Method for reducing quenching residual stress of large 7xxx aluminum alloy T-shaped section long beam forgings

Abstract

According to the method for reducing the quenching residual stress of the large 7xxx aluminum alloy T-shaped section long beam type forge piece, a cold pressing die which moves up and down in traditional cold pressing deformation is changed into a rolling die, so that surface contact between the die and the forge piece is changed into line contact, the load on equipment is greatly reduced, and the service life of the forge piece is prolonged. And the phenomena of uneven stress reduction and the like caused by segmented cold pressing of long beam forgings are also avoided. And meanwhile, through the structural design of the upper roller mold cavity, the forge piece is in a multidirectional pressed state in the cold deformation treatment process, reduction of residual stress of the forge piece is facilitated, and uniform distribution of the residual stress is promoted. Under the control of technological parameters, the cold deformation die has little influence on the organization structure and mechanical property of the forge piece, the residual stress eliminating effect is good, deformation of the 7xxx aluminum alloy T-shaped section long beam type forge piece in the machining process can be effectively reduced, and the part yield is improved.

Description

Technical Field

[0001] This invention relates to a method for reducing residual stress during quenching of large 7xxx aluminum alloy T-shaped cross-section long beam forgings, belonging to the field of heat treatment technology for aluminum alloy materials. Background Technology

[0002] Aluminum alloys, due to their low density and high specific strength, are widely used in aerospace applications, resulting in significant weight reduction. Large-size aluminum alloy beam forgings are widely used in aerospace, tank and shipbuilding, and petrochemical industries. With the continuous advancement of my country's aerospace technology, the requirements for the size and performance of forgings are becoming increasingly stringent, and the demand for weight reduction is also growing.

[0003] During the manufacturing process of large aluminum alloy T-section long beam forgings, uneven plastic deformation and temperature distribution can generate significant residual stress both internally and externally. The warped structure design hinders the release of this residual stress, and increasing the forging size further exacerbates its generation. The presence of residual stress can lead to severe warping during subsequent processing, resulting in dimensional defects and scrap. Even dimensionally acceptable parts suffer from varying degrees of impact on their mechanical properties, fatigue performance, and corrosion resistance due to residual stress, shortening their service life and potentially causing accidents. Therefore, effectively reducing and controlling residual stress in large aluminum alloy T-section long beam forgings is a crucial technology for producing qualified parts.

[0004] 7xxx aluminum alloys are age-hardening alloys. The strength increase mainly comes from the formation of a supersaturated solid solution after deformation through solution treatment, which then precipitates uniformly during the aging process, thereby increasing strength. However, during solution quenching, differences in the immersion sequence, thickness, and cooling rate of different parts of the forging result in macroscopic residual stresses in various parts of the forging. The non-uniformity of the temperature and stress fields in the forging leads to uneven precipitation of precipitates, thus affecting the performance of the forging. Furthermore, because T-shaped cross-section long beam forgings are relatively long, they can usually only be quenched vertically, which leads to uneven cooling of different sections, often resulting in large bending and torsional stresses in the forging after quenching.

[0005] Currently, residual stress in T-section long beam forgings is typically reduced through two methods: heat treatment and cold deformation. Heat treatment often results in a loss of the forging's mechanical properties, so the heating temperature is usually low. However, when the heating temperature is insufficient, residual stress is difficult to eliminate, thus heat treatment has limited effectiveness in reducing residual stress. Traditional cold deformation methods mainly use presses to cold-press the forgings. Since T-section long beam forgings are relatively long, they are usually cold-pressed in sections. This leads to problems such as overlapping and uneven deformation, and also requires high-tonnage equipment for cold pressing. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for reducing the residual stress during quenching of large 7xxx aluminum alloy T-shaped cross-section long beam forgings. This method reduces the tonnage requirements of equipment and improves the uniformity of cold deformation of large 7xxx aluminum alloy T-shaped cross-section long beam forgings, thereby effectively reducing the residual stress during quenching and ensuring a uniform distribution of residual stress.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A method for reducing residual stress during quenching of large 7xxx aluminum alloy T-section long beam forgings, the method comprising the following steps:

[0009] (1) The cold deformation die is installed on the rolling mill. The cold deformation die consists of an upper roll die and a lower roll die. The upper roll die is a cylindrical structure with a cavity, and the structure of the cavity is similar to the cross-section of the forging. The lower roll die is a spindle-shaped structure. After the upper roll die and the lower roll die are closed, they can wrap the cross-section of the forging.

[0010] (2) Place the solution-quenched forging on the rolling mill equipped with the cold deformation mold in step (1), and adjust the gap between the upper and lower rolls according to the thickness and deformation of the forging, so that the forging bites into the upper roll and ensures that the upper roll contacts the ribs of the forging.

[0011] (3) Along the length of the forging, the forging is subjected to rolling deformation treatment in one pass each, and the total rolling deformation of the ribs in the two passes is controlled to be 0.5%-1.2%. After the two passes of rolling deformation treatment, the cavity of the upper roll die contacts the bottom plate of the forging.

[0012] (4) Along the length of the forging, the forging is rolled again in one pass each, and the total rolling deformation of the forging in the two passes is controlled to be 1.2%-3.2%.

[0013] (5) Aging treatment is performed on the forgings after rolling deformation to reduce the residual quenching stress of large 7xxx aluminum alloy T-shaped cross-section long beam forgings.

