Production process of annealed 7-series aluminum alloy plate

Abstract

The application provides application of low-temperature quenching in preparation of a 7-series aluminum alloy plate; the low-temperature quenching temperature is 400-420 DEG C; the low-temperature quenching holding time is 20-40 minutes; and the low-temperature quenching process is after rolling and before finished product annealing in the preparation process. Through the low-temperature quenching, the plate obtains a relatively small and uniform grain size before the finished product annealing, so that the product with a grain size of 1-2 levels is obtained after the finished product annealing, and the problem of coarse grain size of the current 7-series aluminum alloy annealing plate with a thickness of 5.0-10.0 mm is solved.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy sheet preparation technology, and relates to the application of low temperature quenching in the preparation of 7-series aluminum alloy sheets and a method for preparing 7-series aluminum alloy sheets, especially to a production process for annealed 7-series aluminum alloy medium plates. Background Technology

[0002] The current 7-series aluminum alloy annealed plates with a thickness of 5.0~10.0mm are mainly produced by precision rolling, finished product annealing, shearing, straightening, sawing, and packaging. The finished product annealing temperature is 380~410℃, which is recommended in the AMS2772 standard, and the holding time is 2~4 hours. The annealed plates obtained by this method have large grain size, exceeding level 3. The main effects are: (1) The large grain size will greatly weaken the strength (tensile strength, yield strength) and hardness of the material, and cannot meet the requirements of the structural components for bearing capacity; at the same time, it will lead to a decrease in plasticity (elongation) and toughness (impact resistance), and it is easy to break directly when subjected to external force or impact, rather than first undergoing plastic deformation warning. (2) Deterioration of forming and processing performance: During the forming process of bending, stamping, etc., the large grain size of the plate is prone to causing "orange peel effect" (the surface appears uneven orange peel-like defects), which seriously affects the appearance quality; and the large grain size leads to uneven deformation, and it is easy to crack at stress concentration points during forming, which greatly reduces the yield. (3) Reduced corrosion resistance: The grain boundary area of ​​coarse grains is smaller, and impurities and precipitates (such as θ phase and S phase) are more likely to accumulate at the grain boundary, forming corrosion channels. This reduces the ability of the plate to resist intergranular corrosion and stress corrosion in humid, acidic and alkaline environments, thus shortening its service life. (4) Poor performance uniformity: Coarse grains are usually accompanied by uneven grain size, which leads to differences in strength and plasticity in different areas of the plate. During subsequent processing or assembly, uneven stress can easily cause local damage, affecting the stability of the overall structure.

[0003] Therefore, developing a superior method for preparing 7-series aluminum alloy sheets that can solve the aforementioned technical problems of existing annealed 7-series aluminum alloy sheets with a thickness of 5.0~10.0mm has become one of the urgent problems to be solved by many front-line researchers in the industry. Summary of the Invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide the application of low-temperature quenching in the preparation of 7-series aluminum alloy plates and a method for preparing 7-series aluminum alloy plates, particularly a production process for annealed 7-series aluminum alloy plates. The present invention, through low-temperature quenching, enables the plate to obtain a relatively small and uniform grain size before finished annealing, thereby obtaining a product with a grain size of 1-2 after finished annealing, solving the problem of coarse grain size in current annealed 7-series aluminum alloy plates with a thickness of 5.0-10.0 mm. Moreover, the preparation method is simple, the conditions are mild, and the controllability is good, making it more suitable for promotion and application in industrial production.

[0005] This invention provides the application of low-temperature quenching in the preparation of 7-series aluminum alloy sheets;

[0006] The temperature for the low-temperature quenching is 400~420℃;

[0007] The holding time for the low-temperature quenching is 20-40 minutes;

[0008] The low-temperature quenching process is performed after rolling and before annealing of the finished product in the preparation process.

[0009] Preferably, the 7-series aluminum alloy sheet includes 7-series clad aluminum annealed sheet or 7-series non-clad aluminum annealed sheet;

[0010] The 7-series aluminum alloy sheet includes a 7-series aluminum alloy O-state medium plate;

[0011] The thickness of the 7-series aluminum alloy sheet is 5~10mm.

