6061 low iron aluminum alloy aluminum scrap remelting and grading recycling method and application
By using high-speed centrifugation, low-temperature drying, dual-chamber melting and refining of 6061 low-iron aluminum alloy scraps, combined with nano-α-Al2O3 treatment, the problems of pollution, oxidation and impurities in the aluminum scrap remelting and recycling process are solved, and a high-purity recycled aluminum alloy is prepared, which is suitable for aerospace and semiconductor manufacturing equipment.
Patent Information
- Application Number
- CN202610337190.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-03-19
- Publication Date
- 2026-05-29
AI Technical Summary
In the existing technology, the remelting and recycling process of 6061 low-iron aluminum alloy aluminum scrap has problems such as serious surface contamination, high oxidation loss rate, difficulty in impurity control and difficulty in guaranteeing purity, resulting in resource waste and failure to meet the requirements of semiconductor-grade materials.
After high-speed centrifugation and low-temperature drying pretreatment, aluminum shavings are melted in a dual-chamber regenerative reverberatory furnace, and then refined by a graphite rotor aluminum liquid lifting system and inert gas, combined with refining agents. After slag removal, settling and filtration, the aluminum is finally cast into a high-purity 6061 low-iron recycled aluminum alloy.
The iron content of 6061 low-iron recycled aluminum alloy is ≤0.10wt%, and the wear resistance and corrosion resistance of aluminum alloy products are improved by nano α-Al2O3 treatment, which meets the high standard requirements of aerospace and semiconductor manufacturing equipment.
Abstract
Description
Technical Field
[0001] This invention relates to the field of iron-aluminum alloy aluminum scrap recycling and application technology, specifically a remelting and grade-preserving recycling method and application for 6061 low-iron aluminum alloy aluminum scrap. Background Technology
[0002] Aerospace and semiconductor manufacturing equipment have stringent requirements for the purity, chemical stability, and mechanical properties of structural materials. 6061 low-iron aluminum alloy (Fe≤0.10wt%) is a key material for manufacturing core components such as chambers, bases, and transmission arms. The high-value aluminum shavings generated during precision machining are often downgraded and remelted into ordinary casting alloys, resulting in significant resource waste. However, remelting these aluminum shavings for use in semiconductor-grade master alloys faces numerous technical challenges: First, severe surface contamination; the large specific surface area leads to the adhesion of large amounts of cutting fluid and moisture, increasing the hydrogen and carbon content of the melt during smelting, generating fumes and inclusions. Second, high oxidation and burn-off rates; the thin aluminum shavings are prone to floating and oxidation, resulting in low metal recovery and the formation of "hard slag." Third, difficulty in composition control; trace impurities such as Fe and Cu introduced during machining easily lead to excessive iron content, failing to meet low-iron requirements. Fourth, difficulty in ensuring purity; oxides and other impurities are difficult to remove effectively, resulting in melt cleanliness that does not meet semiconductor standards.
[0003] In summary, the development and application of a remelting and recycling method for 6061 low-iron aluminum alloy scraps is of great significance. Summary of the Invention
[0004] The purpose of this invention is to provide a method and application for the remelting and recycling of 6061 low-iron aluminum alloy scraps to maintain its grade, in order to solve the problems raised in the prior art.
[0005] To achieve the above objectives, the present invention provides the following technical solution:
[0006] A method for remelting and preserving the grade of 6061 low-iron aluminum alloy scrap includes the following steps:
[0007] Step 1: The 6061 low-iron aluminum alloy chips are subjected to high-speed centrifugation and drying in sequence to obtain pretreated aluminum chips;
[0008] Step 2: (1) Add 6061 low iron aluminum alloy ingots into a double-cavity regenerative reverberatory furnace, melt them, and obtain bottom material; (2) Start the graphite rotor aluminum liquid lifting system, add pretreated aluminum chips into the bottom material, and obtain furnace charge; refine by rotating the graphite rotor refining device, introducing inert gas and refining agent, removing slag, settling, filtering, and casting to obtain 6061 low iron recycled aluminum alloy;
[0009] The raw materials for the refining agent include magnesium chloride and potassium chloride in a mass ratio of 1.2 to 2.0:1; the iron content of the 6061 low-iron recycled aluminum alloy is ≤0.10wt%.
[0010] The more optimized chemical composition of the 6061 low-iron aluminum alloy ingot includes: Si 0.5~0.7wt%, Fe <0.10wt%, Cu 0.2~0.3wt%, Mn 0.05~0.20wt%, Mg 0.8~1.2wt%, Cr 0.15~0.40wt%, with the balance being Al, and unavoidable impurities totaling <0.03%.
[0011] In a more optimized configuration, the 6061 low-iron aluminum alloy ingot accounts for 50-60 wt% of the furnace charge; the flow rate of the inert gas is 20-25 m³ / h. 3 / h; the amount of refining agent added is 0.6~1Kg / t, and the refining time is 15~25 minutes.