[0014] According to an embodiment of the present invention, the present invention uses cold rolling to eliminate residual stress in large 7xxx aluminum alloy T-section long beam forgings. Conventionally, cold pressing is used to eliminate residual stress in forgings, but for long strip forgings, cold pressing can cause overlapping, easily leading to uneven stress elimination and subsequent deformation during processing. Rolling processes are conventionally used for manufacturing aluminum alloy sheets and are not used to eliminate residual stress. However, the inventors of this application unexpectedly discovered that by selecting the specific cold deformation die of the present invention and using the cold rolling process of the present invention, the residual stress in large 7xxx aluminum alloy T-section long beam forgings can be effectively eliminated, and the uniformity of cold deformation of large 7xxx aluminum alloy T-section long beam forgings can be improved, reducing the tonnage requirements of the equipment and achieving significant results.

[0015] According to an embodiment of the present invention, the cold deformation mold of the present invention consists of an upper roller mold and a lower roller mold. The upper roller mold is a cylindrical structure with a cavity, the structure of which is similar to the cross-section of the forging. The lower roller mold is a spindle-shaped structure with a higher middle and slightly lower ends. The cavity structure of the upper roller mold of the present invention can ensure that the upper roller mold and the lower roller mold can wrap the cross-section of the forging after the mold is closed. The structural configuration of the upper roller mold with a cylindrical structure and the lower roller mold with a spindle-shaped structure of the present invention can ensure that the deformation at the rib position of the forging is greater, thereby ensuring that the ribs and the base plate of the forging have similar deformation after the cold rolling process, and ensuring the uniformity of cold deformation of large 7xxx aluminum alloy T-shaped cross-section long beam forgings. By designing the upper rolling die cavity structure and the lower rolling die spindle-shaped structure, space is left in the forging during cold rolling to allow metal to flow to both sides of the base plate. This further controls the total rolling deformation of the forging in the first two passes to 0.5%-1.2%, ensuring that the first two passes of cold rolling only cause plastic deformation to the ribs of the forging, while the latter two passes simultaneously cause plastic deformation to the ribs and base plate. This guarantees the uniformity of cold deformation for large 7xxx aluminum alloy T-section long beam forgings. Furthermore, by changing the motion relationship between the cold pressing die and the forging, the conventional sliding friction is transformed into rolling friction, which significantly reduces the load requirements of the cold deformation equipment. The elimination of the overlapping area in traditional cold pressing methods also makes the overall cold pressing deformation of the forging more uniform, thus more evenly reducing residual stress in the forging.

[0016] According to an embodiment of the present invention, the length of the large 7xxx aluminum alloy T-section long beam forging is ≥4m, for example 4-10m, such as 4.5m, 5m, 6m, 8m or 10m; the width of the large 7xxx aluminum alloy T-section long beam forging is ≥400mm, for example 400-1000mm, such as 500mm, 600mm, 800mm or 1000mm.

[0017] According to an embodiment of the present invention, the radius of curvature of the large 7xxx aluminum alloy T-shaped cross-section long beam forging along its length is 4000-20000 mm, for example, 4000 mm, 5000 mm, 6000 mm, 7000 mm, 8000 mm, 9000 mm, 1000 mm, 11000 mm, 12000 mm, 13000 mm, 14000 mm, 15000 mm, 16000 mm, 17000 mm, 18000 mm, 19000 mm or 20000 mm.

[0018] According to an embodiment of the present invention, the large 7xxx aluminum alloy T-shaped cross-section long beam forging is composed of a base plate and a rib, wherein the rib is disposed on one side of the base plate; the number of the rib is one.

[0019] According to an embodiment of the present invention, the cross-section of the large 7xxx aluminum alloy T-shaped beam forging is axially symmetric or non-axially symmetric T-shaped.

[0020] According to an embodiment of the present invention, the thickness of the base plate is 10-90mm, for example 20-80mm, such as 30-70mm, such as 40mm, 50mm or 60mm; the width of the forging is the width of the base plate.

[0021] According to an embodiment of the present invention, the thickness (which can also be understood as the height of the rib) of the rib is 10-180mm, for example 20-170mm, such as 30-160mm, such as 40mm, 50mm, 60mm, 70mm, 80mm, 90mm, 100mm, 110mm, 120mm, 130mm, 140mm, 150mm or 160mm; the width of the rib is less than the width of the base plate.

[0022] According to an embodiment of the present invention, the width of the rib is similar to the thickness of the base plate; preferably, the difference between the width of the rib and the thickness of the base plate is 0-20mm, for example 0-10mm, such as 0-5mm.

[0023] According to an embodiment of the present invention, the 7xxx aluminum alloy is a commonly used aluminum alloy material known in the art, such as 7075, 7175, 7050, 7B50, 7A04, 7150, 7055 or 7085 aluminum alloy.

[0024] According to an embodiment of the present invention, in step (1), the rolling mill is a device known in the art capable of rolling aluminum alloys.

[0025] According to an embodiment of the present invention, in step (1), the cold deformation die is installed on the rolling mill using a method known in the art; exemplarily, the upper roll die and the lower roll die in the cold deformation die are respectively installed on the rolling mill, and the upper roll die is located above the lower roll die.

[0026] According to an embodiment of the present invention, in step (1), the width of the upper roller mold and the width of the lower roller mold are not specifically defined, and can be the same or different, preferably the same.

[0027] According to an embodiment of the present invention, in step (1), the width of the upper roller die is greater than the width of the forging; the width of the lower roller die is greater than the width of the forging; for example, the width of the upper roller die is greater than the width of the forging by more than 30 mm, such as 40 mm-500 mm, such as 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm, 350 mm, 400 mm, 450 mm or 500 mm; the width of the lower roller die is greater than the width of the forging by more than 30 mm, such as 40 mm-500 mm, such as 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm, 350 mm, 400 mm, 450 mm or 500 mm.

