Method for improving grain size of 2A12-O alloy sheet

Abstract

The invention provides the application of controlling the finish rolling temperature of hot finish rolling in the aspect of reducing the grain size of the sheet in the preparation of the 2A12-O state aluminum alloy sheet. And the finish rolling temperature of the hot finish rolling is 230-250 DEG C. The invention further provides a method for preparing the 2A12 aluminum alloy sheet for improving the grain size of the 2A12-O alloy sheet. By optimizing hot rolling process parameters, increasing cooling emulsion flow, improving pass deformation and strictly controlling the finish rolling temperature, low-temperature rolling of the plate in the hot finish rolling stage is achieved on the basis that the surface quality of the plate is effectively guaranteed. The process not only inhibits dynamic recrystallization of the plate in the hot rolling process, but also enhances the cold deformation energy storage of the plate, so that the grains of the plate are finer after the finished product is annealed. The rolling process is improved, low-temperature rolling of hot finish rolling is realized, cold deformation energy storage of the plate is increased, grains of the plate are fine after a finished product is annealed, and the surface quality of the plate is effectively guaranteed.

Description

Technical Field

[0001] This invention belongs to the field of grain size control technology for 2A12-O alloy thin plates, and relates to the application of controlling the final rolling temperature of hot finishing rolling in reducing the grain size of the plate in the preparation of 2A12-O state aluminum alloy thin plates, as well as a method for preparing 2A12 aluminum alloy thin plates, and particularly relates to a method for improving the grain size of 2A12-O alloy thin plates. Background Technology

[0002] Chemical milling, or chemical milling for short, is a process where the parts of a metal material to be machined are exposed to a chemical medium (primarily sodium hydroxide solution for aluminum alloys) for corrosion, while the parts not to be machined are protected, thus achieving the desired shape and dimensions. Chemical milling differs fundamentally from conventional machining; it utilizes chemical or electrochemical corrosion principles to process parts. By effectively controlling the chemical milling fluid, the base material is removed from predetermined locations, extents, and depths on the workpiece to achieve the required dimensions and precision. The entire surface of the part can be etched away, or selectively, in multiple steps, or tapered. Chemical milling of aluminum alloys has become a reliable machining method for forming parts in the aerospace industry, especially in the machining of aircraft skins, where it is far superior to traditional machining methods.

[0003] 2A12 aluminum alloy belongs to the Al-Cu-Mg series of high-strength duralumin. Due to its high strength, low specific gravity, good formability, and machinability, it is widely used in the manufacture of aircraft skin, frame, and wing ribs. Aircraft skin parts are relatively thin, and the most effective method for localized thinning is chemical milling. Chemical milling can well meet the thickness tolerances of the thinned areas of the skin. The surface quality of the skin sheet after chemical milling directly affects the overall performance of the sheet material. For aerospace aluminum alloys, a surface roughness Ra < 1.6 μm is generally required after chemical milling.

[0004] However, existing processes often result in excessive surface roughness after chemical milling of 2A12 alloy skin sheets with a thickness of 5.0mm or more due to the large grain size of the substrate.

[0005] Therefore, finding a more suitable way to solve the aforementioned technical problems of existing 2A12 alloy skin plates with a thickness of 5.0mm or more has become one of the urgent problems to be solved by many front-line researchers in the industry. Summary of the Invention

[0006] In view of this, the technical problem to be solved by the present invention is to provide an application of controlling the final rolling temperature of hot finishing rolling in reducing the grain size of 2A12-O aluminum alloy thin plates, a method for preparing 2A12 aluminum alloy thin plates, and particularly a method for improving the grain size of 2A12-O alloy thin plates. The present invention effectively controls the grain size of the finished plate by improving the rolling process, thereby ensuring the surface quality of the chemically milled surface and ensuring that the product meets the corresponding technical standards. Moreover, the process is simple, the conditions are mild, and it is highly operable, making it more suitable for promotion and application in industrial production.

[0007] This invention provides the application of controlling the final rolling temperature of hot finishing rolling in reducing the grain size of 2A12-O state aluminum alloy sheets;

[0008] The final rolling temperature of the hot finishing mill is 230~250℃.

[0009] Preferably, the grain size of the plate is specifically the grain size of the substrate in the plate;

[0010] The grain size is 110~130μm;

[0011] The thickness of the 2A12 aluminum alloy sheet is 5~10mm;

[0012] The control of the final rolling temperature of hot finishing rolling specifically involves reducing the final rolling temperature of hot finishing rolling.

[0013] The conditions for this application also include increasing the flow rate of the cooling emulsion during the hot finishing rolling process.

[0014] Preferably, reducing the grain size of the board specifically means reducing the grain size of the board while maintaining the surface roughness of the board;

[0015] The surface roughness of the plate is 1.82~2.03μm;

[0016] No cold rolling step is required after hot finishing;

[0017] The conditions for the application also include controlling the rolling speed of the hot finishing mill and / or adjusting the single-pass reduction of the hot finishing mill.

[0018] The 2A12-O state aluminum alloy sheet is specifically an aluminum alloy sheet used for components in aerospace vehicles.

[0019] This invention provides a method for preparing 2A12 aluminum alloy thin plates, comprising the following steps:

[0020] 1) The semi-continuously cast 2A12 alloy square ingot is homogenized and then milled to obtain a surface-treated ingot.

