Method for preparing heat-treatment-free high-toughness die-casting regenerated aluminum alloy from waste aluminum

Abstract

The invention relates to a method for preparing a heat-treatment-free high-toughness die-casting regenerated aluminum alloy from waste aluminum. According to the method, recycled waste 6061 aluminum is used as a main raw material, and alloys such as Al-Si, Al-Mg, Al-Cu and Al-Sr are added, so that the method is suitable for the die-casting process. According to the method, a new efficient recycling channel is provided for the 6061 aluminum alloy which is widely applied, the cost of raw materials of the die castings can be effectively reduced, energy conservation and carbon emission reduction are focused, economical efficiency and high quality are both considered, and the competitiveness of products is powerfully improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of metal materials, in particular to a heat treatment-free high-strength and high-toughness die-casting recycled aluminum alloy prepared from waste 6061 aluminum alloy and a preparation method thereof. BACKGROUND

[0002] The recycled aluminum produced from recycled waste aluminum as the main raw material through pretreatment and secondary melting and refining meets the urgent needs of the national "double carbon" goal and the development of resource recycling economy. The energy consumption of recycled aluminum is only 3.5% to 5.5% of that of primary aluminum, and the carbon emission is only 2.1% of that of electrolytic aluminum production. Therefore, vigorously developing the recycled aluminum industry not only can reduce the dependence on mineral resources, but also has the advantages of significant energy saving, emission reduction and environmental protection. The widespread use of recycled aluminum will further reduce the production cost of aluminum alloy components and improve the social and economic benefits of enterprises.

[0003] 6061 aluminum alloy is a common commercial aluminum alloy grade, which has medium strength, good corrosion resistance, weldability and processing performance. It is widely used in industrial and military fields, such as manufacturing aircraft parts, automobile parts, building structural parts, bicycle frames, etc. However, a large amount of 6061 aluminum alloy material faces the difficult problem of recycling and reuse after being discarded. Patent CN118162436A discloses a 6061 aluminum alloy chip solid-state recycling extruded material and a preparation method: fine 6061 aluminum chips are cleaned, dried and cold-pressed into a blank, and then the blank is heated and extruded by an extruder to obtain an extruded profile. This method uses fine chips as raw materials, which has high requirements for the shape and specifications of waste aluminum and cannot realize efficient recycling and reuse of large pieces of waste 6061 aluminum.

[0004] Die casting is a kind of metal casting process, which has the advantages of high production efficiency, controllable precision and complex shape of castings, and high material utilization rate, and has realized fully automated production. At present, the automobile industry is one of the main application fields of die casting products. Die castings can not only reduce the total weight of the automobile, but also improve the fuel and motor efficiency, thereby improving the overall performance of the automobile. Generally, commercial high-strength and high-toughness die-casting aluminum alloys use primary aluminum as the main raw material, which has high cost. The use of recycled aluminum will greatly reduce the cost of raw materials, which also provides a new channel for efficient recycling of 6061 aluminum alloy. Patent CN120464889A discloses a heat treatment-free die-casting aluminum alloy based on recycled aluminum and a preparation method thereof: according to the measured composition of recycled aluminum, the required alloying elements are calculated and added to make the final composition of the alloy reach the preset proportion. This method does not have specific requirements for recycled aluminum raw materials, and the composition design is general. For example, it designs up to 8 alloying elements in order to solve the problem of excessive Fe content in recycled aluminum raw materials. However, the Fe content in 6061 aluminum meets the requirements of die casting and does not need to be removed. Using this method will inevitably cause waste and cost increase, and even damage the mechanical properties of the final die-casting alloy product.

[0005] In order to efficiently recycle and utilize waste 6061 aluminum alloy and reduce the cost of die castings under the premise of ensuring high performance, a new method for preparing high strength and toughness die cast recycled aluminum alloy by optimizing the composition of recycled 6061 aluminum alloy as raw material is urgently needed. SUMMARY

[0006] Under the above prior art background, the present application provides a method for preparing heat treatment-free high strength and toughness die cast recycled aluminum alloy from waste 6061 aluminum. The method uses recycled waste 6061 aluminum as the main raw material, and adds Si, Mg, Cu and Sr components to make it suitable for die casting process. The present application not only provides a new channel for efficient recycling and utilization of widely used 6061 aluminum alloy, but also effectively reduces the cost of die casting raw materials, focuses on energy saving and carbon emission reduction, and takes into account economy and high quality, thereby effectively improving the competitiveness of products.