[0012] Preferably, the rolling process includes hot rolling;

[0013] The hot rolling includes hot roughing and hot finishing;

[0014] The temperature of the hot roughing is 350~420℃;

[0015] The temperature of the hot finishing rolling is 270~380℃.

[0016] Preferably, the annealing temperature of the finished product is 380~420℃;

[0017] The annealing time for the finished product is 1 to 3 hours;

[0018] The grain size of the 7-series aluminum alloy sheet is 100~200μm.

[0019] This invention also provides a method for preparing 7-series aluminum alloy sheets, comprising the following steps:

[0020] 1) After the milled ingot is heated, it is hot rough rolling and hot finish rolling to obtain a rolled billet;

[0021] 2) The rolled billet obtained in the above steps is subjected to low-temperature quenching and then stretched and straightened, and then subjected to finished product annealing and straightened to obtain 7 series aluminum alloy sheet.

[0022] Preferably, the 7-series aluminum alloy sheet comprises, by mass percentage: Si≤0.1%, Fe≤0.12%, Cu: 1.2%~1.9%, Mn≤0.06%, Mg: 1.9%~2.6%, Cr: 0.18%~0.25%, Zn: 5.2%~6.2%, Ti≤0.06%, and aluminum;

[0023] The heating process also includes a cladding step with aluminum.

[0024] Preferably, the heating temperature is 390~430℃;

[0025] The final rolling temperature of the hot roughing is 360~400℃;

[0026] The total deformation of the hot roughing is 92% to 95%.

[0027] Preferably, the initial rolling temperature of the hot finishing roll is 340~380℃;

[0028] The final rolling temperature of the hot finishing rolling is 270~310℃;

[0029] The total deformation of the hot finishing rolling is 68% to 78%.

[0030] Preferably, the hot finishing rolling further includes a shearing step;

[0031] The temperature for the low-temperature quenching is 400~420℃;

[0032] The holding time for the low-temperature quenching is 20-40 minutes.

[0033] Preferably, the annealing temperature of the finished product is 380~420℃;

[0034] The annealing time for the finished product is 1 to 3 hours.

[0035] This invention provides the application of low-temperature quenching in the preparation of 7-series aluminum alloy sheets; the low-temperature quenching temperature is 400~420℃; the low-temperature quenching holding time is 20~40 minutes; the low-temperature quenching process is performed after rolling and before annealing in the preparation process. Compared with the prior art, this invention suggests that the current production process for annealed 7-series aluminum alloy sheets with a thickness of 5.0~10.0mm is as follows: ingot milling → cladding → ingot heating → hot rough rolling → hot finish rolling → finished product annealing → large-size shearing → straightening → sawing → packaging. However, it has the following disadvantages: the grain size of the sheet is coarse after annealing (grade 3-4), which worsens the sheet's mechanical forming and processing stability, directly impacting its reliability and thus failing to meet user requirements.

[0036] Based on this, the present invention creatively designs a specific low-temperature quenching process for the preparation of annealed 7-series aluminum alloy sheets with a thickness of 5.0~10.0mm. The present invention also provides a corresponding method for preparing 7-series aluminum alloy sheets. Through low-temperature quenching, the sheet obtains a relatively small and uniform grain size before final annealing, resulting in a product with a grain size of 1~2 after final annealing, thus solving the problem of coarse grain size in current annealed 7-series aluminum alloy sheets with a thickness of 5.0-10.0mm.

