High-ratio recycled aluminum 6-series aluminum alloy and preparation method thereof

Abstract

The application provides a high-proportion recycled aluminum 6-series aluminum alloy and a preparation method thereof, and relates to the technical field of recycled aluminum alloy manufacturing. The alloy comprises the following components in a mass percentage: Mg: 0.6-1.0%; Si: 0.5-0.9%; Cu: 0.15-0.3%; Mn: 0.2-0.66%; Fe: 0.15-0.3%; Cr: 0.1-0.3%; Zn: ≤0.2%; Ti: ≤0.1%; other inevitable impurity elements, single: ≤0.05%, total: ≤0.15%; and the rest is Al; wherein, 1.3≤Mn / Fe≤2.2; 0.8≤Cr / Fe≤1; and 1≤Mg / Si≤1.56. The application improves the tolerance of impurity element Fe in the aluminum matrix, realizes the recycled aluminum addition amount ≥70% or even 100% without iron removal treatment, guarantees the mechanical properties, the bending angle is ≥90°, and the application meets the use requirements of new energy automobile battery box trays, seat structures and the like.

Description

Technical Field

[0001] This invention relates to the field of recycled aluminum alloy manufacturing technology, and in particular to a high-proportion recycled aluminum 6-series aluminum alloy and its preparation method. Background Technology

[0002] Aluminum alloys possess excellent extrusion forming properties and medium-to-high strength, making them widely used in battery box trays, seats, and body structural components of new energy vehicles. They are key structural materials for lightweighting new energy vehicles. Traditional primary aluminum production involves complex processes such as mining, grinding, chemical reaction, electrolysis, smelting, and casting, resulting in high energy consumption and carbon emissions. The electrolysis process alone consumes a huge amount of electricity; in my country, primary aluminum production accounts for more than 6% of the country's total electricity consumption, with approximately 20 tons of carbon emissions per ton of primary aluminum. Furthermore, the production process is accompanied by the emission of pollutants such as fluorides and red mud, significantly impacting the environment. Recycled aluminum can be produced through only smelting and casting, resulting in a shorter process flow, lower energy consumption, and carbon emissions far lower than primary aluminum. The emissions of harmful gases and red mud are almost zero. Moreover, recycled aluminum itself is rich in alloying elements such as Si, Mg, Cu, and Cr, eliminating the need for expensive intermediate alloys and lower raw material costs. It possesses significant advantages in energy saving, environmental protection, and economy, and has broad application prospects in the new energy vehicle field.

[0003] However, the sources of recycled aluminum are complex, and after multiple cycles, the impurity element Fe easily accumulates in the matrix. Conventional primary aluminum contains approximately 0.15 wt.%, while ordinary recycled aluminum easily exceeds 0.18 wt.%, and low-grade recycled materials can even reach over 0.3 wt.%. Excessive Fe forms coarse and brittle phases, severely reducing the mechanical properties and plasticity of aluminum alloys, becoming a key issue restricting the high-proportion application of recycled aluminum. Existing iron removal technologies are costly and complex, making industrial-scale promotion difficult. Therefore, without adopting high-cost iron removal processes, improving the tolerance of aluminum alloys to Fe impurities and controlling the distribution morphology of Fe to avoid performance deterioration are the core technical challenges for achieving high-proportion recycling of recycled aluminum.

[0004] Currently, many OEMs have simple performance requirements for 6-series aluminum alloy battery box trays, only basic mechanical requirements, with little or no requirement for bending angles, ≥60° is sufficient. However, with the increasing frequency of fires involving new energy vehicles, safety requirements are becoming increasingly stringent, especially regarding high bending performance. High bending angle performance means stronger fracture resistance, greater energy absorption in a collision, ensuring the integrity of the battery pack, and preventing breakage and puncture, thereby improving the safety factor of new energy vehicles. However, Fe in recycled aluminum significantly affects the bending performance of the material, preventing its high-proportion use in new energy vehicles. Therefore, how to control the phase distribution of Fe to improve the bending performance of recycled aluminum is a problem that urgently needs to be solved in existing technologies. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention proposes a high-proportion recycled aluminum 6-series aluminum alloy and its preparation method. It utilizes high-proportion recycled aluminum 6-series cast ingots and, through compositional design and homogenization process optimization, mitigates the influence of the Fe content, an impurity element, in the high-proportion recycled aluminum 6-series cast ingots. This results in a 6005A aluminum alloy with high tolerance for Fe impurities in the aluminum matrix and a high recycled aluminum content. Without iron removal treatment, it achieves a recycled aluminum content of ≥70%, or even 100%, while maintaining comparable mechanical properties, with a bending angle ≥90°, meeting the requirements for structural components such as battery box trays and seats in new energy vehicles.