[0021] 2) The upper and lower surfaces of the ingot obtained in the above steps are welded together with LB2 alloy aluminum cladding plates to obtain a welded 2A12 aluminum alloy composite ingot.

[0022] 3) The welded 2A12 aluminum alloy composite ingot obtained in the above steps is heated and kept warm, and then hot rough rolling and hot fine rolling are performed in sequence to obtain hot fine rolled plate. After annealing, the finished 2A12 aluminum alloy sheet is obtained.

[0023] Preferably, the 2A12 aluminum alloy sheet includes a 2A12-O state aluminum alloy sheet;

[0024] The 2A12 alloy square ingot, based on elemental mass content, comprises: Si: ≤0.10wt%; Fe: ≤0.25wt%; Cu: 4.30wt%~4.70wt%; Mn: 0.50wt%~0.70wt%; Mg: 1.30wt%~1.60wt%; Ni: ≤0.10wt%; Zn: ≤0.15wt%; Ti: ≤0.05wt%; the balance being Al and unavoidable impurities;

[0025] The thickness of the square ingot is 400~500mm;

[0026] The width of the square ingot is 1320~2000mm.

[0027] Preferably, the heating rate of the homogenization treatment is 50~90℃ / h;

[0028] The heat preservation temperature for the homogenization treatment is 495~503℃;

[0029] The heat preservation time for the homogenization treatment is 15~30h;

[0030] The cooling rate after homogenization treatment is 80~140℃ / h;

[0031] The milling method includes symmetrical milling;

[0032] The single-sided milling depth of the milled surface is ≥12mm.

[0033] Preferably, the welding specifically involves welding the upper and lower surfaces of the ingot together with LB2 alloy-clad aluminum plates of equal thickness.

[0034] The thickness of the LB2 alloy clad aluminum plate is 25~30mm;

[0035] The temperature for the heating and heat preservation treatment is 460~470℃;

[0036] The heating and heat preservation treatment time is 2~18 hours.

[0037] Preferably, the total reduction in the hot roughing is 420~460mm;

[0038] The hot roughing process involves 20 to 38 passes.

[0039] The rolling speed of the hot roughing is 11~70m / min;

[0040] The initial rolling temperature of the hot finishing mill is 300~400℃.

[0041] Preferably, the hot finishing rolling process involves 3 to 5 passes;

[0042] The single-pass reduction of the hot finishing rolling is 2~10mm;

[0043] The flow rate of the cooling emulsion for hot finishing is 400~600 L / min;

[0044] The hot finishing rolling speed is 60~150m / min;

[0045] The final rolling temperature of the hot finishing mill is 230~250℃.

[0046] Preferably, the thickness of the hot-rolled sheet is ±0.2 mm of the finished sheet thickness;

[0047] The annealing method includes air furnace annealing;

[0048] The annealing heating rate is 25~30℃ / 6h;

[0049] The heat preservation temperature for the homogenization treatment is 360~400℃;

[0050] The heat preservation time for the homogenization treatment is 2-4 hours;

[0051] The cooling rate of the homogenization treatment is 20~26℃ / h.

[0052] This invention provides the application of controlling the final rolling temperature of hot finishing rolling in reducing the grain size of 2A12-O aluminum alloy sheets during preparation; the final rolling temperature of the hot finishing rolling is 230~250℃. Compared with the prior art, this invention addresses the problem that existing 2A12-O aluminum alloy sheets thicker than 5.0mm are prone to coarse grains and excessive grain size in the substrate after rolling, which directly leads to insufficient surface roughness in subsequent chemical milling and seriously affects product quality. Moreover, the research and experiments of this invention have found that adjusting process parameters such as annealing temperature or annealing time has no significant impact on the grain size of the finished sheet while ensuring the strength and toughness of the alloy.

[0053] Based on this, the present invention creatively designs a hot finishing rolling process and uses it to reduce the grain size of 2A12-O aluminum alloy thin sheets. The present invention also provides a corresponding method for preparing 2A12 aluminum alloy thin sheets, which is also a method for improving the grain size of 2A12-O alloy thin sheets. By optimizing hot rolling process parameters, increasing the cooling emulsion flow rate, increasing the deformation per pass, and strictly controlling the final rolling temperature, the present invention achieves low-temperature rolling of the sheet during the hot finishing rolling stage while effectively ensuring the surface quality of the sheet. This process not only inhibits dynamic recrystallization of the sheet during hot rolling but also enhances its cold deformation energy storage, resulting in finer grains in the finished annealed sheet.

[0054] The preparation method provided by this invention effectively controls the grain size of the finished sheet by improving the rolling process, thereby ensuring the surface quality of the chemically milled sheet and ensuring that the product meets the corresponding technical standards. In particular, by adjusting the rolling reduction, controlling the rolling speed, rolling temperature, and increasing the emulsion volume, the final rolling temperature is lowered to prevent dynamic recrystallization during rolling and to increase the energy stored in the cold deformation of the sheet after hot rolling. This results in fine grains in the sheet after annealing, ensuring that the surface roughness of the sheet after chemical milling meets the requirements. Furthermore, to prevent the quenching effect after annealing and to maximize the precipitation of Cu and Mg from the solid solution, the cooling rate is strictly controlled. This invention improves the rolling process, achieving low-temperature hot finishing rolling, increasing the energy stored in the cold deformation of the sheet, resulting in fine grains in the sheet after annealing, and effectively ensuring the surface quality of the sheet. Attached Figure Description