[0037] This invention, through process research, experimental demonstration, and production verification, adds a low-temperature quenching (410±10℃) process before annealing the finished product. This refines the grain size of the annealed sheet, resulting in relatively small and uniform grain sizes that tend towards equiaxed shapes. During annealing, there are numerous and evenly distributed recrystallization nucleation points, and the final grains still maintain a fine, equiaxed, and uniformly sized morphology. Because the sheet obtains a relatively small and uniform grain size before annealing, a product with a fine grain size (grade 1-2) is obtained after annealing. The annealing process provided by this invention successfully solves the problem of coarse grain size in 7-series clad aluminum annealed sheets, and also improves the product's mechanical properties, performance uniformity, forming and processing performance, and corrosion resistance. Attached Figure Description

[0038] Figure 1 Traditional process route diagram for annealed 7-series aluminum alloy sheets with a thickness of 5.0~10.0mm;

[0039] Figure 2 A process flow diagram for annealed 7-series aluminum alloy sheets with a thickness of 5.0~10.0mm provided for this invention;

[0040] Figure 3 This invention provides a comparison of the mechanical properties of O-state plates made from 7475-O products annealed using traditional annealing processes and those annealed using the processes described in this invention.

[0041] Figure 4 This invention provides a comparison of the mechanical properties of the OT761 state sheet material annealed using the conventional annealing process for the 7475-O product and the annealing process of this invention.

[0042] Figure 5 Microscopic grain diagram and physical appearance image of the plate prepared by traditional process;

[0043] Figure 6 The images show the microstructure and physical appearance of the plate material prepared according to this invention. Detailed Implementation

[0044] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims.

[0045] There are no particular restrictions on the source of any raw materials used in this invention; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0046] There are no particular restrictions on the purity of any of the raw materials used in this invention. However, this invention preferably uses industrial-grade pure or the purity requirements commonly used in the preparation of 7-series aluminum alloy sheets.

[0047] All raw materials of this invention are conventional in the field, and each brand name and abbreviation is clear and distinct in its relevant application. Those skilled in the art can purchase them from the market or prepare them by conventional methods based on the brand name, abbreviation and corresponding application.

[0048] The processes used in this invention are all commonly referred to in the field. The specific steps and conventional parameters of each abbreviation are clear and well-defined in their respective fields. Those skilled in the art can implement them using conventional methods based on the abbreviations.

[0049] This invention provides the application of low-temperature quenching in the preparation of 7-series aluminum alloy sheets;

[0050] The temperature for the low-temperature quenching is 400~420℃;

[0051] The holding time for the low-temperature quenching is 20-40 minutes;

[0052] The low-temperature quenching process is performed after rolling and before annealing of the finished product in the preparation process.

[0053] In this invention, the temperature of the low-temperature quenching is 400~420℃, or 404~416℃, or 408~412℃.

[0054] In this invention, the holding time for low-temperature quenching is 20-40 minutes, or 24-36 minutes, or 28-32 minutes.

[0055] In this invention, the 7-series aluminum alloy sheet preferably includes 7-series clad aluminum annealed sheet or 7-series non-clad aluminum annealed sheet.

[0056] In this invention, the 7-series aluminum alloy sheet preferably includes a 7-series aluminum alloy O-state medium plate.

[0057] In this invention, the thickness of the 7-series aluminum alloy sheet can be 5-10mm, 6-9mm, or 7-8mm.

[0058] In this invention, the rolling process preferably includes hot rolling.

[0059] In this invention, the hot rolling preferably includes hot roughing and hot finishing.

[0060] In this invention, the temperature of the hot rolling can be 350~420℃, 360~410℃, 370~400℃, or 380~390℃.

[0061] In this invention, the temperature of the hot finishing rolling can be 270~380℃, 290~360℃, or 310~340℃.

[0062] In this invention, the annealing temperature of the finished product can be 380~420℃, 385~415℃, 390~410℃, or 395~405℃.

[0063] In this invention, the annealing time of the finished product can be 1 to 3 hours, 1.4 to 2.6 hours, or 1.8 to 2.2 hours.

[0064] In this invention, the grain size of the 7-series aluminum alloy sheet can be 100~200μm, 120~180μm, or 140~160μm. That is, according to ASTM standards, the grain size level is G.

[0065] This invention provides a method for preparing 7-series aluminum alloy sheet, comprising the following steps:

[0066] 1) After the milled ingot is heated, it is hot rough rolling and hot finish rolling to obtain a rolled billet;

[0067] 2) The rolled billet obtained in the above steps is subjected to low-temperature quenching and then stretched and straightened, and then subjected to finished product annealing and straightened to obtain 7 series aluminum alloy sheet.