[0006] The core principle of this invention is:

[0007] Iron (Fe) is the most common and unavoidable impurity element in recycled aluminum. It easily forms β-Al5FeSi needle-like / plate-like hard and brittle phases in the aluminum matrix. These phases easily become stress concentration sources during deformation. During crack propagation, these brittle iron phases either fracture on their own or detach from the matrix, providing pathways for cracks. The spatial network distribution of the iron phases can also cause microcracks to connect, accelerating material failure. This invention utilizes the synergistic effect of alloying elements such as Mn, Cr, and Si to allow Fe to exist as AlFeMnSi and AlFeMnCrSi phases. Combined with subsequent heat treatment processes, this further promotes phase transformation, making the Fe phase blocky or spherical, thereby reducing the impact of Fe on the matrix properties and improving the compatibility of recycled aluminum with different Fe contents.

[0008] This invention also includes the following elemental composition and preparation method control mechanism:

[0009] 1. The regulation mechanism of Mn on the Fe phase.

[0010] In 6005A recycled aluminum alloy, Fe impurities readily form a hard and brittle β-Al9Fe2Si2 phase. This phase is needle-like or elongated, severely disrupting the matrix and reducing plasticity and extrusion properties. By appropriately adding / adjusting the amount of Mn, β-Al9Fe2Si2 can be transformed into blocky, Chinese character-shaped, or short rod-like forms. The phase changes the crystal structure of the Fe phase in the matrix, thereby altering the morphological distribution of the Fe phase, eliminating sharp corners, reducing the impact of stress concentration on the matrix, and thus passivating the harmful effects of Fe impurities on the matrix, inhibiting their continuous precipitation along grain boundaries, and increasing the alloy's tolerance limit for Fe.

[0011] according to From the elemental ratio of the phases, we know that Mn / Fe≈1. Under the condition that the Fe content is set at 0.15%-0.3% in this invention, theoretically, it will... Phase completely transformed The required Mn content is 0.15-0.3%, but in reality, not all Mn in the matrix is ​​used for the transformation of the Fe phase. Typically, 0.1% to 0.3% of Mn remains undissolved in the matrix. Therefore, this patent sets the Mn content at 0.25-0.6%, i.e., 1.5 ≤ Mn / Fe ≤ 2, as the optimal ratio, with a preferred range of 1.3 ≤ Mn / Fe ≤ 2.2. Further combining experimental data and practical experience, this patent sets the Mn content range to satisfy 0.20% to 0.66%, and 1.5 ≤ Mn / Fe ≤ 2.5.

[0012] 2. The effect of Cr on the Fe phase and its content.

[0013] In an aluminum matrix, Cr does not neutralize Fe alone, but rather works with Mn to alter the crystal structure of the Fe phase. Because Cr and Fe have similar atomic radii, Cr preferentially enters the Fe phase lattice, replacing Fe atoms and further promoting… Phase transformation into fine, diffuse, and harmless ， Complete Restructuring The phase crystal structure cannot be restored to its needle-like morphology. Furthermore, Cr reduces the formation... Thermodynamic free energy will preferentially be given to Phase precipitation, an irreversible process, facilitates subsequent heat treatment transformation. Towards The transformation provides a thermodynamic basis.

[0014] According to the formation It can be seen that Cr / Fe≈0.9, theoretically forming the most stable phase structure, with an optimal range of 0.8≤Cr / Fe≤1. Based on the Fe content of recycled aluminum in this paper being in the range of 0.15%~0.3%, the Cr content is 0.135%~0.27%. Since the solid solubility of Cr in the aluminum matrix is ​​extremely low at room temperature, almost zero, the optimal range for Cr content is 0.1%~0.3%. In summary, the Cr content range of this patent is 0.1%~0.3% and 0.8≤Cr / Fe≤1.

[0015] 3. Mg and Si alloys and their optimization.

[0016] In 6-series alloys, Si mainly forms in the aluminum matrix. The strengthening phase exists in the form of a solid solution, and its precipitation order is solid solution → GP zone → β'' ( ) → β' ( ) → β( The Mg / Si ratios were 0.72, 1.56, and 1.73, respectively. Table 1 shows the main strengthening phases formed at different Mg / Si ratios.

[0017] Table 1:

[0018]

[0019] Among them, the strengthening phase β'' ( ) has the strongest strengthening effect on strength, β' ( Next, β( ) is the weakest, therefore avoid β ( The formation of β'' is optimal when the Mg / Si content is between 0.72 and 1.56. However, since strength and toughness are inversely proportional, higher strength results in lower toughness, meaning poorer bending performance. Therefore, theoretically, the optimal β'' ( Under the strengthening phase, the toughness is relatively poor, and the bending performance is difficult to reach above 90°; in order to match the best performance, this range should be avoided.

