Low-cost preparation process of regenerated Al-Mg-Si alloy for automobile lightweight

Abstract

The invention relates to a low-cost preparation process of a regenerated Al-Mg-Si alloy for automobile lightweight. The low-cost preparation process comprises the following steps: carrying out pretreatment and component analysis on raw materials; secondary aluminum is smelted and refined through a double-chamber furnace; smelting a primary aluminum ingot; mixing and homogenizing the substances obtained in the steps S2 and S3; s4, refining and standing the product obtained in the step S4; al-Ti-B wires are added into the launder, filtering and degassing are carried out, a finished product is obtained, special equipment and special raw and auxiliary materials are not needed, the aluminum alloy can be prepared only by changing a production method, adaptability is high, secondary aluminum can be used in a guaranteed level after being added, and the use performance of the product is not affected.

Description

Technical Field

[0001] This invention belongs to the field of alloy preparation technology, specifically relating to a low-cost preparation process for recycled Al-Mg-Si alloys used for automotive lightweighting. Background Technology

[0002] Recycled aluminum refers to metallic aluminum that has undergone at least one melting, casting, or processing and has been recycled. The global recycled aluminum industry is developing rapidly, with a market size reaching US$91.3 billion in 2024 and projected to exceed US$161.1 billion by 2034, representing a compound annual growth rate of 7.88%. China, as the world's largest producer and consumer of aluminum, produced approximately 10.55 million tons of recycled aluminum in 2024, accounting for 30% of global production. The core driving force behind the application of recycled aluminum lies in its significant environmental advantages. Producing one ton of recycled aluminum consumes only 5% of the energy of primary aluminum, emits only 4.6% of the carbon emissions of primary aluminum, and saves 5.3 tons of standard coal, reducing carbon dioxide emissions by approximately 14 tons. Under the "dual carbon" target (carbon reduction and emission reduction), recycled aluminum has become a core path for the green transformation of the aluminum industry.

[0003] Extruded aluminum alloys are an important application area for recycled aluminum. Through hot extrusion, recycled aluminum can be processed into various profiles, tubes, and bars, which are widely used in new energy vehicles, construction, and other fields. Traditionally, recycled aluminum is downgraded for reuse, with automotive aluminum alloy profiles used in construction and die-casting product manufacturing. If recycled aluminum could be used while maintaining its grade, production costs could be effectively reduced. However, maintaining the grade of recycled aluminum alloys presents challenges such as compositional complexity and impurity control.

[0004] Chinese patent CN 115976352 B discloses a method for preparing wrought aluminum alloys using recycled aluminum. This technology uses recycled aluminum instead of the original aluminum as a raw material for furnace smelting. In-furnace refining Online melt processing The semi-continuous casting process yields wrought aluminum alloy ingots with a hydrogen content ≤0.12mL / 100gAl, grain size ≤Grade 1, no inclusions or slag, and porosity ≤Grade 1. Because automotive aluminum alloys require high strength, high toughness, excellent corrosion resistance, and consistent product characteristics, their composition range is relatively narrow. This patented method necessitates effective management of recycled aluminum raw materials to ensure stable composition of the recycled aluminum alloy. This method enables in-plant self-circulation of white materials but is not suitable for recycling aluminum scraps and other wrought aluminum alloys available on the market, as commercially available recycled aluminum suffers from compositional inhomogeneity and impurity control issues.

[0005] In view of this, this solution was developed. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the technical problem to be solved by the present invention is to provide a low-cost preparation process for recycled Al-Mg-Si alloys for automotive lightweighting, so as to achieve the grade preservation of wrought aluminum alloys for automotive use.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a low-cost preparation process for recycled Al-Mg-Si alloys for automotive lightweighting. S1. Pre-treatment and component analysis of raw materials; S2. Recycled aluminum is smelted and refined using a dual-chamber furnace; S3, Smelting primary aluminum ingots; S4. Mix and homogenize the results obtained in steps S2 and S3; S5. Refine and let stand the product obtained in step S4. S6. Al-Ti-B filaments are added into the flow channel, and then filtered and degassed to obtain the finished product.

[0008] Furthermore, the specific operation steps of step S1 are as follows: perform small-scale furnace composition testing on the raw materials to preliminarily determine the amount of recycled aluminum alloy to be added.

[0009] Furthermore, the specific operation steps of step S2 are as follows: the recycled aluminum is smelted in a double-chamber furnace, and after the recycled aluminum is melted, it is electromagnetically stirred. After that, a refining agent is introduced into the furnace to refine the recycled aluminum in the furnace. After that, a sample is taken for composition testing.