[0012] This scheme first employs a combined pretreatment process of high-speed centrifugation and low-temperature drying to minimize external factors that could lead to melt contamination and air absorption. A dual-chamber regenerative reverberatory furnace is then used, with the furnace-side graphite rotor aluminum liquid lifting system activated. This creates a strong melt vortex in the side chamber, rapidly drawing aluminum shavings into the melt and melting them under the molten metal, significantly reducing oxidation loss from air contact. The melt is then refined, slag removed, allowed to settle, and filtered in inert gas and refining agents to obtain a high-purity melt (H2 content <0.20 ml / 100gAl, low inclusion level). Finally, it is cast to obtain 6061 low-iron recycled aluminum alloy, achieving low oxidation and high recovery rate.
[0013] An application of a 6061 low-iron aluminum alloy, wherein the 6061 low-iron recycled aluminum alloy is used to prepare aluminum alloy products.
[0014] The following steps are included:
[0015] Step 1: (1) Anodize 6061 low-iron recycled aluminum alloy to form a porous amorphous aluminum oxide layer and obtain anodized pretreated aluminum alloy; (2) Immerse the anodized pretreated aluminum alloy in nano α-Al2O3 suspension (nano α-Al2O3 particle size is 20~60nm) and sonicate, heat treat at 400~500℃ for 30~40 minutes to form α-Al2O3 layer and obtain aluminum alloy product A;
[0016] Step 2: Add Al2(SO4)3·18H2O (CAS No. 7784-31-8) and Fe(NO3)3·9H2O (CAS No. 7782-61-8) to deionized water and mix evenly. Add nano-γ-Al2O3 and disperse ultrasonically to obtain a mixed solution. Add aluminum alloy product A to the mixed solution, add formamide and heat to 80~95℃ to react. Take it out, dry it, and microwave heat treatment to form an α-Fe2O3 / Al2O3 layer (α-iron oxide / alumina layer). Add it to hot hydrochloric acid and sonicate to remove α-Fe2O3 (α-iron oxide). Perform multiple sealing treatments to obtain the aluminum alloy product.
[0017] In this scheme, aluminum sulfate is used as the aluminum source, ferric nitrate as the iron source, formamide as the precipitant, and nano-γ-Al2O3 is added. Under certain conditions, it is deposited in the porous structure of anodized pretreated aluminum alloy. Through microwave heating, γ-Al2O3, being a strong microwave absorber, converts microwave energy into heat energy, thereby forming an α-Fe2O3 / Al2O3 layer in the porous amorphous alumina layer. During the microwave heating process, α-Fe2O3 is also continuously generated and absorbs microwave energy. In this scheme, microwave heating is first performed at low power to generate α-Fe2O3. α-Fe2O3 induces the formation of α-Al2O3 (α-alumina), and since α-Fe2O3 also has a microwave absorption effect, the microwave heating power does not need to be too high, effectively avoiding coating cracking. Finally, when hydrochloric acid is used to remove α-Fe2O3, the porous amorphous alumina layer and other Al2O3 generated in the α-Fe2O3 / Al2O3 layer are excessively eroded, resulting in larger pores. Even after multiple sealing treatments, it is difficult to reduce the porosity, which affects the performance of aluminum alloy products.
[0018] In a more optimized configuration, the porous amorphous alumina layer has a thickness of 8-15 μm, a porosity of 15-27%, and a pore size of 50-130 nm; the nano-α-Al₂O₃ has a particle size of 20-60 nm; the nano-γ-Al₂O₃ has a particle size of 20-60 nm; the α-Al₂O₃ layer has a thickness of 300-600 nm; and the α-Fe₂O₃ / Al₂O₃ layer has a thickness of 100-300 nm.
[0019] In a more optimized form, the electrolyte for anodic oxidation comprises the following components: 1-3 g / L sulfuric acid, 50-80 g / L oxalic acid; and the concentration of the nano-α-Al2O3 suspension is 1-3 g / L.
[0020] In a more optimized configuration, the mass ratio of Al2(SO4)3·18H2O, Fe(NO3)3·9H2O, and formamide is (1.5~3):(3~5):100; the nano-γ-Al2O3 accounts for 3~8 wt% of the mixture; and the hydrochloric acid concentration is 4~5 M.
