Method for reducing residual stress of aluminum alloy C-shaped section ring forging
By rolling aluminum alloy C-shaped cross-section ring forgings in stages within a specific temperature range, the problem of incomplete residual stress reduction in the existing technology is solved, and the uniformity of stress distribution and forming quality are improved, making it suitable for the production of large-size ring forgings.
Patent Information
- Application Number
- CN202610402016.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-03-30
- Publication Date
- 2026-05-05
AI Technical Summary
Existing technologies are insufficient to effectively reduce the residual stress in large-size aluminum alloy C-shaped cross-section ring forgings, and conventional methods suffer from problems such as hardening effects, uneven material flow, and incomplete stress reduction, which cannot meet the stringent requirements of the aerospace field.
By determining the rolling temperature range [T1, T2], a three-stage rolling scheme is planned, an improved rolling mandrel and ring mill are designed, and the feed speed and temperature during the rolling process are controlled to ensure that the aluminum alloy C-shaped cross-section ring forging is rolled within a specific temperature range, thereby eliminating residual stress in stages.
It significantly reduces the hardening effect of aluminum alloy C-shaped cross-section ring forgings, reduces the risk of cracking, improves forming quality, achieves uniform stress distribution and high precision of finished products, is suitable for the production of ultra-large ring forgings of φ10m, and reduces production costs.
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Figure CN121972589A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for reducing residual stress in aluminum alloy C-shaped cross-section ring forgings, belonging to the field of aluminum alloy rolling technology. Background Technology
[0002] Aluminum alloy C-shaped cross-section ring forgings are key force-transmitting connection components in aerospace equipment, commonly used in rocket fuel tank transition rings, missile frames, and other parts. Taking the Long March 5 heavy-lift launch vehicle as an example, its fuel tank transition ring has a diameter of 10 meters and a wall thickness of only 5-25 millimeters. It needs to be precisely assembled with the rocket body and withstand extreme loads such as extremely low temperatures, high pressures, and severe vibrations and shocks from liquid hydrogen / liquid oxygen during service. This poses extremely stringent challenges to the mechanical properties and dimensional accuracy control of aluminum alloy C-shaped cross-section ring forgings.
[0003] The T6 heat treatment (solution quenching + artificial aging) of aluminum alloy ring forgings introduces high-amplitude residual stress, which not only causes warping and distortion during the machining stage but also induces stress corrosion, reducing the service life of the aluminum alloy ring forgings. Therefore, controlling the residual stress in aluminum alloy ring forgings is a key factor in manufacturing high-performance aluminum alloy ring forgings.
[0004] Traditionally, aluminum alloy ring forgings are expanded from the inside out using bulging equipment to induce plastic deformation and release stress. However, the largest bulging equipment in China can only meet the processing requirements of φ6m ring forgings, and cannot meet the stress reduction requirements of φ10m large-size aluminum alloy ring forgings in the aerospace field. Furthermore, the initial investment cost of bulging equipment is high, and the cost of specialized tooling and molds is also high, making it unsuitable for small-batch production.
[0005] In recent years, some researchers have proposed eliminating residual stress in aluminum alloy ring forgings through cold rolling. This method involves cold rolling the aluminum alloy ring forgings on a ring rolling mill to increase their outer diameter by 2% to 3%, thereby eliminating residual stress within the ring. However, this method for real-time stress reduction in aluminum alloy C-section ring forgings presents the following problems: 1. The commonly used room-temperature ring rolling process exhibits a material hardening effect, leading to decreased plasticity and resulting in damage and cracking; 2. During the rolling process, uneven material flow occurs at different thicknesses of the aluminum alloy C-section ring forging, resulting in uneven residual stress remaining in the cross-section after rolling; 3. The stress reduction effect varies significantly across different circumferential regions of the rolled aluminum alloy C-section ring forging, with some areas not experiencing complete stress reduction. Therefore, eliminating residual stress in aluminum alloy ring forgings through cold rolling cannot meet the residual stress control requirements of large-size aluminum alloy C-section ring forgings in the aerospace field. Furthermore, the damage / cracks introduced during the rolling process increase the risk of fracture and failure of large-size aluminum alloy C-section ring forgings under extreme service conditions. Summary of the Invention
[0006] The purpose of this invention is to provide a method for reducing residual stress in aluminum alloy C-shaped cross-section ring forgings, so as to solve the problems existing in the prior art.