[0010] Furthermore, the specific operation steps of step S3 are as follows: the scrap and aluminum ingots are mixed and melted in another smelting furnace, and the melting amount is set according to the furnace feeding ratio based on the composition detection results of the small furnace.

[0011] Furthermore, the melting furnace is a tiltable melting furnace.

[0012] Furthermore, the specific operation steps of step S4 are as follows: after the melting furnace is completed, the recycled aluminum water in the dual-chamber furnace is transferred to the melting furnace for mixing, and the electromagnetic stirring is turned on.

[0013] Furthermore, the specific operation steps of step S5 are as follows: the composition of the product obtained in step S4 is first verified, and after the verification is qualified, it is refined in the furnace and then left to stand.

[0014] Furthermore, the specific steps of step S6 are as follows: the product obtained in step S5 passes through a flow channel, Al-Ti-B wire is added to the flow channel, and degassing and filtration are carried out simultaneously. Finally, an alloy casting rod is obtained through a casting process.

[0015] Furthermore, the waste material mentioned in step S3 is the head and tail of profile sawing or aluminum shavings.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. The recycled aluminum of this invention can be made from commercially available Al-Mg-Si alloy aluminum scraps and other forms of alloys, without the need for excessive control over the recycled aluminum.

[0017] 2. No special equipment or raw materials are required; only the production method needs to be changed, making it highly adaptable.

[0018] 3. The addition of recycled aluminum ensures its continued use without affecting product performance. Attached Figure Description

[0019] Figure 1 Microstructure diagram of a cast rod made with 30% recycled aluminum; Figure 2 Microstructure diagram of casting rods made from pure aluminum molten metal. Detailed Implementation

[0020] To make the above features and advantages of the present invention more apparent and understandable, specific embodiments are described below in conjunction with the accompanying drawings for detailed explanation.

[0021] This embodiment provides a low-cost preparation process for recycled Al-Mg-Si alloys for automotive lightweighting, including the following steps: S1. Pre-treatment and component analysis of raw materials; S2. Recycled aluminum is smelted and refined using a dual-chamber furnace; S3, Smelting primary aluminum ingots; S4. Mix and homogenize the results obtained in steps S2 and S3; S5. Refine and let stand the product obtained in step S4. S6. Al-Ti-B filaments are added into the flow channel, and then filtered and degassed to obtain the finished product.

[0022] The specific steps of step S1 are as follows: pre-treat the raw materials (crush, magnetically separate, and dry the aluminum shavings, which can significantly reduce the introduction of gases and impurities during the smelting process and improve the quality of the final melt), perform small furnace composition testing, and preliminarily determine the amount of recycled aluminum alloy to be added.

[0023] Preferably, a recycled aluminum raw material database can be established in step S1. Systematic small-scale furnace testing is performed on different types of recycled aluminum (such as aluminum scrap from different sources, end-of-life automotive parts, etc.) to record their typical elemental content and impurity range. This helps to quickly and accurately predict the feed ratio, reducing the difficulty of subsequent adjustments.

[0024] The specific operation steps of step S2 are as follows: the recycled aluminum is smelted in a double-chamber furnace at a smelting temperature of 720℃-730℃. After the recycled aluminum is melted, it is stirred electromagnetically. After that, a refining agent is introduced into the furnace to refine the recycled aluminum in the furnace. After that, a sample is taken for composition testing.

[0025] The specific operation steps of step S3 are as follows: In another smelting furnace, the scrap and aluminum ingots are mixed and melted at a smelting temperature of 720℃-730℃. The melting amount is set according to the furnace feeding ratio based on the small furnace composition detection results. The smelting furnace is an inclined smelting furnace. The scrap is the head and tail of profile sawing (white material) or aluminum chips or other shredded waste.

[0026] The specific operation steps of step S4 are as follows: After the product is melted in the melting furnace, the recycled aluminum liquid in the double chamber furnace is transferred to the melting furnace for mixing, and the electromagnetic stirring is turned on.

[0027] Preferably, two hours before the end of the mixing time in step S4, samples are taken every 30 minutes for rapid composition analysis (adjustment during the mixing stage). If the composition is unqualified, fine-tuning can be performed (e.g., adding an intermediate alloy, such as Mg alloying element) to achieve closed-loop control. The specific steps are as follows: Within 2 minutes after the electromagnetic stirring stops, samples are taken from three different depths (top, middle, and bottom) of the melting furnace (specific sampling points are set on the melting furnace), and the samples are poured into a preheated metal mold to make a sample block for spectral analysis. This process should be rapid to prevent excessive oxidation of the melt surface and compositional segregation.