[0055] Figure 1 This is a grain structure diagram of the 2A12-O state aluminum alloy thin plate prepared according to an embodiment of the present invention;

[0056] Figure 2 Grain structure diagram of 2A12-O state aluminum alloy thin sheet prepared by conventional process;

[0057] Figure 3 This is a low-magnification grain image of the 2A12-O state aluminum alloy thin plate prepared in Example 1 of the present invention;

[0058] Figure 4 This is a low-magnification grain image of the 2A12-O state aluminum alloy thin plate prepared in Example 2 of the present invention;

[0059] Figure 5 This is a low-magnification grain image of the 2A12-O state aluminum alloy thin plate prepared in Example 3 of the present invention;

[0060] Figure 6 This is a low-magnification grain diagram of the 2A12-O state aluminum alloy thin plate prepared in Comparative Example 1 of the present invention. Detailed Implementation

[0061] 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.

[0062] 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.

[0063] There are no particular restrictions on the purity of any raw materials used in this invention. However, this invention preferably uses industrial-grade pure materials or materials with the purity requirements commonly used in the preparation of 2A12-O alloy thin plates.

[0064] 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.

[0065] 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.

[0066] This invention provides the application of controlling the final rolling temperature of hot finishing rolling in reducing the grain size of 2A12-O state aluminum alloy sheets;

[0067] The final rolling temperature of the hot finishing mill is 230~250℃.

[0068] In this invention, the final rolling temperature of the hot finishing rolling is 230~250℃, or it can be 234~246℃ or 238~242℃.

[0069] In this invention, the grain size of the plate is preferably the grain size of the substrate in the plate.

[0070] In this invention, the grain size is preferably 110~130μm, more preferably 114~126μm, and even more preferably 118~122μm.

[0071] It should be noted that when the final rolling temperature is 230~250℃, the grain size is controlled at 110~130μm. However, when the final rolling temperature is 280℃, the grain size increases significantly, reaching 215~234μm.

[0072] In this invention, the thickness of the 2A12 aluminum alloy sheet is preferably 5-10 mm, more preferably 6-9 mm, and even more preferably 7-8 mm. Specifically, it can be 5.2, 5.5, 5.8, 6.5, or 7.5 mm.

[0073] In this invention, the control of the final rolling temperature of hot finishing rolling is preferably to reduce the final rolling temperature of hot finishing rolling.

[0074] In this invention, the conditions for the application preferably include increasing the flow rate of the cooling emulsion during the hot finishing rolling process.

[0075] In this invention, the reduction of the grain size of the plate is preferably achieved by reducing the grain size of the plate while maintaining the surface roughness of the plate.

[0076] In this invention, the surface roughness of the plate is preferably 1.82~2.03μm, more preferably 1.87~1.98μm, and even more preferably 1.92~1.93μm.

[0077] It should be noted that when the final rolling temperature is 230~250℃, the surface roughness of the plate after chemical milling is controlled at 1.82~2.03μm. However, when the final rolling temperature is 280℃, the surface roughness of the plate after chemical milling is significantly improved, reaching 3.16~3.37μm.

[0078] In this invention, the hot finishing rolling process preferably does not require a cold rolling step.

[0079] In this invention, the conditions for application preferably include controlling the rolling speed of the hot finishing mill and / or adjusting the single-pass reduction of the hot finishing mill, more preferably controlling the rolling speed of the hot finishing mill or adjusting the single-pass reduction of the hot finishing mill.

[0080] In this invention, the 2A12-O state aluminum alloy sheet is preferably an aluminum alloy sheet used for components in aerospace vehicles.

[0081] This invention provides a method for preparing 2A12 aluminum alloy thin plates, comprising the following steps:

[0082] 1) The semi-continuously cast 2A12 alloy square ingot is homogenized and then milled to obtain a surface-treated ingot.

[0083] 2) The upper and lower surfaces of the ingot obtained in the above steps are welded together with LB2 alloy aluminum cladding plates to obtain a welded 2A12 aluminum alloy composite ingot.

[0084] 3) The welded 2A12 aluminum alloy composite ingot obtained in the above steps is heated and kept warm, and then hot rough rolling and hot fine rolling are performed in sequence to obtain hot fine rolled plate. After annealing, the finished 2A12 aluminum alloy sheet is obtained.

[0085] The present invention first homogenizes the semi-continuously cast 2A12 alloy square ingot, and then mills the surface to obtain the surface-treated ingot.

[0086] In this invention, the 2A12 aluminum alloy sheet preferably includes a 2A12-O state aluminum alloy sheet.

[0087] In this invention, the 2A12 alloy square ingot preferably comprises, by elemental mass content: Si: ≤0.10wt%; Fe: ≤0.25wt%; Cu: 4.30wt%~4.70wt%; Mn: 0.50wt%~0.70wt%; Mg: 1.30wt%~1.60wt%; Ni: ≤0.10wt%; Zn: ≤0.15wt%; Ti: ≤0.05wt%; the balance being Al and unavoidable impurities. More preferably, it comprises Si: ≤0.08wt%; Fe: ≤0.20wt%; Cu: 4.35wt%. %~4.65wt%; Mn: 0.54wt%~0.66wt%; Mg: 1.35wt%~1.55wt%; Ni: ≤0.08wt%; Zn: ≤0.13wt%; Ti: ≤0.04wt%, more preferably Si: ≤0.06wt%; Fe: ≤0.15wt%; Cu: 4.4wt%~4.6wt%; Mn: 0.58wt%~0.62wt%; Mg: 1.4wt%~1.5wt%; Ni: ≤0.06wt%; Zn: ≤0.10wt%; Ti: ≤0.03wt%.

