A low energy processing method for 6xxx series aluminum alloy sheet

Abstract

The application relates to a low-energy processing method of a 6XXX series aluminum alloy plate, which comprises the following steps: melting and casting, hot rolling, cold rolling, low-temperature pretreatment, solid solution and aging; the temperature of the low-temperature pretreatment is not higher than 290 DEG C. The low-temperature pretreatment process not higher than 290 DEG C is added after rolling deformation and before solid solution treatment, on the one hand, the morphology of the iron-rich brittle phase can be improved, and on the other hand, the deformation damage around the iron-rich phase can be passivated, so that the strength and plasticity of the 6XXX series aluminum alloy plate are simultaneously improved without the need of ingot homogenization annealing treatment.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy technology, and in particular to a low-energy processing method for 6XXX series aluminum alloy sheets. Background Technology

[0002] Aluminum alloys are widely used in transportation, engineering machinery, and building structures due to their excellent specific strength, corrosion resistance, and weldability. Among them, 6XXX series aluminum alloys (Al-Mg-Si), with their medium-to-high strength and good weldability, are widely used in the manufacture of structural components such as rail transit car bodies, automobiles, ships, and cryogenic pressure vessels. In the traditional production process of this series of aluminum alloys, ingots typically require homogenization annealing to eliminate intragranular segregation, promote the dissolution of non-equilibrium phases, and improve the morphology of the second phase, thereby enhancing the mechanical properties of the aluminum alloy. However, homogenization annealing requires holding at 530~580℃ for 6~24 hours, resulting in high energy consumption. Furthermore, prolonged high-temperature heating easily leads to grain coarsening, accelerated surface oxidation, and increased material loss, while significantly reducing equipment turnover.

[0003] To address the aforementioned issues, attempts have been made to achieve homogenization-free annealing of 6XXX series aluminum alloys through process adjustments or composition optimization. For example, Chinese patent CN 121046700 A discloses an aluminum alloy material and its preparation method and application that does not require homogenization heat treatment. By adding microalloying elements such as Yb, Zr, and La, and combining this with low-frequency electromagnetic stirring of the melt, homogenization-free heat treatment is achieved. However, this method heavily relies on the addition of specific rare elements and additional electromagnetic stirring equipment, which increases the cost of alloy raw materials and the difficulty of recycling, as well as the complexity of the process and the investment in equipment.

[0004] Therefore, it is necessary to improve the existing processing methods for 6XXX series aluminum alloys. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a low-energy processing method for 6XXX series aluminum alloy sheets.

[0006] The technical solution adopted in this invention is as follows: This invention provides a low-energy processing method for 6XXX series aluminum alloy sheets, comprising the following steps: Melting and casting, hot rolling, cold rolling, low-temperature pretreatment, solution treatment and aging; The temperature of the low-temperature pretreatment shall not exceed 290°C.

[0007] Preferably, the hot rolling temperature is 460~495℃, and the total reduction rate of the hot rolling is 55~65%.

[0008] Preferably, the total reduction rate of the cold rolling is 20-30%.

[0009] Preferably, the temperature of the low-temperature pretreatment is 235~280℃, and the heat preservation time of the low-temperature pretreatment is 4~12h.

[0010] Preferably, the solution temperature is 530~550℃, and the solution holding time is 1~3h.

[0011] Preferably, after the low-temperature pretreatment is completed, the temperature is increased to the solution temperature at a rate of 5~15℃ / min.

[0012] Preferably, the aging temperature is 165~180℃, and the aging holding time is 4~10h.

[0013] Preferably, a water quenching step is included between the solution treatment and the aging process.

[0014] The beneficial effects of this invention are: (1) By adding a low-temperature pretreatment process of no more than 290°C after rolling deformation and before solution treatment, the present invention can improve the morphology of the iron-rich brittle phase on the one hand and passivate the deformation damage around the iron-rich phase on the other hand, thereby achieving the simultaneous improvement of the strength and plasticity of 6XXX series aluminum alloy plates without the need for ingot homogenization annealing treatment.

[0015] (2) The 6XXX series aluminum alloy sheets prepared by the method of this invention exhibit significantly improved mechanical properties compared to the traditional homogenization annealing process, achieving a balance between low energy consumption and high performance. Specifically, the yield strength of 6063 aluminum alloy is increased by approximately 4.8%, the tensile strength by approximately 5.7%, and the elongation by approximately 25.8%; while the yield strength of 6061 aluminum alloy is increased by approximately 3.2%, the tensile strength by approximately 3.1%, and the elongation by approximately 2.2%.

