Method for improving interlayer performance uniformity of large-size high-toughness 7xxx aluminum alloy pre-stretched super-thick plate

Abstract

The invention discloses a method for improving the interlayer performance uniformity of a large-size high-toughness 7xxx aluminum alloy pre-stretched super-thick plate, and relates to the field of improvement of interlayer performance differences of high-strength aluminum alloy pre-stretched super-thick plates. The method aims at solving the problems that in the subsequent part machining and application process of the 7xxx alloy super-thick pre-stretched thick plate, the performance difference of a plate thickness layer is large, the damage resistance of the position where the performance of the plate is weak is reduced, the part loses efficacy, and the model safety is reduced. The method comprises the steps of controlling the uniformity of cross-section structure components of a large-size cast ingot, performing strong rolling deformation of plate interlayer performance uniformity, and performing strong quenching for improving the hardenability of the plate. According to the plate prepared through the method, the bottleneck that the comprehensive performance of the plate is synergistically improved is broken through, the overall performance of the thick plate is improved, the service life of parts is prolonged, the structural safety is enhanced, and the market competitiveness of products is improved. The method disclosed by the invention is used for controlling the interlayer performance uniformity of the 7xxx large-specification, super-thick and ultrahigh-strength aluminum alloy pre-stretched thick plate.

Description

Technical Field

[0001] The invention relates to the field of improving interlayer performance differences of high-strength aluminum alloy ultra-thick pre-stretched plates. Background Art

[0002] With the development trend of integration and large-scale development of aircraft parts, the performance uniformity requirements for thick plates used in ultra-large structural parts are becoming more and more stringent. This patent relates to a method for improving the interlayer performance difference in the thickness direction of ultra-thick pre-stretched plates of high-strength aluminum alloys. The present invention mainly solves the problem that in the subsequent parts processing and application of 7xxx alloy ultra-thick pre-stretched plates, there are large performance differences in the thickness layers, which leads to a decrease in the damage resistance of the weak position of the plate performance, thereby affecting the synergistic improvement of the application performance of the entire plate. It reduces the application field and use range of the plate, reduces the advantage space and market share, and seriously affects the comprehensive performance of the plate in its final state.

[0003] The performance difference of thickness layers of 7xxx ultra-thick plates seriously restricts the application areas and market share of the plates. In order to ensure that the plates present stable and consistent performance in various application fields, improve the overall quality and reliability of the plates, avoid stress concentration during the use of parts, and improve the safety and reliability of the structure, it is very important to improve the uniformity of performance between layers of ultra-thick plates. Summary of the invention

[0004] The present invention aims to solve the problem that during the subsequent parts processing and application of 7xxx alloy ultra-thick pre-stretched thick plates, there are large performance differences in the thickness layers of the plates, which leads to a decrease in the damage resistance of the weak positions of the plates, resulting in part failure and reduced model safety. A method is provided to improve the uniformity of interlayer performance of large-size, high-strength and tough 7xxx aluminum alloy pre-stretched ultra-thick plates.

[0005] A method for improving the interlayer performance uniformity of large-size high-strength and tough 7xxx aluminum alloy pre-stretched ultra-thick plates is specifically carried out in the following steps:

[0006] 1. Preparation of low segregation ingot:

[0007] Cast large-size ingots, then homogenize, heat treat, saw, and mill the ingots to obtain low-segregation ingots;

[0008] The mass percentage of each element in the large-size ingot is: Si≤0.06%, Fe≤0.08%, Cu: 1.9%-2.3%, Mn≤0.04%, Mg: 1.5%-1.8%, Cr≤0.04%, Zn: 7.1%-8.3%, Ti≤0.06%, Zr: 0.05%-0.15% and the balance Al;

[0009] During the casting process, the casting speed is controlled at 35mm / min~50mm / min and the cooling water flow rate is controlled at 35~60m 3 / h / root, pouring temperature 670℃~690℃, water retaining plate height 380mm~420mm; reduce the segregation of ingots during the casting process, and improve the uniformity of the structure and composition of large-size ingot cross-section (520mm×1620mm) for ultra-thick plates;

[0010] 2. Strong deformation rolling:

[0011] The low segregation ingot obtained in step 1 is rolled, the hot working temperature is controlled to be 400° C. to 420° C., the single-pass deformation rate is 20% to 30%, and the single-pass deformation rate is increased to ensure that the plate is fully deformed, which can reduce the difference in the structure of different thickness layers during the rolling process of the ultra-thick plate, and obtain the rolled plate;

[0012] 3. Plate solid solution quenching:

[0013] The rolled plate obtained in step 2 is subjected to solution quenching. The quenching parameters are: the water flow rate in the strong cooling zone is 330 L / s

[0014] ~360L / s, the water flow rate in the weak cooling zone is 330L / s~360L / s, and the residence time in the cooling zone is ≥10min; quickly reduce the temperature gradient between the surface and the core layer during the solution cooling of ultra-thick plates, and improve the uniformity of plate performance;

[0015] 4. Perform aging treatment on the plate treated in step 3 to obtain large-size, high-strength and tough 7xxx aluminum alloy pre-stretched ultra-thick plate.

