The Defects Of Large Flange And Simulating The Microstructure Evolution

In recent years,with the increase of environmental pollution,China's increasing emphasis on the development of clean energy,especially wind power construction by more attention.Large flange forgings are one of the important connecting parts of wind power generation equipment.Due to the working environment of wind power equipment,large flange parts are required to have good compression resistance and corrosion resistance.In addition to the aerospace and mechanical transport and other industries with the rapid development of demand for large flange parts is also a rapid increase.As a result of processing and other reasons,not only the need for dimensional accuracy must ensure that within a reasonable range of errors,but also need to have a good micro-organizational structure to ensure the stability of its performance.In this paper,the macroscopic finite element model of large flange pieces is established on the DEFORM software platform.Based on the volume invariant principle of metal shaping deformation,numerical simulation of finite element analysis of upsetting and rolling process on the software platform is carried out.Firstly,the evolution law of stress field and temperature field in the process of forming process is analyzed,and then the microstructural evolution of upsetting process is studied.The following research results are obtained:(1)Under the same reduction rate,the greater the height-to-diameter ratio,the smaller the stress and strain changes.At the same height-to-diameter ratio,the greater the strain rate becomes more pronounced.In the blank upsetting process,the strain is caused by the middle part of the upper and lower mold the heart is getting bigger and bigger.(2)The ratio of height to diameter,the coefficient of friction,the void position and the reduction rate are the main factors that affect the closure of the void.The closer the hole diameter is closer to 1,the easier it is that the upper and lower ends are bound by friction;the friction coefficient affects the size of the friction,so the greater the coefficient of friction,theworse the material flow,the more difficult the empty closure;in the central axis of the hollow position compared to the most likely to close,the central axis is the farthest from the cross section,suffered the weakest cross-section;the reduction rate is the most important factor affecting the empty closure,close to the proportional function.(3)Different temperature,strain rate,initial grain size and friction factor also have different effects on the microstructure surrounding the voids.The degree of grain recrystallization increases with the increase of temperature,and the grain size increases with the increase of strain rate,and decreases with the decrease of initial grain size.(4)The degree of empty closure is determined by the degree of recrystallization and the grain size of the surrounding tissue,and the higher the degree of recrystallization,the smaller the grain size is.In this paper,macroscopic and microscopic studies on the rolling process are carried out.Based on the distribution of stress and temperature and temperature,the microstructures are based on the grain size change and the dynamic recrystallization ratio.At the same time,There is a static recrystallization.In this paper,the microstructure of the forming process is studied by dynamic recrystallization volume fraction and average grain size,and the following research results are obtained:(1)The initial temperature of the blank,the ratio of height to diameter and the rolling ratio and the velocity of the roll are the main factors that affect the stress strain and the uneven temperature distribution.The higher the initial temperature,the higher the diameter ratio,the greater the rotational speed of the drive roller and the cone roller,the more uniform the stress and strain distribution.(2)The process parameters such as reduction rate,initial temperature,coefficient of friction and aspect ratio of the upsetting process have a significant effect on the dynamic recrystallization volume fraction and the average grain size of the rolling process.(3)The speed of the roll during the rolling process,the initial temperature is an important factor affecting the finished part of the ring.The greater the rotational speed of the roll,the more uniform the dynamic recrystallization distribution and the better the tissue performance.The greater the feed rate,the smaller the grain size,the more uniform the distribution.The higher the initial temperature,the higher the degree of recrystallization and the smaller thegrain size.(4)The process of dynamic recrystallization is carried out from the inside to the middle,from the inside to the middle,from the upper and lower bottom surfaces to the intermediate area.