[0016] (3) The method of the present invention omits the homogenization annealing process in the traditional process, and does not require component modification and special equipment, which greatly reduces production energy consumption and cost, shortens the production cycle, and is easy to promote and apply on a large scale. Attached Figure Description

[0017] Figure 1 The stress-strain curves of the 6063 aluminum alloy sheets prepared in Example 1 and Comparative Examples 1-4 are shown. Figure 2 The stress-strain curves of the 6061 aluminum alloy sheets prepared in Example 2 and Comparative Examples 5-6 are shown. Figure 3 SEM image of the 6063 aluminum alloy sheet prepared in Comparative Example 1. Figure 4 SEM image of the 6063 aluminum alloy sheet prepared in Comparative Example 2; Figure 5 The image shows a SEM image of the 6063 aluminum alloy sheet prepared in Example 1. Detailed Implementation

[0018] The technical solution of the present invention will be further explained and described below through specific embodiments.

[0019] This invention provides a low-energy processing method for 6XXX series aluminum alloy sheets, comprising the following steps: Melting and casting, hot rolling, cold rolling, low-temperature pretreatment, solution treatment and aging; The temperature for low-temperature pretreatment should not exceed 290℃.

[0020] This invention, by introducing a low-temperature pretreatment at no higher than 290℃ after rolling deformation, can play a dual role in improving the morphology of the iron-rich phase and passivating deformation damage: (1) breaking the continuous long strip-shaped iron-rich brittle phase inherited in the as-cast state and dispersing it into small short rods or granules, greatly weakening the stress concentration effect of the continuous brittle phase; (2) passivating the deformation damage around the iron-rich phase, releasing the stress in the phase interface, and coordinating the deformation capacity of the second phase and the matrix, thereby enabling the 6XXX series aluminum alloy plates that do not require homogenization annealing to obtain excellent mechanical properties. If the temperature of the low-temperature pretreatment is higher than 290℃, it will cause the strengthening elements such as Mg and Si to precipitate and coarsen prematurely, weakening the precipitation strengthening effect in the subsequent solid solution and aging process, which is not conducive to the improvement of mechanical properties. This invention does not impose special restrictions on the grade of 6XXX series aluminum alloys. Appropriate aluminum alloys can be selected according to actual needs. For example, it can be 6063 aluminum alloy, 6061 aluminum alloy, 6060 aluminum alloy, 6082 aluminum alloy, 6005 aluminum alloy, etc.

[0021] In a preferred embodiment, the hot rolling temperature is 460~495℃, and the total reduction rate of the hot rolling is 55~65%. For example, the hot rolling temperature can be 460℃, 465℃, 470℃, 475℃, 480℃, 485℃, 490℃, 495℃, etc.; the total reduction rate of the hot rolling can be 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, etc.

[0022] In a preferred embodiment, the total reduction rate of cold rolling is 20-30%. For example, the total reduction rate of cold rolling can be 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, etc.

[0023] In this invention, the total reduction rate of hot rolling and the total reduction rate of cold rolling are both calculated based on the thickness of aluminum alloy ingots. After hot rolling and cold rolling, the total reduction rate of the sheet is 75-95%. At the same time, this invention does not impose any particular limitation on the number of hot rolling and cold rolling cycles; it can be done once or multiple times.

[0024] In a preferred embodiment, the low-temperature pretreatment temperature is 235~280℃, and the holding time is 4~12h. This invention selects the above-mentioned low-temperature pretreatment conditions, which can significantly improve the morphology of the iron-rich phase and passivate deformation damage around the iron-rich phase, thereby improving the microstructure and properties of the aluminum alloy, while preserving deformation energy storage and preventing premature coarsening of the strengthening phase. If the low-temperature pretreatment temperature is too low, the atomic diffusion motive force is insufficient, the iron-rich phase is difficult to effectively break down and disperse, deformation damage passivation is insufficient, and the performance improvement effect is limited. For example, the low-temperature pretreatment conditions can be 235℃×12h, 260℃×8h, 280℃×4h, etc.

[0025] In a preferred embodiment, the solution temperature is 530~550℃, and the solution holding time is 1~3h. For example, the solution conditions can be 530℃×3h, 540℃×2h, 550℃×1h, etc.

[0026] In a preferred embodiment, after the low-temperature pretreatment, the temperature is increased to the solution temperature at a rate of 5~15℃ / min. For example, the aluminum alloy after low-temperature pretreatment can be heated to the solution temperature range at rates of 5℃ / min, 7℃ / min, 9℃ / min, 11℃ / min, 13℃ / min, and 15℃ / min for solution treatment.

[0027] In a preferred embodiment, the aging temperature is 165~180℃, and the aging time is 4~10h. For example, the aging conditions can be 165℃×10h, 170℃×8h, 175℃×6h, 180℃×4h, etc.