[0021] In this method, anodized pretreated aluminum alloy is immersed in a mixture containing nano-α-Al₂O₃ and ultrasonically injected to fill the porous amorphous alumina layer. After drying, it is heat-treated to improve the adhesion of nano-α-Al₂O₃ and the porous amorphous alumina layer, transforming most of the porous amorphous alumina layer into γ-Al₂O₃ and preventing the porous amorphous alumina layer from becoming loose. The thickness of the nano-α-Al₂O₃ and the heat treatment time are controlled to prevent sealing of the porous amorphous alumina layer, which would otherwise affect the α-Fe₂O₃ content. The process involves adhering Al2O3; then preparing an α-Al2O3 layer using a homogeneous precipitation method; and effectively removing α-Fe2O3 in a short time using a combination of ultrasound and hot hydrochloric acid to prevent excessive iron content in the aluminum alloy product. Furthermore, during microwave heating, the porous amorphous alumina layer can be transformed into α-Al2O3 or γ-Al2O3. This synergistic effect of the α-Fe2O3 / Al2O3 layer effectively prevents excessive corrosion by hot hydrochloric acid, thus preventing increased porosity. After sealing, a wear-resistant and corrosion-resistant aluminum alloy product is obtained.
[0022] The optimized anodizing process conditions are: temperature 10~30℃, voltage 25~45V, and current density 1.0~2.5A / dm³. 2 The microwave heating process conditions are: output power of 300~900W, microwave frequency of 2~2.5GHz, and time of 15~35 minutes; the iron content of the aluminum alloy product is ≤0.11wt%.
[0023] Compared with the prior art, the beneficial effects of the present invention are:
[0024] 1. The iron content in the 6061 low-iron recycled aluminum alloy prepared in this scheme is ≤0.10wt%.
[0025] 2. The aluminum alloy products prepared by this method have good wear resistance and corrosion resistance; the iron content of the aluminum alloy products is ≤0.11wt%. Detailed Implementation
[0026] 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.
[0027] Example 1: A method for remelting and preserving the grade of 6061 low-iron aluminum alloy scraps, comprising the following steps:
[0028] Step 1: The 6061 low-iron aluminum alloy aluminum chips are subjected to high-speed centrifugation (3000 rpm) and drying (200℃) to obtain pretreated aluminum chips.
[0029] Step 2: (1) Add 6061 low iron aluminum alloy ingots (6061 low iron aluminum alloy ingots account for 55wt% of the furnace charge) into a double-cavity regenerative reverberatory furnace, melt them, and obtain the bottom material;
[0030] (2) Start the graphite rotor aluminum liquid lifting system, add the pretreated aluminum chips to the bottom material to obtain the furnace charge; through the rotating graphite rotor refining device, introduce argon gas (gas flow rate of 25m³ / h). 3 The aluminum alloy was refined for 25 minutes with 0.8 kg / t of refining agent (including magnesium chloride and potassium chloride in a mass ratio of 1.5:1). After slag removal and settling, the alloy was filtered through a foam ceramic filter plate with a porosity of 30 ppi and then cast to obtain 6061 low-iron recycled aluminum alloy (iron content ≤0.10 wt%).
[0031] An application of 6061 low-iron aluminum alloy includes the following steps:
[0032] Step 1: (1) Anodize 6061 low-iron recycled aluminum alloy to form a porous amorphous aluminum oxide layer and obtain anodized pretreated aluminum alloy; (2) Immerse the anodized pretreated aluminum alloy in nano α-Al2O3 suspension and sonicate, ultrasonically wash, dry at 40°C, and heat treat at 450°C for 40 minutes to form an α-Al2O3 layer with a thickness of 512nm and obtain aluminum alloy product A;
[0033] The solvent for the nano-α-Al₂O₃ suspension was anhydrous ethanol, and the amount of citric acid added was 0.1 wt%.
[0034] The electrolyte for anodizing comprises the following components: 1 g / L sulfuric acid, 55 g / L oxalic acid, and deionized water as the solvent; the concentration of nano-α-Al2O3 in the nano-α-Al2O3 suspension is 2.5 g / L.
[0035] The anodizing process conditions are: temperature 22℃, voltage 27V, and current density 1.3A / dm³. 2 ;
[0036] The porous amorphous alumina layer has a thickness of 8.7 μm, a porosity of 17.6%, and a pore size of 62.4 nm.
[0037] Step 2: Weigh Al2(SO4)3·18H2O, Fe(NO3)3·9H2O, and formamide in a mass ratio of 1.5:5:100;
[0038] Al2(SO4)3·18H2O and Fe(NO3)3·9H2O were added to deionized water and mixed evenly. Nano-γ-Al2O3 (7wt% of the mixture, with an average particle size of 30nm) was added and ultrasonically dispersed to obtain a mixture. Aluminum alloy product A was added to the mixture, and formamide was added and heated to 90℃ to react. The mixture was then removed, dried, and microwave-treated to form an α-Fe2O3 / Al2O3 layer with a thickness of 287nm. The mixture was then ultrasonically treated (80W power) in 100℃ hot hydrochloric acid (5M concentration) for 30 minutes to remove α-Fe2O3. The mixture was then impregnated and sealed three times with aluminum hydroxide solution to obtain the aluminum alloy product. The iron content of the aluminum alloy product was ≤0.13wt%.
