A method of using a recycled A356 aluminum for aluminum automotive parts

Abstract

This invention provides a method for using recycled A356 aluminum in aluminum automotive parts. The method involves sequentially classifying, pre-treating, melting, mixing, refining, radiographic testing, casting, and heat treatment of the recycled A356 material. The recycled material is classified and subjected to targeted pre-treatment. Pure aluminum is used to neutralize the recycled aluminum, and the amount of pure aluminum added is precisely controlled using a measuring spoon. AlTi5B / AlSr is added during the refining process. 10 / Mg. Cast aluminum treated according to the above S1-S7 can achieve a yield rate of ≥95%. Cast aluminum after S8 heat treatment can achieve a yield strength of ≥220MPa, tensile strength of ≥290MPa, elongation of ≥8%, hardness of ≥85HB, and secondary dendrite spacing of ≤50um, which can meet the requirements of aluminum for automotive use.

Description

Technical Field

[0001] This invention relates to a waste aluminum recycling manufacturing process, specifically a method for using A356 recycled aluminum in aluminum automotive parts. Background Technology

[0002] In the context of lightweighting in the automotive industry, aluminum alloys are gradually replacing iron materials in automobile manufacturing due to their advantages such as light weight, corrosion resistance, and good plasticity. The increased use of aluminum in automobiles can reduce vehicle weight, lower energy consumption, and improve operating speed. Aluminum alloys can be used in almost all automotive components, including steering knuckles, control arms, shock absorber towers, subframes, and more. A356 is a typical Al-Si-Mg ternary alloy with good fluidity and no tendency to hot cracking, making it the most widely used cast aluminum alloy. In automobiles, A356 is commonly used in the manufacture of wheel hubs, steering knuckles, control arms, and subframes.

[0003] As a recyclable metal, the recycling of aluminum alloys has always been a key issue in the industry, especially for high-performance automotive aluminum alloys. However, recycled aluminum contains a large amount of oil, water, foreign matter, and impurities, resulting in increased aluminum slag content and severe air absorption, which may lead to lower product performance and increased scrap rates. Currently, recycled aluminum is generally used in the market to manufacture products with lower strength requirements, such as doors, windows, housings, and radiators. However, for fields like automotive manufacturing, which involve personal safety, strict requirements are placed on the composition of aluminum materials. Existing technologies in the automotive manufacturing industry typically involve adding pure aluminum, usually at a content of 50-80%, along with some scrap parts, to keep the performance of the recycled aluminum within an acceptable range. As the scrap aluminum content continues to increase, the yield of finished cast aluminum will significantly decrease.

[0004] To address the aforementioned existing technologies, incorporating recycled A356 aluminum alloy into the manufacture of automotive parts of the same grade allows for the reuse of recycled aluminum in these parts, significantly reducing both costs and carbon emissions. Therefore, it is necessary to provide a method for manufacturing recycled aluminum that improves its utilization rate and ensures a stable yield of finished cast aluminum products. Summary of the Invention

[0005] This invention provides a method for using recycled A356 aluminum in the manufacture of automotive parts, comprising the following steps:

[0006] S1. Scrap Aluminum Classification: Control the initial stage of A356 scrap aluminum recycling to ensure clear source and single grade. The largest source of scrap aluminum is aluminum shavings and scrap aluminum parts. Recycling scrap aluminum is managed and classified according to aluminum shavings and aluminum parts. A large amount of aluminum shavings are generated during casting production. For example, in casting cutting processes, aluminum shavings account for approximately 20%-30% of the casting weight. Aluminum shavings are characterized by their shaving-like or filamentous appearance and are easily mixed with other impurities. Recycled aluminum parts in automobiles mainly consist of scrap wheel hubs, as well as other scrap aluminum parts or externally purchased remelted aluminum ingots. Aluminum parts are characterized by stable composition; impurities come from foreign matter on the part surface, paint, etc.

