12%Cr超超临界转子钢锻造裂纹机理分析及损伤模型建立

Forging crack mechanism analysis and damage model establishment of 12%Cr ultra-supercritical rotor steel

针对12%Cr超超临界转子钢锻造表面裂纹严重的问题,从变形条件及应力-应变状态的角度出发,基于热拉伸实验获取了相应条件下的应力-应变曲线。通过分析断口形貌,判断了12%Cr超超临界转子钢高温拉伸断裂为典型的韧性断裂,并分析了锻造裂纹的产生与析出相的关系。通过观察试样断口切片,发现了大量相互缠结的位错,这些相互缠结的位错也是导致金属断裂的原因。通过对临界损伤值的比对发现,在应变速率为0.5 s^(-1)、温度为1100~1200℃时锻造最不易产生裂纹;在Normalized Cockcroft&Latham损伤模型的基础上引入温度补偿的应变速率因子Zener-Hollomon参数,建立了临界损伤值与Zener-Hollomon参数的关系式,得到考虑了温度和应变速率综合影响的高温损伤模型。

Aming at the problem of serious forging surface crack of 12%Cr ultra-supercritical rotor steel,from the view of deformation conditions and stress-strain states,the stress-strain curves under the corresponding conditions were obtained based on thermal tensile experiments.By analyzing the fracture morphologies,it is concluded that the high temperature tensile fracture of 12%Cr ultra-supercritical rotor steel is a typical ductile fracture,and the relationship between the formation of forging crack and the precipitated phase is analyzed.By observing the fracture sections of the specimens,a large number of intertangled dislocations are found,and these intertangled dislocations are also the cause of metal fracture.By comparing the critical damage value,it is found that the the steel is the uneasiest to crack when forging with the strain rate of 0.5 s^(-1) at 1100-1200℃.Based on Normalized Cockcroft&Latham damage model,the strain rate factor Zener-Hollomon parameter compensated by temperature was introduced,and the relationship between critical damage values and Zener-Hollomon parameter was established,and a high temperature damage model considering the comprehensive effects of temperature and strain rate was obtained.