[0020] The experiments of this invention show that when the Mg / Si ratio is 0.73, 1.19, and 1.30, the measured bending angles are 85.2°, 98.8°, and 102.1°, respectively. Therefore, it can be concluded that when the Mg / Si ratio is close to 0.72, the Mg / Si phase forms the dominant strengthening phase. This is most detrimental to bending performance; when Mg / Si is close to 1.2 or 1.3, the main strengthening phase formed is... This is beneficial to the toughness of the material and most beneficial to its bending performance; to achieve the best bending performance, Mg / Si ≥ 1.2 is set, preferably greater than Mg / Si ≥ 1.

[0021] In summary, to match the strength and bending performance of the material, we set 1≤Mg / Si≤1.56.

[0022] 4. The role of Cu and its selection range.

[0023] Because this patent uses a high proportion of recycled aluminum, the alloying element Cu is inevitably present in the raw materials. Within a certain range, Cu has a beneficial effect on the 6-series aluminum alloy matrix. Cu atoms replace some Mg or Si atoms in the MgSi phase, forming more stable, fine, and dispersed β'', β', or Q phases, which strengthen the matrix and improve its strength without affecting other properties. When the Cu content is below 0.15%, the strengthening effect is not significant; when the Cu content is above 0.40%, the strength increases significantly, but the corrosion resistance decreases significantly, which should be avoided; when 0.15%≤Cu≤0.3%, the alloy strength is improved while the corrosion resistance does not decrease significantly, resulting in the best overall performance. Therefore, this patent sets the content at 0.15%≤Cu≤0.3%.

[0024] 5. Optimized heat treatment.

[0025] The 6-series aluminum alloy rods of this invention are subjected to a solution-quenching heat treatment process. The purpose of this process is to fully dissolve the strengthening elements in the alloy and precipitate dispersed strengthening phases during the subsequent aging process, while optimizing the morphology of impurity phases and improving the overall mechanical properties of the alloy.

[0026] During the solution treatment process, the coarse MgSi phase in the as-cast structure gradually dissolves, and Mg and Si atoms dissolve in the aluminum matrix as solutes, forming a uniform single-phase solid solution structure. Simultaneously, the brittle and hard alloy exhibiting needle-like and elongated structures... Under high-temperature holding conditions, the iron phase undergoes spheroidization and granulation transformation, which can transform into rounded phases containing Mn and Cr. This reduces the cutting effect of iron on the matrix, improves the alloy's plasticity and toughness, compensates for the impact of high Fe content in recycled aluminum on the matrix properties, and increases the tolerance of recycled aluminum to Fe. The β→α phase transformation diffusion process is affected by temperature; high temperatures significantly accelerate atomic diffusion. Therefore, the homogenization heat treatment temperature used in this paper is slightly higher than the conventional 6-series aluminum alloys (Fe≤0.2%) (550-565℃) to promote the β→α phase transformation process. The homogenization temperature is increased to between 565°C and 575°C to promote acicular phase formation. The phase dissolves rapidly, for The phase nucleus provides the solute while preventing the aluminum rod from overheating due to excessive temperature or prolonged residence time.

[0027] The quenching process rapidly cools the high-temperature solid solution structure to room temperature, resulting in a supersaturated solid solution. The cooling rate directly determines the supersaturation of the solid solution: the faster the cooling rate, the fewer Si, Mg, and Cu atoms precipitate in the cooling range, leading to a higher matrix supersaturation and providing sufficient solute conditions for subsequent age hardening. If the cooling rate is too slow, solute atoms are prone to prematurely precipitating coarse equilibrium phases at grain boundaries and within grains, resulting in a significant decrease in matrix supersaturation, greatly weakening the age hardening effect, and causing a reduction in mechanical properties. To ensure strict control of the cooling rate, this patent employs strong water cooling, cooling from 570℃ to room temperature in 30 minutes, with a cooling rate ≥1100℃ / h. By controlling the solution temperature and quenching cooling rate, the degree of solid solution, precipitation size, quantity, and distribution of the phases can be adjusted, and the morphology of the ferrous phase can be optimized, ultimately enabling 6-series aluminum alloy rods to achieve ideal strength and bending properties.

[0028] Based on the above principles and analysis, the component mass percentage of a high-proportion recycled aluminum 6-series aluminum alloy provided by this invention is as follows:

[0029] Mg: 0.6-1.0%; Si: 0.5-0.9%; Cu: 0.15-0.3%; Mn: 0.2-0.66%; Fe: 0.15-0.3%; Cr: 0.1-0.3%; Zn: ≤0.2%; Ti: ≤0.1%; Other unavoidable impurity elements, single: ≤0.05%, total: ≤0.15%; the remainder is Al;

[0030] Among them, Mn / Fe = 1.3~2.2 and Cr / Fe = 0.8~1; 1≤Mg / Si≤1.56.