[0016] The invention provides a large-scale ingot cross-sectional composition uniformity control technology: improve the cooling conditions of the ingot during the casting process (casting speed 35mm / min-50mm / min, cooling water flow 40m 3 / h~60m 3 / h / root, water baffle height 380mm~420mm) to control the crystallization and solidification mode of the ingot, and the equipment upgrade and improvement adopt the low liquid level crystallizer and water baffle combination technology to improve the uniformity of the cross-sectional structure and composition of the ingot. The difference between the grain size of the ingot surface and the core is significantly improved. The ingot grain size before and after improvement ( Figure 1 ) Grain size improvement Figure 2 ), it can be seen that the difference in grain size from the ingot surface to the T / 4 position to the ingot core is significantly improved, and the effect is obvious.

[0017] The present invention adopts a larger single-pass reduction, which greatly increases the single-pass deformation rate during the plate rolling process: the single-pass deformation rate is (20% to 30%), which improves the synergistic deformation effect of each layer and achieves full deformation, which is beneficial to improve the uniformity of the plate. Figure 3 and Figure 4 ), it can be seen that the strong rolling with increased single-pass deformation rate is beneficial to the deformation penetration from the surface to the core of the plate, achieving the coordinated deformation of layers with different thicknesses and improving the uniformity of the structure.

[0018] The strong quenching technology after the plate solution treatment: "fast transfer out of the furnace - roller bottom spray quenching strong cooling - stay in the cooling zone" minimizes the temperature difference between the surface and the core of the plate during the quenching and cooling process. It is suitable for improving the interlayer performance of the 7xxx alloy pre-stretched thick plate. The interlayer performance difference of the 7065-T7451 alloy 120mm plate prepared by the test is within 15MPa. The uniformity of the different thickness layers of the plate after quenching is good, and the width of the deformation strip and the amount of residual phase from the surface to the core layer are not much different.

[0019] Beneficial effects of the present invention:

[0020] The present invention mainly adopts the control of uniformity of the cross-sectional structure of large-sized ingots, strong rolling deformation for uniformity of interlayer performance of plates, and strong quenching to improve the hardenability of plates. The plates prepared according to the present invention break through the bottleneck of synergistic improvement of the overall performance of plates, improve the overall performance of thick plates and extend their service life, enhance structural safety, and enhance the market competitiveness of products.

[0021] The present invention combines technologies such as uniformity of large-sized ingot structure, coordinated plastic deformation of various thickness layers during plate rolling, and synchronous cooling of the surface and core during plate quenching to minimize the performance difference between layers of large-sized ultra-thick and ultra-high-strength aluminum alloy pre-stretched thick plates, broaden the application space of the plates, and improve the design and use value of the model.

[0022] The method of the present invention is used for controlling the interlayer performance uniformity of 7xxx large-size ultra-thick ultra-high-strength aluminum alloy pre-stretched thick plates. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The grain size diagram of the ingot before improvement, where a is the ingot surface, b is the T / 4 position, and c is the ingot center;

[0024] Figure 2 This is the grain size diagram of the ingot after improvement of the present invention, where a is the surface of the ingot, b is the T / 4 position, and c is the center of the ingot;

[0025] Figure 3 This is a deformation penetration simulation image with a single-pass reduction of 10 mm;

[0026] Figure 4 This is a deformation penetration simulation image with a single-pass reduction of 30 mm;

[0027] Figure 5 The photos of different layers of the rolled plate obtained by strong deformation rolling in Example 2, where a is the surface layer, b is the 1 / 4 layer, and c is the core;

[0028] Figure 6 These are photos of different layers of the solid solution state of Example 2, where a is the surface layer, b is the 1 / 4 layer, and c is the core. DETAILED DESCRIPTION

[0029] Specific implementation method 1: This implementation method is a method for improving the interlayer performance uniformity of large-size high-strength and tough 7xxx aluminum alloy pre-stretched ultra-thick plates, which is specifically carried out in the following steps:

[0030] 1. Preparation of low segregation ingot:

[0031] Cast large-size ingots, then homogenize, heat treat, saw, and mill the ingots to obtain low-segregation ingots;

[0032] The mass percentage of each element in the large-size ingot is: Si≤0.06%, Fe≤0.08%, Cu: 1.9%-2.3%, Mn≤0.04%, Mg: 1.5%-1.8%, Cr≤0.04%, Zn: 7.1%-8.3%, Ti≤0.06%, Zr: 0.05%-0.15% and the balance Al;

[0033] During the casting process, the casting speed is controlled at 35mm / min~50mm / min and the cooling water flow rate is controlled at 35~60m 3 / h / root, pouring temperature 670℃~690℃, water retaining plate height 380mm~420mm;

[0034] 2. Strong deformation rolling:

[0035] Rolling the low segregation ingot obtained in step 1, controlling the hot working temperature to be 400° C. to 420° C., and the single-pass deformation rate to be 20% to 30%, to obtain a rolled plate;

[0036] 3. Plate solid solution quenching:

[0037] The rolled plate obtained in step 2 is subjected to solution quenching. The quenching parameters are: the water flow rate in the strong cooling zone is 330 L / s

[0038] ~360L / s, the water flow rate in the weak cooling zone is 330L / s~360L / s, and the residence time in the cooling zone is ≥10min;

[0039] 4. Perform aging treatment on the plate treated in step 3 to obtain large-size, high-strength and tough 7xxx aluminum alloy pre-stretched ultra-thick plate.

[0040] Specific implementation method 2: This implementation method is different from the specific implementation method 1 in that the casting speed of the large-size ingot in step 1 is 45 mm / min to 50 mm / min. The rest is the same as the specific implementation method 1.

[0041] Specific implementation method three: This implementation method is different from specific implementation methods one or two in that: the cooling water flow rate in step one is 50-60m 3 / h / root. The rest is the same as the first or second embodiment.

[0042] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that: the pouring temperature in step 1 is 670°C to 685°C, and the height of the water retaining plate is 380mm to 400mm. The rest is the same as specific embodiments 1 to 3.

[0043] Specific implementation method 5: This implementation method is different from specific implementation methods 1 to 4 in that the hot rolling temperature is controlled to be 400° C. to 415° C. The rest is the same as specific implementation methods 1 to 4.

[0044] Specific implementation method 6: This implementation method is different from specific implementation methods 1 to 5 in that the rolling temperature in step 2 is 408-410° C. The rest is the same as specific implementation methods 1 to 5.

[0045] Specific implementation method 7: This implementation method is different from specific implementation methods 1 to 6 in that the deformation rate of a single pass in step 2 is 22% to 30%. The rest is the same as specific implementation methods 1 to 6.

[0046] Specific embodiment 8: This embodiment differs from specific embodiments 1 to 7 in that: in step 3, the water flow rate of the strong cooling zone is controlled to be 340L / s to 360L / s, and the water flow rate of the weak cooling zone is controlled to be 350L / s to 360L / s. The rest is the same as specific embodiments 1 to 7.

[0047] Specific embodiment 9: This embodiment differs from specific embodiments 1 to 8 in that: step 3 uses a roller hearth furnace for solution quenching. The rest is the same as specific embodiments 1 to 8.

[0048] Specific embodiment 10: This embodiment differs from specific embodiments 1 to 9 in that the quenching transfer speed in step 3 is 80-85 mm / s. The rest is the same as specific embodiments 1 to 9.

[0049] The content of the present invention is not limited to the content of the above-mentioned embodiments. The combination of one or several specific embodiments can also achieve the purpose of the invention.

[0050] Embodiment 1:

[0051] A method for improving the interlayer performance uniformity of large-size high-strength and tough 7xxx aluminum alloy pre-stretched ultra-thick plates is specifically carried out in the following steps:

[0052] 1. Preparation of high quality low segregation ingot:

[0053] A large-size ingot with a cross-sectional specification of 520 mm × 1620 mm is cast, and then the ingot is subjected to homogenization heat treatment, sawing, and milling to obtain a low-segregation ingot;

[0054] The mass percentage of each element in the large-size ingot is: Si≤0.06%, Fe≤0.08%, Cu: 1.9%-2.3%, Mn≤0.04%, Mg: 1.5%-1.8%, Cr≤0.04%, Zn: 7.1%-8.3%, Ti≤0.06%, Zr: 0.05%-0.15% and the balance Al;

[0055] During the casting process, the casting speed is controlled at 50 mm / min and the cooling water flow rate is 35 m 3 / h / root, pouring temperature 680℃, water retaining plate height 380mm;