[0007] The technical scheme of the present application is as follows:

[0008] A method for preparing heat treatment-free high strength and toughness die cast recycled aluminum alloy from waste aluminum, comprising the following steps:

[0009] (1) cleaning, polishing and then cutting and crushing the waste aluminum alloy into blocks;

[0010] Among them, the waste aluminum alloy is waste 6061 aluminum alloy;

[0011] (2) preheating and drying the waste aluminum alloy treated in step (1) and the added alloy to obtain a to-be-melted alloy;

[0012] Among them, the added alloy is Al-Si, Al-Mg, Al-Cu and Al-Sr alloy;

[0013] The mass of the waste aluminum alloy is 50% to 70% of the mass of the to-be-melted alloy;

[0014] In the to-be-melted alloy, the percentage of each element component in the mass of the to-be-melted alloy includes: Si 9.0-11.0%, Mg 0.5-1.5%, Cu 0.5-1.5%, Sr 0.05-0.2%, Fe<1.0%;

[0015] In the Al-Si alloy, the content of Si element is 20-35wt.%;

[0016] In the Al-Mg alloy, the content of Mg element is 5-30wt.%;

[0017] In the Al-Cu alloy, the content of Cu element is 5-40wt.%;

[0018] In the Al-Sr alloy, the content of Sr element is 5-30wt.%;

[0019] (3) Melting: Put the raw material treated in step (2) into a crucible, heat and melt, and keep warm, after complete melting, add a refining agent for refining and slagging, and then cast into an ingot.

[0020] The final requirement of the cleaning in step (1) is that the surface is free of visible impurities. The waste 6061 aluminum alloy scrap of different shapes is cut into a suitable size that can be easily put into the corresponding melting furnace.

[0021] To further improve the recycling rate of waste 6061 aluminum alloy, the inherent element content of 6061 aluminum alloy is fully considered when calculating the alloy ratio and alloy amount in step (2).

[0022] The preheating temperature in step (2) is 180-200℃ to remove residual water vapor.

[0023] The holding temperature in step (3) is 700-800℃.

[0024] The refining agent in step (3) is magnesium chloride or calcium chloride, and the amount of refining agent added is 0.2-0.5% of the weight of the melt.

[0025] The casting into an ingot in step (3) can be prepared by various methods such as gravity casting and semi-continuous casting, but is not limited thereto.

[0026] The substantial features of the present application are:

[0027] The inventors found through extensive research that the Si content in die-cast aluminum-silicon alloy has a significant effect on the casting performance, strength, and plasticity of the alloy. When the Si content is 12.6wt.%, eutectic reaction occurs at 577℃, at which point the flowability of the aluminum alloy is best. The waste 6061 alloy scrap is used as the main raw material in the present application, but its Si content is only 0.4-0.8wt.%, so the first priority of the present application is to increase the Si content; the Al-Si intermediate alloy directly affects the recycling rate of waste 6061 aluminum alloy in the heat-free high-strength and tough die-cast recycled aluminum alloy material, the more Si content in the Al-Si intermediate alloy, the higher the recycling rate of waste 6061 aluminum alloy. However, too much Si content will greatly increase the melting point of the Al-Si alloy, increase the melting cost, and reduce the service life of the melting equipment.

[0028] Further, the inventors have found that increasing the Si content alone cannot meet the high strength and toughness performance requirements of the alloy, and the 6061 aluminum alloy contains a plurality of other beneficial elements in addition to Si, but after adding the Al-Si intermediate alloy, the total amount of elements is greatly diluted and cannot guarantee high performance. Based on this, the present application additionally adds Mg and Cu elements to increase the strength of the alloy, but at the expense of part of the plasticity of the alloy. To solve the problem of plasticity reduction, the present application introduces Sr element, which has a modification and refinement effect on the eutectic phase in the alloy, solving the problem of strength-plasticity inversion under the condition of die casting. In summary, the present application obtains a high-strength and high-toughness die-casting recycled aluminum alloy material with high recycling rate under the premise of ensuring excellent casting performance and heat treatment-free.