[0039] The process conditions for microwave heating treatment are: output power of 350W, microwave frequency of 2GHz, microwave heating time of 6 minutes, increasing to 750W, microwave frequency of 2.5GHz, microwave heating time of 20 minutes.
[0040] Example 2 is based on Example 1, except that the anodizing conditions and the amount of Fe(NO3)3·9H2O added are different; it includes the following steps:
[0041] Step 1: The 6061 low-iron aluminum alloy aluminum chips are subjected to high-speed centrifugation (3000 rpm) and drying (200℃) to obtain pretreated aluminum chips.
[0042] Step 2: (1) Add 6061 low iron aluminum alloy ingots (6061 low iron aluminum alloy ingots account for 55wt% of the furnace charge) into a double-cavity regenerative reverberatory furnace, melt them, and obtain the bottom material;
[0043] (2) Start the graphite rotor aluminum liquid lifting system, add the pretreated aluminum chips to the bottom material to obtain the furnace charge; through the rotating graphite rotor refining device, introduce argon gas (gas flow rate of 25m³ / h). 3 The aluminum alloy was refined for 25 minutes with 0.8 kg / t of refining agent (including magnesium chloride and potassium chloride in a mass ratio of 1.5:1). After slag removal and settling, the alloy was filtered through a foam ceramic filter plate with a porosity of 30 ppi and then cast to obtain 6061 low-iron recycled aluminum alloy (iron content ≤0.10 wt%).
[0044] An application of 6061 low-iron aluminum alloy includes the following steps:
[0045] Step 1: (1) Anodize 6061 low-iron recycled aluminum alloy to form a porous amorphous aluminum oxide layer and obtain anodized pretreated aluminum alloy; (2) Immerse the anodized pretreated aluminum alloy in nano α-Al2O3 suspension and sonicate, ultrasonically wash, dry at 40°C, and heat treat at 450°C for 40 minutes to form an α-Al2O3 layer with a thickness of 515nm and obtain aluminum alloy product A;
[0046] The solvent for the nano-α-Al₂O₃ suspension was anhydrous ethanol, and the amount of citric acid added was 0.1 wt%.
[0047] The raw materials for the electrolyte in anodizing include the following components: 1 g / L sulfuric acid, 50 g / L oxalic acid; the concentration of nano-α-Al2O3 in the nano-α-Al2O3 suspension is 2.5 g / L;
[0048] The anodizing process conditions are: temperature 15℃, voltage 35V, and current density 2.0A / dm³. 2 ;
[0049] The porous amorphous alumina layer has a thickness of 12.6 μm, a porosity of 22.5%, and a pore size of 92.6 nm.
[0050] Step 2: Weigh Al2(SO4)3·18H2O, Fe(NO3)3·9H2O, and formamide in a mass ratio of 1.5:4.3:100;
[0051] Al2(SO4)3·18H2O and Fe(NO3)3·9H2O were added to deionized water and mixed evenly. Nano-γ-Al2O3 (7wt% of the mixture) was added and ultrasonically dispersed to obtain a mixture. Aluminum alloy product A was added to the mixture, and formamide was added and heated to 90℃ to react. The mixture was then removed, dried, and microwave-treated to form an α-Fe2O3 / Al2O3 layer with a thickness of 285nm. The mixture was then immersed in 100℃ hot hydrochloric acid (5M concentration) and ultrasonically treated (80W power) for 35 minutes to remove α-Fe2O3. The mixture was then impregnated and sealed three times with aluminum hydroxide solution to obtain the aluminum alloy product. The iron content of the aluminum alloy product was ≤0.12wt%.
[0052] The process conditions for microwave heating treatment are: output power of 350W, microwave frequency of 2GHz, microwave heating time of 6 minutes, increasing to 750W, microwave frequency of 2.5GHz, microwave heating time of 20 minutes.
[0053] Example 3 is based on Example 2, except that the anodizing conditions and the amount of Fe(NO3)3·9H2O added are different; it includes the following steps:
[0054] Step 1: The 6061 low-iron aluminum alloy aluminum chips are subjected to high-speed centrifugation (3000 rpm) and drying (200℃) to obtain pretreated aluminum chips.
[0055] Step 2: (1) Add 6061 low iron aluminum alloy ingots (6061 low iron aluminum alloy ingots account for 55wt% of the furnace charge) into a double-cavity regenerative reverberatory furnace, melt them, and obtain the bottom material;
[0056] (2) Start the graphite rotor aluminum liquid lifting system, add the pretreated aluminum chips to the bottom material to obtain the furnace charge; through the rotating graphite rotor refining device, introduce argon gas (gas flow rate of 25m³ / h). 3 The aluminum alloy was refined for 25 minutes with 0.8 kg / t of refining agent (including magnesium chloride and potassium chloride in a mass ratio of 1.5:1). After slag removal and settling, the alloy was filtered through a foam ceramic filter plate with a porosity of 30 ppi and then cast to obtain 6061 low-iron recycled aluminum alloy (iron content ≤0.10 wt%).