[0056] 2. Strong deformation rolling:

[0057] The low segregation ingot obtained in step 1 is rolled, the hot working start rolling temperature is controlled to be 408° C., the maximum pass deformation rate is 25%, and the hot rolled plate is ensured to be sufficiently deformed from the surface to the core and have a uniform structure to obtain a rolled plate;

[0058] 3. Plate solid solution quenching:

[0059] After trimming the rolled plate obtained in step 2, a 24m roller hearth furnace is used for solution quenching. The quenching transfer speed is 80mm / s. The quenching parameters are: the water flow rate in the strong cooling zone is 340L / s-360L / s, the water flow rate in the weak cooling zone is 350L / s-360L / s, the cooling water temperature is 26°C, and the residence time in the cooling zone is 10min.

[0060] 4. Perform aging treatment on the plate treated in step 3 to obtain a large-size, high-strength and tough 7xxx aluminum alloy pre-stretched ultra-thick plate with a thickness of 120 mm.

[0061] After aging treatment, the pre-stretched thick plate with small performance differences in each layer is obtained. The performance difference of different thickness layers of the produced 7065-T7451 thick plate is small, and the strength difference is no more than 15MPa.

[0062] The performance results of the pre-stretched thick plate prepared in this example are shown in Table 1.

[0063] Table 1 Performance results of different layers of 7065 alloy 120 mm thick plate after industrial aging

[0064]

[0065] Embodiment 2:

[0066] A method for improving the interlayer performance uniformity of large-size high-strength and tough 7xxx aluminum alloy pre-stretched ultra-thick plates is specifically carried out in the following steps:

[0067] 1. Preparation of high quality low segregation ingot:

[0068] A large-size ingot with a cross-sectional specification of 520 mm × 1620 mm is cast, and then the ingot is subjected to homogenization heat treatment, sawing, and milling to obtain a low-segregation ingot;

[0069] The mass percentage of each element in the large-size ingot is: Si≤0.06%, Fe≤0.08%, Cu: 1.9%-2.3%, Mn≤0.04%, Mg: 1.5%-1.8%, Cr≤0.04%, Zn: 7.1%-8.3%, Ti≤0.06%, Zr: 0.05%-0.15% and the balance Al;

[0070] During the casting process, the casting speed is controlled at 45 mm / min and the cooling water flow rate is 40 m 3 / h / root, pouring temperature 689℃, water retaining plate height 400mm;

[0071] 2. Strong deformation rolling:

[0072] The low segregation ingot obtained in step 1 is rolled, the hot working start rolling temperature is controlled to be 410° C., the maximum pass deformation rate is 22%, and the hot rolled plate is ensured to be sufficiently deformed from the surface to the core and have a uniform structure to obtain a rolled plate;

[0073] 3. Plate solid solution quenching:

[0074] After trimming the rolled plate obtained in step 2, a 24m roller hearth furnace is used for solution quenching. The quenching transfer speed is 85mm / s. The quenching parameters are: the water flow rate in the strong cooling zone is 340L / s-350L / s, the water flow rate in the weak cooling zone is 330L / s-350L / s, the cooling water temperature is 28°C, and the residence time in the cooling zone is 12min.

[0075] 4. Perform aging treatment on the plate treated in step 3 to obtain the 7xxx large-size ultra-thick ultra-high strength aluminum alloy pre-stretched thick plate with improved interlayer performance uniformity, with a thickness of 150 mm.

[0076] After aging treatment, the pre-stretched thick plate with small performance differences between layers is obtained. The performance difference of different thickness layers of the produced 7065-T7451 thick plate is small, the interlayer performance of the plate is within 13MPa, and the uniformity is good. The performance results are shown in Table 2.

[0077] Table 2 Performance results of different layers of 7065 alloy 150mm thick plate after industrial aging

[0078]

[0079] Figure 5 The photos of different layers of the rolled plate obtained by strong deformation rolling in Example 2, where a is the surface layer, b is the 1 / 4 layer, and c is the core;

[0080] Figure 6 These are photos of different layers of the solid solution state of Example 2, where a is the surface layer, b is the 1 / 4 layer, and c is the core.

[0081] "Quick transfer out of the furnace - roller bottom spray quenching strong cooling - stay in the cooling zone" minimizes the temperature difference between the surface and the core of the plate during the quenching and cooling process. It is suitable for improving the interlayer performance of 7xxx alloy pre-stretched thick plates. The interlayer performance difference of the 7065-T7451 alloy 120mm plate produced by the research and trial production is within 15MPa. Figure 6 It can be seen that the microstructure uniformity of layers of different thicknesses of the plate after quenching is good, and the width of the deformation band and the amount of residual phase from the surface to the core layer are not much different.