[0007] To address the aforementioned technical problems, this invention provides a method for reducing residual stress in aluminum alloy C-shaped cross-section ring forgings, comprising:
[0008] Step 1: Determine the rolling temperature range [T1, T2] of the C-shaped cross-section ring forging: T1 is the critical temperature of the C-shaped cross-section ring forging when the strain sensitivity coefficient is 0, and T2 is the peak aging temperature of the C-shaped cross-section ring forging;
[0009] Step 2: Plan the rolling scheme for C-shaped cross-section ring forgings: Plan the rolling process of C-shaped cross-section ring forgings into three stages, and determine the feed speed of the rolling mandrel in each stage, the feed amount at the end of the first and second stages, and the end conditions of each stage.
[0010] Step 3: Design and fabricate the rolling mandrel: Define the initial mandrel as a roll with a work roll surface that perfectly matches the inner wall of the C-shaped cross-section ring forging. The two ends of the initial mandrel are small-diameter sections, and the middle of the initial mandrel is a large-diameter section. The large-diameter section of the initial mandrel is connected to the two small-diameter sections of the initial mandrel through a transition surface. The radius of the large-diameter section of the initial mandrel is D, and the radius of the large-diameter section of the rolling mandrel is R. ’ It is calculated using the following formula.
[0011] The minor diameter sections at both ends of the rolling mandrel are identical to those at both ends of the initial mandrel. Both ends of the major diameter section of the rolling mandrel are connected to the minor diameter sections at both ends of the rolling mandrel via transition surfaces. The fillets between the transition surfaces of the rolling mandrel and the corresponding major diameter sections, and the fillets between the transition surfaces of the rolling mandrel and the corresponding two minor diameter sections, are identical to the corresponding fillets of the initial mandrel. The rolling mandrel is manufactured according to these dimensions, where k is an integer between 2 and 4, and B... max B min These represent the maximum and minimum wall thicknesses of the C-shaped cross-section ring forging before rolling, respectively; ε0 represents the first feed amount at the end of the first stage; and ε1 represents the second feed amount at the end of the second stage.
[0012] Step 4: Improve the ring mill: Change the mandrel of the ring mill to the rolling mandrel produced in step 2, while keeping the other parts of the ring mill unchanged, to obtain an improved ring mill;
[0013] Step 5: Determine the range of linear velocity of the drive roller and feed speed of the rolling core roller;
[0014] Step 6: Heating the C-shaped cross-section ring forging: The C-shaped cross-section ring forging after solution quenching is heated in an aluminum alloy-specific aging furnace to ensure that the temperature of the C-shaped cross-section ring forging is within its rolling temperature range, and held at that temperature for 5 to 30 minutes.
[0015] Step 7: Place the heat-insulated C-shaped cross-section ring forging on the improved ring rolling mill;
[0016] Step 8: Start the improved ring mill to roll the C-section ring forging: Set the linear speed of the drive roller and the feed speed of the rolling mandrel, start the improved ring mill to roll the C-section ring forging according to the planned rolling scheme, and the entire rolling process of the C-section ring forging needs to be completed within 5 hours after its solution quenching treatment.
[0017] In one specific embodiment, the improved ring mill is equipped with a drive roll, a rear clamping roll, a front clamping roll, a rolling mandrel, an upper tapered roll, and a lower tapered roll. The rolling mandrel is manufactured in step 3. A C-shaped cross-section ring forging is placed on the improved ring mill. The outer side of the C-shaped cross-section ring forging is in contact with the drive roll, the rear clamping roll, and the front clamping roll. The drive roll is located between the rear clamping roll and the front clamping roll. The rolling mandrel is in contact with the inner side of the C-shaped cross-section ring forging. The axes of the drive roll, the rear clamping roll, the front clamping roll, and the rolling mandrel are all parallel to the axis of the C-shaped cross-section ring forging. The centers of the circles on the same cross section of the C-shaped cross-section ring forging, the drive roll, and the rolling mandrel are on the same straight line. The upper end of the C-shaped cross-section ring forging on the side away from the drive roll is in contact with the upper tapered roll, and the lower end of the C-shaped cross-section ring forging on the side away from the drive roll is in contact with the lower tapered roll.