[0028] According to an embodiment of the present invention, in step (1), the diameter of the lower roller die is greater than the diameter of the upper roller die; exemplarily, the minimum diameter of both sides of the lower roller die is greater than the diameter of the upper roller die; such a structural arrangement can ensure the accuracy of the curvature of the forging, that is, the degree of warping of the forging is not affected by the cold deformation treatment.

[0029] According to an embodiment of the present invention, in step (1), the diameter of the upper roller die and the diameter of the lower roller die (specifically the middle diameter of the lower roller die and the diameters of both ends of the lower roller die) can be reasonably selected according to the radius of curvature of the forging, and it is only necessary to ensure that the diameter of the lower roller die is greater than the diameter of the upper roller die.

[0030] According to an embodiment of the present invention, in step (1), the cavity of the upper roller mold is axially symmetric or non-axially symmetric T-shaped.

[0031] According to an embodiment of the present invention, in step (1), the width of the cavity of the upper roller die is greater than the width of the base plate; preferably, the width of the cavity of the upper roller die is slightly greater than the width of the base plate; exemplaryly, the width of the cavity of the upper roller die is 5-20 mm larger than the width of the base plate. The width of the cavity is the width at the position corresponding to the base plate of the forging, and can also be understood as the maximum width of the cavity of the upper roller die. By setting such structural parameters, it can be ensured that the forging can be bitten into the upper roller die, and space is left for the forging during the cold rolling process to ensure that the metal flows to both sides of the base plate.

[0032] According to an embodiment of the present invention, in step (1), the thickness of the cavity of the upper roller die is 1.012-1.035 times the thickness of the forging, for example, 1.012 times, 1.015 times, 1.020 times, 1.025 times, 1.030 times, or 1.035 times. The thickness of the forging is the sum of the thickness of the base plate and the thickness of the ribs. The thickness of the cavity of the upper roller die is the thickness at the position corresponding to the base plate and ribs of the forging, which can also be understood as the maximum thickness of the cavity of the upper roller die. By setting such structural parameters, it can be ensured that the cavity part of the upper roller die does not contact the upper surface of the base plate during the first two cold rolling processes of the forging, and only the ribs can be cold deformed.

[0033] According to an embodiment of the present invention, in step (1), the side wall slope of the cavity of the upper roller mold is greater than the draft angle of the ribs of the forging; the setting of the side wall slope of the cavity of the upper roller mold and the draft angle of the ribs of the forging can ensure that the upper roller mold can effectively perform cold deformation treatment on the forging, and is also conducive to the demolding of the forging after cold deformation treatment; for example, the side wall slope of the cavity of the upper roller mold is greater than the draft angle of the ribs of the forging by more than 1°; Preferably, the sidewall slope of the upper roller die cavity is 1-3° greater than the draft angle of the ribs of the forging; exemplaryly, the sidewall slope of the upper roller die cavity is 4-15°, such as 5°, 6°, 7°, 8°, 9°, 10°, 11°, 12°, 13°, 14° or 15°; the draft angle of the ribs of the forging is 3-10°, such as 3°, 4°, 5°, 6°, 7°, 8°, 9° or 10°.

[0034] According to an embodiment of the present invention, in step (1), the radius R1 of the fillet at the root of the rib of the upper roller mold cavity is greater than the radius r1 of the fillet at the corresponding position of the forging; preferably, the radius R1 of the fillet at the root of the rib of the upper roller mold cavity is greater than the radius r1 of the fillet at the connection between the bottom plate and the rib in the forging. This structural arrangement can effectively prevent the cold deformation mold from squeezing the root of the forging (specifically the connection between the bottom plate and the rib in the forging), leaving space for metal flow during cold deformation, and also preventing the root of the forging from cracking due to excessive deformation.

[0035] According to an embodiment of the present invention, in step (1), the radius R2 of the root fillet at the bottom plate of the upper roller mold cavity is greater than the radius r2 of the corresponding fillet at the forging position; preferably, the radius R2 of the root fillet at the bottom plate of the upper roller mold cavity is greater than the radius r2 of the fillets on both sides of the bottom plate in the forging. This structural arrangement can effectively prevent the cold deformation die from squeezing the root of the forging (specifically, the two sides of the bottom plate in the forging), leaving space for metal flow during the cold deformation process, and also preventing the root of the forging from cracking due to excessive deformation.

[0036] According to an embodiment of the present invention, in step (1), the middle diameter of the lower rolling die is 1%-3% larger than the end diameter of the lower rolling die, thereby forming a spindle-shaped lower rolling die; such a structure can provide better support for the rib positions of the forging, so as to ensure that the rib positions obtain a larger amount of cold deformation; at the same time, it leaves deformation space for the base plate during the cold deformation process, controls the base plate metal to flow from the middle of the base plate to both sides along the width direction of the base plate during the cold deformation process, and ensures the uniformity of the forging deformation.

[0037] According to an embodiment of the present invention, in step (2), the solution quenching temperature is (470-475℃)±5℃; the solution quenching time is determined according to the maximum cross-sectional size of the forging, the quenching transfer time is ≤30s, and the quenching water temperature is (20-60℃)±5℃.

[0038] According to an embodiment of the present invention, in step (2), the gap between the upper and lower roller dies is adjusted so that the forging bites into the upper roller die and ensures that the upper roller die contacts the ribs of the forging, but does not contact the upper surface of the base plate. Preferably, the gap between the upper and lower roller dies is adjusted to 1.5-5mm, such as 1.5mm, 1.7mm, 1.8mm, 1.9mm, 2mm, 2.1mm, 2.2mm, 2.3mm, 2.4mm, 2.5mm, 2.6mm, 2.7mm, 2.8mm, 2.9mm, 3mm, 3.2mm, 3.5mm, 3.6mm, 3.8mm, 4mm, 4.2mm, 4.4mm, 4.5mm, 4.6mm, 4.8mm, 5mm, or a range consisting of the above two endpoint values. For example, the gap between the lower surface of the upper roller die and the upper surface of the lower roller die is adjusted to 1.7-2.2 mm, or 2.6-3.0 mm, or 2.0-2.6 mm.