[0088] In this invention, the thickness of the square ingot is preferably 400-500mm, more preferably 420-480mm, even more preferably 440-460mm, and specifically 450mm.

[0089] In this invention, the width of the square ingot is preferably 1320~2000mm, more preferably 1420~1900mm, more preferably 1520~1800mm, more preferably 1620~1700mm, and specifically 1690mm.

[0090] In this invention, the heating rate of the homogenization treatment is preferably 50~90℃ / h, more preferably 55~85℃ / h, more preferably 60~80℃ / h, and even more preferably 65~75℃ / h.

[0091] In this invention, the heat preservation temperature for the homogenization treatment is preferably 495~503℃, more preferably 496~502℃, more preferably 497~501℃, and even more preferably 498~500℃.

[0092] In this invention, the heat preservation time for the homogenization treatment is preferably 15~30h, more preferably 18~27h, and even more preferably 21~24h.

[0093] In this invention, the cooling rate after homogenization treatment is preferably 80~140℃ / h, more preferably 90~130℃ / h, and even more preferably 100~120℃ / h.

[0094] In this invention, the milling method preferably includes symmetrical milling.

[0095] In this invention, the single-sided milling amount of the milled surface is preferably ≥12mm, more preferably ≥13mm, and even more preferably ≥15mm.

[0096] The present invention further uses LB2 alloy cladding aluminum plates to weld the upper and lower surfaces of the ingot obtained in the above steps to obtain a welded 2A12 aluminum alloy composite ingot.

[0097] In this invention, the welding is preferably performed by welding the upper and lower surfaces of the ingot with LB2 alloy-clad aluminum plates of equal thickness.

[0098] In this invention, the thickness of the LB2 alloy-clad aluminum plate is preferably 25~30mm, more preferably 26~29mm, and even more preferably 27~28mm.

[0099] Finally, the 2A12 aluminum alloy composite ingot obtained by the above steps is heated and kept warm, and then subjected to hot rough rolling and hot fine rolling in sequence to obtain hot fine rolled plate. After annealing, the finished 2A12 aluminum alloy sheet is obtained.

[0100] In this invention, the temperature of the heating and heat preservation treatment is preferably 460~470℃, more preferably 462~468℃, and even more preferably 464~466℃.

[0101] In this invention, the heating and heat preservation treatment time is preferably 2 to 18 hours, more preferably 5 to 15 hours, and even more preferably 8 to 12 hours.

[0102] In this invention, the total reduction of the hot roughing is preferably 420~460mm, more preferably 425~455mm, more preferably 430~450mm, and even more preferably 435~445mm.

[0103] In this invention, the number of passes in the hot roughing is preferably 20 to 38, more preferably 24 to 34, and even more preferably 28 to 30.

[0104] In this invention, the rolling speed of the hot roughing is preferably 11~70m / min, more preferably 21~60m / min, and even more preferably 31~50m / min.

[0105] In this invention, the initial rolling temperature of the hot finishing rolling is preferably 300~400℃, more preferably 320~380℃, and even more preferably 340~360℃.

[0106] In this invention, the hot finishing rolling process is preferably performed 3 to 5 times, more preferably 3, 4, or 5 times.

[0107] In this invention, the single-pass reduction of the hot finishing rolling is preferably 2~10mm, more preferably 3.5~8.5mm, and even more preferably 5~7mm.

[0108] In this invention, the flow rate of the cooling emulsion for hot finishing is preferably 400~600L / min, more preferably 440~560L / min, and even more preferably 480~520L / min.

[0109] In this invention, the rolling speed of the hot finishing mill is preferably 60~150m / min, more preferably 80~130m / min, and even more preferably 100~110m / min.

[0110] In this invention, the final rolling temperature of the hot finishing rolling is preferably 230~250℃, more preferably 234~246℃, and even more preferably 238~242℃.

[0111] In this invention, the thickness of the hot-rolled sheet is preferably ±0.2mm, ±0.15mm, or ±0.1mm.

[0112] In this invention, the annealing method preferably includes air furnace annealing.

[0113] In this invention, the heating rate of the annealing is preferably 25~30℃ / 6h, more preferably 26~29℃ / 6h, and even more preferably 27~28℃ / 6h.

[0114] In this invention, the heat preservation temperature for the homogenization treatment is preferably 360~400℃, more preferably 365~395℃, more preferably 370~390℃, and even more preferably 375~385℃.

[0115] In this invention, the heat preservation time for the homogenization treatment is preferably 2 to 4 hours, more preferably 2.4 to 3.6 hours, and even more preferably 2.8 to 3.2 hours.

[0116] In this invention, the cooling rate of the homogenization treatment is preferably 20~26℃ / h, more preferably 21~25℃ / h, and even more preferably 22~24℃ / h.

[0117] This invention aims to complete and refine the overall technical solution, better guarantee the performance and microstructure of 2A12 aluminum alloy thin plates, further reduce the grain size and surface roughness of 2A12 aluminum alloy thin plates, and specifically includes the application of controlling the final rolling temperature of hot finishing in reducing the grain size of 2A12-O state aluminum alloy thin plates, as well as a method for improving the grain size of 2A12-O alloy thin plates. The method may include the following:

[0118] Process flow: Ingot casting → Homogenization → Milling → Aluminum cladding → Ingot heating → Hot rough rolling → Hot finish rolling → Finished product annealing.