[0007] S2. Pre-treatment: Before smelting, recycled aluminum scrap needs to be cleaned as much as possible. Sorting the scrap allows for targeted processing. Pre-treatment methods for aluminum shavings include crushing, degreasing, dehydration, and removal of iron foreign objects; recycling of aluminum parts includes removing foreign objects and accessories, shot peening to remove paint, and baling the scrap aluminum. After crushing, the aluminum shavings are separated from the cutting fluid by high-speed rotation. The cutting fluid, after passing through 3-5 layers of filtration, is pumped back to the main cutting fluid supply station for recycling. During drying, the aluminum shavings rotate around a fixed high-temperature hot air pipe and gradually heat up. The residual organic matter on the surface of the aluminum shavings vaporizes and is introduced into a dedicated incinerator for combustion. The high-temperature hot air is then introduced into the high-temperature hot air pipe to preheat the aluminum shavings, thus saving energy.

[0008] S3. Smelting: The pre-treated A356 recycled aluminum is transferred to the recycling furnace for melting. Slag removal is performed before feeding. Waste wheel hubs after S2 pre-treatment are fed into the recycling furnace through the furnace door. Aluminum scrap is preheated to 150-250℃ and then fed into the aluminum scrap well of the recycling furnace. Each batch of recycled aluminum is discharged one hour after feeding. The recycling furnace is dealuminized and slag removed every 4 hours using a refining agent. Feeding and discharging of recycled aluminum can be carried out simultaneously. During the smelting process, aluminum liquid is sampled and its composition is tested. Recycled aluminum is continuously added to maintain the composition of the aluminum liquid at Si 6.5-7.5%, Fe≤0.15%, Ti≤0.30%, Mn≤0.10%, Zn≤0.10%, Cu≤0.10%, Mg≤0.45%, Sr≤0.030%, and the total of unavoidable impurities ≤0.15%, with the balance being Al. Compared to the composition of conventional A356 aluminum alloy, the composition of recycled aluminum is slightly more lenient in terms of Mg and Ti.

[0009] S4. Mixing: The recycled aluminum liquid from the recycling furnace is transferred to the holding furnace, while the pure aluminum liquid from the aluminum ingot furnace is transferred to the same holding furnace for mixing and discharge. The proportion of recycled aluminum liquid in the mixed aluminum liquid is ≤80%. The recycled aluminum liquid and pure aluminum liquid are transferred using a flow channel between the recycling furnace, aluminum ingot furnace, and holding furnace. The holding furnace is equipped with graduations. Recycled aluminum liquid and pure aluminum liquid are added until the graduations are reached. A measuring spoon is then used to fine-tune the content of the mixed solution. This allows for precise adjustment of the proportion of recycled aluminum liquid in the mixed aluminum liquid according to specific needs and reduces heat loss during the circulation process. After mixing, the composition of the mixed aluminum liquid in the holding furnace is measured.

[0010] S5. Refining: For the mixed aluminum liquid treated by the S4 mixing process, a refining agent is added at a temperature of 700-740℃ to remove aluminum and slag. Then, according to the target value of the aluminum alloy chemical composition, AlTi5B / AlSr is added in a quantitative amount. 10 / Mg. The target chemical composition of the aluminum alloy is Si 6.5-7.5%, Fe≤0.15%, Mg0.25-0.45%, Ti≤0.25%, Mn≤0.10%, Zn≤0.10%, Cu≤0.10%, Sr≤0.030%, and the total of unavoidable impurities≤0.15%, with the balance being Al.

[0011] Mg forms the Mg2Si phase in the matrix, which is the main strengthening phase in aluminum alloys and increases the strength of cast aluminum alloys. However, adding too much Mg will reduce the elongation of the alloy. To balance the strength and plasticity of the cast aluminum alloy, the Mg content of the target aluminum alloy is set at 0.33-0.37%. AlTi5B is a grain refiner in the reaction, which can refine the grains. However, too much Ti will become an impurity and negatively affect the alloy properties. Therefore, the Ti content is controlled between 0.12-0.20%. The refining method of the aluminum liquid involves uniformly sprinkling about 350g of refining agent on the surface of the aluminum liquid, and then introducing 99.9% pure argon gas at a flow rate of 400-500 rpm for refining.