[0028] The prepared sample blocks are immediately sent to a direct-reading spectrometer located next to the furnace for analysis. The spectrometer provides precise content data of major alloying elements (such as Mg, Si, Fe, Cu, Mn, Cr, etc.) and impurity elements in the melt within one minute. The key is to ensure the calibration and stability of the analytical equipment to guarantee the reliability of the data.

[0029] The spectral analysis results are compared with the internal control standards of the target alloy grade. The system automatically calculates the amount of alloying element that needs to be added. The formula for calculating the amount to be added is as follows: Required intermediate alloy weight (kg) = [(target composition % - analyzed composition %) × total melt weight (kg)] / effective content of the element in the intermediate alloy.

[0030] Another detection method is small furnace detection, which is the method used in this embodiment.

[0031] If multiple elements (such as Mg and Si) need to be adjusted simultaneously, it is necessary to consider whether the added master alloy will introduce other non-target elements, and to prioritize the addition scheme with the least impact on the final composition. The calculated master alloy (such as AlMg50, AlSi20, etc.) should be broken into uniformly sized blocks (e.g., 50-100mm). Add the alloy using a wire feeder or rotary jet method, and continue electromagnetic stirring until stirring is complete.

[0032] The specific operation steps of step S5 are as follows: First, the composition of the product obtained in step S4 is verified. After the verification is qualified, it is refined in the furnace and then left to stand.

[0033] The specific steps of step S6 are as follows: the material obtained in step S5 passes through a flow channel, Al-Ti-B wire is added to the flow channel, and filtration and degassing are carried out at the same time. Finally, an alloy casting rod is obtained through a semi-continuous casting process.

[0034] In steps S5 and S6, the refining temperature is 720-730℃, and the refining agent dosage is 2.0-2.5% of the total feed. The refining time is 20±2 minutes for dual-tube refining. The refining method involves slowly and evenly moving the refining tube into the lower part of the molten aluminum, ensuring the bubbles are small, uniform, and dense, without boiling or splashing. Microstructure after adding different recycled aluminum is observed. Slag removal is then performed at a temperature of 720-730℃. The requirement is to remove the slag from the surface of the melt, holding it at the furnace door and furnace edge for 6-10 seconds until no obvious slag remains in any part of the furnace. Composition analysis is then performed. After passing the analysis, the mixture is allowed to stand for 30 minutes before casting begins. During casting, the wire feeder speed is calculated based on the Ti content in the alloy composition, and the wire is added online. Subsequently, online degassing is performed in an argon degassing box at a rotor speed of 300-800 Rpm and an argon flow rate of 10-25 L / min. Then, online hydrogen measurement and data recording were performed, and casting began after two-stage filtration. The filter plate sizes were 40+50 PPI.

[0035] The finished product stage composition analysis steps in steps S5 and S6 are as follows: Small furnace detection - specific case of main furnace batching compensation (the batching compensation and compensation logic corresponding to different Si / Mg / Fe / Cu / Zn contents) Mechanical properties under different recycled aluminum addition ratios (20%, 40%, 60%): yield strength, tensile strength, elongation comparison data with 100% aluminum ingot route, impurity hydrogen content control data.

[0036] The burn-off rate in the small furnace is higher than that in the double-chamber furnace. The burn-off rate is in the order of Mg > Zn > Si > Cu > Mn > Cr > Ti. Since Mg will cause burn-off, Si, Fe, and Mn, which have lower burn-off rates and greater impact on the finished product during regeneration, are selected as the calculation values. The compensation logic for the small furnace is as follows: the Si and Fe compositions in the small furnace are measured (which do not change significantly during smelting), the amount of recycled aluminum to be added and the amount of aluminum ingots melted are calculated, and smelting begins simultaneously. After mixing, the composition is measured again, and Mg is added according to the composition. Example of a method for calculating the amount of aluminum added to the large furnace after smelting in a small furnace: After smelting recycled aluminum in a small furnace, the alloy composition is tested as follows: Si: 0.75, Fe: 0.55, Mn: 0.55; the composition of the cast rod to be produced is: Si: 0.5-0.6, Fe: 0.2, Mn: 0.1; 99.7% pure aluminum contains: Si: 0.1, Fe: 0.1, and no Mn. According to the formula (weight of recycled aluminum * alloy element content of recycled aluminum + weight of aluminum ingot * alloy element content of aluminum ingot (weight of recycled aluminum + weight of aluminum ingot) * target content), we can obtain: 0.55 / 0.1 - 1 - 4.5, which means that Mn should be diluted to the target composition at least 1:4.5 between recycled aluminum and aluminum ingot. Similarly, Fe should be diluted to the target composition at least 1:3 between recycled aluminum and aluminum ingot. Si should be diluted to the target composition at least 4:9 between recycled aluminum and aluminum ingot. In conclusion, it can be determined that the amount of recycled aluminum added to this furnace should not exceed 25%.

