超超临界机组叶片钢KT5331的热变形行为

Hot deformation behavior of blades steel KT5331 for ultra-supercritical units

利用Gleeble-1500热模拟实验机进行压缩实验,研究了KT5331钢变形温度为850~1200℃,应变速率为0.01~12 s-1条件下的热变形行为。结果表明,随变形温度升高、应变速率降低,动态再结晶越容易发生,再结晶晶粒尺寸增加,完全动态再结晶温度约为1100℃。完全动态再结晶温度以下,随变形温度升高和应变速率降低,动态再结晶晶粒体积分数增加;完全动态再结晶温度以上,在低应变速率下,经60%压缩变形后,出现混晶形貌,应变速率较高时为等轴晶。通过拟合得到热变形激活能Q为436.541 k J/mol,建立了热变形双曲正弦本构方程,εexp（436541/RT）=6.12×101 5[sinh（0.009344σp）]4.739,具有较高预测精度,根据模型计算所得预测值与实验值之间的平均相对误差为5.9%。

The hot deformation behavior of KT5331 steel was investigated through high temperature compression tests on Gleeble-1500 thermal- mechanical simulator at 850-1200 ℃ and strain rate of O. 01-12 s -1. The results of the hot deformation test show that dynamic reerystallization of the steel is more likely to occur, and recrystallized grain size increases with increasing deformation temperature and decreasing deformation strain rate. Fully dynamic recrystallization can be happen above 1100 ℃. The volume fraction of dynamic recrystallized grains increases with increasing temperature and decreasing strain rate below 1100 ℃. Mixed structure and isometric crystal can appear after compressing 60% with low and high strain rates respeetively above 1100 ℃. Thermal deformation aetivity energy is ealeulated as 436. 541 kJ/mol. And the hot deformation hyperbolic sine constitutive equation is established as εexp （436541/RT） = 6. 12 × 1015 [ sinh （0. 009344σp ） ]4 739, which has a high prediction precision, and the average relative error of predicted and measured value is 5.9%.