[0031] The preparation method includes the following steps:

[0032] Step 1: Add recycled material according to the target composition by mass percentage, wherein the proportion of recycled aluminum added is ≥70%; melt the recycled aluminum into a melt in the melting chamber, and fine-tune it to the target alloy composition according to the measured composition;

[0033] Step 2: Refine the melt obtained in Step 1 through multiple cycles;

[0034] The cyclic refining method is as follows: a mixture of refining agent and argon is introduced into the melt at 730-750℃ and stirred thoroughly for 30-40 minutes, then allowed to stand for 20-35 minutes, and the scum is skimmed off; this method is repeated 3-5 times.

[0035] Step 3: The melt obtained in Step 2 is subjected to dual-rotor degassing, dual-stage filtration + deep bed filtration, and then the liquid aluminum alloy is melted and cast into aluminum alloy rods.

[0036] Step 4: After homogenizing the aluminum rod obtained in Step 3 at 565-575℃ for 6-16h, use strong water cooling at a rate ≥1100℃ / h.

[0037] Step 5: Preheat the aluminum rod obtained in Step 4 to 500-530℃, and extrude it into the corresponding product using an extruder. The product quenching temperature is ≥520℃, and the product is cooled to room temperature using air cooling / mist cooling / water cooling methods.

[0038] Step Six: The product obtained in Step Five shall be subjected to aging heat treatment at 175-200℃ for 3-10 hours.

[0039] Compared with the prior art, the aluminum alloy provided by the present invention improves the tolerance of impurity element Fe in the aluminum matrix, and achieves the addition of recycled aluminum of ≥70% or even 100% without iron removal treatment, while ensuring comparable mechanical properties and bending angle ≥90°, meeting the usage requirements of structural components such as battery box trays and seats in new energy vehicles. Attached Figure Description

[0040] Figure 1This is a cast metallographic diagram of a high-proportion recycled aluminum 6-series aluminum alloy disclosed in this invention.

[0041] Figure 2 This is a metallographic diagram of a high-proportion recycled aluminum 6-series aluminum alloy after solution treatment and quenching heat treatment, as disclosed in this invention.

[0042] Figure 3 The image shows the metallographic structure of the aluminum alloy obtained in Example 1.

[0043] Figure 4 The image shows the metallographic structure of the aluminum alloy obtained in Example 2.

[0044] Figure 5 The image shows the metallographic structure of the aluminum alloy obtained in Example 3.

[0045] Figure 6 The image shows the metallographic structure of the aluminum alloy obtained in Comparative Example 1.

[0046] Figure 7 The image shows the metallographic structure of the aluminum alloy obtained in Comparative Example 2.

[0047] Figure 8 The image shows the metallographic structure of the aluminum alloy obtained in Comparative Example 3.

[0048] Figure 9 The image shows the metallographic structure of the aluminum alloy obtained in Comparative Example 4.

[0049] Figure 10 The image shows the metallographic structure of the aluminum alloy obtained in Comparative Example 5.

[0050] Figure 11 The image shows the metallographic structure of the aluminum alloy obtained in Comparative Example 6.

[0051] Figure 12 The image shows the metallographic structure of the aluminum alloy obtained in Comparative Example 7. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention, and the steps in the described embodiments do not limit the scope of execution of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0053] This invention provides an embodiment of a 6-series aluminum alloy with a high proportion of recycled aluminum, such as... Figure 1 , Figure 2 As shown. Furthermore, the alloy properties are further demonstrated through the following examples and comparative examples.

[0054] Example 1:

[0055] The mass percentage of the alloy components is as follows:

[0056] Mg: 0.7%; Si: 0.65%; Cu: 0.2%; Mn: 0.35%; Fe: 0.23%; Cr: 0.23%; Zn: ≤0.15%; Ti: ≤0.1%; Other unavoidable impurity elements, single: ≤0.05%, total: ≤0.15%; the remainder is Al;

[0057] Among them, Mn / Fe=1.52, Cr / Fe=1.00; Mg / Si=1.08.

[0058] The preparation method includes the following steps:

[0059] Step 1: Add recycled material according to the target composition by mass percentage, wherein the proportion of recycled aluminum added is ≥70%; melt the recycled aluminum into a melt in the melting chamber, and fine-tune it to the target alloy composition according to the measured composition;

[0060] Step 2: Refine the melt obtained in Step 1 through multiple cycles;

[0061] The cyclic refining method is as follows: a mixture of refining agent and argon is introduced into the melt at 730-750℃ and stirred thoroughly for 30-40 minutes, then allowed to stand for 20-35 minutes, and the scum is skimmed off; this method is repeated 3-5 times.

[0062] Step 3: The melt obtained in Step 2 is subjected to dual-rotor degassing, dual-stage filtration + deep bed filtration, and then the liquid aluminum alloy is melted and cast into aluminum alloy rods.