[0029] The present application has the following beneficial effects:

[0030] 1. The heat-free high-strength and high-toughness die-casting recycled aluminum alloy prepared from waste 6061 aluminum alloy recycling materials has important industrial application value. The typical technical indicators of the die-casting recycled aluminum alloy are as follows: good die-casting performance can be achieved, the yield strength is 120-200 MPa, the tensile strength is 270-310 MPa, and the elongation is 4-7%, which can meet the application requirements of high-performance die-casting parts in the automobile industry.

[0031] 2. The present application uses recycled 6061 aluminum alloy waste as the main raw material, and the utilization rate of waste aluminum reaches 50-70 wt.%. The data in 2025 shows that the price of raw Al is about 20700 yuan / ton, and the price of waste 6061 aluminum is about 17000 yuan / ton. The present application can significantly reduce the cost of die-casting recycled aluminum alloy, providing a new and effective way for recycling and reusing waste 6061 aluminum alloy, and having the advantages of saving production resources and reducing carbon emissions. It can effectively increase the enterprise profit and increase the product competitiveness. DETAILED DESCRIPTION

[0032] The present application provides a heat treatment-free high-strength and high-toughness die-casting recycled aluminum alloy prepared from waste 6061 aluminum, wherein the main raw material of the die-casting recycled aluminum alloy is recycled waste 6061 aluminum alloy, and the mass percentage of each component of the alloy elements is Si 9.0-11.0%, Mg 0.5-1.5%, Cu 0.5-1.5%, Sr 0.05-0.2%, Fe<1.0%; the balance is Al and other elements inherent to 6061 aluminum alloy and unavoidable impurities.

[0033] The high-strength and high-toughness die-casting recycled aluminum alloy material contains 50-70% of recycled waste aluminum. The proportion interval can be any value from 50 wt.% to 70 wt.%, but is not limited to the specific values listed in the examples. Other values not listed in the value range are also applicable.

[0034] Al-Si intermediate alloy is a main additive alloy, directly affecting the recycling rate of the waste 6061 aluminum alloy in the heat-free high-strength and high-toughness die-casting recycled aluminum alloy material. The more the Si content in the Al-Si intermediate alloy, the higher the recycling rate of the waste 6061 aluminum alloy. However, too much Si content will greatly increase the melting point of the Al-Si alloy, increase the smelting cost, and reduce the service life of the smelting equipment. After comprehensive consideration, the Si element content in the Al-Si intermediate alloy used in the present application is 20-35wt.%, for example, it can be 20wt.%, 25wt.%, 30wt.% or 35wt.%, but is not limited to the above listed values, and the values not listed in the range are also applicable.

[0035] Because the addition amount of other alloy elements is small, the influence of the related intermediate alloy on the utilization rate of the waste 6061 alloy is low, so appropriate Al-Si, Al-Mg, Al-Cu, Al-Sr intermediate alloys and their addition ratios need to be selected according to the melting point and cost.

[0036] The present application is further described below in conjunction with specific embodiments.

[0037] The 6061 aluminum alloy involved in the present application is a known material, and the mass percentage of the main elements is: Si 0.4-0.8%, Fe≤0.7%, Cu 0.15-0.4%, Mn 0.15%, Mg 0.8-1.2%, Cr 0.04-0.35%, Zn 0.25%, Ti 0.15%, and the rest is Al.

[0038] Example 1

[0039] A method for preparing a heat-free high-strength and high-toughness die-casting recycled aluminum alloy using waste 6061 aluminum alloy recycling material, comprising the following steps:

[0040] (1) cleaning and crushing: using recycled waste 6061 aluminum alloy building templates as raw materials, using a high-pressure water gun to wash the surface stains, polishing the surface residual cement mortar and paint surface, cutting the cleaned 6061 aluminum alloy templates to about 5cm x 5cm in size, and drying at 150℃ for 1h;