[0037] Table 1: Performance Comparison of Recycled Aluminum and Primary Aluminum After Soaking in Water

[0038] Table 2: Mechanical Properties of Different Products After Extrusion

[0039] like Figure 1 and Figure 2 As shown in the figure, the microstructure of the cast rod produced by this method reveals that the iron-rich phase at the grain boundaries of the alloy exhibits needle-like and more numerous characteristics after the addition of recycled aluminum. Tables 1 and 2 show that although the performance of the cast rod is not significantly different after adding recycled aluminum, and the product performance after extrusion is quite similar, the performance is slightly worse after adding recycled aluminum, but still far exceeds the product performance requirements, enabling the use of wrought aluminum alloys for automotive applications while maintaining their grade.

[0040] The foregoing has shown and described the basic principles and main features of the present invention, as well as its advantages. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the present invention. Various changes and modifications can be made to the present invention without departing from its spirit and scope. All such changes and modifications fall within the scope of the present invention as claimed, which is defined by the appended claims and their equivalents.

Claims

1. A low-cost preparation process for recycled Al-Mg-Si alloys for automotive lightweighting, characterized in that: S1. Pre-treatment and component analysis of raw materials; S2. Recycled aluminum is smelted and refined using a dual-chamber furnace; S3, Smelting primary aluminum ingots; S4. Mix and homogenize the results obtained in steps S2 and S3; S5. Refine and let stand the product obtained in step S4. S6. Al-Ti-B filaments are added into the flow channel, and then filtered and degassed to obtain the finished product.

2. The low-cost preparation process of recycled Al-Mg-Si alloy for automotive lightweighting according to claim 1, characterized in that: The specific operation steps of step S1 are as follows: perform small-scale furnace composition testing on the raw materials to preliminarily determine the amount of recycled aluminum alloy to be added.

3. The low-cost preparation process of recycled Al-Mg-Si alloy for automotive lightweighting according to claim 1, characterized in that: The specific operation steps of step S2 are as follows: the recycled aluminum is smelted in a double-chamber furnace. After the recycled aluminum is melted, it is stirred electromagnetically. After that, a refining agent is introduced into the furnace to refine the recycled aluminum in the furnace. After that, a sample is taken for composition testing.

4. The low-cost preparation process of recycled Al-Mg-Si alloy for automotive lightweighting according to claim 1, characterized in that: The specific operation steps of step S3 are as follows: In another smelting furnace, the scrap and aluminum ingots are mixed and melted, and the melting amount is set according to the composition detection results of the small furnace to determine the furnace feeding ratio.

5. The low-cost preparation process of recycled Al-Mg-Si alloy for automotive lightweighting according to claim 4, characterized in that: The melting furnace is a tiltable melting furnace.

6. A low-cost preparation process for recycled Al-Mg-Si alloys for automotive lightweighting according to claim 4 or 5, characterized in that: The specific operation steps of step S4 are as follows: after the melting furnace is completed, the recycled aluminum water in the double chamber furnace is transferred to the melting furnace for mixing, and the electromagnetic stirring is turned on.

7. The low-cost preparation process of recycled Al-Mg-Si alloy for automotive lightweighting according to claim 1, characterized in that: The specific operation steps of step S5 are as follows: the composition of the product obtained in step S4 is first verified, and after the verification is qualified, it is refined in the furnace and then left to stand.

8. The low-cost preparation process of recycled Al-Mg-Si alloy for automotive lightweighting according to claim 1, characterized in that: The specific steps of step S6 are as follows: the material obtained in step S5 passes through a flow channel, Al-Ti-B wire is added to the flow channel, and degassing and filtration are carried out simultaneously. Finally, an alloy casting rod is obtained through a casting process.

9. The low-cost preparation process of recycled Al-Mg-Si alloy for automotive lightweighting according to claim 1, characterized in that: The waste material mentioned in step S3 is the head and tail of profile sawing or aluminum shavings.

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