[0063] Step 4: After homogenizing the aluminum rod obtained in Step 3 at 565℃ for 14h, use strong water cooling at a rate ≥1100℃ / h.

[0064] Step 5: Preheat the aluminum rod obtained in Step 4 to 500-530℃, and extrude it into the corresponding product using an extruder. The product quenching temperature is ≥520℃, and the product is cooled to room temperature using air cooling / mist cooling / water cooling methods.

[0065] Step Six: The product obtained in Step Five shall be subjected to aging heat treatment at 175℃ for 8 hours.

[0066] Example 2:

[0067] The mass percentage of the alloy components is as follows:

[0068] Mg: 0.95%; Si: 0.85%; Cu: 0.15%; Mn: 0.2%; Fe: 0.15%; Cr: 0.13%; Zn: ≤0.15%; Ti: ≤0.1%; Other unavoidable impurity elements, single: ≤0.05%, total: ≤0.15%; the remainder is Al;

[0069] Among them, Mn / Fe=1.33, Cr / Fe=0.87; Mg / Si=1.12.

[0070] Preparation method: Except for the following parameter settings, the preparation method is the same as in Example 1.

[0071] The homogenization heat treatment regime in step four is: 570℃ / 12h;

[0072] The heat aging treatment regime in step six is: 190℃ / 6h.

[0073] Example 3:

[0074] The mass percentage of the alloy components is as follows:

[0075] Mg: 0.8%; Si: 0.55%; Cu: 0.2%; Mn: 0.6%; Fe: 0.28%; Cr: 0.23%; Zn: ≤0.15%; Ti: ≤0.1%; Other unavoidable impurity elements, single: ≤0.05%, total: ≤0.15%; the remainder is Al;

[0076] Among them, Mn / Fe=2.14, Cr / Fe=0.82; Mg / Si=1.45.

[0077] Preparation method: Except for the following parameter settings, the preparation method is the same as in Example 1.

[0078] The homogenization heat treatment regime in step four is: 575℃ / 8h;

[0079] The heat aging treatment regime in step six is: 200℃ / 3h.

[0080] Comparative Example 1:

[0081] The mass percentage of the alloy components was adjusted based on Example 1, with the Mn content modified; specifically:

[0082] Mg: 0.7%; Si: 0.65%; Cu: 0.2%; Mn: 0.66%; Fe: 0.23%; Cr: 0.23%; Zn: ≤0.15%; Ti: ≤0.1%; Other unavoidable impurity elements, single: ≤0.05%, total: ≤0.15%; The remainder is Al;

[0083] Among them, Mn / Fe=2.87, Cr / Fe=1.00; Mg / Si=1.08.

[0084] Preparation method: Same as in Example 1.

[0085] Comparative Example 2:

[0086] The mass percentage of the alloy components was adjusted based on Example 1, with the Mn content modified; specifically:

[0087] Mg: 0.7%; Si: 0.65%; Cu: 0.2%; Mn: 0.2%; Fe: 0.23%; Cr: 0.23%; Zn: ≤0.15%; Ti: ≤0.1%; Other unavoidable impurity elements, single: ≤0.05%, total: ≤0.15%; the remainder is Al;

[0088] Among them, Mn / Fe=0.87, Cr / Fe=1.00; Mg / Si=1.08.

[0089] Preparation method: Same as in Example 1.

[0090] Comparative Example 3:

[0091] The mass percentage of the alloy components was adjusted based on Example 2, with the Cr content modified; specifically:

[0092] Mg: 0.95%; Si: 0.85%; Cu: 0.15%; Mn: 0.2%; Fe: 0.15%; Cr: 0.3%; Zn: ≤0.15%; Ti: ≤0.1%; Other unavoidable impurity elements, single: ≤0.05%, total: ≤0.15%; the remainder is Al;

[0093] Among them, Mn / Fe=1.33, Cr / Fe=2.00; Mg / Si=1.12.

[0094] Preparation method: Same as in Example 2.

[0095] Comparative Example 4:

[0096] The mass percentage of the alloy components was adjusted based on Example 2, with the Cr content modified; specifically:

[0097] Mg: 0.95%; Si: 0.85%; Cu: 0.15%; Mn: 0.2%; Fe: 0.15%; Cr: 0.1%; Zn: ≤0.15%; Ti: ≤0.1%; Other unavoidable impurity elements, single: ≤0.05%, total: ≤0.15%; the remainder is Al;

[0098] Among them, Mn / Fe=1.33, Cr / Fe=0.67; Mg / Si=1.12.

[0099] Preparation method: Same as in Example 2.