[0119] See Table 1, which shows the composition of the 2A12 alloy square ingot produced by the semi-continuous casting method of the present invention.

[0120] Table 1

[0121]

[0122] The specific process is as follows:

[0123] (i) A 2A12 alloy square ingot was prepared by a semi-continuous casting method. The aluminum alloy square ingot has a thickness of 450 mm, a width of 1690 mm, and a composition as shown in Table 1.

[0124] (ii) The ingots obtained in step one are homogenized.

[0125] Specifically, the homogenization process is as follows: heating rate of 50~90℃ / h, holding at 495~503℃ for 15~30h, followed by cooling at a rate of 80~140℃ / h.

[0126] (iii) The homogenized ingot obtained in step two is subjected to milling and head and tail sawing processes to obtain a smooth ingot substrate.

[0127] Specifically, the milling process for ingots is as follows: symmetrical milling, single-sided milling amount ≥12mm, the thickness of the ingot after milling is required to be 426±2mm, and the transverse thickness difference of the ingot after milling is ≤1mm, and the longitudinal thickness difference is ≤2mm.

[0128] (iv) The upper and lower surfaces of the milled ingot are welded together with LB2 alloy aluminum plates of equal thickness on both sides to obtain the welded 2A12 aluminum alloy composite ingot.

[0129] Specifically, the aluminum cladding process requires: double-sided aluminum cladding, LB2 aluminum alloy cladding plate, cladding rate ≥2%, and aluminum plate thickness 28±0.30mm.

[0130] (v) Heat the welded 2A12 aluminum alloy composite ingot to 460℃~470℃ and keep it at that temperature for 2h~18h.

[0131] (vi) The heated ingot is hot rough rolled to a thickness of 20 mm, and finally hot finish rolled to a finished thickness of 5.0 ± 0.15 mm. After rolling, the plate is cleaned to ensure that the emulsion on the plate is clean.

[0132] Specifically, to ensure that the sheet retains sufficient energy for cold deformation, resulting in fine grains after annealing, the final rolling temperature of the hot finishing roll should be controlled at 230~250℃. This can be achieved by slow rolling, increasing the flow rate of the cooling emulsion, and increasing the deformation per pass.

[0133] Specifically, the present invention does not require cold rolling after hot finishing.

[0134] (vii) Anneal the hot rolled sheet obtained in step six to obtain the finished sheet.

[0135] Specifically, the finished product is annealed in an air furnace with a heating rate of 25-30℃ / 6h, a holding temperature of 360-400℃ / 6h, and a cooling rate of approximately 20-26℃ / h.

[0136] See Table 2, which compares the performance parameters of plates prepared at different hot finishing temperatures provided by the present invention.

[0137] Table 2

[0138]

[0139] As can be seen from the data requirements in Table 2, the mechanical properties of 2A12-O state aluminum alloy sheets need to be controlled within the standard range. This invention reduces grain size, which on the one hand helps reduce sheet roughness and ensures surface quality after chemical milling; on the other hand, if the grains are too large, deformation lines or "orange peel" phenomena are easily generated during subsequent processing such as bending and stretching, making it difficult to meet the subsequent processing requirements of 2A12-O state aluminum alloy sheets. Based on the needs of its subsequent applications, moderate mechanical properties are sufficient. For 2A12 aluminum alloy sheets, the good plasticity of the O state significantly reduces the difficulty and cracking risk of complex forming processes such as deep drawing and bending, while T3 or T4 state sheets are prone to cracking due to their poor plasticity during such processing.

[0140] The present invention provides the application of controlling the final rolling temperature of hot finishing rolling in reducing the grain size of 2A12-O aluminum alloy sheets, and a method for improving the grain size of 2A12-O alloy sheets. The present invention designs a hot finishing rolling process and uses it to reduce the grain size of 2A12-O aluminum alloy sheets. The present invention also provides a corresponding method for preparing 2A12 aluminum alloy sheets, which is also a method for improving the grain size of 2A12-O alloy sheets. By optimizing hot rolling process parameters, increasing the flow rate of the cooling emulsion, increasing the deformation per pass, and strictly controlling the final rolling temperature, the present invention achieves low-temperature rolling of the sheet during the hot finishing stage while effectively ensuring the surface quality of the sheet. This process not only inhibits the dynamic recrystallization of the sheet during hot rolling but also enhances its cold deformation energy storage, resulting in finer grains in the annealed finished sheet.

[0141] The preparation method provided by this invention effectively controls the grain size of the finished sheet by improving the rolling process, thereby ensuring the surface quality of the chemically milled sheet and ensuring that the product meets the corresponding technical standards. In particular, by adjusting the rolling reduction, controlling the rolling speed, rolling temperature, and increasing the emulsion volume, the final rolling temperature is lowered to prevent dynamic recrystallization during rolling and to increase the energy stored in the cold deformation of the sheet after hot rolling. This results in fine grains in the sheet after annealing, ensuring that the surface roughness of the sheet after chemical milling meets the requirements. Furthermore, to prevent the quenching effect after annealing and to maximize the precipitation of Cu and Mg from the solid solution, the cooling rate is strictly controlled. This invention improves the rolling process, achieving low-temperature hot finishing rolling, increasing the energy stored in the cold deformation of the sheet, resulting in fine grains in the sheet after annealing, and effectively ensuring the surface quality of the sheet.