[0057] An application of 6061 low-iron aluminum alloy includes the following steps:
[0058] Step 1: (1) Anodize 6061 low-iron recycled aluminum alloy to form a porous amorphous aluminum oxide layer and obtain anodized pretreated aluminum alloy; (2) Immerse the anodized pretreated aluminum alloy in nano α-Al2O3 suspension and sonicate, ultrasonically wash, dry at 40°C, and heat treat at 450°C for 40 minutes to form an α-Al2O3 layer with a thickness of 518nm and obtain aluminum alloy product A;
[0059] The solvent for the nano-α-Al₂O₃ suspension was anhydrous ethanol, and the amount of citric acid added was 0.1 wt%.
[0060] The electrolyte for anodizing comprises the following components: 1.8 g / L sulfuric acid, 50 g / L oxalic acid; and the nano-α-Al2O3 suspension contains 2.5 g / L nano-α-Al2O3.
[0061] The anodizing process conditions are: temperature 10℃, voltage 42V, and current density 2.0A / dm³. 2 ;
[0062] The porous amorphous alumina layer has a thickness of 14.6 μm, a porosity of 24.2%, and a pore size of 117.5 nm.
[0063] Step 2: Weigh Al2(SO4)3·18H2O, Fe(NO3)3·9H2O, and formamide in a mass ratio of 1.5:4.0:100;
[0064] Al2(SO4)3·18H2O and Fe(NO3)3·9H2O were added to deionized water and mixed evenly. Nano-γ-Al2O3 (7wt% of the mixture) was added and ultrasonically dispersed to obtain a mixture. Aluminum alloy product A was added to the mixture, and formamide was added and heated to 90℃ to react. The mixture was then removed, dried, and microwaved to form an α-Fe2O3 / Al2O3 layer with a thickness of 286nm. The mixture was then ultrasonically treated (80W power) in 100℃ hot hydrochloric acid (5M concentration) for 40 minutes to remove α-Fe2O3. The mixture was then impregnated and sealed three times with aluminum hydroxide solution to obtain the aluminum alloy product. The iron content of the aluminum alloy product was ≤0.11wt%.
[0065] The process conditions for microwave heating treatment are: output power of 350W, microwave frequency of 2GHz, microwave heating time of 6 minutes, increasing to 750W, microwave frequency of 2.5GHz, microwave heating time of 20 minutes.
[0066] Comparative Example 1 is based on Example 3, but uses only potassium chloride as a refining agent; the other operating steps are the same.
[0067] Step 1: The 6061 low-iron aluminum alloy aluminum chips are subjected to high-speed centrifugation (3000 rpm) and drying (200℃) to obtain pretreated aluminum chips.
[0068] Step 2: (1) Add 6061 low iron aluminum alloy ingots (6061 low iron aluminum alloy ingots account for 55wt% of the furnace charge) into a double-cavity regenerative reverberatory furnace, melt them, and obtain the bottom material;
[0069] (2) Start the graphite rotor aluminum liquid lifting system, add the pretreated aluminum chips to the bottom material to obtain the furnace charge; through the rotating graphite rotor refining device, introduce argon gas (gas flow rate of 25m³ / h). 3 The aluminum alloy was refined for 25 minutes with 0.8 kg / t of refining agent (potassium chloride) and 0.8 kg / t of refining agent. After slag removal and settling, it was filtered with a foam ceramic filter plate with a porosity of 30 ppi and cast to obtain 6061 low iron recycled aluminum alloy (iron content ≤ 0.16 wt%).
[0070] Comparative Example 2 is based on Example 3, with micro-arc oxidation performed after anodizing; the remaining operation steps are the same.
[0071] Step 1: (1) Anodize 6061 low-iron recycled aluminum alloy to form a porous amorphous aluminum oxide layer, and obtain anodized pretreated aluminum alloy; use it as aluminum alloy product A;
[0072] The solvent for the nano-α-Al₂O₃ suspension was anhydrous ethanol, and the amount of citric acid added was 0.1 wt%.
[0073] The electrolyte for anodizing comprises the following components: 1.8 g / L sulfuric acid, 50 g / L oxalic acid; and the nano-α-Al2O3 suspension contains 2.5 g / L nano-α-Al2O3.
[0074] The anodizing process conditions are: temperature 10℃, voltage 42V, and current density 2.0A / dm³. 2 ;
[0075] The porous amorphous alumina layer has a thickness of 14.6 μm, a porosity of 24.2%, and a pore size of 117.5 nm.