[0100] Comparative Example 5:

[0101] The mass percentage of the alloy components is as follows:

[0102] Mg: 0.95%; Si: 0.55%; Cu: 0.2%; Mn: 0.6%; Fe: 0.28%; Cr: 0.23%; Zn: ≤0.15%; Ti: ≤0.1%; Other unavoidable impurity elements, single: ≤0.05%, total: ≤0.15%; The remainder is Al;

[0103] Among them, Mn / Fe=2.14, Cr / Fe=0.82; Mg / Si=1.73.

[0104] Preparation method: Same as in Example 3.

[0105] Comparative Example 6:

[0106] The mass percentage of the alloy components is as follows:

[0107] Mg: 0.65%; Si: 0.85%; Cu: 0.15%; Mn: 0.25%; Fe: 0.15%; Cr: 0.13%; Zn: ≤0.15%; Ti: ≤0.1%; Other unavoidable impurity elements, single: ≤0.05%, total: ≤0.15%; the remainder is Al;

[0108] Among them, Mn / Fe=1.67, Cr / Fe=0.87; Mg / Si=0.76.

[0109] Preparation method: Same as in Example 2.

[0110] Comparative Example 7:

[0111] The mass percentage of the alloy components is the same as in Example 1.

[0112] Preparation method: Except for the following parameter settings, the preparation method is the same as in Example 1.

[0113] Cooling rate in step four: 500℃~600℃ / h.

[0114] The elemental composition, some preparation parameters, and alloy performance parameters of Examples 1-3 are shown in Table 2.

[0115] Table 2:

[0116]

[0117] The elemental composition, some preparation parameters, and alloy performance parameters of Comparative Examples 1-7 are shown in Table 3.

[0118] Table 3:

[0119]

[0120] Comparative analysis of Example 1, Comparative Example 1, and Comparative Example 2:

[0121] In Example 1, Comparative Example 1, and Comparative Example 2, the Mn / Fe ratios were 1.52, 2.87, and 0.87, respectively. The technical solution of this invention sets 1.3 ≤ Mn / Fe ≤ 2.2. The Mn / Fe ratios in Comparative Example 1 and Comparative Example 2 exceeded and did not meet this range requirement, respectively.

[0122] Corresponding to Example 1 Figure 3 Corresponding to Comparative Example 1 Figure 6 The comparison shows that when Mn / Fe > 2.2, for Figure 6 The amount of gray phase increased significantly, and some local phases became noticeably coarser, indicating an increase in the amount of Fe phase precipitates and coarsening. This suggests that excessive Mn promotes the formation of Fe-rich phases and leads to coarsening. A comparison between Example 1 and Comparative Example 2 shows that when Mn / Fe ≤ 1.3, the corresponding value in Comparative Example 2 is... Figure 7 The gray phase is clearly aggregated and has a needle-like size, and cannot be refined as in Example 1, breaking into continuous teardrop shapes. Therefore, when Mn / Fe > 2.2 or Mn / Fe ≤ 1.3, the morphology of the Fe phase cannot be effectively guaranteed.

[0123] The relevant mechanical properties of the alloy are as follows:

[0124] Example 1: R m =293MPa, R p0.2 =274MPa, A 50 =11.5%, bending angle @ 2mm =128°;

[0125] Comparative Example 1: R m =296MPa, R p0.2 =272MPa, A 50 =10.3%, bending angle @ 2mm =97°;

[0126] Comparative Example 2: R m =289MPa, R p0.2 =269MPa, A 50 =9.8%, bending angle @ 2mm =93°.

[0127] The comparative analysis of the above indicators shows that the Mn / Fe ratio has little effect on the mechanical properties of the material, but it has a significant impact on the bending performance: when Mn / Fe > 2.2, the bending angle of Comparative Example 1 is 97°; when Mn / Fe ≤ 1.3, the bending angle of Comparative Example 2 is 93°; and when 1.3 ≤ Mn / Fe ≤ 2.2, the bending angle of Example 1 is 128°. This indicates that the Mn / Fe content significantly affects the bending performance. When Mn / Fe is too high or too low, the bending angle is significantly poor. Further analysis shows that this result is related to the distribution of the Fe phase morphology: when Mn / Fe > 2.2, Mn promotes the formation of Fe-rich phases and leads to coarsening; when Mn / Fe ≤ 1.3, Fe is significantly aggregated and needle-like in size, which is unfavorable for the homogeneous bending performance. Only when the Mn / Fe ratio is appropriate is the bending performance optimal.

[0128] Comparative analysis of Example 2, Comparative Example 3, and Comparative Example 4:

[0129] In Example 2, Comparative Example 3, and Comparative Example 4, the Cr / Fe ratios were 0.87, 2.0, and 0.67, respectively. The technical solution of this invention sets 0.8 ≤ Cr / Fe ≤ 1.0. The Cr / Fe ratios in Comparative Example 3 and Comparative Example 4 are greater than and less than the technical requirement range, respectively.

