Production method of high-strength 2xxx series aluminum alloy plate

Abstract

The invention relates to the technical field of aluminum alloy production, and provides a high-strength 2xxx series aluminum alloy plate production method which comprises the following steps: casting an aluminum alloy slab ingot; homogenizing treatment: hot rolling; the preheating temperature is 440 + / -20 DEG C, and the heat preservation time is 2-4 hours; the finish rolling temperature is not lower than 300 DEG C; carrying out solid solution quenching treatment; the solid solution temperature is 496 + / -3 DEG C, and the solid solution time is 20-500 min; the quenching cooling mode is water cooling; stretching is conducted; performing natural aging treatment; and the standing time of the plate is not less than 4 days in a room temperature environment. Therefore, by optimizing the hot rolling process, the solid solution quenching process, the aging process and the component proportion, the strength of the aluminum alloy plate is improved. The mechanical property requirements in the special field are met, and the method is suitable for the high-strength field. The technical problem that the strength of an aluminum alloy plate produced through an existing technology cannot meet the strength standard in the special field is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of aluminum alloy production, and in particular relates to a method for producing a high-strength 2xxx series aluminum alloy plate. Background Art

[0002] 2xxx series aluminum alloys (Al-Cu-Mg alloys) have the characteristics of low density, high specific strength, high specific modulus, good machining performance and fatigue performance. They are widely used in modern high-end equipment manufacturing industries such as aerospace, weapons, and high-speed rail. For example, 2024-T351 aluminum alloy sheets are widely used in fuselages.

[0003] However, with the improvement of aircraft performance requirements, the performance requirements for 2024-T351 aluminum alloy sheets are becoming more and more stringent. Especially for some special workpieces, the mechanical properties of the sheets are far beyond the ordinary standards. The 2024 aluminum alloy sheets produced by the existing process are not strong enough, which greatly limits their application in special fields.

[0004] In summary, the prior art obviously has inconveniences and defects in practical use, so it is necessary to improve it. Summary of the invention

[0005] In view of the above-mentioned defects, the present invention mainly provides a method for producing high-strength 2xxx series aluminum alloy plates to solve the technical problem that the strength of aluminum alloy plates produced by existing processes cannot meet the strength standards of special fields.

[0006] In order to solve the above problems, the present invention provides a method for producing a high-strength 2xxx series aluminum alloy plate, comprising the following steps:

[0007] S1, cast aluminum alloy ingot;

[0008] The thickness of aluminum alloy slab is 420mm-480mm;

[0009] S2, homogenization treatment: make the composition in the ingot more uniform and eliminate micro segregation structure;

[0010] The homogenization temperature is 496±3°C and the holding time is 30 hours;

[0011] S3, hot rolling: rolling the aluminum alloy flat ingot into a plate;

[0012] The preheating temperature of the hot rolling is: 440℃±20℃, the holding time is: 2~4h; the final rolling temperature is not less than 300℃;

[0013] S4, solution quenching treatment;

[0014] Solution temperature: 496±3℃, solution time: 20-500min; quenching cooling method is water cooling;

[0015] S5, stretch;

[0016] The aluminum alloy plate is stretched to correct the plate shape and eliminate internal stress; the stretching deformation is: 1.5-3.0%; the stretching residence time does not exceed 30 minutes;

[0017] S6, natural aging treatment;

[0018] The board should be left at room temperature for no less than 4 days.

[0019] According to the high-strength 2xxx series aluminum alloy plate production method of the present invention, the casting process includes smelting, refining, online slag removal, degassing and filtering treatment; the smelting temperature is: 690-755°C; the refining temperature is: 700-750°C, and the refining time is: 20-90 minutes.

[0020] According to the method for producing high-strength 2xxx series aluminum alloy sheet materials of the present invention, the aluminum alloy slab is subjected to sawing and milling treatment after homogenization treatment;

[0021] The sawing and milling process includes flat ingot milling and eight-sided milling: the large face milling surface area is 10-25mm, and the small face milling surface area is 5-20mm; the sawing amount: the gate end is ≥100mm, and the expansion end is ≥300mm.

[0022] According to the method for producing high-strength 2xxx series aluminum alloy plates of the present invention, the final rolling temperature is set to 300-330°C.

[0023] According to the method for producing high-strength 2xxx series aluminum alloy plates of the present invention, the final rolling temperature is increased by increasing the preheating temperature or reducing the number of processing passes.

[0024] According to the method for producing high-strength 2xxx series aluminum alloy plates of the present invention, the hot rolling step includes first performing 2-4 cross-rolling passes, then rotating the ingot by 90°C and then performing longitudinal rolling until the aluminum alloy flat ingot is rolled to a predetermined thickness.

