CN-121972589-A - Method for reducing residual stress of aluminum alloy C-shaped section ring forging

CN121972589ACN 121972589 ACN121972589 ACN 121972589ACN-121972589-A

Abstract

The invention provides a method for reducing residual stress of an aluminum alloy C-shaped section ring forging, which comprises the steps of 1, determining a rolling temperature interval [ T 1 ,T 2 ] of the C-shaped section ring forging, 2, planning a rolling scheme of the C-shaped section ring forging, 3, designing and manufacturing a rolling core roller, 4, improving a ring rolling machine, 5, determining the linear speed of a driving roller and the feeding speed range of the rolling core roller, 6, heating the C-shaped section ring forging, 7, placing the C-shaped section ring forging after heat preservation on the improved ring rolling machine, and 8, starting the improved ring rolling machine to roll the C-shaped section ring forging. The invention can effectively improve the residual stress condition of the large-specification aluminum alloy C-shaped section ring forging, improve the forming quality of the C-shaped section ring forging, and reduce the production cost.

Inventors

GONG HAI
ZHANG LONG
ZHANG TAO
LIU ZHILIN
WU YUNXIN
ZHONG JUE

Assignees

中南大学

Dates

Publication Date: 20260505
Application Date: 20260330

Claims (7)

1. A method for reducing residual stress of an aluminum alloy C-section ring forging, comprising: Step 1, determining a rolling temperature interval [ T 1 ,T 2 ]：T 1 is the critical temperature of the C-shaped section ring forging when the strain sensitivity coefficient is 0, and T 2 is the peak aging temperature of the C-shaped section ring forging; step 2, planning a rolling scheme of the C-shaped section ring forging, namely planning a rolling process of the C-shaped section ring forging into three stages, and determining the feeding speed of a rolling core roller in each stage, the feeding amount at the end of the first stage and the second stage and the end condition of each stage; Step 3, designing and manufacturing a rolled core roller, namely defining a roller with a working roller surface which is completely matched with the inner wall of the C-shaped section ring forging as an initial core roller, wherein two ends of the initial core roller are small-diameter sections, the middle of the initial core roller is a large-diameter section, the large-diameter sections of the initial core roller are connected with the two small-diameter sections of the initial core roller through transition surfaces, the radius of the large-diameter section of the initial core roller is D, the radius R ' of the large-diameter section of the rolled core roller is calculated by the following formula, The method comprises the steps that small diameter sections at two ends of a rolling core roller are respectively consistent with small diameter sections at two ends of an initial core roller, two ends of a large diameter section of the rolling core roller are connected with the small diameter sections at two ends of the rolling core roller through transition surfaces, the sizes of round corners between the transition surfaces of the rolling core roller and the corresponding large diameter sections and the sizes of round corners between the transition surfaces of the rolling core roller and the corresponding two small diameter sections are respectively consistent with the sizes of the corresponding round corners of the initial core roller, the rolling core roller is manufactured according to the above sizes, wherein k is an integer between 2 and 4, B max 、B min is respectively the maximum wall thickness and the minimum wall thickness of a C-shaped section ring forging piece before rolling, epsilon 0 is the first feeding quantity at the end of a first stage, and epsilon 1 is the second feeding quantity at the end of a second stage; step 4, improving the ring rolling mill, namely changing the core roller of the ring rolling mill into the rolling core roller manufactured by the step 2, wherein other parts of the ring rolling mill are unchanged so as to obtain an improved ring rolling mill; Step 5, determining the linear speed of the driving roller and the range of the feeding speed of the rolling core roller; Heating the C-shaped section ring forging by adopting an aging furnace special for aluminum alloy, so that the temperature of the C-shaped section ring forging is within a rolling temperature range of the C-shaped section ring forging, and preserving heat for 5-30 minutes; step 7, placing the insulated C-shaped section ring forging on an improved ring rolling mill; And 8, starting the improved ring rolling mill to roll the C-shaped section ring forging, namely setting the linear speed of the driving roller and the feeding speed of the rolling core roller, and starting the improved ring rolling mill to roll the C-shaped section ring forging according to a planned rolling scheme, wherein the rolling process of the whole C-shaped section ring forging is required to be completed within 5 hours after solution quenching treatment.