[0039] According to an embodiment of the present invention, in step (3), the forging includes a first end along the length direction and a second end opposite to the first end; the rolling deformation treatment of the forging in one pass each can be performed first in the direction from the first end to the second end of the forging, and then in the direction from the second end to the first end of the forging; or it can be performed first in the direction from the second end to the first end of the forging, and then in the direction from the first end to the second end of the forging.

[0040] According to an embodiment of the present invention, in step (3), during the rolling deformation process, the rotation speed of the upper die is 0.1-0.8 mm / s, for example, 0.1 mm / s, 0.2 mm / s, 0.3 mm / s, 0.4 mm / s, 0.5 mm / s, 0.6 mm / s, 0.7 mm / s, or 0.8 mm / s; preferably, during the rolling deformation process, after the forging stroke begins, the rotation speed of the upper die is 0.5-0.8 mm / s, and after the forging stroke reaches 50%-70%, the rotation speed of the upper die is 0.1-0.4 mm / s. By controlling the rotation speed of the upper die during the rolling deformation process, the degree of metal deformation at each position during the cold deformation process can be adjusted, thereby reducing the deformation resistance, making the cold deformation of the forging more uniform, and thus better reducing residual stress. This is because the performance of forgings changes significantly with the increase of rolling deformation. In the early stage of rolling deformation, the deformation resistance of forgings is small, and using a larger upper roll rotation speed is beneficial to improving the processing efficiency of forgings. In the later stage of rolling deformation, the deformation resistance of forgings is large, and reducing the upper roll rotation speed is beneficial to the transmission of deformation at various positions of forgings, making the deformation of forgings more uniform.

[0041] According to an embodiment of the present invention, in step (3), the total rolling deformation of the two secondary reinforcing bars is 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, or 1.2%.

[0042] According to an embodiment of the present invention, in step (3), the rolling deformation of a single pass of reinforcing bar is 0.2%-0.6%, for example, 0.2%, 0.3%, 0.4%, 0.5% or 0.6%.

[0043] According to the embodiment of the present invention, the rolling deformation process in step (3) can realize the cold deformation process of the ribs; and after the rolling deformation process in step (3), the cavity of the upper roll die can contact the upper surface of the bottom plate of the forging, so as to ensure that the rolling deformation process in step (4) can ensure that the ribs and the bottom plate have similar deformation amounts, thereby improving the uniformity of cold deformation of the forging.

[0044] According to an embodiment of the present invention, in step (4), the forging includes a first end along the length direction and a second end opposite to the first end; the forging is subjected to rolling deformation treatment in one pass each in the same direction. This can be done by first performing rolling deformation treatment in the direction from the first end to the second end of the forging, and then performing rolling deformation treatment in the direction from the second end to the first end of the forging; or it can be done by first performing rolling deformation treatment in the direction from the second end to the first end of the forging, and then performing rolling deformation treatment in the direction from the first end to the second end of the forging.

[0045] According to an embodiment of the present invention, in step (4), during the rolling deformation process, the rotation speed of the upper die is 0.1-0.8 mm / s, for example, 0.1 mm / s, 0.2 mm / s, 0.3 mm / s, 0.4 mm / s, 0.5 mm / s, 0.6 mm / s, 0.7 mm / s, or 0.8 mm / s; preferably, during the rolling deformation process, after the forging stroke begins, the rotation speed of the upper die is 0.5-0.8 mm / s, and after the forging stroke reaches 50%-70%, the rotation speed of the upper die is 0.1-0.4 mm / s. By controlling the rotation speed of the upper die during the rolling deformation process, the degree of metal deformation at each position during the cold deformation process can be adjusted, thereby reducing the deformation resistance, making the cold deformation of the forging more uniform, and thus better reducing residual stress. This is because the performance of forgings changes significantly with the increase of rolling deformation. In the early stage of rolling deformation, the deformation resistance of forgings is small, and using a larger upper roll rotation speed is beneficial to improving the processing efficiency of forgings. In the later stage of rolling deformation, the deformation resistance of forgings is large, and reducing the upper roll rotation speed is beneficial to the transmission of deformation at various positions of forgings, making the deformation of forgings more uniform.

[0046] According to an embodiment of the present invention, in step (4), the total rolling deformation of the two forging passes is 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.5%, 2.6%, 2.8%, 3%, or 3.2%.

[0047] According to an embodiment of the present invention, in step (4), the rolling deformation of the single-pass forging is 0.6%-1.6%, for example 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5% or 1.6%.

[0048] According to the embodiment of the present invention, the rolling deformation process in step (4) can achieve cold deformation of the ribs and the base plate, and can ensure that the ribs and the base plate have relatively similar deformation amounts.

[0049] According to the embodiment of the present invention, in the rolling deformation process of steps (3) and (4), the forging is rolled in a total of 4 passes; wherein, in the first two passes, only the ribs are cold deformed, and the total rolling deformation of the ribs is controlled to be 0.5%-1.2%; in the last two passes, the ribs and the base plate are cold deformed simultaneously, and the total rolling deformation of the forging is controlled to be 1.2%-3.2%; the ribs and the base plate are supported and squeezed by the side wall of the upper roll die cavity and the lower roll die during the rolling process, which will cause the forging to bear compressive stress from multiple directions during the cold deformation process, which is more conducive to the reduction and uniform distribution of residual stress in the forging.