[0025] According to the method for producing high-strength 2xxx series aluminum alloy plates of the present invention, the solution temperature is 496° C. and the solution time is 43 minutes.

[0026] According to the method for producing high-strength 2xxx series aluminum alloy plates of the present invention, the standing time of the natural aging treatment is 4-7 days.

[0027] According to the method for producing high-strength 2xxx series aluminum alloy sheet materials of the present invention, the material of the aluminum alloy sheet materials is 2024-T351 aluminum alloy.

[0028] According to the high-strength 2xxx series aluminum alloy sheet production method of the present invention, the composition of the 2024-T351 aluminum alloy sheet is, Si: 0-0.08, Fe: 0-0.10%, Cu: 4.0-4.4%, Mn: 0.6-0.9%, Mg: 1.4-1.6%, Cr: 0-0.10%; Zn: 0-0.20%, Ti: 0.02-0.06%, impurity elements ≤0.15%, and the rest is Al.

[0029] In summary, the present invention improves the strength of the aluminum alloy sheet by optimizing the hot rolling process, the solution quenching process, the aging process and the composition ratio. It meets the mechanical property requirements of special fields and can be applied to high-strength fields. It solves the technical problem that the strength of the aluminum alloy sheet produced by the existing process cannot meet the strength standards of special fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a backscattered SEM morphology image of a fracture of an aluminum alloy plate according to an embodiment of the present invention; DETAILED DESCRIPTION

[0031] The present invention provides a method for producing a high-strength 2xxx series aluminum alloy plate, comprising the following steps:

[0032] S1, cast aluminum alloy ingot;

[0033] The thickness of the aluminum alloy flat ingot of the present invention is 420 mm to 480 mm, so that the subsequent rolling has a sufficient reduction amount.

[0034] As an implementation method, the casting process includes smelting, refining, online slag removal, degassing and filtering treatment; the smelting temperature is: 690-755°C; the refining temperature is: 700-750°C, and the refining time is: 20-90 minutes.

[0035] S2, homogenization treatment: make the composition of the ingot more uniform, eliminate micro segregation structure, improve the processing deformation ability of the ingot and increase the mechanical properties, elongation after fracture and other indicators of the plate.

[0036] The temperature of the homogenization treatment of the present invention is: 496±3°C, and the insulation time is 30 hours;

[0037] Furthermore, the aluminum alloy slab of the present invention is sawn and milled after homogenization to remove the macroscopic component segregation portion on the surface of the ingot.

[0038] The sawing and milling process includes: flat ingot milling and eight-sided milling: large face milling surface area is 10-25mm, small face milling surface area is 5-20mm; sawing amount: gate end ≥100mm, expansion end ≥300mm;

[0039] S3, hot rolling: rolling the aluminum alloy flat ingot into a plate;

[0040] As an embodiment, the preheating temperature of the hot rolling of the present invention is: 440°C ± 20°C, the holding time is: 2 to 4h; the final rolling temperature is not less than 300°C;

[0041] Preferably, the aluminum alloy slab of the present invention is kept warm for 2 hours before being rolled out of the furnace to avoid abnormal grain growth; during hot rolling, the reduction amount of the last pass is controlled. Work hardening occurs after rolling, so that the mechanical properties of the finished plate are improved.

[0042] The inventors set different final rolling temperatures and rolled the plates to the same thickness. After processing them into finished products according to the method of this patent, they tested their mechanical properties. The test results are shown in Table 1.

[0043] The present invention adopts a higher final rolling temperature to significantly improve the mechanical properties of the finished plate. Preferably, the final rolling temperature of the present invention is set to 300-330°C.

[0044] As an implementation method of increasing the final rolling temperature, the final rolling temperature can be increased by increasing the preheating temperature. Optionally, the preheating temperature can be increased by 10-20°C to approach the upper limit, but recrystallization of the sheet should be avoided.

[0045] As an implementation method for increasing the final rolling temperature, the final rolling temperature can be increased by reducing the number of processing passes and shortening the rolling time, for example, reducing 15 passes to 11-13 passes or reducing 21 passes to 15-18 passes.

[0046] As an embodiment of the hot rolling step, the hot rolling step includes firstly performing 2-4 cross-rolling passes, then rotating the ingot by 90°C and then performing longitudinal rolling until the aluminum alloy flat ingot is rolled to a predetermined thickness.