[0130] Compared to Example 2 Figure 4 When Cr / Fe > 1, the corresponding value in Comparative Example 3 is... Figure 8 The amount of gray phase increased significantly, and some local phases became noticeably coarser, indicating an increase in the amount of Fe phase precipitates and coarsening. This suggests that excessive Cr promotes the formation of Fe-rich phases and leads to coarsening. This is compared to Comparative Example 4. Figure 9 The comparison shows that when Cr / Fe ≤ 0.8, the gray phase is significantly reduced, and most of the Fe phase is refined, similar to... Figure 4 The Fe phase is fine and breaks into continuous teardrop shapes, but there are still a few needle-like structures in some local areas, indicating that there is too little Cr and the refining effect is insufficient. Therefore, it can be inferred that when Cr / Fe > 1, the Fe phase coarsens, but when Cr / Fe ≤ 0.8, although refining is achieved, the refining effect is not sufficient.

[0131] The relevant mechanical properties of the alloy are as follows:

[0132] Example 2: R m =348MPa, R p0.2 =321MPa, A 50 =12.3%, bending angle @ 2mm =109°;

[0133] Comparative Example 3: R m =352MPa, R p0.2 =323MPa, A 50=11.3%, bending angle @ 2mm =85°;

[0134] Comparative Example 4: R m =345MPa, R p0.2 =317MPa, A 50 =10.6%, bending angle @ 2mm =95°.

[0135] The comparative analysis of the above indicators shows that the Cr / Fe ratio has little effect on the mechanical properties of the material, but it has a significant impact on the bending performance: when Cr / Fe > 1, the bending angle of Comparative Example 3 is 85°; when Cr / Fe ≤ 0.8, the bending angle of Comparative Example 4 is 95°; when 0.8 ≤ Cr / Fe ≤ 1.0, the bending angle of Example 2 is 109°. This indicates that the Cr / Fe content significantly affects the bending performance. When Cr / Fe is too high, the bending angle decreases from 109° to 85°, which is related to the fact that excessive Cr promotes the formation of Fe-rich phase and leads to coarse phase. When Cr / Fe ≤ 0.8, the bending angle decreases to some extent from 109° to 95°, which is due to insufficient Cr phase refinement, but it is significantly better than the case of excessive Cr. The bending performance is optimal when 0.8 ≤ Cr / Fe ≤ 1.0.

[0136] Comparative analysis of Example 3 and Comparative Example 5:

[0137] The relevant parameters and alloy mechanical properties are as follows:

[0138] Example 3: Mg / Si = 1.45; Mechanical properties: R m =272MPa, R p0.2 =254MPa, A 50 =11.5%; bending angle @ 2mm =136°;

[0139] Comparative Example 5: Mg / Si = 1.73; Mechanical properties: R m =278MPa, R p0.2 =257MPa, A 50 =11.2%; bending angle @ 2mm =96°.

[0140] This patented technical solution requires a Mg / Si ratio range of 1~1.56. Comparing Example 3 (Mg / Si=1.45) and Comparative Example 5 (Mg / Si=1.73), it can be seen that the mechanical properties of the two are not significantly different; Figure 5 , Figure 10 As shown, when Mg / Si ≥ 1.56, i.e., when Mg is in excess, it has virtually no effect on the mechanical properties of the material. The main reason is that excess Mg cannot form an effective reinforcing phase β'' with Si. ), β' ( This indicates that Mg contributes little to the performance and there is no need for excessive amounts. The comparison of bending angle performance shows that, compared to Example 3, the bending angle in Comparative Example 5 decreased from 136° to 96°, indicating that Mg / Si ≥ 1.56 significantly reduces the bending performance of the material. The main reason is the formation of a large amount of β-( This is detrimental to the bending performance of the material.

[0141] Comparative analysis of Example 2 and Comparative Example 6:

[0142] Example 2: Mg / Si = 1.12; Mechanical properties: R m =348MPa, R p0.2 =321MPa, A 50 =12.3%, bending angle @ 2mm =109°;

[0143] Comparative Example 6: Mg / Si = 0.76; Mechanical properties: R m =319MPa, R p0.2 =298MPa, A 50 =10.2%; bending angle @ 2mm =83°.

[0144] Comparing Example 2 (Mg / Si=1.12) and Comparative Example 6 (Mg / Si=0.76), it can be seen that when Mg / Si≤1, as... Figure 11 As shown, when Mg is insufficient, the mechanical properties of the material decrease from 348 MPa to 319 MPa. In the alloy of Comparative Example 6, the main factor is β'' ( To increase strength, it is impossible to form enough β' ( ) to enhance strength, β'' ( It is detrimental to bending performance, and the bending angle decreases from 109° to 83°.