[0018] In one specific embodiment, the rolling scheme for the C-shaped cross-section ring forging is as follows: In the first stage, the rolling mandrel moves radially at a first feed speed v. 芯1 The core roll moves towards the drive roll at a speed of v until the feed amount reaches the first feed amount ε0; in the second stage, the core roll moves towards the drive roll at a second feed speed v. 芯2 The mandrel moves at a speed towards the drive roll until the C-shaped ring forging completes one full rotation and the feed rate reaches the second feed rate ε1; in the third stage, the mandrel moves at a third feed speed v. 芯3 The feed motion is directed towards the drive roller at a speed of v, rolling the C-shaped cross-section ring forging at least one revolution until roundness correction is achieved, ending the rolling of the C-shaped cross-section ring forging. At the end of rolling, the temperature of the C-shaped cross-section ring forging is higher than (T1-15)℃; wherein the first feed speed v 芯1 Second feed rate v 芯2 and the third feed rate v 芯3 All at feed rate v 芯 Within the range.
[0019] In one specific implementation, the rotational speed v of the drive roller 驱The feed speed v of the rolling mandrel is determined based on the improved rolling capacity of the ring mill. 芯 The range is determined based on the bite-in conditions of C-section ring forging rolling, specifically by calculating the feed speed v of the rolling mandrel according to the following formula. 芯 Scope:
[0020] Among them, v 驱 To improve the linear speed of the drive roll of the ring mill, R is the maximum outer radius of the C-shaped cross-section ring forging before rolling, and r is the minimum inner radius of the C-shaped cross-section ring forging before rolling. 驱 R' is the radius of the drive roller, and R' is the radius of the large diameter section of the rolling mandrel.
[0021] In one specific implementation, the critical temperature T1 is obtained as follows:
[0022] Step a: Perform tensile tests on the solution-treated aluminum alloy, which is the same material as the C-shaped ring forging to be rolled, and obtain stress-strain curves at different temperatures.
[0023] Step b: Based on the stress-strain curve data obtained in step a, calculate the strain sensitivity coefficient m at different temperatures using the following formula.
[0024] in, and These represent the strain rates, respectively. and Rheological stress under the following conditions The value is 10 -1 s -1 ;
[0025] Step c: Plot the corresponding temperature-strain rate sensitivity coefficient scatter plot, and obtain the critical temperature T1 when the strain sensitivity coefficient m is 0 by polynomial fitting and bisection method. T1 is the critical temperature of the C-shaped cross-section ring forging when the strain sensitivity coefficient m is 0.
[0026] In one specific implementation, the first feed amount ε0 and the second feed amount ε1 satisfy the following relationship: .
[0027] In one specific embodiment, the dimensions of the C-shaped cross-section ring forging before rolling are as follows: maximum outer diameter of 1000~12000mm, total axial height H1 of 100~500mm, C-shaped opening width H2 of 50~200mm, H2 / H1=0.3~0.6, and maximum wall thickness B. max The minimum wall thickness is B, ranging from 50 to 250 mm. min30~150mm, B max / B min =1.2~2.5.
[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0029] 1. The present invention rolls C-shaped cross-section ring forgings within the rolling temperature range of C-shaped cross-section ring forgings, which can reduce the hardening effect of C-shaped cross-section ring forgings, significantly reduce the risk of cracking of C-shaped cross-section ring forgings during rolling, and improve the forming quality of C-shaped cross-section ring forgings;
[0030] 2. The rolling process of the present invention is divided into three stages, and the feed speed of the rolling mandrel is different in each stage. This ensures that the extrusion amount in each area of the C-shaped cross-section ring forging is consistent in the circumferential direction, thus solving the problem of incomplete stress reduction in some areas of the C-shaped cross-section ring forging in the circumferential direction.
[0031] 3. The present invention improves the mandrel of the ring rolling mill, thereby improving the uneven material flow during rolling of C-shaped cross-section ring forgings in different thickness areas, resulting in lower stress levels and more uniform distribution in the cross-section of the rolled C-shaped cross-section ring forgings.
[0032] 4. This invention does not require special forming equipment. Stress reduction of ultra-large C-shaped cross-section ring forgings with a diameter of φ10m can be achieved using a ring rolling mill. It has a wide range of applications and does not require additional investment in special tooling, effectively reducing production costs. Attached Figure Description
[0033] Figure 1 This is a flowchart of the method for reducing residual stress in aluminum alloy C-shaped cross-section ring forgings according to the present invention.
[0034] Figure 2 This is a schematic diagram of the improved ring mill and the movement of the C-shaped cross-section ring forging during the rolling process of the C-shaped cross-section ring forging of the present invention.
[0035] Figure 3 This is a schematic diagram showing the positional relationship between the C-shaped cross-section ring forging and the rolling mandrel of the present invention.