[0142] To further illustrate the present invention, the following describes in detail, with reference to embodiments, the application of the control of the final rolling temperature of hot finishing in reducing the grain size of 2A12-O state aluminum alloy thin plates provided by the present invention, and a method for preparing 2A12 aluminum alloy thin plates. However, it should be understood that these embodiments are implemented under the premise of the technical solution of the present invention, and detailed implementation methods and specific operating procedures are given only to further illustrate 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.

[0143] Example 1

[0144] The composition of the semi-continuously cast 2A12 alloy square ingot is shown in Table 3.

[0145] Table 3

[0146]

[0147] (i) A 2A12 alloy square ingot was prepared by a semi-continuous casting method. The aluminum alloy square ingot has a thickness of 450 mm, a width of 1690 mm, and a composition as shown in Table 3.

[0148] (ii) The ingot obtained in step one is subjected to homogenization treatment. The homogenization treatment process is as follows: heating rate of 70℃ / h, holding at 498℃ for 20h, followed by cooling at a cooling rate of 80℃ / h.

[0149] (iii) The homogenized ingot obtained in step two is subjected to milling and head and tail sawing processes to obtain a smooth ingot substrate. The ingot milling process is as follows: symmetrical milling, single-sided milling amount of 12.5mm, the thickness of the ingot after milling is required to be 425mm, the transverse thickness difference of the ingot after milling is ≤1mm, and the longitudinal thickness difference is ≤2mm.

[0150] (iv) The upper and lower surfaces of the milled ingot are welded together with LB2 alloy cladding plates of equal thickness on both sides to obtain the welded 2A12 aluminum alloy composite ingot. Cladling process requirements: double-sided cladding, LB2 alloy cladding plate, cladding rate ≥2%, cladding plate thickness 28mm.

[0151] (v) Heat the welded 2A12 aluminum alloy composite ingot to 460°C and keep it at that temperature for 4 hours.

[0152] (vi) The heated ingot is hot rough rolled to a thickness of 20 mm, and then hot finish rolled to a finished thickness of 5.0 mm. After rolling, the plate is cleaned to ensure that the emulsion on the plate is completely removed. The final rolling temperature of the hot finish rolling of the plate is controlled at 240℃.

[0153] (vii) Anneal the hot-rolled sheet obtained in step six to obtain the finished sheet. The finished sheet is annealed in an air furnace with a heating rate of 30℃ / 6h, a holding time of 380℃ / 6h, and a cooling rate of approximately 23℃ / h.

[0154] The 2A12-O state aluminum alloy thin plate prepared in Example 1 of the present invention was characterized, compared and tested.

[0155] See Figure 1 , Figure 1 This is a grain structure diagram of the 2A12-O state aluminum alloy thin plate prepared according to an embodiment of the present invention.

[0156] See Figure 2 , Figure 2 Grain structure diagram of 2A12-O state aluminum alloy thin sheet prepared by conventional process.

[0157] The test results show that the low-magnification grain size of the prepared 2A12-O state aluminum alloy thin plate substrate is approximately grade 1, such as... Figure 3 As shown, the surface roughness of the substrate is 1.82 μm. Figure 3This is a low-magnification grain image of the 2A12-O state aluminum alloy sheet prepared in Example 1 of the present invention. The mechanical properties of the sheet substrate are tensile strength of 161 MPa, yield strength of 85 MPa, and elongation of 24.5%.

[0158] Example 2

[0159] The composition of the semi-continuously cast 2A12 alloy square ingot is shown in Table 3.

[0160] (i) A 2A12 alloy square ingot was prepared by a semi-continuous casting method. The aluminum alloy square ingot has a thickness of 450 mm, a width of 1690 mm, and a composition as shown in Table 3.

[0161] (ii) The ingot obtained in step one is subjected to homogenization treatment. The homogenization treatment process is as follows: heating rate of 70℃ / h, holding at 498℃ for 20h, followed by cooling at a cooling rate of 80℃ / h.

[0162] (iii) The homogenized ingot obtained in step two is subjected to milling and head and tail sawing processes to obtain a smooth ingot substrate. The ingot milling process is as follows: symmetrical milling, single-sided milling amount of 12.5mm, the thickness of the ingot after milling is required to be 425mm, the transverse thickness difference of the ingot after milling is ≤1mm, and the longitudinal thickness difference is ≤2mm.

[0163] (iv) The upper and lower surfaces of the milled ingot are welded together with LB2 alloy cladding plates of equal thickness on both sides to obtain the welded 2A12 aluminum alloy composite ingot. Cladling process requirements: double-sided cladding, LB2 alloy cladding plate, cladding rate ≥2%, cladding plate thickness 28mm.

[0164] (v) Heat the welded 2A12 aluminum alloy composite ingot to 460°C and keep it at that temperature for 4 hours.

[0165] (vi) The heated ingot is hot rough rolled to a thickness of 20 mm, and then hot finish rolled to a finished thickness of 5.0 mm. After rolling, the plate is cleaned to ensure that the emulsion on the plate is completely removed. The final rolling temperature of the plate is controlled at 230℃.