[0028] In a preferred embodiment, a water quenching step is also included between solution treatment and aging. Water quenching is performed immediately after solution treatment to quickly fix the supersaturated solid solution formed at high temperature; and aging treatment is performed within 10 minutes after quenching to avoid natural aging during room temperature holding, ensuring that the strengthening phase is fully dispersed and precipitated in the subsequent aging stage, which is conducive to exerting the aging strengthening effect.

[0029] Example 1 A low-energy processing method for 6XXX series aluminum alloy sheets includes the following steps: Melting and casting: 6063 aluminum alloy raw materials (raw material composition based on 100% weight includes: Mg: 0.6%, Si: 0.5%, Fe: 0.13%, with the balance being Al and unavoidable impurities) are melted and semi-continuously cast to obtain aluminum alloy ingots. Hot rolling: Take an aluminum alloy ingot of 100×20×8mm, heat it to 480℃ and hold it for 30min, perform the first hot rolling with a reduction of 3mm, and then hold it at 480℃ for 5min, perform the second hot rolling with a reduction of 2mm, to obtain hot-rolled aluminum alloy sheet. Cold rolling: After the hot-rolled aluminum alloy sheet cools to room temperature, it is cold rolled twice, with a reduction of 1 mm each time, to obtain a cold-rolled aluminum alloy sheet with a thickness of 1 mm. Low-temperature pretreatment: Cold-rolled aluminum alloy sheet is subjected to low-temperature pretreatment at 250℃ for 10 hours to obtain low-temperature pretreated aluminum alloy sheet; Solution treatment: The low-temperature pretreated aluminum alloy sheet is heated to 540℃ at a rate of 10℃ / min for solution treatment for 1 hour, and then water quenched after solution treatment. Aging: After water quenching, the aluminum alloy sheet was aged at 175℃ for 400 minutes to obtain 6063 aluminum alloy sheet.

[0030] Comparative Example 1 The difference between this comparative example and Example 1 is that the low-temperature pretreatment is omitted. The remaining steps remain unchanged.

[0031] Comparative Example 2 The difference between this comparative example and Example 1 is that the low-temperature pretreatment is omitted and a homogenization annealing treatment is used. Specifically, the following steps are included: casting is carried out according to the steps of Example 1, an aluminum alloy ingot of 100×20×8mm is taken, heated to 550℃ at a rate of 10℃ / min for homogenization heat treatment for 10h, quenched in water and cooled to room temperature, and then hot rolling, cold rolling, solution treatment and aging are carried out according to the steps of Example 1.

[0032] Comparative Example 3 The difference between this comparative example and Example 1 is that the low-temperature pretreatment temperature is different, adjusted from 250°C in Example 1 to 220°C. The remaining steps remain unchanged.

[0033] Comparative Example 4 The difference between this comparative example and Example 1 is that the low-temperature pretreatment temperature is different, adjusted from 250°C in Example 1 to 300°C. The remaining steps remain unchanged.

[0034] Example 2 The difference between this embodiment and Embodiment 1 is that the aluminum alloy grade is different; 6061 aluminum alloy is used as the raw material. The raw material composition, based on 100% by weight, includes: Mg: 0.88%, Si: 0.71%, Cu: 0.28%, Fe: 0.31%, Mn: 0.1%, Cr: 0.16%, with the balance being Al and unavoidable impurities. The remaining steps remain unchanged.

[0035] Comparative Example 5 The difference between this comparative example and Example 2 is that the low-temperature pretreatment is omitted. The remaining steps remain unchanged.

[0036] Comparative Example 6 The difference between this comparative example and Example 2 is that the low-temperature pretreatment is omitted and a homogenization annealing treatment is used. Specifically, the following steps are included: casting is carried out according to the steps of Example 2, an aluminum alloy ingot of 100×20×8mm is taken, heated to 550℃ at a rate of 10℃ / min for homogenization heat treatment for 10h, quenched in water and cooled to room temperature, and then hot rolling, cold rolling, solution treatment and aging are carried out according to the steps of Example 2.

[0037] Example 3 The difference between this embodiment and Embodiment 1 lies in the aluminum alloy grade and the low-temperature pretreatment conditions. 6060 aluminum alloy is used, and the raw material composition, by weight (100%), includes: Mg: 0.45%, Si: 0.42%, Fe: 0.21%, with the balance being Al and unavoidable impurities. The low-temperature pretreatment condition is holding at 235°C for 12 hours. The remaining steps remain unchanged.

[0038] Example 4 The difference between this embodiment and Embodiment 1 lies in the aluminum alloy grade and the low-temperature pretreatment conditions. 6082 aluminum alloy is used, and the raw material composition, by weight (100%), includes: Mg: 0.83%, Si: 1.02%, Mn: 0.65%, Fe: 0.35%, with the balance being Al and unavoidable impurities. The low-temperature pretreatment condition is holding at 280°C for 4 hours. The remaining steps remain unchanged.