[0036] Figure 4 This is a line graph showing the change in the feed rate of the rolling mandrel over time during the rolling process of the C-shaped cross-section ring forging of the present invention.
[0037] Figure 5 These are Mises equivalent stress distribution cloud maps of the C-shaped cross-section ring forging before and after rolling in Embodiment 1 of the present invention, where a is the Mises equivalent stress distribution cloud map of the C-shaped cross-section ring forging before rolling, and b is the Mises equivalent stress distribution cloud map of the C-shaped cross-section ring forging after rolling.
[0038] Figure 6This is a comparison diagram of the residual stress distribution in the circumferential direction of the C-shaped cross-section ring forging in the embodiments of the present invention and the comparative examples;
[0039] Figure 7 This is a comparison diagram of the residual stress distribution on the cross section of the C-shaped ring forging in the embodiments and comparative examples of the present invention.
[0040] In the figure: 1. Drive roller; 2. Rear clamping roller; 3. Front clamping roller; 4. Rolling core roller; 5. C-shaped cross-section ring forging; 6. Upper conical roller; 7. First stage; 8. Second stage; 9. Third stage; 41. Working roller surface of the initial core roller; 42. Working roller surface of the rolling core roller. Detailed Implementation
[0041] The present invention will now be described in detail with reference to the embodiments and accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.
[0042] Example
[0043] refer to Figure 1 A method for reducing residual stress in aluminum alloy C-shaped cross-section ring forgings includes the following specific steps:
[0044] Step 1: Determine the rolling temperature range [T1, T2] of the C-shaped cross-section ring forging: T1 is the critical temperature of the C-shaped cross-section ring forging when the strain sensitivity coefficient is 0, and T2 is the peak aging temperature of the C-shaped cross-section ring forging; Specifically, the critical temperature T1 is obtained as follows:
[0045] Step a: Perform a tensile test on the aluminum alloy in the solid solution state, which is the same material as the C-shaped cross-section ring forging to be rolled, and obtain the stress-strain curves at different temperatures;
[0046] Step b: Based on the stress-strain curve data obtained in step a, calculate the strain sensitivity coefficient m at different temperatures using the following formula;
[0047] in, and These represent the strain rates, respectively. and Rheological stress under the following conditions The value is 10 -1 s -1 ;
[0048] Step c: Plot the corresponding temperature-strain rate sensitivity coefficient scatter plot, and obtain the critical temperature T1 when the strain sensitivity coefficient m is 0 by polynomial fitting and bisection method. T1 is the critical temperature of the C-shaped cross-section ring forging when the strain sensitivity coefficient m is 0.
[0049] Preferably, the dimensions of the C-shaped cross-section ring forging before rolling are as follows: maximum outer diameter of 1000~12000mm, total axial height H1 of 100~500mm, C-shaped opening width H2 of 50~200mm, H2 / H1=0.3~0.6, and maximum wall thickness B. max The minimum wall thickness is B, ranging from 50 to 250 mm. min 30~150mm, B max / B min =1.2~2.5.
[0050] Step 2: Plan the rolling scheme for the C-shaped cross-section ring forging: The rolling process of the C-shaped cross-section ring forging is planned into three stages, and the feed speed of the rolling mandrel in each stage, the feed amount at the end of the first and second stages, and the end conditions of each stage are determined; specifically as follows: In the first stage, the rolling mandrel moves radially at a first feed speed v 芯1 The core roll moves towards the drive roll at a speed of v until the feed amount reaches the first feed amount ε0; in the second stage, the core roll moves towards the drive roll at a second feed speed v. 芯2 The mandrel moves at a speed towards the drive roll until the C-shaped ring forging completes one full rotation and the feed rate reaches the second feed rate ε1; in the third stage, the mandrel moves at a third feed speed v. 芯3 The feed motion is directed towards the drive roller at a speed of v, rolling the C-shaped cross-section ring forging at least one revolution until roundness correction is achieved, ending the rolling of the C-shaped cross-section ring forging. At the end of rolling, the temperature of the C-shaped cross-section ring forging is higher than (T1-15)℃; wherein the first feed speed v 芯1 Second feed rate v 芯2 and the third feed rate v 芯3 All at feed rate v 芯 Within the range, the first feed rate ε0 and the second feed rate ε1 satisfy the following relationship: .