[0050] According to an embodiment of the present invention, in step (5), a two-stage aging process is adopted; wherein, the temperature of the first-stage aging is (105-120)℃±3℃, and the holding time is 4-8 hours, and the temperature of the second-stage aging is (160-180)℃±3℃, and the holding time is 6-10 hours; for example, the two-stage aging process is adopted, with the first-stage aging temperature at 120±3℃ and the holding time at 6 hours, and the second-stage aging temperature at 177±3℃ and the holding time at 6 hours; or, the two-stage aging process is adopted, with the first-stage aging temperature at 120±3℃ and the holding time at 4 hours, and the second-stage aging temperature at 162±3℃ and the holding time at 9 hours; or, the two-stage aging process is adopted, with the first-stage aging temperature at 107±3℃ and the holding time at 6 hours, and the second-stage aging temperature at 177±3℃ and the holding time at 8 hours, followed by air cooling after removal from the furnace.

[0051] The beneficial effects of this invention are:

[0052] This invention provides a method for reducing residual stress during quenching of large 7xxx aluminum alloy T-section long beam forgings. Targeting the structural characteristics of these forgings, this invention, based on traditional cold pressing methods for residual stress reduction, selects a cold deformation die with a specific structure to reduce equipment load and effectively reduce residual stress in the forgings. This invention replaces the vertically moving cold pressing die in traditional cold pressing with a rolling die, changing the contact between the die and the forging from surface to line contact. This significantly reduces the load requirements on the equipment and avoids the uneven stress reduction phenomenon caused by segmented cold pressing of long beam forgings. Simultaneously, the structural design of the upper roller mold cavity places the forging in a multi-directional compression state during cold deformation, which is more conducive to reducing residual stress and promoting its uniform distribution. Under the process parameter control of this invention, the cold deformation die has minimal impact on the microstructure and mechanical properties of the forging, achieving good residual stress elimination and effectively reducing deformation during the machining process of 7xxx aluminum alloy T-section long beam forgings, thus improving the part yield. Attached Figure Description

[0053] Figure 1 This is a structural schematic diagram of the 7xxx aluminum alloy T-shaped cross-section long beam forging of the present invention.

[0054] Figure 2 This is a schematic diagram of the upper roller mold according to a preferred embodiment of the present invention.

[0055] Figure 3 This is a schematic diagram of the structure of the lower rolling die according to a preferred embodiment of the present invention.

[0056] Figure 4 This is a schematic diagram of the cold deformation process after assembly according to the present invention. Wherein: 1. Upper roller die; 2. Forging; 3. Lower roller die. Detailed Implementation

[0057] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0058] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0059] The 7xxx aluminum alloy T-section long beam forgings used in the following examples are prepared from ingots through forging, pre-forging and final forging processes.

[0060] Example 1

[0061] The purpose of this embodiment is to reduce the residual quenching stress of a 7050 aluminum alloy T-shaped cross-section long beam forging. The 7050 aluminum alloy T-shaped cross-section long beam forging has a length of 4.5m and a width of 500mm. The radius of curvature along its length is approximately 12000mm. The 7050 aluminum alloy T-shaped cross-section long beam forging consists of a base plate and a rib, with the rib located on one side of the base plate. There is one rib. The cross-section of the 7050 aluminum alloy T-shaped cross-section long beam forging is an axisymmetric T-shape. The base plate has a thickness of 50mm and a width of 500mm. The rib has a thickness (i.e., height) of 70mm and a width of 45mm. The draft angle of the rib is 3°.

[0062] The cold deformation mold used in this embodiment consists of an upper roller mold and a lower roller mold;

[0063] The upper roller die is a cylindrical structure with a cavity; the width of the upper roller die is 800mm; the diameter of the upper roller die is 500mm; the cavity structure of the upper roller die is similar to the cross-section of the forging, and the thickness of the cavity of the upper roller die is 1.025 times the thickness of the forging; the width of the cavity of the upper roller die is slightly larger than (5-8mm) the width of the bottom plate; the slope of the side wall of the cavity of the upper roller die is 4°; the radius R1 of the fillet at the root of the rib of the cavity of the upper roller die is larger than the radius r1 of the fillet at the corresponding position of the forging; the radius R2 of the fillet at the root of the bottom plate of the cavity of the upper roller die is larger than the radius r2 of the fillet at the corresponding position of the forging.

[0064] The lower die has a spindle-shaped structure; the width of the lower die is 800mm; the middle diameter of the lower die is 550mm; the middle diameter of the lower die is 1% larger than the end diameter of the lower die. When the upper and lower dies are closed, they can enclose the cross-section of the forging.

[0065] The 7050 aluminum alloy T-shaped cross-section long beam forging is subjected to solution quenching at a temperature of 475℃±5℃. It is then immersed in water perpendicularly along its length at a water temperature of 60℃±5℃, with a quenching transfer time of less than 15s. The 7050 aluminum alloy T-shaped cross-section long beam forging is kept in water for 20 minutes to complete the quenching process.

[0066] The solution-quenched forging is placed on a rolling mill equipped with the aforementioned cold deformation die. The gap between the upper and lower roll dies is adjusted to 1.7mm-2.2mm according to the thickness and deformation of the forging, so that the forging bites into the upper roll die and ensures that the upper roll die contacts the ribs of the forging, but does not contact the upper surface of the base plate.