2. The method for reducing residual stress of aluminum alloy C-shaped section ring forging according to claim 1, wherein the improved ring rolling mill is provided with a driving roller, a rear holding roller, a front holding roller, a rolling core roller, an upper cone roller and a lower cone roller, the rolling core roller is manufactured through the step 3, the C-shaped section ring forging is placed on the improved ring rolling mill, the outer side of the C-shaped section ring forging is contacted with the driving roller, the rear holding roller and the front holding roller, the driving roller is positioned between the rear holding roller and the front holding roller, the rolling core roller is contacted with the inner side of the C-shaped section ring forging, the axes of the driving roller, the rear holding roller, the front holding roller and the rolling core roller are all parallel to the axis of the C-shaped section ring forging, the centers of the C-shaped section ring forging, the driving roller and the rolling core roller on the same section are on the same straight line, the upper end of one side of the C-shaped section ring forging, which is far away from the driving roller, is contacted with the upper cone roller, and the lower cone roller.
3. The method according to claim 2, wherein the rolling scheme of the C-shaped section ring forging is characterized in that in the first stage, the rolling core roller performs feeding motion towards the driving roller along the radial direction at the speed of a first feeding speed v Core(s) 1 until the feeding amount reaches a first feeding amount epsilon 0 , in the second stage, the rolling core roller performs feeding motion towards the driving roller at the speed of a second feeding speed v Core(s) 2 until the C-shaped section ring forging completes one complete circle rolling and the feeding amount reaches a second feeding amount epsilon 1 , in the third stage, the rolling core roller performs feeding motion towards the driving roller at the speed of a third feeding speed v Core(s) 3 , at least one circle rolling is performed on the C-shaped section ring forging until roundness correction is finished, and the temperature of the C-shaped section ring forging is higher than (T 1 -15) DEG C at the end of rolling, wherein the first feeding speed v Core(s) 1 , the second feeding speed v Core(s) 2 and the third feeding speed v Core(s) 3 are all in the range of speed v Core(s) .
4. A method of reducing residual stress in an aluminium alloy C-section ring forging as claimed in claim 3, wherein the rotational speed v Driving device of the drive roller is determined in accordance with the improved rolling capacity of the ring rolling mill, the range of feed speed v Core(s) of the rolling core roller is determined in accordance with the rolling bite conditions of the C-section ring forging, in particular the range of feed speed v Core(s) of the rolling core roller is calculated in accordance with the following formula: Wherein v Driving device is the linear speed of the improved ring rolling mill driving roller, R is the maximum outer radius of the C-shaped section ring forging before rolling, R is the minimum inner radius of the C-shaped section ring forging before rolling, R Driving device is the radius of the driving roller, and R' is the radius of the large-diameter section of the rolling core roller.
5. The method for reducing residual stress of aluminum alloy C-section ring forging as recited in claim 4, wherein the obtaining method of the critical temperature T 1 is as follows: Step a, carrying out a tensile experiment on the solid solution state aluminum alloy which is the same as the material of the C-shaped section ring forging to be rolled to obtain stress-strain curves at different temperatures, Step b, calculating the strain sensitivity coefficient m at different temperatures based on the stress-strain curve data obtained in the step a through the following formula, Wherein, the And Respectively at strain rate And The rheological stress of the lower part of the steel plate, The value is 10 -1 s -1 ; And C, drawing a corresponding temperature-strain rate sensitivity coefficient scatter diagram, and obtaining a critical temperature T 1 ,T 1 when the strain sensitivity coefficient m is 0, namely, a critical temperature of the C-shaped section ring forging when the strain sensitivity coefficient m is 0 through polynomial fitting and a dichotomy.
6. The method of reducing residual stress in an aluminum alloy C-section ring forging of claim 5, wherein the first feed amount ε 0 and the second feed amount ε 1 satisfy the following relationship: 。
7. The method for reducing residual stress of an aluminum alloy C-section ring forging according to claim 6, wherein the C-section ring forging before rolling has a size such that the maximum outer diameter is 1000-12000 mm, the total axial height H 1 is 100-500 mm, the C-shaped opening width H 2 is 50-200 mm, H 2 / H 1 =0.3-0.6, the maximum wall thickness B max is 50-250 mm, the minimum wall thickness B min is 30-150 mm, and B max / B min =1.2-2.5.