[0076] Step 2: Place aluminum alloy product A in an electrolyte solution for micro-arc oxidation, wash and dry to form a micro-arc oxidation layer with a thickness of 26.5 μm. Then, perform three immersion sealing treatments with aluminum hydroxide solution to obtain the aluminum alloy product. The iron content of the aluminum alloy product is ≤0.10 wt%.
[0077] The electrolyte raw materials include the following components: sodium phosphate 30 g / L, sodium tetraborate 15 g / L, sodium tungstate 4.5 g / L, sodium hexametaphosphate 30 g / L, and 4 g / L of nano α-Al2O3 particles.
[0078] The process conditions for micro-arc oxidation are: current density of 8 A / dm³. 2 The frequency is 500Hz, the duty cycle is 12%, and the temperature is 35℃.
[0079] Comparative Example 3 is based on Example 3, but without immersion in the α-Al2O3 suspension; the remaining operating steps are the same.
[0080] Step 1: (1) Anodize 6061 low-iron recycled aluminum alloy to form a porous amorphous aluminum oxide layer, and obtain anodized pretreated aluminum alloy, which is used as aluminum alloy product A.
[0081] The electrolyte for anodizing comprises the following components: 1.8 g / L sulfuric acid and 50 g / L oxalic acid;
[0082] The anodizing process conditions are: temperature 10℃, voltage 42V, and current density 2.0A / dm³. 2 ;
[0083] The porous amorphous alumina layer has a thickness of 14.6 μm, a porosity of 24.2%, and a pore size of 117.5 nm.
[0084] Step 2: Weigh Al2(SO4)3·18H2O, Fe(NO3)3·9H2O, and formamide in a mass ratio of 1.5:4.0:100;
[0085] Al2(SO4)3·18H2O and Fe(NO3)3·9H2O were added to deionized water and mixed evenly. Nano-γ-Al2O3 (7wt% of the mixture) was added and ultrasonically dispersed to obtain a mixture. Aluminum alloy product A was added to the mixture, and formamide was added and heated to 90℃ to react. The mixture was then removed, dried, and microwave-treated to form an α-Fe2O3 / Al2O3 layer with a thickness of 286nm. The mixture was then ultrasonically dissolved in 100℃ hot hydrochloric acid (5M concentration) for 40 minutes to remove the α-Fe2O3. The mixture was then impregnated and sealed three times with aluminum hydroxide solution to obtain the aluminum alloy product. The iron content of the aluminum alloy product was ≤0.11wt%.
[0086] The process conditions for microwave heating treatment are: output power of 350W, microwave frequency of 2GHz, microwave heating time of 6 minutes, increasing to 750W, microwave frequency of 2.5GHz, microwave heating time of 20 minutes.
[0087] Comparative Example 4 is based on Example 3, but the thickness of the porous amorphous alumina layer is reduced to 4.3 μm; the remaining operation steps are the same.
[0088] Step 1: (1) Anodize 6061 low-iron recycled aluminum alloy to form a porous amorphous aluminum oxide layer and obtain anodized pretreated aluminum alloy; (2) Immerse the anodized pretreated aluminum alloy in nano α-Al2O3 suspension and sonicate, ultrasonically wash, dry at 40°C, and heat treat at 450°C for 40 minutes to form an α-Al2O3 layer with a thickness of 518nm and obtain aluminum alloy product A;
[0089] The solvent for the nano-α-Al₂O₃ suspension was anhydrous ethanol, and the amount of citric acid added was 0.1 wt%.
[0090] The electrolyte for anodizing comprises the following components: 1.8 g / L sulfuric acid, 50 g / L oxalic acid; and the nano-α-Al2O3 suspension contains 2.5 g / L nano-α-Al2O3.
[0091] The anodizing process conditions are: temperature 22℃, voltage 27V, and current density 1.5A / dm³. 2 ;
[0092] The porous amorphous alumina layer has a thickness of 4.3 μm, a porosity of 12.6%, and a pore size of 42.4 nm.
[0093] Step 2: Weigh Al2(SO4)3·18H2O, Fe(NO3)3·9H2O, and formamide in a mass ratio of 1.5:4.0:100;
[0094] Al2(SO4)3·18H2O and Fe(NO3)3·9H2O were added to deionized water and mixed evenly. Nano-γ-Al2O3 (7wt% of the mixture) was added and ultrasonically dispersed to obtain a mixture. Aluminum alloy product A was added to the mixture, and formamide was added and heated to 90℃ to react. The mixture was then removed, dried, and microwave-treated to form an α-Fe2O3 / Al2O3 layer with a thickness of 286nm. The mixture was then ultrasonically dissolved in 100℃ hot hydrochloric acid (5M concentration) for 40 minutes to remove the α-Fe2O3. The mixture was then impregnated and sealed three times with aluminum hydroxide solution to obtain the aluminum alloy product. The iron content of the aluminum alloy product was ≤0.11wt%.