[0012] S6. Inspection: After refining for 10-20 minutes, test the chemical composition, density, and K-die fracture surface of the mixture. Inspection conditions: Within 30 seconds of removing the mixture, apply a vacuum to -0.09 MPa and maintain for 5 minutes; Inspection standard: All fracture surfaces of the K-die should be free of slag, and the density should be ≥2.57 g / cm³. 3 The components of the mixture are located within the target components.

[0013] S7. Casting Aluminum: Casting parts within 4 hours after the A356 mixed aluminum liquid, which has been treated by S6 and passed the inspection, is used to process the aluminum.

[0014] S8. Heat treatment: The aluminum alloys cast by S7 are subjected to heat treatment: The heat treatment process includes solution treatment at 530-540℃ for 3-4 hours; water cooling for 25 seconds at a water cooling temperature of 50-60℃; and aging at 165-175℃ for 2-3 hours.

[0015] This invention provides a method for using recycled A356 aluminum in the manufacture of automotive parts. The method involves the following steps: sorting, pretreatment, smelting, mixing (using a measuring spoon to precisely control the amount of pure aluminum added), refining (adjusting the alloy composition to a suitable range by adding a refining agent), radiographic inspection, casting, and heat treatment. The recycled material is sorted and subjected to targeted pretreatment. Pure aluminum is used to neutralize the recycled aluminum. The amount of pure aluminum added is precisely controlled using a measuring spoon. AlTi5B / AlSr is added during the refining process. 10 / Mg.

[0016] A356 Cast Aluminum Good Product Standard: (1) Meets the composition requirements of DIN 1706: Cast aluminum composition Si 6.5-7.5%, Fe ≤ 0.15%, Ti ≤ 0.20%, Mn ≤ 0.10%, Zn ≤ 0.10%, Cu ≤ 0.10%, Mg ≤ 0.45%, Sr ≤ 0.030%, and unavoidable impurities ≤ 0.15%, with the balance being Al. (2) During radiographic testing, internal defects of the parts shall not exceed the level 2 defects of ASTM E155. (3) During penetrant testing, external defects such as cracks and cold shuts shall be absent from the parts.

[0017] According to the above S1-S7 treatment, the cast aluminum can achieve a yield rate of ≥95%. After S8 heat treatment, the cast aluminum can achieve a yield strength of ≥220MPa, tensile strength of ≥290MPa, elongation of ≥8%, hardness of ≥85HB, and secondary dendrite spacing of ≤50um, which meets the requirements of aluminum for automotive use. Detailed Implementation

[0018] Example

[0019] (1) Sprinkle 2-3 kg of refining agent evenly on the surface of the aluminum liquid in the recycling furnace, stir with tools, and remove aluminum and slag once.

[0020] (2) After the A356 machined aluminum chips are crushed, degreased, dewatered and de-ironed, they are preheated to 150-250℃ and continuously fed into the aluminum chip well of the recycling furnace at a feeding rate of 600Kg / h for melting.

[0021] (3) One hour after feeding, start discharging according to the ratio. The feeding and discharging of recycled aluminum can be carried out simultaneously.

[0022] (4) Add the pure aluminum liquid from the aluminum ingot furnace to the recycling furnace and mix and discharge. The recycling furnace discharges a total of 527 kg and the aluminum ingot furnace discharges 133 kg. The proportion of recycled aluminum liquid is 79.8% and the proportion of aluminum liquid from the aluminum ingot furnace is 20.2%. In order to control the proportion accurately, a measuring spoon is used to discharge the aluminum liquid.

[0023] (5) The temperature of the mixed aluminum liquid in step 4 was measured to be 723℃, which meets the temperature requirements before refining. 350g of refining agent was evenly sprinkled on the surface of the aluminum liquid, stirred and dealuminized, and then the slag was removed. Based on the measured current chemical element content and target content, the alloy addition range was calculated. 1005g of AlTi5B alloy, 1002g of AlSr10 alloy and 215g of Mg were added. After evenly sprinkling about 350g of refining agent on the surface of the aluminum liquid, 99.9% pure argon gas was passed through at a flow rate of 400-500rpm for refining for 10 minutes.