[0068] The present invention first heats the milled ingot, and then performs hot rough rolling and hot finish rolling to obtain a rolled billet.

[0069] In this invention, the 7-series aluminum alloy sheet preferably comprises, by mass percentage: Si≤0.1%, Fe≤0.12%, Cu: 1.2%~1.9%, Mn≤0.06%, Mg: 1.9%~2.6%, Cr: 0.18%~0.25%, Zn: 5.2%~6.2%, Ti≤0.06%, and aluminum.

[0070] In this invention, the 7-series aluminum alloy sheet preferably further includes, by mass percentage, a total impurity content of ≤0.15% and / or a single impurity content of ≤0.05%.

[0071] See Table 1, which details the elemental content of the 7-series aluminum alloy sheet provided by this invention.

[0072] Table 1

[0073]

[0074] Specifically, the amount of Si added can be ≤0.1%, ≤0.09%, or ≤0.09%.

[0075] The amount of Fe added can be ≤0.12%, ≤0.11%, or ≤0.1%.

[0076] The amount of Cu added can be 1.2%~1.9%, 1.3%~1.8%, 1.4%~1.7%, or 1.5%~1.6%.

[0077] The amount of Mn added can be ≤0.06%, ≤0.05%, or ≤0.04%.

[0078] The amount of Mg added can be 1.9%~2.6%, 2.0%~2.5%, 2.1%~2.4%, or 2.2%~2.3%.

[0079] The amount of Cr added can be 0.18%~0.25%, 0.19%~0.24%, 0.20%~0.23%, or 0.21%~0.22%.

[0080] The amount of Zn added can be 5.2%~6.2%, 5.4%~6.0%, or 5.6%~5.8%.

[0081] The amount of Ti added can be ≤0.06%, ≤0.05%, or ≤0.04%.

[0082] In this invention, the step of cladding with aluminum is preferably included before heating.

[0083] In this invention, the heating temperature (i.e. the initial rolling temperature of hot roughing) can be 390~430℃, 395~425℃, 400~420℃, or 405~415℃.

[0084] In this invention, the final rolling temperature of the hot roughing can be 360~400℃, 365~395℃, 370~390℃, or 375~385℃.

[0085] In this invention, the total deformation of the hot rough rolling can be 92%~95%, 92.5%~94.5%, or 93%~94%.

[0086] In this invention, the initial rolling temperature of the hot finishing rolling can be 340~380℃, 345~375℃, 350~370℃, or 355~365℃.

[0087] In this invention, the final rolling temperature of the hot finishing rolling can be 270~310℃, 275~305℃, 280~300℃, or 285~295℃.

[0088] In this invention, the total deformation of the hot finishing rolling can be 68%~78%, 70%~76%, or 72%~74%.

[0089] In this invention, the hot finishing rolling preferably also includes a shearing step.

[0090] Finally, the rolled billet obtained in the above steps is subjected to low-temperature quenching and then stretched and straightened, and then subjected to finished product annealing and straightening to obtain 7-series aluminum alloy sheet.

[0091] In this invention, the temperature of the low-temperature quenching can be 400~420℃, 404~416℃, or 408~412℃.

[0092] In this invention, the holding time for low-temperature quenching can be 20-40 minutes, 24-36 minutes, or 28-32 minutes.

[0093] In this invention, the annealing temperature of the finished product can be 380~420℃, 385~415℃, 390~410℃, or 395~405℃.

[0094] In this invention, the annealing time of the finished product can be 1 to 3 hours, 1.4 to 2.6 hours, or 1.8 to 2.2 hours.