[0095] The process conditions for microwave heating treatment are: output power of 350W, microwave frequency of 2GHz, microwave heating time of 6 minutes, increasing to 750W, microwave frequency of 2.5GHz, microwave heating time of 20 minutes.
[0096] Test 1:
[0097] The iron content of the 6061 low-iron recycled aluminum alloys prepared in Examples 1-3 and Comparative Example 1 was tested; and the iron content of the aluminum alloy products prepared in Examples 1-3 and Comparative Examples 2-4 was tested.
[0098] Table 1
[0099] Iron content of 6061 low-iron recycled aluminum alloy Iron content of aluminum alloy products Example 1 Iron content ≤0.10wt% Iron content ≤0.13wt% Example 2 Iron content ≤0.10wt% Iron content ≤0.12wt% Example 3 Iron content ≤0.10wt% Iron content ≤0.11wt% Comparative Example 1 Iron content ≤0.16wt% - Comparative Example 2 Iron content ≤0.10wt% Iron content ≤0.10wt% Comparative Example 3 Iron content ≤0.10wt% Iron content ≤0.11wt% Comparative Example 4 Iron content ≤0.10wt% Iron content ≤0.11wt%
[0100] Conclusion: Comparative Example 1 used only potassium chloride as a refining agent and did not use a refining system of magnesium chloride and potassium chloride. The resulting 6061 low-iron recycled aluminum alloy had an increased iron content, which could not meet the stringent requirements of low-iron aluminum alloys used in aerospace and semiconductor manufacturing equipment. Therefore, it is not suitable for the above-mentioned high-end application fields.
[0101] Test Example 2: (1) Friction and wear test: The aluminum alloy products prepared in Examples 1-3 and Comparative Examples 2-4 were fixed on the sample stage of the friction testing machine; zirconia ceramic balls were used as the grinding material, with a reciprocating stroke of 5 mm; wherein, the diameter of the zirconia ceramic balls was 10 mm, the frequency was 2 Hz, the load was 5 N, the time was 30 minutes, and the wear rate (mm) was tested. 3 / N / m).
[0102] (2) Corrosion resistance test: The potentiodynamic polarization curves of aluminum alloy products prepared in Examples 1-3 and Comparative Examples 2-4 in sodium chloride solution (concentration of 3.5wt%) were detected using a three-electrode system, and the corrosion current density of different aluminum alloy products was calculated; the test area was 1 cm². 2 An aluminum alloy product is used as the working electrode, an SCE is used as the reference electrode, and a platinum sheet is used as the auxiliary electrode.
[0103] Table 2
[0104] <![CDATA[Wear rate (mm 3 / N / m)]]> <![CDATA[Corrosion current density (A / cm 2 )]]> Example 1 <![CDATA[1.94×10 -6 ]]> <![CDATA[2.18×10 -9 ]]> Example 2 <![CDATA[1.67×10 -6 ]]> <![CDATA[2.12×10 -9 ]]> Example 3 <![CDATA[1.40×10 -6 ]]> <![CDATA[2.03×10 -9 ]]> Comparative Example 2 <![CDATA[6.46×10 -6 ]]> <![CDATA[1.71×10 -8 ]]> Comparative Example 3 <![CDATA[5.02×10 -5 ]]> <![CDATA[8.64×10 -6 ]]> Comparative Example 4 <![CDATA[1.34×10 -5 ]]> <![CDATA[2.06×10 -7 ]]>
[0105] Conclusion: Comparative Example 2, based on Example 3, underwent micro-arc oxidation after anodic oxidation. Although α-Al2O3 was added to the electrolyte for micro-arc oxidation, the dispersion of nano-α-Al2O3 was poor. Although the content of α-Al2O3 increased, γ-Al2O3 was still the main product, resulting in slightly worse performance than Example 3. Comparative Example 2, based on Example 3, was not impregnated with an α-Al2O3 suspension. Comparative Example 3, based on Example 3, was not impregnated with an α-Al2O3 suspension. Due to the lack of α-Al2O3 barrier effect and the failure to improve the density of the porous layer through heat treatment, the performance was slightly worse than that of Example 3. Although microwaves can transform porous amorphous alumina into α / γ-Al2O3, ultrasonic hot hydrochloric acid easily penetrates the pores, excessively corroding γ-Al2O3 and further eroding the 6061 aluminum alloy matrix, forming cavities. Sealing treatment alone is insufficient to fully fill the cavities, resulting in a decrease in the corrosion resistance and wear resistance of the final product. Comparative Example 4, based on Example 3, reduced the thickness of the porous amorphous alumina layer to 4.3 μm. In hot hydrochloric acid, the reduced thickness of the porous amorphous alumina layer led to excessive corrosion, enlarged pores, and reduced sealing effect, thus causing a decline in performance.