[0067] The cold deformation process is carried out using the aforementioned cold deformation die: Specifically, the forging is rolled and deformed in two passes along its length, with each pass yielding a deformation of 0.5%. The total deformation of the ribs is 1.0%. After the two passes, the cavity of the upper die contacts the upper surface of the forging's base plate. During this rolling deformation process, the initial rotation speed of the upper die is 0.5 mm / s, and after the forging's stroke exceeds 70%, the rotation speed of the upper die is 0.15 mm / s.

[0068] Along the length of the forging, the forging is subjected to rolling deformation treatment in two passes, one pass each. The deformation amount of each pass is 1%, and the total rolling deformation of the ribs and bottom plate in the two passes is about 2.0%. During this rolling deformation treatment, the initial rotation speed of the upper roll is 0.5 mm / s, and after the stroke of the forging exceeds 70%, the rotation speed of the upper roll is 0.15 mm / s.

[0069] The forgings after rolling deformation are subjected to aging treatment; specifically, a two-stage aging process is adopted, with the first-stage aging temperature at 120±3℃ and a holding time of 6 hours, the second-stage aging temperature at 177±3℃ and a holding time of 6 hours, followed by air cooling after removal from the furnace.

[0070] The residual stress and mechanical properties of the forging at various locations were measured after aging treatment. The maximum residual stress was 46 MPa, the minimum was 8 MPa, the tensile strength was 522 MPa, and the yield strength was 462 MPa. The maximum machining deformation of the forging was 1.1 mm.

[0071] Comparative Example 1

[0072] The other operations are the same as in Example 1, the difference being the cold deformation process:

[0073] The solution-quenched forging is placed on a cold-pressing die. The lower die is a flat anvil, and the upper die has a cavity structure similar to the cross-section of the forging. The cold-pressing die is 1.0m long, and the compression is 1.4mm, which is 2.0% of the base plate thickness. After each compression, the forging is moved so that the uncompressed part is on the die, with an overlap of 10cm-15cm. The forging is moved sequentially for cold pressing to ensure that all parts of the forging are cold-pressed.

[0074] The residual stress and mechanical properties of the forging at various locations were measured after aging treatment. The maximum residual stress was 103 MPa, the minimum was 58 MPa, the tensile strength was 518 MPa, and the yield strength was 455 MPa. The maximum machining deformation of the forging was 3.1 mm.

[0075] Example 2

[0076] The purpose of this embodiment is to reduce the residual quenching stress of a 7050 aluminum alloy T-shaped cross-section long beam forging. The 7085 aluminum alloy T-shaped cross-section long beam forging has a length of 5.0 m and a width of 600 mm. The radius of curvature along its length is approximately 11000 mm. The forging consists of a base plate and a rib, with the rib positioned on one side of the base plate. There is one rib. The cross-section of the forging is an axisymmetric T-shape. The base plate has a thickness of 50 mm and a width of 600 mm. The rib has a thickness (height) of 80 mm and a width of 45 mm. The draft angle of the rib is 5°.

[0077] The cold deformation mold used in this embodiment consists of an upper roller mold and a lower roller mold;

[0078] The upper roller die is a cylindrical structure with a cavity; the width of the upper roller die is 800mm; the diameter of the upper roller die is 500mm; the cavity structure of the upper roller die is similar to the cross-section of the forging, and the thickness of the cavity of the upper roller die is 1.015 times the thickness of the forging; the width of the cavity of the upper roller die is slightly larger than (5-8mm) the width of the bottom plate; the slope of the side wall of the cavity of the upper roller die is 6°; the radius R1 of the fillet at the root of the rib of the cavity of the upper roller die is larger than the radius r1 of the fillet at the corresponding position of the forging; the radius R2 of the fillet at the root of the bottom plate of the cavity of the upper roller die is larger than the radius r2 of the fillet at the corresponding position of the forging.

[0079] The lower die has a spindle-shaped structure; the width of the lower die is 800mm; the middle diameter of the lower die is 550mm; the middle diameter of the lower die is 1% larger than the end diameter of the lower die. When the upper and lower dies are closed, they can enclose the cross-section of the forging.

[0080] The 7085 aluminum alloy T-shaped cross-section long beam forging was solution hardened at a temperature of 471℃±5℃. It was then immersed perpendicularly in water along its length at a quenching water temperature of 40℃±5℃, with a quenching transfer time of less than 15 seconds. The 7085 aluminum alloy T-shaped cross-section long beam forging was then kept in water for 20 minutes to complete the quenching process.

[0081] The solution-quenched forging is placed on a rolling mill equipped with the aforementioned cold deformation die. The gap between the upper and lower roll dies is adjusted to 2.0mm-2.6mm according to the thickness and deformation of the forging, so that the forging bites into the upper roll die and ensures that the upper roll die contacts the ribs of the forging, but does not contact the upper surface of the base plate.

[0082] The cold deformation process is performed using the aforementioned cold deformation die: Specifically, along the length of the forging, the forging is subjected to one pass of rolling deformation in each direction, with a deformation amount of 0.6% for each pass and a total deformation amount of 1.2% for the ribs. After the two passes, the cavity of the upper die contacts the upper surface of the forging's base plate. During this rolling deformation process, the initial rotation speed of the upper die is 0.5 mm / s, and after the forging's stroke exceeds 70%, the rotation speed of the upper die is 0.20 mm / s. Then, along the length of the forging, the forging is subjected to another pass of rolling deformation in each direction, with a deformation amount of 0.8% for each pass and a total deformation amount of approximately 1.6% for the ribs and base plate. During this rolling deformation process, the initial rotation speed of the upper die is 0.5 mm / s, and after the forging's stroke exceeds 70%, the rotation speed of the upper die is 0.20 mm / s.