[0095] This invention provides a complete and refined overall technical solution to better ensure the structure, refine the grain size and composition of 7-series aluminum alloy sheets, and further improve the mechanical properties, corrosion resistance and formability of 7-series aluminum alloy sheets. The application of the aforementioned low-temperature quenching in the preparation of 7-series aluminum alloy sheets and a production process for annealed 7-series aluminum alloy medium plates may specifically include the following:

[0096] Introduction to the composition and principle of the present invention

[0097] This invention employs a low-temperature quenching process, resulting in a relatively small and uniform grain size structure in the sheet material before final annealing, thus yielding a product with fine grain size (grade 1-2) after annealing. The traditional process route differs from the new process route in that the new process adds a low-temperature quenching step. The process route is as follows:

[0098] See Figure 1 , Figure 1 This is a traditional process route diagram for annealed 7-series aluminum alloy sheets with a thickness of 5.0~10.0mm.

[0099] See Figure 2 , Figure 2 The process flow diagram for annealed 7-series aluminum alloy sheets with a thickness of 5.0~10.0mm provided by the present invention.

[0100] Principles, Scheme and Explanation

[0101] The principle of this invention: The main strengthening phase of 7-series aluminum alloys is the η phase (MgZn2), etc. During quenching at 410±10℃, due to the low temperature, the strengthening phase cannot fully dissolve into the α solid solution, resulting in a large number of undissolved second-phase particles in the microstructure after quenching. Because the heating temperature is relatively low, the driving force for grain growth is weak, resulting in relatively small and uniform grain sizes after quenching, tending towards equiaxed shapes. After annealing, the initial sheet material, which is "small and uniform equiaxed crystals," has many and evenly distributed recrystallization nucleation points during annealing, ultimately forming grains that remain fine, equiaxed, and of uniform size, without obvious directionality. Sheets produced by traditional processes initially have a "flattened and elongated fibrous structure." Due to uneven deformation in the rolling direction, during annealing and recrystallization, areas with large deformation nucleation occur quickly, and grains grow easily, while areas with small deformation grow slowly. This ultimately results in uneven grain sizes (some are coarse) and a slightly directional microstructure, making it impossible to completely eliminate fibrous traces.

[0102] The key to this invention lies in adding a low-temperature quenching process (quenching temperature 410±10℃, holding time 20-40 minutes), the specific process route is as follows: Figure 2 The process route in the text.

[0103] The present invention provides the application of low-temperature quenching in the preparation of 7-series aluminum alloy sheets and a production process for annealed 7-series aluminum alloy medium plates. The present invention applies a specific low-temperature quenching process to the preparation of annealed 7-series aluminum alloy sheets with a thickness of 5.0~10.0 mm. The present invention also provides a corresponding method for preparing 7-series aluminum alloy sheets. Through low-temperature quenching, the sheet obtains a relatively small and uniform grain size before final annealing, resulting in a product with a grain size of 1~2 after final annealing, thus solving the problem of coarse grain size in current annealed 7-series aluminum alloy sheets with a thickness of 5.0-10.0 mm.

[0104] This invention, through process research, experimental demonstration, and production verification, adds a low-temperature quenching (410±10℃) process before annealing the finished product. This refines the grain size of the annealed sheet, resulting in relatively small and uniform grain sizes that tend towards equiaxed shapes. During annealing, there are numerous and evenly distributed recrystallization nucleation points, and the final grains still maintain a fine, equiaxed, and uniformly sized morphology. Because the sheet obtains a relatively small and uniform grain size before annealing, a product with a fine grain size (grade 1-2) is obtained after annealing. The annealing process provided by this invention successfully solves the problem of coarse grain size in 7-series clad aluminum annealed sheets, and also improves the product's mechanical properties, performance uniformity, forming and processing performance, and corrosion resistance.

[0105] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, illustrates the application of the low-temperature quenching provided by the present invention in the preparation of 7-series aluminum alloy plates and a method for preparing 7-series aluminum alloy plates. However, it should be understood that these embodiments are implemented under the premise of the technical solution of the present invention, and provide detailed implementation methods and specific operating procedures. They are only for further illustrating the features and advantages of the present invention, and are not intended to limit the scope of the claims of the present invention. The scope of protection of the present invention is not limited to the following embodiments.

[0106] Example 1

[0107] T279166, 7475-O, finished product specifications: 6*1200*3200mm.