[0166] (vii) Anneal the hot-rolled sheet obtained in step six to obtain the finished sheet. The finished sheet is annealed in an air furnace with a heating rate of 30℃ / 6h, a holding time of 380℃ / 6h, and a cooling rate of approximately 23℃ / h.

[0167] The 2A12-O state aluminum alloy thin plate prepared in Example 2 of the present invention was characterized and tested.

[0168] The test results show that the low-magnification grain size of the prepared 2A12-O state aluminum alloy thin plate substrate is approximately grade 1, such as... Figure 4 As shown, the surface roughness of the substrate is 1.97 μm. Figure 4 This is a low-magnification grain image of the 2A12-O state aluminum alloy sheet prepared in Example 2 of the present invention. The mechanical properties of the sheet substrate are tensile strength of 162 MPa, yield strength of 84 MPa, and elongation of 23.5%.

[0169] Example 3

[0170] The composition of the semi-continuously cast 2A12 alloy square ingot is shown in Table 3.

[0171] (i) A 2A12 alloy square ingot was prepared by a semi-continuous casting method. The aluminum alloy square ingot has a thickness of 450 mm, a width of 1690 mm, and a composition as shown in Table 3.

[0172] (ii) The ingot obtained in step one is subjected to homogenization treatment. The homogenization treatment process is as follows: heating rate of 70℃ / h, holding at 498℃ for 20h, followed by cooling at a cooling rate of 80℃ / h.

[0173] (iii) The homogenized ingot obtained in step two is subjected to milling and head and tail sawing processes to obtain a smooth ingot substrate. The ingot milling process is as follows: symmetrical milling, single-sided milling amount of 12.5mm, the thickness of the ingot after milling is required to be 425mm, the transverse thickness difference of the ingot after milling is ≤1mm, and the longitudinal thickness difference is ≤2mm.

[0174] (iv) The upper and lower surfaces of the milled ingot are welded together with LB2 alloy cladding plates of equal thickness on both sides to obtain the welded 2A12 aluminum alloy composite ingot. Cladling process requirements: double-sided cladding, LB2 alloy cladding plate, cladding rate ≥2%, cladding plate thickness 28mm.

[0175] (v) Heat the welded 2A12 aluminum alloy composite ingot to 460°C and keep it at that temperature for 4 hours.

[0176] (vi) The heated ingot is hot rough rolled to a thickness of 20 mm, and then hot finish rolled to a finished thickness of 5.0 mm. After rolling, the plate is cleaned to ensure that the emulsion on the plate is completely removed. The final rolling temperature of the plate is controlled at 250℃.

[0177] (vii) Anneal the hot-rolled sheet obtained in step six to obtain the finished sheet. The finished sheet is annealed in an air furnace with a heating rate of 30℃ / 6h, a holding time of 380℃ / 6h, and a cooling rate of approximately 23℃ / h.

[0178] The 2A12-O state aluminum alloy thin plate prepared in Example 3 of the present invention was characterized and tested.

[0179] The test results show that the low-magnification grain size of the prepared 2A12-O state aluminum alloy thin plate substrate is approximately grade 1, such as... Figure 5As shown, the surface roughness of the substrate is 2.03 μm. Figure 5 This is a low-magnification grain image of the 2A12-O state aluminum alloy thin sheet prepared in Example 3 of the present invention. The mechanical properties of the thin sheet substrate are tensile strength of 158 MPa, yield strength of 86 MPa, and elongation of 25%.

[0180] Comparative Example 1

[0181] The composition of the semi-continuously cast 2A12 alloy square ingot is shown in Table 3.

[0182] (i) A 2A12 alloy square ingot was prepared by a semi-continuous casting method. The aluminum alloy square ingot has a thickness of 450 mm, a width of 1690 mm, and a composition as shown in Table 3.

[0183] (ii) The ingot obtained in step one is subjected to homogenization treatment. The homogenization treatment process is as follows: heating rate of 70℃ / h, holding at 498℃ for 20h, followed by cooling at a cooling rate of 80℃ / h.

[0184] (iii) The homogenized ingot obtained in step two is subjected to milling and head and tail sawing processes to obtain a smooth ingot substrate. The ingot milling process is as follows: symmetrical milling, single-sided milling amount of 12.5mm, the thickness of the ingot after milling is required to be 425mm, the transverse thickness difference of the ingot after milling is ≤1mm, and the longitudinal thickness difference is ≤2mm.

[0185] (iv) The upper and lower surfaces of the milled ingot are welded together with LB2 alloy cladding plates of equal thickness on both sides to obtain the welded 2A12 aluminum alloy composite ingot. Cladling process requirements: double-sided cladding, LB2 alloy cladding plate, cladding rate ≥2%, cladding plate thickness 28mm.

[0186] (v) Heat the welded 2A12 aluminum alloy composite ingot to 460°C and keep it at that temperature for 4 hours.

[0187] (vi) The heated ingot is hot rough rolled to a thickness of 20 mm, and then hot finish rolled to a finished thickness of 5.0 mm. After rolling, the plate is cleaned to ensure that the emulsion on the plate is completely removed. The final rolling temperature of the plate is controlled at 300℃.

[0188] (vii) Anneal the hot-rolled sheet obtained in step six to obtain the finished sheet. The finished sheet is annealed in an air furnace with a heating rate of 30℃ / 6h, a holding time of 380℃ / 6h, and a cooling rate of approximately 23℃ / h.