[0083] The forgings after rolling deformation are subjected to aging treatment; specifically, a two-stage aging process is adopted, with the first-stage aging temperature at 120±3℃ and a holding time of 4 hours, and the second-stage aging temperature at 162±3℃ and a holding time of 9 hours, followed by air cooling after removal from the furnace.

[0084] The residual stress and mechanical properties of the forging at various locations were measured after aging treatment. The maximum residual stress was 41 MPa, the minimum was 19 MPa, the tensile strength was 525 MPa, and the yield strength was 470 MPa. The maximum machining deformation of the forging was 0.8 mm.

[0085] Comparative Example 2

[0086] The other operations are the same as in Example 2, except that the cold deformation process is different:

[0087] The solution-quenched forging is placed on a cold-pressing die. The lower die is a flat anvil, and the upper die has a cavity structure similar to the cross-section of the forging. The cold-pressing die is 1.0m long, and the compression is 1.0mm, which is 2.0% of the base plate thickness. After each compression, the forging is moved so that the uncompressed part is on the die, with an overlap of 10cm-15cm. The forging is moved sequentially for cold pressing to ensure that all parts of the forging are cold-pressed.

[0088] The residual stress and mechanical properties of the forging at various locations were measured after aging treatment. The maximum residual stress was 120 MPa, the minimum was 31 MPa, the tensile strength was 518 MPa, and the yield strength was 465 MPa. The maximum machining deformation of the forging was 2.1 mm.

[0089] Example 3

[0090] The purpose of this embodiment is to reduce the residual quenching stress of a 7175 aluminum alloy T-shaped cross-section long beam forging. The 7175 aluminum alloy T-shaped cross-section long beam forging has a length of 4.0 m and a width of 500 mm. The radius of curvature along its length is approximately 10000 mm. The 7175 aluminum alloy T-shaped cross-section long beam forging consists of a base plate and a rib, with the rib located on one side of the base plate. There is one rib. The cross-section of the 7175 aluminum alloy T-shaped cross-section long beam forging is an axisymmetric T-shape. The base plate has a thickness of 50 mm and a width of 500 mm. The rib has a thickness (i.e., height) of 100 mm and a width of 50 mm. The draft angle of the rib is 7°.

[0091] The cold deformation mold used in this embodiment consists of an upper roller mold and a lower roller mold;

[0092] The upper roller die is a cylindrical structure with a cavity; the width of the upper roller die is 800mm; the diameter of the upper roller die is 500mm; the cavity structure of the upper roller die is similar to the cross-section of the forging, and the thickness of the cavity of the upper roller die is 1.025 times the thickness of the forging; the width of the cavity of the upper roller die is slightly larger than (5-8mm) the width of the bottom plate; the slope of the side wall of the cavity of the upper roller die is 9°; the radius R1 of the fillet at the root of the rib of the cavity of the upper roller die is larger than the radius r1 of the fillet at the corresponding position of the forging; the radius R2 of the fillet at the root of the bottom plate of the cavity of the upper roller die is larger than the radius r2 of the fillet at the corresponding position of the forging.

[0093] The lower die has a spindle-shaped structure; the width of the lower die is 800mm; the middle diameter of the lower die is 550mm; the middle diameter of the lower die is 1% larger than the end diameter of the lower die. When the upper and lower dies are closed, they can enclose the cross-section of the forging.

[0094] The 7175 aluminum alloy T-shaped cross-section long beam forging was solution hardened at a temperature of 475℃±5℃. It was then immersed vertically in water along its length and quenched at room temperature with a quenching transfer time of less than 15 seconds. The 7175 aluminum alloy T-shaped cross-section long beam forging was then kept in water for 20 minutes to complete the quenching process.

[0095] The solution-quenched forging is placed on a rolling mill equipped with the aforementioned cold deformation die. The gap between the upper and lower roll dies is adjusted to 2.6mm-3.0mm according to the thickness and deformation of the forging, so that the forging bites into the upper roll die and ensures that the upper roll die contacts the ribs of the forging, but does not contact the upper surface of the base plate.

[0096] The cold deformation process is carried out using the aforementioned cold deformation die: Specifically, the forging is rolled and deformed in two passes along its length, with each pass yielding a deformation of 0.3%. The total deformation of the ribs is 0.6%. After the two passes, the cavity of the upper die contacts the upper surface of the forging's base plate. During this rolling deformation process, the initial rotation speed of the upper die is 0.5 mm / s, and after the forging's stroke exceeds 70%, the rotation speed of the upper die is 0.20 mm / s.

[0097] Along the length of the forging, the forging is subjected to rolling deformation treatment in two passes, one pass each. The deformation amount of each pass is 0.6%, and the total deformation of the ribs and bottom plate in the two passes is about 1.2%. During this rolling deformation treatment, the initial rotation speed of the upper roll is 0.5 mm / s, and after the forging stroke exceeds 70%, the rotation speed of the upper roll is 0.20 mm / s.

[0098] The forgings after rolling deformation are subjected to aging treatment; specifically, a two-stage aging process is adopted, with the first-stage aging temperature at 107±3℃ and a holding time of 6 hours, and the second-stage aging temperature at 177±3℃ and a holding time of 8 hours, followed by air cooling after removal from the furnace.

[0099] The residual stress and mechanical properties of the forging at various locations were measured after aging treatment. The maximum residual stress was 47 MPa, the minimum was 22 MPa, the tensile strength was 545 MPa, and the yield strength was 481 MPa. The maximum machining deformation of the forging was 1.0 mm.