[0108] Step 1: Milling the surface of the ingot

[0109] The original specifications were 401*1290*4000mm, with milled thicknesses of 10mm and 11mm on the top and bottom surfaces of the main surface, respectively. The thickness after milling the ingot was 380*1290*4000mm.

[0110] Step 2: Aluminum Coating

[0111] After cleaning and milling, the ingot is cast. Aluminum is then clad on the upper and lower surfaces of the cleaned ingot. The aluminum cladding plate has dimensions of 12.0*1265*3702mm.

[0112] Step 3: Heating

[0113] Heating process for clad aluminum ingots: The required metal temperature is 420℃±10℃, the holding time is ≥2 hours, the holding time begins when the metal temperature reaches 410℃, the holding time in the clad aluminum ingot holding furnace is 6.5 hours, the furnace heating time is 28.5 hours, and the metal temperature measured after exiting the furnace is 422℃.

[0114] Step 4: Hot rough rolling

[0115] The initial rolling temperature of the ingot is 412℃. The rough rolling process consists of 20 passes to produce a finished roll with a thickness of 22.05mm. The final rolling temperature of the rough rolling process is 375℃.

[0116] Step 5: Hot finishing rolling

[0117] The initial rolling temperature is 370℃, the thickness is 6.05mm after 3 passes, and the final rolling temperature is 304℃.

[0118] Step 6: Cut

[0119] Cutting length 6800mm, with padding paper between boards.

[0120] Step 7: Low-temperature quenching

[0121] Quenching was performed in a roller hearth furnace at a furnace gas temperature of 410℃ for 15 minutes, followed by a holding time of 20 minutes. After holding, the furnace was removed and water-cooled.

[0122] Step 8: Stretching and straightening

[0123] The sheet material is stretched and leveled in a 400-ton stretching machine, and then stacked with annealed sheet material.

[0124] Step 9: Annealing of finished product

[0125] For temperature-controlled production, the metal requires a temperature of 380~420℃. The furnace gas is initially set at 480℃. When the metal temperature reaches the high point of 380℃, the converter gas is set at 410℃. When the metal temperature reaches the low point of 385℃, heat preservation begins and lasts for 90 minutes. After heat preservation, the metal is cooled in the furnace at a rate not exceeding 25℃ per hour to 250℃ before being removed from the furnace and air-cooled.

[0126] Step 10: Straightening

[0127] The sheet material is stretched and straightened in a 400-ton stretching machine. After stretching, the unevenness is 3mm, and then the material is stacked and sawn into stacks.

[0128] Step 11: Sawing

[0129] The board was cut to size on the saw, and the finished board dimensions were 5.96*1202*3203mm.

[0130] Step 12: Performance Testing

[0131] See Table 2, which shows the mechanical property test results of the 7475-O aluminum alloy prepared in the embodiments of the present invention and the mechanical property test results of its OT761 state.

[0132] See Table 3, which shows the grain size and other test results of the 7475-O aluminum alloy prepared in the embodiments of the present invention, as well as the grain size and other test results of the OT761 state.

[0133] It should be noted that the O state refers to the state of the sheet material prepared by the present invention, while the OT761 state refers to the state of the sheet material after quenching before subsequent application or after the sheet material has been shaped and then quenched according to the use requirements.

[0134] See Table 4, which shows the chemical composition of the 7475-O aluminum alloy prepared in the embodiments of the present invention.

[0135] Table 2

[0136]

[0137] Table 3

[0138]

[0139] Table 4

[0140]

[0141] Based on the test data, the mechanical properties of products annealed using the traditional process and those annealed using the process of this invention are comparable. However, the performance of the new process OT761 is superior to that of the traditional process. (See details...) Figure 3 , Figure 4 .

[0142] See Figure 3 , Figure 3 This invention provides a comparison of the mechanical properties of O-state plates made from products annealed using the traditional annealing process and those annealed using the process described in this invention.