[0082] In summary, the present invention combines three key technologies: high-quality low-segregation ingot preparation, ultra-thick plate collaborative deformation rolling, and strong cooling technology after plate solid solution, to achieve a significant improvement in the uniformity of performance of different thickness layers of 7065 alloy ultra-thick plates, which is an important technical basis for improving the uniformity of performance of subsequent high-strength 7xxx ultra-thick pre-stretched plates and solves common technical problems. It broadens the application channels of 7065 plates and improves the performance and safety of key aerospace models.

Claims

1. A method for improving the interlayer performance uniformity of large-size high-strength and tough 7xxx aluminum alloy pre-stretched ultra-thick plates, characterized in that The method is specifically carried out in the following steps:

1. Preparation of low segregation ingot: Cast large-size ingots, then homogenize, heat treat, saw, and mill the ingots to obtain low-segregation ingots; The mass percentage of each element in the large-size ingot is: Si≤0.06%, Fe≤0.08%, Cu: 1.9%-2.3%, Mn≤0.04%, Mg: 1.5%-1.8%, Cr≤0.04%, Zn: 7.1%-8.3%, Ti≤0.06%, Zr: 0.05%-0.15% and the balance Al; During the casting process, the casting speed is controlled at 35mm / min~50mm / min and the cooling water flow rate is controlled at 35~60m 3 / h / root, pouring temperature 670℃~690℃, water retaining plate height 380mm~420mm; 2. Strong deformation rolling: Rolling the low segregation ingot obtained in step 1, controlling the hot working temperature to be 400° C. to 420° C., and the single-pass deformation rate to be 20% to 30%, to obtain a rolled plate; 3. Plate solid solution quenching: The rolled plate obtained in step 2 is subjected to solution quenching, and the quenching parameters are: the water flow rate in the strong cooling zone is 330L / s to 360L / s, the water flow rate in the weak cooling zone is 330L / s to 360L / s, and the residence time in the cooling zone is ≥10min; 4. Perform aging treatment on the plate treated in step 3 to obtain large-size, high-strength and tough 7xxx aluminum alloy pre-stretched ultra-thick plate.

2. A method for improving the interlayer performance uniformity of large-size high-strength and tough 7xxx aluminum alloy pre-stretched ultra-thick plate according to claim 1, characterized in that The casting speed of the large-sized ingot in step 1 is 45 mm / min to 50 mm / min.

3. A method for improving the interlayer performance uniformity of large-size high-strength and tough 7xxx aluminum alloy pre-stretched ultra-thick plate according to claim 1, characterized in that The cooling water flow rate in step 1 is 50-60m 3 / h / root.

4. A method for improving the interlayer performance uniformity of large-size high-strength and tough 7xxx aluminum alloy pre-stretched ultra-thick plate according to claim 1, characterized in that The pouring temperature in step 1 is 670°C to 685°C, and the height of the water retaining plate is 380mm to 400mm.

5. A method for improving the interlayer performance uniformity of large-size high-strength and tough 7xxx aluminum alloy pre-stretched ultra-thick plate according to claim 1, characterized in that Step 2: Control the hot rolling temperature to 400°C to 415°C.

6. A method for improving the interlayer performance uniformity of large-size high-strength and tough 7xxx aluminum alloy pre-stretched ultra-thick plate according to claim 1, characterized in that Step 2: The rolling temperature is 408-410°C.

7. A method for improving the interlayer performance uniformity of large-size high-strength and tough 7xxx aluminum alloy pre-stretched ultra-thick plate according to claim 1, characterized in that The deformation rate of a single pass in step 2 is 22% to 30%.

8. A method for improving the interlayer performance uniformity of large-size high-strength and tough 7xxx aluminum alloy pre-stretched ultra-thick plate according to claim 1, characterized in that Step 3: Control the water flow rate in the strong cooling zone to 340L / s~360L / s, and the water flow rate in the weak cooling zone to 350L / s~360L / s.

9. A method for improving the interlayer performance uniformity of large-size high-strength and tough 7xxx aluminum alloy pre-stretched ultra-thick plate according to claim 1, characterized in that Step three uses a roller hearth furnace for solution quenching.

10. A method for improving the interlayer performance uniformity of large-size high-strength and tough 7xxx aluminum alloy pre-stretched ultra-thick plate according to claim 1, characterized in that Step 3: The quenching transfer speed is 80-85 mm / s.

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