[0051] Step 3: Design and fabricate the rolling mandrel: Define the initial mandrel as a roll with a work roll surface that perfectly matches the inner wall of the C-shaped cross-section ring forging. The two ends of the initial mandrel are small-diameter sections, and the middle of the initial mandrel is a large-diameter section. The large-diameter section of the initial mandrel is connected to the two small-diameter sections of the initial mandrel through a transition surface. The radius of the large-diameter section of the initial mandrel is D, and the radius of the large-diameter section of the rolling mandrel is R. ’ It is calculated using the following formula.
[0052] The minor diameter sections at both ends of the rolling mandrel are identical to those at both ends of the initial mandrel. Both ends of the major diameter section of the rolling mandrel are connected to the minor diameter sections at both ends of the rolling mandrel via transition surfaces. The fillets between the transition surfaces of the rolling mandrel and the corresponding major diameter sections, and the fillets between the transition surfaces of the rolling mandrel and the corresponding two minor diameter sections, are identical to the corresponding fillets of the initial mandrel. The rolling mandrel is manufactured according to these dimensions, where k is an integer between 2 and 4, and B... max B min These represent the maximum and minimum wall thicknesses of the C-shaped cross-section ring forging before rolling, respectively; ε0 represents the first feed amount at the end of the first stage; and ε1 represents the second feed amount at the end of the second stage.
[0053] Step 4: Improve the ring mill: Change the mandrel of the ring mill to the rolling mandrel produced in step 2, while keeping the other parts of the ring mill unchanged, to obtain an improved ring mill.
[0054] Step 5: Determine the range of rotational speed of the drive roller and the feed speed of the mandrel, as follows: Calculate the feed speed v of the mandrel according to the following formula. 芯 Scope:
[0055] Among them, v 驱 To improve the linear speed of the drive roll of the ring mill, R is the maximum outer radius of the C-shaped cross-section ring forging before rolling, and r is the minimum inner radius of the C-shaped cross-section ring forging before rolling. 驱 R' is the radius of the drive roller, and R' is the radius of the large diameter section of the rolling mandrel.
[0056] Step 6: Heating the C-shaped cross-section ring forging: The C-shaped cross-section ring forging after solution quenching is heated in an aluminum alloy-specific aging furnace to ensure that the temperature of the C-shaped cross-section ring forging is within its rolling temperature range, and held at that temperature for 5 to 30 minutes.
[0057] Step 7: Place the heat-insulated C-shaped cross-section ring forging on the improved ring rolling mill, refer to... Figure 2 The improved ring mill is equipped with a drive roll, a rear clamping roll, a front clamping roll, a rolling mandrel roll, an upper conical roll, and a lower conical roll. A C-shaped cross-section ring forging is placed on the improved ring mill. The rolling mandrel roll is manufactured in step 2. The outer side of the C-shaped cross-section ring forging is in contact with the drive roll, the rear clamping roll, and the front clamping roll. The drive roll is located between the rear clamping roll and the front clamping roll. The inner side of the C-shaped cross-section ring forging is in contact with the rolling mandrel roll. The positional relationship between the rolling mandrel roll and the C-shaped cross-section ring forging is referenced. Figure 3The axes of the drive roller, rear clamping roller, front clamping roller, and rolling core roller are all parallel to the axis of the C-shaped cross-section ring forging. The centers of the circles on the same cross-section of the C-shaped cross-section ring forging, drive roller, and rolling core roller are on the same straight line. The upper end of the C-shaped cross-section ring forging on the side away from the drive roller contacts the upper tapered roller, and the lower end of the C-shaped cross-section ring forging on the side away from the drive roller contacts the lower tapered roller.
[0058] Step 8: Start the improved ring mill to roll the C-section ring forging: Set the linear speed of the drive roll and the feed speed of the rolling mandrel. Start the improved ring mill to roll the C-section ring forging according to the planned rolling scheme. The entire rolling process of the C-section ring forging needs to be completed within 5 hours after its solution quenching treatment. When the rolling of the C-section ring forging is completed, the temperature of the C-section ring forging is higher than (T1-15℃). Air cool the rolled C-section ring forging to room temperature.
[0059] Example
[0060] Taking a φ3650mm specification 2219 aluminum alloy C-shaped cross-section ring forging as an example, the implementation process of this invention will be further explained. The dimensional parameters of the C-shaped cross-section ring forging are: maximum outer radius of 3650mm, minimum inner radius of 3550mm, total axial height H1 of 450mm, and maximum wall thickness B of the C-shaped cross-section ring forging. max and minimum wall thickness B min The sizes are 150mm and 100mm respectively.