[0024] (6) After refining, chemical composition samples, K-mold samples, and density samples were taken. The chemical composition was tested and found to be Si 7.1%, Fe 0.11%, Mg 0.35%, Ti 0.17%, Sr 0.015%, Mn 0.008%, Cu 0.005%, Zn 0.02%, with individual impurities ≤0.03% and total impurities ≤0.15%. The chemical composition met the requirements. All fracture surfaces of the K-mold were free of slag, and the density was 2.61 g / cm3. The aluminum liquid temperature was 719℃, which met the requirements.

[0025] (7) After the above qualified aluminum liquid was slag removed, it was transferred to the casting machine to cast 118 steering knuckle parts.

[0026] (8) After casting, the aluminum parts are transferred to a heat treatment rack, and after solution treatment at 530-540℃ for 3-4 hours, they are aged at 165-175℃ for 2-3 hours. They are then immersed in water within 25 seconds, and the water temperature is maintained at 50-60℃.

[0027] After heat treatment, the hardness of the parts was measured at the locations shown in the drawings. Tensile test bars and metallographic samples were taken. The results are as follows: yield strength 254.1 MPa, tensile strength 322.1 MPa, elongation 11.6%, hardness 111.6 HB, secondary dendrite spacing 34.9 μm. Among them, 3 parts were defective, and the yield rate reached 97.5%, which met the requirements. Example

[0028] (1) Sprinkle 2-3 kg of refining agent evenly on the surface of the aluminum liquid in the recycling furnace, stir with tools, and remove aluminum and slag once.

[0029] (2) The A356 recycled remelted aluminum ingots that have undergone foreign object removal and shot blasting to remove paint are put into the recycling furnace through the furnace door for melting.

[0030] (3) One hour after feeding, start discharging according to the ratio. Feeding and discharging can be carried out simultaneously.

[0031] (4) Add the pure aluminum liquid from the aluminum ingot furnace to the recycling furnace and mix and discharge. The recycling furnace discharges a total of 356 kg and the aluminum ingot furnace discharges 304 kg. The recycled aluminum liquid accounts for 53.9% and the aluminum ingot furnace accounts for 46.1%. In order to accurately control the proportion, a measuring spoon is used to discharge the aluminum liquid.

[0032] (5) The temperature of the mixed aluminum liquid was measured at 728℃, which meets the temperature requirements before refining. 350g of refining agent was evenly sprinkled on the surface of the aluminum liquid, stirred and dealuminized, and then the slag was removed. Based on the measured current chemical element content and target content, the alloy addition range was calculated, and 1014g of AlTi5B alloy, 1057g of AlSr10 alloy and 195g of pure magnesium were added. After evenly sprinkling about 350g of refining agent on the surface of the aluminum liquid, 99.9% pure argon gas was introduced at a flow rate of 400-500rpm for refining.

[0033] (6) After refining for 10-20 minutes, take chemical composition samples, K-mold samples, and density samples. The chemical composition is as follows: Si 7.3%, Fe 0.13%, Mg 0.36%, Ti 0.15%, Sr 0.014%, Mn 0.008%, Cu 0.005%, Zn 0.03%, with individual impurities ≤0.03% and total impurities ≤0.15%. The chemical composition meets the requirements. All fracture surfaces of the K-mold are free of slag, and the density is 2.62 g / cm3. The aluminum liquid temperature is 724℃, which meets the requirements.

[0034] (7) After the above qualified aluminum liquid was slag removed, it was transferred to the casting machine to cast 186 steering knuckle parts.

[0035] (8) After casting, the aluminum parts are transferred to a heat treatment rack, and after solution treatment at 530-540℃ for 3-4 hours, they are aged at 165-175℃ for 2-3 hours. They are then immersed in water within 25 seconds, and the water temperature is maintained at 50-60℃.

[0036] After heat treatment, the hardness of the parts was measured at the locations shown in the drawings. Tensile test bars and metallographic samples were taken. The results are as follows: yield strength 252.3 MPa, tensile strength 324 MPa, elongation 11.1%, hardness 105.8 HB, secondary dendrite spacing 37.6 μm, 5 scraps, yield rate 97.3%, meeting the requirements. Example

[0037] (1) Sprinkle 2-3 kg of refining agent evenly on the surface of the aluminum liquid in the recycling furnace, stir with tools, and remove aluminum and slag once.