[0039] The aluminum alloy sheets prepared in Examples 1-4 and Comparative Examples 1-6 were characterized and their performance was tested. The results are recorded in Table 1 and 2. Figures 1-5 .

[0040] Table 1

[0041] Unlike the traditional casting-homogenization annealing-rolling deformation-solution-aging process, the alloy produced by this invention does not require energy-intensive homogenization annealing. Instead, it undergoes direct rolling deformation followed by low-temperature pretreatment, resulting in aluminum alloys with superior mechanical properties compared to conventional homogenized annealed alloys. For example... Figure 1 , Figure 2As shown in Table 1, the aluminum alloys prepared in Examples 1-2 of this invention exhibit significantly higher tensile strength and yield strength than the aluminum alloys without low-temperature pretreatment (Comparative Examples 1 and 5) and those treated with conventional homogenization annealing (Comparative Examples 2 and 6). Comparing Examples 1 and Comparative Examples 3-4 reveals that in Comparative Example 3, the low-temperature pretreatment temperature was too low, making it difficult to effectively alleviate deformation damage around the iron-rich phase, resulting in limited improvement in the strength and plasticity of the aluminum alloy. In Comparative Example 4, the excessively high low-temperature pretreatment temperature weakened the strengthening effect during subsequent solution treatment and aging processes, leading to a decrease in mechanical properties. Therefore, both excessively low and excessively high low-temperature pretreatment temperatures are detrimental to improving the mechanical properties of aluminum alloys. Only by performing low-temperature pretreatment within a suitable temperature range can a better balance of strength and plasticity be achieved.

[0042] Depend on Figure 3 It can be seen that the iron-containing phase of the aluminum alloy directly rolled without homogenization (Comparative Example 1) tends to be distributed in elongated, plate-like, and chain-like shapes, with obvious agglomeration in some areas. This indicates that the coarse iron-rich phase inherited from the casting state is elongated and broken during the rolling process, but not fully dispersed, and has a certain tendency to agglomerate. Figure 4 It can be seen that the aluminum alloy treated with traditional homogenization degradation (Comparative Example 2) has less overall iron-containing phase, which is elongated and continuous, and the local agglomeration phenomenon is not obvious, indicating that high-temperature homogenization has an improving effect on the morphology and distribution of iron-rich phase. Figure 5 As can be seen, the iron-containing phase still exists in Example 1, but compared with Comparative Example 1, its morphology is shorter, more dispersed, and more discrete. The elongated continuous iron-rich phase is significantly reduced, and it is more manifested as fine particles, short rods, or locally discontinuous distribution. The degree of agglomeration is weakened, and the continuous connection between the iron-containing phases is effectively broken. In summary, low-temperature pretreatment can significantly improve the morphology and distribution of the iron-rich phase, resulting in a synergistic improvement in the strength and plasticity of aluminum alloys. At the same time, the method of the present invention does not rely on composition adjustment and can effectively improve the comprehensive mechanical properties of alloys within the 6XXX series without homogenization, realizing low-energy consumption and low-cost manufacturing of 6XXX high-performance alloys within the series.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A low-energy processing method for 6XXX series aluminum alloy sheets, characterized in that, Includes the following steps: Melting and casting, hot rolling, cold rolling, low-temperature pretreatment, solution treatment and aging; The temperature of the low-temperature pretreatment shall not exceed 290°C.

2. The low-energy processing method for 6XXX series aluminum alloy sheets as described in claim 1, characterized in that, The hot rolling temperature is 460~495℃, and the total reduction rate of the hot rolling is 55~65%.

3. The low-energy processing method for 6XXX series aluminum alloy sheets as described in claim 1, characterized in that, The total reduction rate of the cold rolling is 20-30%.

4. The low-energy processing method for 6XXX series aluminum alloy sheets as described in claim 1, characterized in that, The temperature of the low-temperature pretreatment is 235~280℃, and the holding time of the low-temperature pretreatment is 4~12h.

5. The low-energy processing method for 6XXX series aluminum alloy sheets as described in claim 1, characterized in that, The solution temperature is 530~550℃, and the solution holding time is 1~3h.

6. The low-energy processing method for 6XXX series aluminum alloy sheets as described in claim 1, characterized in that, After the low-temperature pretreatment is completed, the temperature is increased to the solution temperature at a rate of 5~15℃ / min.

7. The low-energy processing method for 6XXX series aluminum alloy sheets as described in claim 1, characterized in that, The aging temperature is 165~180℃, and the aging holding time is 4~10h.

8. The low-energy processing method for 6XXX series aluminum alloy sheets as described in claim 1, characterized in that, The solution treatment and aging processes also include a water quenching step.

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