[0061] Step a: Determine the rolling temperature range [T1, T2] of the C-shaped cross section ring forging: Take the 2219 aluminum alloy ring forging material after solution quenching treatment, process it into samples and conduct high temperature tensile tests to obtain its stress-strain curves at 25℃, 50℃, 100℃, 150℃ and 200℃.
[0062] According to the formula Calculate the strain rate sensitivity coefficient of 2219 aluminum alloy ring forging material at various temperatures, where, and These represent the strain rates, respectively. and Rheological stress under the following conditions The value is 10 -1 s -1 ;
[0063] Plot the corresponding temperature-strain rate sensitivity coefficient scatter plot. Obtain the critical temperature T1 when the strain sensitivity coefficient m is 0 using polynomial fitting and the bisection method. T1 is 158℃. The peak aging temperature T2 of the 2219 aluminum alloy ring forging is known to be 175℃. Therefore, the rolling temperature range of the 2219 aluminum alloy C-section ring forging is [158℃, 175℃].
[0064] Step b: According to step 2 of the present invention, the rolling scheme is planned as follows:
[0065] In the first stage, the rolling mandrel moves radially towards the drive roll at a speed of 1.0 mm / s until the feed amount reaches 3.5 mm; in the second stage, the rolling mandrel moves radially towards the drive roll at a speed of 0.05 mm / s until the C-shaped cross-section ring forging completes one full rotation, with a feed amount reaching 4.2 mm; in the third stage, the rolling mandrel moves radially towards the drive roll at a speed of 0.03 mm / s to perform two rotations of rolling on the C-shaped cross-section ring forging.
[0066] Step c: Design and manufacture the rolling core roll according to step 3 of the present invention.
[0067] Step d: Improve the ring mill: Change the mandrel of the ring mill to a rolling mandrel made in step c, while keeping the other parts of the ring mill unchanged, to obtain an improved ring mill.
[0068] Step e: Determine the linear velocity v of the drive roller according to step 5 of this document. 驱 The feed speed of the rolling core roll is 0.6 m / s. 芯的 The range is: v 芯 ≥0.018mm / s.
[0069] Step f: Heating the C-shaped cross-section ring forging: The C-shaped cross-section ring forging after solution quenching is heated in an aluminum alloy-specific aging furnace until the temperature reaches 170℃ and is held for 15 minutes.
[0070] Step g: Place the heat-insulated C-shaped cross-section ring forging on an improved ring rolling mill.
[0071] Step h: Start the improved ring mill to roll the C-shaped cross-section ring forging according to the planned rolling scheme. During the rolling process, the drive roll moves clockwise, driving the C-shaped cross-section ring forging to rotate counterclockwise. The rolling mandrel moves counterclockwise toward the drive roll. The C-shaped cross-section ring forging drives the upper tapered roll to rotate counterclockwise, and the C-shaped cross-section ring forging drives the lower tapered roll, rear clamping roll, and front clamping roll to rotate clockwise. Refer to the schematic diagram of the movement of the improved ring mill and the C-shaped cross-section ring forging. Figure 2 The feed rate of the rolling mandrel during the rolling process over time is referenced. Figure 4 .
[0072] When the rolling of the C-shaped cross-section ring forging is completed, the temperature of the C-shaped cross-section ring forging is higher than 143℃ (i.e., T1-15℃). The rolled C-shaped cross-section ring forging is then air-cooled to room temperature.
[0073] refer to Figure 5As shown in the figure, before rolling, the C-shaped cross-section ring forging has a high residual stress of 100~125MPa inside and outside. After rolling by the method proposed in this invention, the overall stress of the C-shaped cross-section ring forging is reduced to below 60MPa, and the residual stress of the C-shaped cross-section ring forging is significantly eliminated.
[0074] Comparative Example
[0075] The material and dimensions of the C-shaped cross-section ring forging in this comparative example are the same as those of the C-shaped cross-section ring forging in the embodiment.
[0076] The C-shaped cross-section ring forging after solution quenching is placed on a ring mill without improved mandrels. The drive roll of the ring mill without improved mandrels is set to rotate at a constant speed of 1.2 mm / s, and the unimproved mandrels are fed at a constant speed of 0.2 mm / s. Rolling is stopped when the outer diameter of the aluminum alloy C-shaped cross-section ring expands to 5%.