[0038] (2) The A356 recycled waste wheel hubs, which have undergone foreign object removal and shot blasting to remove paint, are put into the recycling furnace through the furnace door for melting.

[0039] (3) One hour after feeding, start discharging according to the ratio. The feeding and discharging of recycled aluminum can be carried out simultaneously.

[0040] (4) 432 kg of recycled aluminum liquid was discharged and 228 kg was discharged from the aluminum ingot furnace. The recycled aluminum liquid accounted for 65.4% and the aluminum liquid from the conventional smelting furnace accounted for 34.6%. In order to control the proportions accurately, a measuring spoon was used to discharge the aluminum liquid.

[0041] (5) The temperature of the mixed aluminum liquid was measured at 719℃, which meets the temperature requirements before refining. 350g of refining agent was evenly sprinkled on the surface of the aluminum liquid, stirred and dealuminized, and then the slag was removed. Based on the measured current chemical element content and target content, the alloy addition range was calculated, and 1018g of AlTi5B alloy, 1025g of AlSr10 alloy and 282g of Mg were added. After evenly sprinkling about 350g of refining agent on the surface of the aluminum liquid, the graphite rotor was purged with 99.9% pure argon gas at a flow rate of 400-500rpm for 10 minutes for refining.

[0042] (6) After refining, chemical composition samples, K-mold samples, and density samples were taken and tested. The chemical composition was Si 6.9%, Fe 0.12%, Mg 0.33%, Ti 0.18%, Sr 0.016%, Mn 0.009%, Cu 0.005%, Zn 0.02%, with individual impurities ≤0.03% and total impurities ≤0.15%. The chemical composition met the requirements. All fracture surfaces of the K-mold were free of slag, and the density was 2.60 g / cm3. The aluminum liquid temperature was 718℃, which met the requirements.

[0043] (7) After the above qualified aluminum liquid was slag removed, it was transferred to the casting machine to cast 186 control arm parts.

[0044] (8) After casting, the aluminum parts are transferred to a heat treatment rack, and after solution treatment at 530-540℃ for 3-4 hours, they are aged at 165-175℃ for 2-3 hours. They are then immersed in water within 25 seconds, and the water temperature is maintained at 50-60℃.

[0045] After heat treatment, the hardness of the parts was measured at the locations shown in the drawings. Tensile test bars and metallographic samples were taken. The results are as follows: yield strength 242.3 MPa, tensile strength 315 MPa, elongation 9.1%, hardness 104.6 HB, secondary dendrite spacing 37.4 μm, 8 scrap parts, and the yield rate reached 95.7%, which meets the requirements.