[0100] Comparative Example 3

[0101] The other operations are the same as in Example 3, except that the cold deformation process is different:

[0102] The solution-quenched forging is placed on a cold-pressing die. The lower die is a flat anvil, and the upper die has a cavity structure similar to the cross-section of the forging. The cold-pressing die is 1.0m long, and the compression is 1.0mm, which is 2.0% of the base plate thickness. After each compression, the forging is moved so that the uncompressed part is on the die, with an overlap of 10cm-15cm. The forging is moved sequentially for cold pressing to ensure that all parts of the forging are cold-pressed.

[0103] The residual stress and mechanical properties of the forging at various locations were measured after aging treatment. The maximum residual stress was 141 MPa, the minimum was 55 MPa, the tensile strength was 503 MPa, and the yield strength was 432 MPa. The maximum machining deformation of the forging was 4.2 mm.

[0104] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for reducing residual stress during quenching of large 7xxx aluminum alloy T-section long beam forgings, the method comprising the following steps: (1) The cold deformation die is installed on the rolling mill. The cold deformation die consists of an upper roll die and a lower roll die. The upper roll die is a cylindrical structure with a cavity, and the structure of the cavity is similar to the cross-section of the forging. The lower roll die is a spindle-shaped structure. After the upper roll die and the lower roll die are closed, they can wrap the cross-section of the forging. (2) Place the solution-quenched forging on the rolling mill equipped with the cold deformation mold in step (1), and adjust the gap between the upper and lower rolls according to the thickness and deformation of the forging, so that the forging bites into the upper roll and ensures that the upper roll contacts the ribs of the forging. (3) Along the length of the forging, the forging is subjected to rolling deformation treatment in one pass each, and the total rolling deformation of the ribs in the two passes is controlled to be 0.5%-1.2%. After the two passes of rolling deformation treatment, the cavity of the upper roll die contacts the bottom plate of the forging. (4) Along the length of the forging, the forging is rolled again in one pass each, and the total rolling deformation of the forging in the two passes is controlled to be 1.2%-3.2%. (5) Aging treatment is performed on the forgings after rolling deformation to reduce the residual quenching stress of large 7xxx aluminum alloy T-shaped cross-section long beam forgings.

2. The method according to claim 1, wherein, The length of the large 7xxx aluminum alloy T-shaped cross-section long beam forging is ≥4m; the width of the large 7xxx aluminum alloy T-shaped cross-section long beam forging is ≥400mm. Preferably, the radius of curvature of the large 7xxx aluminum alloy T-shaped cross-section long beam forging along its length is 4000-20000 mm.

3. The method according to claim 1 or 2, wherein, The large 7xxx aluminum alloy T-shaped cross-section long beam forging consists of a base plate and a rib, with the rib located on one side of the base plate; the number of ribs is one; the cross-section of the large 7xxx aluminum alloy T-shaped cross-section long beam forging is axially symmetric or non-axially symmetric T-shaped; the thickness of the base plate is 10-90mm; the thickness of the rib is 10-180mm.

4. The method according to any one of claims 1-3, wherein, In step (1), the diameter of the lower roller mold is greater than the diameter of the upper roller mold. Preferably, in step (1), the width of the cavity of the upper roller mold is greater than the width of the base plate; preferably, the width of the cavity of the upper roller mold is 5-20mm larger than the width of the base plate. Preferably, in step (1), the thickness of the cavity of the upper roller mold is 1.012-1.035 times the thickness of the forging. Preferably, in step (1), the side wall slope of the cavity of the upper roller mold is greater than the draft angle of the ribs of the forging.

5. The method according to any one of claims 1-4, wherein, In step (1), the radius R1 of the root fillet at the rib of the upper roller mold cavity is greater than the radius r1 of the fillet at the corresponding position of the forging; the radius R2 of the root fillet at the bottom plate of the upper roller mold cavity is greater than the radius r2 of the fillet at the corresponding position of the forging. Preferably, in step (1), the diameter of the middle part of the lower roller die is 1%-3% larger than the diameter of the end part of the lower roller die.

6. The method according to any one of claims 1-5, wherein, In step (2), the solution quenching temperature is (470-475℃)±5℃; the quenching transfer time is ≤30s; and the quenching water temperature is (20-60℃)±5℃.

7. The method according to any one of claims 1-6, wherein, In step (2), adjust the gap between the upper and lower roller dies to 1.5-5mm so that the forging bites into the upper roller die and ensures that the upper roller die contacts the ribs of the forging, but does not contact the upper surface of the base plate.

8. The method according to any one of claims 1-7, wherein, In step (3), during the rolling deformation process, the upper roller die rotates at a speed of 0.1-0.8 mm / s. Preferably, during the rolling deformation process, after the forging stroke begins, the upper roller rotates at a speed of 0.5-0.8 mm / s, and after the forging stroke reaches 50%-70%, the upper roller rotates at a speed of 0.1-0.4 mm / s. Preferably, in step (3), the rolling deformation of a single pass of reinforcing bar is 0.2%-0.6%.

9. The method according to any one of claims 1-8, wherein, In step (4), during the rolling deformation process, the upper roller rotates at a speed of 0.1-0.8 mm / s. Preferably, during the rolling deformation process, after the forging stroke begins, the upper roller rotates at a speed of 0.5-0.8 mm / s, and after the forging stroke reaches 50%-70%, the upper roller rotates at a speed of 0.1-0.4 mm / s. Preferably, in step (4), the rolling deformation of a single forging is 0.6%-1.6%.

10. The method according to any one of claims 1-9, wherein, In step (5), a two-stage aging process is adopted; wherein, the temperature of the first-stage aging is (105-120)℃±3℃, and the holding time is 4-8 hours, and the temperature of the second-stage aging is (160-180)℃±3℃, and the holding time is 6-10 hours.

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