[0077] refer to Figure 6 As shown in the figure, the stress distribution in the circumferential direction of the C-shaped cross-section ring forging in the embodiment is uniform. The circumferential and radial stresses in the regions where feature points A1 to A5 are located are reduced to below 40 MPa. In contrast, the stress distribution in the circumferential direction of the C-shaped cross-section ring forging in the comparative example is uneven. The stress in regions A2 and A4 reaches above 80 MPa, and the stress in some local areas has not been completely released.
[0078] refer to Figure 7 As shown in the figure, the circumferential and radial stress levels of the C-shaped cross-section ring forging in the embodiment are below 40 MPa along Path-1, with a range within 20 MPa. In contrast, the circumferential stress distribution of the C-shaped cross-section ring forging in the comparative embodiment is uneven along Path-1, with stresses ranging from 20 to 80 MPa and a range exceeding 60 MPa. There is a difference in stress levels between the thicker and thinner regions of the C-shaped cross-section ring forging. Path-1 is the axial path on the cross-section at a distance of (R+r) / 2 from the center of the circle. This indicates that the C-shaped cross-section ring forging rolled using the present invention has a lower and more uniform stress level on the cross-section.
[0079] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions and substitutions can be made without departing from the inventive concept, and all such modifications and substitutions should be considered within the scope of protection of the present invention.
Claims
1. A method for reducing residual stress in aluminum alloy C-shaped cross-section ring forgings, characterized in that, include: Step 1: Determine the rolling temperature range [T1, T2] of the C-shaped cross-section ring forging: T1 is the critical temperature of the C-shaped cross-section ring forging when the strain sensitivity coefficient is 0, and T2 is the peak aging temperature of the C-shaped cross-section ring forging; Step 2: Plan the rolling scheme for C-shaped cross-section ring forgings: Plan the rolling process of C-shaped cross-section ring forgings into three stages, and determine the feed speed of the rolling mandrel in each stage, the feed amount at the end of the first and second stages, and the end conditions of each stage. Step 3: Design and fabricate the rolling mandrel: Define the initial mandrel as a roll with a work roll surface that perfectly matches the inner wall of the C-shaped cross-section ring forging. The two ends of the initial mandrel are small-diameter sections, and the middle of the initial mandrel is a large-diameter section. The large-diameter section of the initial mandrel is connected to the two small-diameter sections of the initial mandrel through a transition surface. The radius of the large-diameter section of the initial mandrel is D, and the radius of the large-diameter section of the rolling mandrel is R. ’ It is calculated using the following formula. The minor diameter sections at both ends of the rolling mandrel are identical to those at both ends of the initial mandrel. Both ends of the major diameter section of the rolling mandrel are connected to the minor diameter sections at both ends of the rolling mandrel via transition surfaces. The fillets between the transition surfaces of the rolling mandrel and the corresponding major diameter sections, and the fillets between the transition surfaces of the rolling mandrel and the corresponding two minor diameter sections, are identical to the corresponding fillets of the initial mandrel. The rolling mandrel is manufactured according to these dimensions, where k is an integer between 2 and 4, and B... max B min These represent the maximum and minimum wall thicknesses of the C-shaped cross-section ring forging before rolling, respectively; ε0 represents the first feed amount at the end of the first stage; and ε1 represents the second feed amount at the end of the second stage. Step 4: Improve the ring mill: Change the mandrel of the ring mill to the rolling mandrel produced in step 2, while keeping the other parts of the ring mill unchanged, to obtain an improved ring mill; Step 5: Determine the range of linear velocity of the drive roller and feed speed of the rolling core roller; Step 6: Heating the C-shaped cross-section ring forging: The C-shaped cross-section ring forging after solution quenching is heated in an aluminum alloy-specific aging furnace to ensure that the temperature of the C-shaped cross-section ring forging is within its rolling temperature range, and held at that temperature for 5 to 30 minutes. Step 7: Place the heat-insulated C-shaped cross-section ring forging on the improved ring rolling mill; Step 8: Start the improved ring mill to roll the C-section ring forging: Set the linear speed of the drive roller and the feed speed of the rolling mandrel, start the improved ring mill to roll the C-section ring forging according to the planned rolling scheme, and the entire rolling process of the C-section ring forging needs to be completed within 5 hours after its solution quenching treatment.