[0143] See Figure 4 , Figure 4 This invention provides a comparison of the mechanical properties of the OT761 state sheet material annealed using the traditional annealing process for the 7475-O product and the annealing process of this invention.

[0144] from Figure 3 , Figure 4 As can be seen from the data curves, the mechanical properties of O-state boards produced by the traditional process and the optimized process of this invention are comparable, and the performance of OT761 produced by the process of this invention is better than that of the traditional process.

[0145] See Figure 5 , Figure 5 Microscopic grain diagram and physical appearance image of the plate prepared by traditional process.

[0146] See Figure 6 , Figure 6 The images show the microstructure and physical appearance of the plate material prepared according to this invention.

[0147] from Figure 5 , 6 As shown in the organizational diagram, the annealed sheet produced by this invention has a grain size of 1-2, which is far superior to the grain size of traditional processes, resulting in excellent overall performance of the sheet.

[0148] The application of low-temperature quenching provided by this invention in the preparation of 7-series aluminum alloy plates and a production process for annealed 7-series aluminum alloy medium plates have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention, including the best mode, and also to enable any person skilled in the art to practice this invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those skilled in the art, several improvements and modifications can be made to this invention without departing from the principles of this invention, and these improvements and modifications also fall within the protection scope of the claims of this invention. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements that are not different from the wording of the claims, or if they include equivalent structural elements that are not substantially different from the wording of the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. Application of low-temperature quenching in the preparation of 7-series aluminum alloy sheets; The temperature for the low-temperature quenching is 400~420℃; The holding time for the low-temperature quenching is 20-40 minutes; The low-temperature quenching process is performed after rolling and before annealing of the finished product in the preparation process.

2. The application according to claim 1, characterized in that, The 7-series aluminum alloy sheet includes 7-series clad aluminum annealed sheet or 7-series non-clad aluminum annealed sheet; The 7-series aluminum alloy sheet includes a 7-series aluminum alloy O-state medium plate; The thickness of the 7-series aluminum alloy sheet is 5~10mm.

3. The application according to claim 1, characterized in that, The rolling process includes hot rolling; The hot rolling includes hot roughing and hot finishing; The temperature of the hot roughing is 350~420℃; The temperature of the hot finishing rolling is 270~380℃.

4. The application according to claim 1, characterized in that, The annealing temperature of the finished product is 380~420℃; The annealing time for the finished product is 1 to 3 hours; The grain size of the 7-series aluminum alloy sheet is 100~200μm.

5. A method for preparing 7-series aluminum alloy sheet, characterized in that, Includes the following steps: 1) After the milled ingot is heated, it is hot rough rolling and hot finish rolling to obtain a rolled billet; 2) The rolled billet obtained in the above steps is subjected to low-temperature quenching and then stretched and straightened, and then subjected to finished product annealing and straightened to obtain 7 series aluminum alloy sheet.

6. The preparation method according to claim 5, characterized in that, The 7-series aluminum alloy sheet comprises, by mass percentage: Si≤0.1%, Fe≤0.12%, Cu: 1.2%~1.9%, Mn≤0.06%, Mg: 1.9%~2.6%, Cr: 0.18%~0.25%, Zn: 5.2%~6.2%, Ti≤0.06%, and aluminum; The heating process also includes a cladding step with aluminum.

7. The preparation method according to claim 5, characterized in that, The heating temperature is 390~430℃; The final rolling temperature of the hot roughing is 360~400℃; The total deformation of the hot roughing is 92% to 95%.

8. The preparation method according to claim 5, characterized in that, The initial rolling temperature of the hot finishing roll is 340~380℃; The final rolling temperature of the hot finishing rolling is 270~310℃; The total deformation of the hot finishing rolling is 68% to 78%.

9. The preparation method according to claim 5, characterized in that, The hot finishing rolling also includes a shearing step; The temperature for the low-temperature quenching is 400~420℃; The holding time for the low-temperature quenching is 20-40 minutes.

10. The preparation method according to claim 5, characterized in that, The annealing temperature of the finished product is 380~420℃; The annealing time for the finished product is 1 to 3 hours.

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