[0145] Comparative analysis of Example 1 and Comparative Example 7:

[0146] Example 1 and Comparative Example 7 have the same alloy composition, but the cooling rates in their preparation methods differ significantly, being ≥1100℃ / h and 500~600℃ / h, respectively.

[0147] Example 1: The alloy phase surface is smooth, composed of... Figure 3 As can be seen, the gray Fe phase is almost entirely discontinuous in the form of water droplets, with small and dispersed sizes, generally not exceeding 10 μm.

[0148] Comparative Example 7 also has a smooth metallographic surface, made of Figure 12It can be seen that most of the gray Fe phase breaks into water droplet shapes, but some are concentrated and have a larger cut size, reaching 20 μm. This indicates that the cooling rate during the quenching process is very important for improving the phase of Fe. When the rate is too slow, the Fe phase undergoes re-dissolution, which is detrimental to performance. At the same time, there are many black spots on its surface, which are precipitated MgSi phases and they are coarsened, indicating poor homogenization effect, which is also caused by the slow cooling rate.

[0149] The relevant mechanical properties of the alloy are as follows:

[0150] Example 1: R m =293MPa, R p0.2 =274MPa, A 50 =11.5%; bending angle @ 2mm =128°;

[0151] Comparative Example 7: R m =285MPa, R p0.2 =262MPa, A 50 =11.6%; Bend angle @ 2mm =83°.

[0152] As can be seen from the comparison, there is a significant difference in performance between the two. When the cooling rate slows down, the strength R... m The pressure decreased from 293 MPa to 285 MPa, and the bending angle decreased from 128° to 83°. The main reason is that the cooling rate was slow, which led to the precipitation of MgSi phase, insufficient strengthening, and coarsening.

Claims

1. A 6-series aluminum alloy with a high proportion of recycled aluminum, characterized in that, The mass percentage of the alloy components is as follows: Mg: 0.6-1.0%; Si: 0.5-0.9%; Cu: 0.15-0.3%; Mn: 0.2-0.66%; Fe: 0.15-0.3%; Cr：0.1-0.3%； Zn: ≤0.2%; Ti: ≤0.1%; other unavoidable impurity elements, single: ≤0.05%, total: ≤0.15%; the remainder is Al; Among them, 1.3≤Mn / Fe≤2.2; 0.8≤Cr / Fe≤1; 1≤Mg / Si≤1.56; The alloying method includes the following steps: Step 1: Add recycled aluminum according to the mass percentage of the components, and melt to obtain a melt; Step 2: Refine the melt 3-5 times at 730-750℃; Step 3: The melt is subjected to dual-rotor degassing, dual-stage filtration + deep bed filtration, and then the liquid aluminum alloy is melted and cast into aluminum alloy rods. Step 4: After homogenizing the cast rod at 565-575℃ for 6-16h, use strong water cooling for 30min and a cooling rate ≥1100℃ / h. Step 5: Preheat the aluminum rod obtained in Step 4 to 500-530℃, and extrude it into the corresponding product using an extruder. The product quenching temperature is ≥520℃, and the product is cooled to room temperature using air cooling / mist cooling / water cooling methods. Step Six: Perform aging heat treatment on the product at 175-200℃ for 3-10 hours; The alloy has an elongation of 11.50-12.30% over 50mm and a bending angle of 109°-136° over 2mm.

2. The aluminum alloy according to claim 1, characterized in that, The mass percentage of Cr is 0.13-0.23%.

3. The aluminum alloy according to claim 2, characterized in that, The mass percentage of Mg is 0.7-0.95%.

4. The aluminum alloy according to claim 3, characterized in that, The mass percentage of Si is 0.55-0.85%.

5. The aluminum alloy according to claim 4, characterized in that, The mass percentage of Cu is 0.15-0.2%.

6. The aluminum alloy according to claim 5, characterized in that, The alloy's mass composition satisfies the following conditions: 1.33≤Mn / Fe≤2.14; 0.82≤Cr / Fe≤1; 1.08≤Mg / Si≤1.

45.

7. The aluminum alloy according to any one of claims 1-6, characterized in that, In step one, the proportion of recycled aluminum added is 70-100%, and the alloy composition is fine-tuned according to the measured composition.

8. The aluminum alloy according to any one of claims 1-6, characterized in that, The cyclic refining method is as follows: a mixture of refining agent and argon is introduced and stirred thoroughly for 30-40 minutes, then allowed to stand for 20-35 minutes, and the scum is skimmed off.

9. The aluminum alloy according to any one of claims 1-6, characterized in that, In step four, the homogenization heat treatment regime is: 565℃ / 14h, 570℃ / 12h, 575℃ / 8h.

10. The aluminum alloy according to any one of claims 1-6, characterized in that, The alloy has a tensile strength of 272-348 MPa and a yield strength of 254-321 MPa.

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