[0189] The 2A12-O state aluminum alloy sheet prepared in Comparative Example 1 of this invention was characterized and tested.

[0190] The test results show that the low-magnification grain size of the prepared 2A12-O state aluminum alloy thin plate substrate is significantly worse than that of the present invention, such as... Figure 6 As shown, the surface roughness of the substrate is 4.16 μm. Figure 6 This is a low-magnification grain diagram of the 2A12-O state aluminum alloy sheet prepared in Comparative Example 1 of this invention. The mechanical properties of the sheet substrate are tensile strength 161 MPa, yield strength 86 MPa, and elongation 24%.

[0191] The foregoing has provided a detailed description of the application of controlling the final rolling temperature of hot finishing in reducing the grain size of 2A12-O aluminum alloy thin plates, as well as a method for improving the grain size of 2A12-O alloy thin plates. Specific examples have been used to illustrate the principles and implementation methods of the invention. The above descriptions of the embodiments are merely for the purpose of helping to understand the method and core ideas of the invention, including the best mode, and also to enable any person skilled in the art to practice the 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 the invention without departing from the principles of the invention, and these improvements and modifications also fall within the scope of protection of the claims of the 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 textual description of the claims, or if they include equivalent structural elements that are not substantially different from the textual description of the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. Use of controlling the finishing temperature of hot finishing in reducing the grain size of a 2A12-O state aluminum alloy sheet in preparation; The finishing temperature of the hot finishing is 230-250℃.

2. Use according to claim 1, characterized in that, The grain size of the sheet is specifically the grain size of the base material in the sheet; The grain size is 110-130μm in size; The thickness of the 2A12 aluminum alloy sheet is 5-10mm; The controlling of the finishing temperature of the hot finishing is specifically reducing the finishing temperature of the hot finishing; The conditions of the use further include increasing the flow of the cooling emulsion in the hot finishing process.

3. Use according to claim 1, characterized in that, The reducing of the grain size of the sheet is specifically reducing the grain size of the sheet while ensuring the roughness of the surface of the sheet; The roughness of the surface of the sheet is 1.82-2.03μm; The hot finishing is followed by no cold rolling step; The conditions of the use further include controlling the rolling speed of the hot finishing and / or adjusting the single pass reduction of the hot finishing; The 2A12-O state aluminum alloy sheet is specifically an aluminum alloy sheet used in components in an aerospace vehicle.

4. A method of producing a 2A12 aluminum alloy sheet, characterized by, The method comprises the following steps: 1) homogenizing a semi-continuous cast 2A12 alloy ingot, then after face milling, obtaining a surface-treated ingot; 2) welding the upper and lower surfaces of the ingot obtained in the above step respectively using LB2 alloy aluminum clad plates, obtaining a welded 2A12 aluminum alloy composite ingot; 3) heating and holding the welded 2A12 aluminum alloy composite ingot obtained in the above step, then sequentially passing through hot rough rolling and hot finishing, obtaining a hot finished sheet, and then after annealing, obtaining a finished 2A12 aluminum alloy sheet.

5. The method of claim 1, wherein, The 2A12 aluminum alloy sheet includes a 2A12-O state aluminum alloy sheet; The 2A12 alloy ingot comprises, in terms of element mass content: Si: ≤0.10wt%; Fe: ≤0.25wt%; Cu: 4.30wt%-4.70wt%; Mn: 0.50wt%-0.70wt%; Mg: 1.30wt%-1.60wt%; Ni: ≤0.10wt%; Zn: ≤0.15wt%; Ti: ≤0.05wt%; the balance of Al and unavoidable impurities; The thickness of the ingot is 400-500mm; The width of the ingot is 1320-2000mm.

6. The method of claim 1, wherein, The heating rate of the homogenization treatment is 50-90℃ / h; The holding temperature of the homogenization treatment is 495-503℃; The holding time of the homogenization treatment is 15-30h; The cooling rate after the homogenization treatment is 80-140℃ / h; The face milling method includes symmetrical face milling; The single face milling amount of the face milling is ≥12mm.

7. The method of claim 1, wherein, The welding is specifically welding the upper and lower surfaces of the ingot respectively using LB2 alloy aluminum clad plates with equal thickness; The thickness of the LB2 alloy aluminum clad plate is 25-30mm; The temperature of the heating and holding treatment is 460-470℃; The time of the heating and holding treatment is 2-18h.

8. The method of claim 1, wherein, The total reduction of the hot rough rolling is 420-460mm; The number of passes of the hot rough rolling is 20-38. The rolling speed of the hot rough rolling is 11-70 m / min; The opening rolling temperature of the hot finish rolling is 300-400 ℃.

9. The method of claim 1, wherein, The pass number of the hot finish rolling is 3-5 times; The single pass reduction of the hot finish rolling is 2-10 mm; The cooling emulsion flow of the hot finish rolling is 400-600 L / min; The rolling speed of the hot finish rolling is 60-150 m / min; The final rolling temperature of the hot finish rolling is 230-250 ℃.

10. The method of claim 1, wherein, The thickness of the hot finish rolling plate is the finished plate thickness ± 0.2 mm; The annealing mode comprises air furnace annealing; The heating rate of the annealing is 25-30 ℃ / 6 h; The holding temperature of the homogenization treatment is 360-400 ℃; The holding time of the homogenization treatment is 2-4 h; The cooling rate of the homogenization treatment is 20-26 ℃ / h.

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