[0106] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.
Claims
1. A method for the remelting and grade-preserving recycling of 6061 low-iron aluminum alloy scrap, characterized in that: The following steps are included: Step 1: The 6061 low-iron aluminum alloy chips are subjected to high-speed centrifugation and drying in sequence to obtain pretreated aluminum chips; Step 2: (1) Add 6061 low iron aluminum alloy ingots into a double-cavity regenerative reverberatory furnace, melt them, and obtain bottom material; (2) Start the graphite rotor aluminum liquid lifting system, add pretreated aluminum chips into the bottom material, and obtain furnace charge; refine by rotating the graphite rotor refining device, introducing inert gas and refining agent, removing slag, settling, filtering, and casting to obtain 6061 low iron recycled aluminum alloy; The raw materials for the refining agent include magnesium chloride and potassium chloride in a mass ratio of 1.2 to 2.0:1; the iron content of the 6061 low-iron recycled aluminum alloy is ≤0.10wt%.
2. The method for remelting and preserving the grade of 6061 low-iron aluminum alloy scraps according to claim 1, characterized in that: The chemical composition of the 6061 low-iron aluminum alloy ingot includes: Si 0.5~0.7wt%, Fe <0.10wt%, Cu 0.2~0.3wt%, Mn 0.05~0.20wt%, Mg 0.8~1.2wt%, Cr 0.15~0.40wt%, with the balance being Al, and unavoidable impurities totaling <0.03%.
3. The method for remelting and recycling 6061 low-iron aluminum alloy scraps according to claim 1, wherein the 6061 low-iron recycled aluminum alloy is prepared, characterized in that: The 6061 low-iron aluminum alloy ingot accounts for 50-60 wt% of the furnace charge; the flow rate of the inert gas is 20-25 m³ / h. 3 / h; the amount of refining agent added is 0.6~1Kg / t, and the refining time is 15~25 minutes.
4. An application of a 6061 low-iron aluminum alloy, characterized in that: The 6061 low-iron recycled aluminum alloy of claim 1 is used to prepare aluminum alloy products; the method for preparing the aluminum alloy products includes the following steps: Step 1: (1) Anodize 6061 low-iron recycled aluminum alloy to form a porous amorphous aluminum oxide layer and obtain anodized pretreated aluminum alloy; (2) Immerse the anodized pretreated aluminum alloy in nano α-Al2O3 suspension and sonicate it, and heat treat it at 400~500℃ for 30~40 minutes to form an α-Al2O3 layer and obtain aluminum alloy product A; Step 2: Add Al2(SO4)3·18H2O and Fe(NO3)3·9H2O to deionized water and mix evenly. Add nano-γ-Al2O3 and disperse by ultrasonication to obtain a mixed solution. Add aluminum alloy product A to the mixed solution, add formamide and heat to 80~95℃ to react. Take it out, dry it, and microwave it to form an α-Fe2O3 / Al2O3 layer. Add it to hot hydrochloric acid and sonicate for 30~40 minutes to remove α-Fe2O3. Repeat the sealing treatment to obtain the aluminum alloy product.
5. The application of a 6061 low-iron aluminum alloy according to claim 4, characterized in that: The porous amorphous alumina layer has a thickness of 8-15 μm, a porosity of 15-27%, and a pore size of 50-130 nm; the nano-α-Al₂O₃ has a particle size of 20-60 nm; the nano-γ-Al₂O₃ has a particle size of 20-60 nm; the α-Al₂O₃ layer has a thickness of 300-600 nm; and the α-Fe₂O₃ / Al₂O₃ layer has a thickness of 100-300 nm.
6. The application of a 6061 low-iron aluminum alloy according to claim 4, characterized in that: The raw materials for the electrolyte used in the anodic oxidation process include the following components: 1~3 g / L sulfuric acid, 50~80 g / L oxalic acid; and the concentration of the nano α-Al2O3 suspension is 1~3 g / L.
7. The application of a 6061 low-iron aluminum alloy according to claim 4, characterized in that: The mass ratio of Al2(SO4)3·18H2O, Fe(NO3)3·9H2O, and formamide is (1.5~3):(3~5):100; the nano-γ-Al2O3 accounts for 3~8 wt% of the mixture; and the concentration of hydrochloric acid is 4~5 M.
8. The application of a 6061 low-iron aluminum alloy according to claim 4, characterized in that: The anodizing process conditions are as follows: temperature 10~30℃, voltage 25~45V, and current density 1.0~2.5A / dm³. 2 The microwave heating process conditions are: output power of 300~900W, microwave frequency of 2~2.5GHz, and time of 15~35 minutes; the iron content of the aluminum alloy product is ≤0.11wt%.