[0041] (2) Drying ingredients: The waste 6061 aluminum alloy scrap and Al-25Si, Al-20Mg, Al-30Cu, Al-20Sr master alloys treated in step (1) were cut into blocks of about 1-5 cm according to the designed composition and weighed to form the alloy to be melted. The designed composition of each element in the alloy to be melted was Si 9.5%, Mg 1.1%, Cu 0.7%, Sr 0.1%, and the rest was Al and other elements inherent to the 6061 alloy. The total amount of the alloy was 600 g (including 6061 aluminum 353.6 g, Al-25Si alloy 214.1 g, Al-20Mg alloy 17.6 g, Al-30Cu alloy 11.6 g, and Al-20Sr alloy 3 g). The mass of the waste 6061 aluminum alloy was 58.9% of the mass of the alloy to be melted. Then, the materials were dried at 200°C for 1 h.

[0042] (3) Melting: The raw materials treated in step (2) were placed in a crucible and melted in an atmosphere protection melting furnace at 750°C for 2 h. After the alloy was completely melted, 2 g of magnesium chloride refining agent was added, and the components were fully mixed using an electric mechanical stirrer for 5 min. After standing in the furnace for 5 min, the slag was removed, and then gravity casting was used to cast ingots.

[0043] The ingots obtained in step (3) were sampled, and the actual composition was measured by spectroscopy (national standard GBT7999-2007) to be Si: 9.6 wt.%, Mg: 1.0 wt.%, Cu: 0.6 wt.%, Sr: 0.1 wt.%, Al: 88.2 wt.%, and the rest was impurity elements.

[0044] (4) Die casting experiment: The recycled aluminum ingots prepared in step (3) were melted in a muffle furnace, and the temperature of the aluminum liquid was 750°C. The die casting equipment was set to a shooting speed of 5 m / s, a mold temperature of 200°C, and a shooting pressure of 30 MPa. The aluminum liquid was immediately die cast after being transferred into the feeding port of the die casting equipment, and a group of die cast tensile bars were obtained.

[0045] After the flash of the die cast tensile sample prepared in step (4) was removed, room temperature tensile test was carried out according to GB / T 228.1-2021 national standard. The test instrument was UTM5105G type electronic universal testing machine, and the tensile rate was 1 mm / min. The average yield strength of the die cast sample was 180±8 MPa, the average ultimate tensile strength was 302±5 MPa, and the elongation was 5.6±1.3%.

[0046] The yield strength of the following example 1 was 180±8 MPa, the average ultimate tensile strength was 302±5 MPa, and the elongation was 5.6±2%. The comprehensive performance of the recycled aluminum alloy was better than that of the current commercial high-strength and high-toughness die cast aluminum for vehicles. The comparison data are shown in Table 1.

[0047] Table 1 Comparison of mechanical properties of the present application and typical commercial die-casting aluminum alloys

[0048] Typical Grade YS / MPa UTS / MPa El. / ％ Example 1 172～188 297～307 4.3～6.9 ADC12 127～157 216～214 3～6 A380 160 320 2.5 YL113 170 230 1

[0049] Example 2

[0050] Other steps are the same as Example 1, except that the designed composition (percentage of each element in the mass of the alloy to be melted) in Example 1 is replaced by: Si 10.0%, Mg 1.0%, Cu 1.0%, Sr 0.1%, and the rest is Al and other elements inherent to 6061 alloy; the actual composition is measured as Si: 10.2wt.%, Mg: 0.9wt.%, Cu: 1.0wt.%, Sr: 0.1wt.%, Al: 87.2wt.%, and the rest is impurity elements.

[0051] The obtained material has a yield strength of 175±6 MPa, an average ultimate tensile strength of 298±6 MPa, and an elongation of 4.9±0.9%.

[0052] Example 3

[0053] Other steps are the same as Example 1, except that the designed composition (percentage of each element in the mass of the alloy to be melted) in Example 1 is replaced by: Si 9.0%, Mg 0.8%, Cu 1.0%, Sr 0.1%, and the rest is Al and other elements inherent to 6061 alloy; the actual composition is measured as Si: 9.1wt.%, Mg: 0.8wt.%, Cu: 1.1wt.%, Sr: 0.1wt.%, Al: 88.3wt.%, and the rest is impurity elements.