[0046] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for using recycled A356 aluminum in aluminum automotive parts, characterized in that: Includes the following steps: S1. Scrap Aluminum Classification: Control the initial stage of A356 scrap aluminum recycling, and collect the recycled scrap aluminum according to aluminum scrap and aluminum parts; S2. Pre-treatment: Pre-treatment of sorted recycled waste aluminum. Pre-treatment methods for aluminum shavings include crushing, degreasing and dehydration, and removal of iron foreign objects; pre-treatment methods for aluminum parts include removal of foreign objects and attachments, and shot blasting to remove paint. S3. Smelting: The pre-treated recycled aluminum material is transferred to the recycling furnace for melting. The recycling furnace is deslag-removed before feeding. Each batch of recycled aluminum is discharged one hour after feeding. The recycling furnace is dealuminized and slag-removed with a refining agent every 4 hours. The feeding and discharging of recycled aluminum are carried out simultaneously. During the smelting process, the aluminum liquid is sampled and its composition is tested. Recycled aluminum is continuously added to ensure that the composition of the aluminum liquid is within the following range: Si 6.5-7.5%, Fe≤0.15%, Ti≤0.30%, Mn≤0.10%, Zn≤0.10%, Cu≤0.10%, Mg≤0.45%, Sr≤0.030%, and the total of unavoidable impurities ≤0.15%, with the balance being Al. S4. Mixing: The recycled aluminum liquid from the recycling furnace is transferred to the holding furnace, and the pure aluminum liquid from the aluminum ingot furnace for smelting pure aluminum is transferred to the same holding furnace for mixing and discharge. The proportion of recycled aluminum liquid in the mixed aluminum liquid is ≤80%. S5. Refining: For the mixed aluminum liquid treated by the S4 mixing process, a refining agent is added at a temperature of 700-740℃ to remove aluminum and slag. Then, according to the target value of the aluminum alloy chemical composition, AlTi5B / AlSr is added in a quantitative amount. 10 / Mg; The target values ​​for the chemical composition of the aluminum alloy are Si 6.5-7.5%, Fe≤0.15%, Mg0.25-0.45%, Ti≤0.25%, Mn≤0.10%, Zn≤0.10%, Cu≤0.10%, Sr≤0.030%, and the total of unavoidable impurities≤0.15%, with the balance being Al; S6. Inspection: After refining for 10-20 minutes, test the chemical composition, density, and K-mold fracture surface of the mixture; Inspection conditions: Within 30 seconds of removing the mixture, apply a vacuum to -0.09 MPa and maintain for 5 minutes; Inspection standard: All fracture surfaces of the K-mold are free of slag, and the density is ≥2.57 g / cm³. 3 The components of the mixture are located within the target components; S7. Casting Aluminum: Casting parts within 4 hours after the A356 mixed aluminum liquid, which has been treated by S6 and passed the inspection, is used to process the aluminum.

2. The method for using recycled A356 aluminum in aluminum automotive parts as described in claim 1, characterized in that: In S4, the recycled aluminum liquid and pure aluminum liquid are transferred using a trough between the recycling furnace, the aluminum ingot furnace and the holding furnace. The holding furnace is equipped with a scale. The recycled aluminum liquid and pure aluminum liquid are added until the scale is reached. Then, the content of the mixed solution is finely adjusted using a measuring spoon.

3. The method for using recycled A356 aluminum in aluminum automotive parts as described in claim 2, characterized in that: In S3, aluminum scraps are added to the recycling furnace and preheated to 150-250℃.

4. The method for using recycled A356 aluminum in aluminum automotive parts as described in claim 3, characterized in that: In step S2, after the aluminum chips are crushed, the cutting fluid is separated by high-speed rotation. After passing through 3-5 layers of filtration, the cutting fluid is pumped back to the main cutting fluid supply station for machining.

5. The method for using recycled A356 aluminum in aluminum automotive parts as described in claim 3, characterized in that: Before step S3, when the aluminum chips are preheated, they rotate around a fixed high-temperature hot air pipe and gradually heat up and move forward. The residual organic matter on the surface of the aluminum chips is vaporized and introduced into a special incinerator for combustion. The high-temperature hot air is then introduced into the high-temperature hot air pipe to preheat the aluminum chips.

6. The method for using recycled A356 aluminum in aluminum automotive parts as described in claim 1, characterized in that: The S6 refining process includes the following steps: After uniformly sprinkling 350g of refining agent on the surface of the molten aluminum, 99.9% pure argon gas is introduced at a flow rate of 400-500 rpm for refining.

7. A method for using recycled A356 aluminum in aluminum automotive parts as described in claim 3, characterized in that: In S5, the target value of the chemical composition of the aluminum alloy is 0.33-0.37% Mg.

8. The method for using recycled A356 aluminum in aluminum automotive parts as described in claim 3, characterized in that: In S5, the target value of the chemical composition of the aluminum alloy is Ti 0.12-0.20%.

9. A method for using recycled A356 aluminum in aluminum automotive parts as described in any one of claims 1-8, characterized in that: It also includes S8. Heat treatment: Heat treatment of aluminum alloys completed by S7 casting: The heat treatment process includes solution treatment at 530-540℃ for 3-4 hours; water cooling for 25 seconds at a water cooling temperature of 50-60℃; and aging at 165-175℃ for 2-3 hours.