Description

Method for reducing residual stress of aluminum alloy C-shaped section ring forging Technical Field The invention relates to a method for reducing residual stress of an aluminum alloy C-shaped section ring forging, and belongs to the technical field of aluminum alloy rolling. Background The aluminum alloy C-shaped section ring forging is a key force transmission connecting component in aerospace equipment and is commonly used for the transition ring, the missile frame body and other parts of rocket fuel storage tanks. Taking a heavy carrier rocket with a long sign No. five as an example, the diameter of a transition ring of a fuel storage tank reaches 10 meters, the wall thickness is only 5-25 mm, the transition ring is required to be accurately assembled with an rocket body, and extreme loads such as extremely low temperature, high pressure, severe vibration impact and the like caused by liquid hydrogen/liquid oxygen are born in service, so that extremely severe challenges are provided for controlling the mechanical properties and the dimensional accuracy of an aluminum alloy C-shaped section ring forging. The T6 heat treatment (solution quenching and artificial aging) of the aluminum alloy ring forging introduces high-amplitude quenching residual stress, which not only can cause the warping and distortion of the aluminum alloy ring forging in the machining stage, but also can cause the stress corrosion phenomenon of the aluminum alloy ring forging, thereby reducing the service life of the aluminum alloy ring forging. Therefore, controlling the residual stress of the aluminum alloy ring forging becomes a key factor in manufacturing high performance aluminum alloy ring forgings. In the conventional method, an aluminum alloy ring forging is expanded from inside to outside by a bulging device to generate plastic deformation and release stress. However, the largest bulging equipment in China can only meet the processing requirement of phi 6m ring forgings, cannot meet the stress reduction requirement of phi 10 m-class large-specification aluminum alloy ring forgings in the aerospace field, is high in one-time investment cost, high in special tooling die cost and not suitable for small-batch production. In recent years, it has been proposed to eliminate the residual stress of an aluminum alloy ring forging by cold rolling, which is performed by cold rolling the aluminum alloy ring forging by a ring rolling mill to expand the outer diameter thereof by 2% -3% so as to eliminate the residual stress in the ring. When the method is used for reducing the real-time stress of the aluminum alloy C-shaped section ring forging piece, the problems are that firstly, a common normal-temperature ring rolling process has a hardening effect, plasticity is poor, damage and cracking occur, secondly, in the rolling process, the material flows at different thicknesses of the aluminum alloy C-shaped section ring forging piece are uneven, uneven residual stress still exists on the section of the rolled aluminum alloy C-shaped section ring forging piece, thirdly, the stress reduction effect difference of all areas of the rolled aluminum alloy C-shaped section ring forging piece in the circumferential direction is large, and partial area stress is not completely reduced. The residual stress of the aluminum alloy ring forging piece is eliminated in a cold rolling mode, the control requirement of the large-specification aluminum alloy C-shaped section ring forging piece on the residual stress in the aerospace field cannot be met, and damage/cracks introduced in the rolling process also increase the risk of breakage and damage of the large-specification aluminum alloy C-shaped section ring forging piece under the extreme service condition. Disclosure of Invention The invention aims to provide a method for reducing residual stress of an aluminum alloy C-shaped section ring forging, so as to solve the problems in the prior art. In order to solve the technical problems, the invention provides a method for reducing residual stress of an aluminum alloy C-shaped section ring forging, which comprises the following steps: Step 1, determining a rolling temperature interval [ T 1,T2]：T1 is the critical temperature of the C-shaped section ring forging when the strain sensitivity coefficient is 0, and T 2 is the peak aging temperature of the C-shaped section ring forging; step 2, planning a rolling scheme of the C-shaped section ring forging, namely planning a rolling process of the C-shaped section ring forging into three stages, and determining the feeding speed of a rolling core roller in each stage, the feeding amount at the end of the first stage and the second stage and the end condition of each stage; Step 3, designing and manufacturing a rolled core roller, namely defining a roller with a working roller surface which is completely matched with the inner wall of the C-shaped section ring forging as an initial core roller, wherein two ends of t