[0054] The obtained material has a yield strength of 171±7 MPa, an average ultimate tensile strength of 291±4 MPa, and an elongation of 5.4±1.2%.

[0055] Comparative Example 1

[0056] Other steps are the same as Example 1, except that the designed composition (percentage of each element in the mass of the alloy to be melted) in Example 1 is replaced by: Si 13.0%, Mg 1.0%, Cu 1.0%, Sr 0.1%, and the rest is Al and other elements inherent to 6061 alloy; the actual composition is measured as Si: 13.2wt.%, Mg: 1.1wt.%, Cu: 0.9wt.%, Sr: 0.1wt.%, Al: 84.1wt.%, and the rest is impurity elements.

[0057] The obtained material has a yield strength of 142±6 MPa, an average ultimate tensile strength of 261±4 MPa, and an elongation of 2.0±0.2%. The excessive content of Si leads to an increase in brittle eutectic phase, which deteriorates the mechanical properties of the alloy.

[0058] Comparative Example 2

[0059] Other steps are the same as Example 1, except that the design components (the percentage of each element in the mass of the alloy to be melted) in Example 1 are replaced by: Si 9.5%, Mg 3.0%, Cu 0.5%, Sr 0.1%, and the rest is Al and other elements inherent in 6061 alloy; the actual components measured are Si: 9.4wt.%, Mg: 3.2wt.%, Cu: 0.7wt.%, Sr: 0.1wt.%, Al: 85.9wt.%, and the rest is impurity elements.

[0060] Excessive Mg content leads to serious inclusions and shrinkage holes in the sample, and the mechanical properties cannot be tested.

[0061] The above-described examples are only preferred embodiments of the present application, and are only used to explain the present application, and are not intended to limit the scope of the present application. For those skilled in the art, other embodiments can be easily made by substitution or change based on the technical content disclosed in the present specification, and therefore, any changes and improvements made within the principles and process conditions of the present application should be included in the scope of the present application.

[0062] The remaining matters of the present application are known technologies.

Claims

1. A method for preparing heat-free, high-strength, high-toughness, die-cast recycled aluminum alloys from waste aluminum, characterized in that: The method includes the following steps: (1) Clean and polish the waste aluminum alloy in sequence, and then cut and crush it into blocks; Among them, the scrap aluminum alloy is scrap 6061 aluminum alloy; (2) The waste aluminum alloy and added alloy processed in step (1) are preheated and dried to obtain the alloy to be smelted; Among them, the added alloys are Al-Si, Al-Mg, Al-Cu and Al-Sr alloys; The weight of scrap aluminum alloy should be 50% to 70% of the weight of the alloy to be smelted; In the alloy to be melted, the percentage of each element component by mass of the alloy to be melted includes: Si 9.0-11.0%, Mg 0.5-1.5%, Cu 0.5-1.5%, Sr 0.05-0.2%, Fe <1.0%; (3) Smelting: The raw materials processed in step (2) are placed in a crucible, heated and melted and kept warm. After complete melting, a refining agent is added for refining and slag removal, and then cast into ingots.

2. The method for preparing heat-free, high-strength, and tough die-cast recycled aluminum alloys from waste aluminum as described in claim 1, characterized in that: In step (2), the Si content in the Al-Si alloy is 20-35 wt.%. In the Al-Mg alloy, the Mg content is 5-30 wt.%. In the Al-Cu alloy, the Cu content is 5-40 wt.%. In the Al-Sr alloy, the Sr element content is 5-30 wt.%.

3. The method for preparing heat-free, high-strength, and tough die-cast recycled aluminum alloys from waste aluminum as described in claim 1, characterized in that: The preheating temperature in step (2) is 180-200℃.

4. The method for preparing heat-free, high-strength, and tough die-cast recycled aluminum alloys from waste aluminum as described in claim 1, characterized in that: The insulation temperature in step (3) is 700-800℃.

5. The method for preparing heat-free, high-strength, and tough die-cast recycled aluminum alloys from waste aluminum as described in claim 1, characterized in that: Step (3) The refining agent is magnesium chloride or calcium chloride, and the amount of refining agent added is 0.2-0.5% of the melt weight.