[0047] The present invention effectively improves the transverse mechanical properties by first performing transverse rolling and then performing longitudinal rolling, thereby reducing the difference between the transverse and longitudinal properties of the plate.

[0048] Table 1: Relationship between final rolling temperature and mechanical properties of plates

[0049]

[0050]

[0051] S4, solution quenching treatment;

[0052] Solution temperature: 496±3℃, solution time: 20-500min; quenching cooling method is water cooling;

[0053] As an embodiment, the quenching cooling method of the present invention is: cooling water is sprayed on the upper and lower surfaces of the plate at the same time; after the plate reaches the insulation time, it is transferred out of the heating furnace. During the transfer process, cooling water is sprayed on the upper and lower surfaces of the plate at the same time to ensure the hardenability of the plate and retain more solute atoms.

[0054] Furthermore, the ratio of the water spray volume on the upper and lower surfaces is 0.65-0.85, which ensures the uniformity of cooling on the upper and lower surfaces.

[0055] Preferably, the temperature of cooling water does not exceed 30°C to ensure flatness and hardenability.

[0056] Preferably, the transfer speed of the plate is not less than 100 mm / s, preferably 100-400 mm / s, to ensure the shape of the plate out of the oven.

[0057] S5, stretch;

[0058] The aluminum alloy plate is stretched to correct the plate shape and eliminate internal stress; the stretching deformation is: 1.5-3.0%; the stretching residence time does not exceed 30 minutes;

[0059] The inventor selected multiple plates of the same thickness, changed the amount of tensile deformation, and processed them into finished products according to the method of this patent, and then tested their mechanical properties. The test results are shown in Table 2.

[0060] Preferably, the stretching deformation of the present invention is 2.0-2.5%.

[0061] Table 2: Relationship between tensile deformation and mechanical properties

[0062] Sample No. Tensile deformation / % Tensile strength / MPa Yield strength / MPa Elongation after break / % 1 1.4～1.5 466 296 19.5 2 1.7～1.8 467 298 18.5 3 1.9～2.0 468 297 20.0 4 2.0～2.1 468 298 18.5 5 2.1～2.3 469 296 20.0 6 2.3～2.5 470 298 18.5

[0063] S6, natural aging treatment;

[0064] The board should be left at room temperature for no less than 4 days;

[0065] The inventor selected a plurality of plates of the same thickness; solution temperature: 496°C, solution time: 43 min; tested the mechanical properties of the plates with different standing times, and the test results are shown in Table 3.

[0066] As an embodiment, the standing time of the natural aging treatment of the present invention is 4-7 days.

[0067] Table 3: Relationship between static time and mechanical properties

[0068]

[0069] Aluminum alloy sheets form supersaturated solid solutions after solution quenching. As the natural aging process proceeds, the solute atoms in the supersaturated solid solution form cluster atoms (GPB zones). Through the short-distance diffusion of atoms, the GPB zones grow rapidly, causing the strength of the sheet to increase sharply and the elongation after fracture to decrease sharply. As the standing time increases, the diffusion rate of solute atoms slows down, the growth rate of the GPB zones also slows down accordingly, and the change in the mechanical properties of the sheet also slows down accordingly. Eventually, the GPB zones grow into ordered atomic clusters, the strength reaches the maximum value, and the elongation after fracture reaches the minimum value. After 4 days, the performance tends to be stable.

[0070] As an embodiment, the material of the aluminum alloy plate of the present invention is 2024-T351 aluminum alloy; the composition is, Si: 0~0.08, Fe: 0~0.10%, Cu: 4.0~4.4%, Mn: 0.6~0.9%, Mg: 1.4~1.6%, Cr: 0~0.10%; Zn: 0~0.20%, Ti: 0.02~0.06%, impurity elements ≤0.15%, and the rest is Al.

[0071] The impurity elements of the present invention may be a mixture of multiple elements, wherein the content of any one element does not exceed 0.05%.

[0072] The Fe and Si contents of the present invention are relatively low, which can effectively reduce impurities and compounds, so that the plate has higher strength and better toughness. Meanwhile, the lower Fe content can effectively reduce the intermetallic compounds formed by Fe and Cu, so that the Cu element can form a beneficial phase and strengthen the performance of the plate.

[0073] The inventors adopted the production method of the present invention to prepare 2024-T351 aluminum alloy plates with thicknesses of 78 mm and 85 mm, respectively, and tested the mechanical properties, and the results are shown in Table 4. Referring to Table 5, according to the requirements of the AMS-A-250 / 4 standard for 2024-T351 aluminum alloy plates, the aluminum alloy plates prepared by the method of the present invention have various mechanical property indicators that far exceed the requirements of the standard and can meet the use requirements of special fields.

