused as a smelting covering agent.

9. The closed-loop recycling process for aluminum alloy template processing waste according to claim 1, characterized in that, The composition pre-compensation control is implemented based on the element burn-off database of multi-cycle regeneration of aluminum alloy templates; the burn-off rate of core alloy elements and the accumulation rate of harmful elements are predicted according to the number of cycles of waste. During the smelting and batching stage, the core alloying elements are pre-compensated in advance, and the harmful impurities are removed in a targeted manner simultaneously.

10. The closed-loop recycling process for aluminum alloy template processing waste according to claim 1, characterized in that, The refined purified aluminum liquid is directly used to produce aluminum alloy template profiles using a short-process continuous casting and extrusion process; the concrete waste removed during the pre-sorting and pre-treatment process is crushed, ground, and surface modified to prepare a template release agent, which is then reused in the template production and turnover process.