2. The method for reducing residual stress in aluminum alloy C-shaped cross-section ring forgings as described in claim 1, characterized in that, The improved ring mill is equipped with a drive roll, a rear clamping roll, a front clamping roll, a rolling mandrel, an upper conical roll, and a lower conical roll. The rolling mandrel is manufactured in step 3. A C-shaped cross-section ring forging is placed on the improved ring mill. The outer side of the C-shaped cross-section ring forging is in contact with the drive roll, the rear clamping roll, and the front clamping roll. The drive roll is located between the rear clamping roll and the front clamping roll. The rolling mandrel is in contact with the inner side of the C-shaped cross-section ring forging. The axes of the drive roll, the rear clamping roll, the front clamping roll, and the rolling mandrel are all parallel to the axis of the C-shaped cross-section ring forging. The centers of the circles on the same cross section of the C-shaped cross-section ring forging, the drive roll, and the rolling mandrel are on the same straight line. The upper end of the C-shaped cross-section ring forging on the side away from the drive roll is in contact with the upper conical roll, and the lower end of the C-shaped cross-section ring forging on the side away from the drive roll is in contact with the lower conical roll.
3. The method for reducing residual stress in aluminum alloy C-shaped cross-section ring forgings as described in claim 2, characterized in that, The rolling scheme for the C-shaped cross-section ring forging is as follows: In the first stage, the rolling mandrel moves radially at a first feed speed v 芯1 The core roll moves towards the drive roll at a speed of v until the feed amount reaches the first feed amount ε0; in the second stage, the core roll moves towards the drive roll at a second feed speed v. 芯2 The mandrel moves at a speed towards the drive roll until the C-shaped ring forging completes one full rotation and the feed rate reaches the second feed rate ε1; in the third stage, the mandrel moves at a third feed speed v. 芯3 The feed motion is directed towards the drive roller at a speed of v, rolling the C-shaped cross-section ring forging at least one revolution until roundness correction is achieved, ending the rolling of the C-shaped cross-section ring forging. At the end of rolling, the temperature of the C-shaped cross-section ring forging is higher than (T1-15)℃; wherein the first feed speed v 芯1 Second feed rate v 芯2 and the third feed rate v 芯3 All at feed rate v 芯 Within the range.
4. The method for reducing residual stress in aluminum alloy C-shaped cross-section ring forgings as described in claim 3, characterized in that, The rotational speed v of the drive roller 驱 The feed speed v of the rolling mandrel is determined based on the improved rolling capacity of the ring mill. 芯 The range is determined based on the bite-in conditions of C-section ring forging rolling, specifically by calculating the feed speed v of the rolling mandrel according to the following formula. 芯 Scope: Among them, v 驱 To improve the linear speed of the drive roll of the ring mill, R is the maximum outer radius of the C-shaped cross-section ring forging before rolling, and r is the minimum inner radius of the C-shaped cross-section ring forging before rolling. 驱 R' is the radius of the drive roller, and R' is the radius of the large diameter section of the rolling mandrel.
5. The method for reducing residual stress in aluminum alloy C-shaped cross-section ring forgings as described in claim 4, characterized in that, The method for obtaining the critical temperature T1 is as follows: Step a: Perform tensile tests on the solution-treated aluminum alloy, which is the same material as the C-shaped ring forging to be rolled, and obtain stress-strain curves at different temperatures. Step b: Based on the stress-strain curve data obtained in step a, calculate the strain sensitivity coefficient m at different temperatures using the following formula. in, and These represent the strain rates. and Rheological stress under the following conditions The value is 10 -1 s -1 ; Step c: Plot the corresponding temperature-strain rate sensitivity coefficient scatter plot, and obtain the critical temperature T1 when the strain sensitivity coefficient m is 0 by polynomial fitting and bisection method. T1 is the critical temperature of the C-shaped cross-section ring forging when the strain sensitivity coefficient m is 0.
6. The method for reducing residual stress in aluminum alloy C-shaped cross-section ring forgings as described in claim 5, characterized in that, The first feed rate ε0 and the second feed rate ε1 satisfy the following relationship: 。 7. The method for reducing residual stress in aluminum alloy C-shaped cross-section ring forgings as described in claim 6, characterized in that, The dimensions of the C-shaped cross-section ring forging before rolling are as follows: maximum outer diameter of 1000~12000mm, total axial height H1 of 100~500mm, C-shaped opening width H2 of 50~200mm, H2 / H1=0.3~0.6, and maximum wall thickness B. max The minimum wall thickness is B, ranging from 50 to 250 mm. min 30~150mm, B max / B min =1.2~2.5.