[0074] See also Figure 1 The inventors also selected the sample with the lowest elongation from each embodiment and observed the fracture morphology using a backscattered scanning electron microscope. It can be seen that the strengthening phase is relatively evenly distributed on the aluminum matrix, which improves the mechanical properties of the plate and ensures the elongation.

[0075] Table 4: Mechanical properties test results of the embodiments of the present invention

[0076]

[0077] Table 5: Requirements of AMS-A-250 / 4 standard for 2024-T351 aluminum alloy plates

[0078] Thickness range / mm Tensile strength / MPa Yield strength / Mpa Elongation after break / % 25.4-44.45 427 290 7 44.45-50.8 427 290 6 50.8-76.2 414 290 4 76.2-101.6 393 283 4

[0079] In summary, the present invention provides a method for producing a high-strength 2xxx series aluminum alloy sheet, which improves the strength of the aluminum alloy sheet by optimizing the hot rolling process, the solution quenching process, the aging process and the composition ratio. The mechanical property requirements of special fields are met and the sheet can be applied to high-strength fields. The technical problem that the strength of the aluminum alloy sheet produced by the existing process cannot meet the strength standards of special fields is solved.

[0080] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art may make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for producing a high-strength 2xxx series aluminum alloy sheet, characterized in that: The steps include: S1, cast aluminum alloy ingot; The thickness of aluminum alloy slab is 420mm-480mm; S2, homogenization treatment: make the composition in the ingot more uniform and eliminate micro segregation structure; The homogenization temperature is 496±3°C and the holding time is 30 hours; S3, hot rolling: rolling the aluminum alloy flat ingot into a plate; The preheating temperature of the hot rolling is: 440℃±20℃, the holding time is: 2~4h; the final rolling temperature is not less than 300℃; S4, solution quenching treatment; Solution temperature: 496±3℃, solution time: 20-500min; quenching cooling method is water cooling; S5, stretch; The aluminum alloy plate is stretched to correct the plate shape and eliminate internal stress; the stretching deformation is: 1.5-3.0%; the stretching residence time does not exceed 30 minutes; S6, natural aging treatment; The board should be left at room temperature for no less than 4 days.

2. The method for producing a high-strength 2xxx series aluminum alloy sheet material according to claim 1, characterized in that: The casting process includes smelting, refining, online slag removal, degassing and filtering treatment; the smelting temperature is: 690-755°C; the refining temperature is: 700-750°C, and the refining time is: 20-90 minutes.

3. The method for producing a high-strength 2xxx series aluminum alloy sheet material according to claim 1, wherein: The aluminum alloy slab is sawn and milled after homogenization; The sawing and milling process includes flat ingot milling and eight-sided milling: the large face milling surface area is 10-25mm, and the small face milling surface area is 5-20mm; the sawing amount: the gate end is ≥100mm, and the expansion end is ≥300mm.

4. The method for producing a high-strength 2xxx series aluminum alloy sheet material according to claim 1, wherein: The final rolling temperature is set at 300-330°C.

5. The method for producing a high-strength 2xxx series aluminum alloy sheet material according to claim 4, wherein: Increase the final rolling temperature by increasing the preheating temperature or reducing the number of processing passes.

6. The method for producing a high-strength 2xxx series aluminum alloy sheet material according to claim 1, wherein: The hot rolling step includes firstly performing 2-4 cross-rolling passes, then rotating the ingot by 90°C and then performing longitudinal rolling until the aluminum alloy flat ingot is rolled to a predetermined thickness.

7. The method for producing a high-strength 2xxx series aluminum alloy sheet material according to claim 1, wherein: The solution temperature is 496° C. and the solution time is 43 minutes.

8. The method for producing a high-strength 2xxx series aluminum alloy sheet material according to claim 1, wherein: The standing time of the natural aging treatment is 4-7 days.

9. The method for producing a high-strength 2xxx series aluminum alloy sheet material according to any one of claims 1 to 8, characterized in that: The material of the aluminum alloy plate is 2024-T351 aluminum alloy.

10. The method for producing a high-strength 2xxx series aluminum alloy sheet material according to claim 9, wherein: The composition of the 2024-T351 aluminum alloy plate is Si: 0-0.08%, Fe: 0-0.10%, Cu: 4.0-4.4%, Mn: 0.6-0.9%, Mg: 1.4-1.6%, Cr: 0-0.10%; Zn: 0-0.20%, Ti: 0.02-0.06%, impurity elements ≤0.15%, and the rest is Al.

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