形变组织对水电用高强度贝氏体钢再加热奥氏体晶粒长大的影响

对某水电用800 MPa调质贝氏体高强钢进行了热变形-热处理晶粒长大的实验室联合试验。采用Gleeble-3500热力模拟试验机对钢试样进行不同工艺热压缩变形后冷却至室温，随后对试样进行模拟淬火再加热，在900～1200℃不同温度和保温时间条件下奥氏体化，研究热变形组织的差异对重新奥氏体化晶粒长大的影响规律。结果表明，不同应变速率(0.01～10 s^-1)、变形温度(900～1150℃)和60%工程应变下，试验钢获得的变形组织大致可分为3类：带有明显变形特征的组织、均匀细小的完全再结晶组织和已长大粗化的再结晶组织。3类组织再加热过程中其晶粒长大趋势基本相同，起始晶粒尺寸越大则最终奥氏体晶粒尺寸越大；但在950℃等温时，带有明显变形特征组织的变形试样奥氏体晶粒先缓慢长大后又迅速长大粗化。经评估验证，所建立的Sellars模型、Beck模型和Hillert模型晶粒长大动力学方程对于试验钢的奥氏体晶粒长大行为均有比较满意的预测效果。3类变形组织对应的Hillert模型及Sellars模型中奥氏体长大激活能基本相同，说明同一成分钢种的初始组织的差异并未显著影响晶粒长大机制...

Effect of deformation microstructure on reheating austenite grain growth of high strength bainite steel for hydropower

Combined tests of hot deformation and heat treatment for austenite grain growth of a 800 MPa quenched and tempered bainite high strength steel for hydropower were carried out on Gleeble-3500. The steel specimens were deformed by various hot compression and cooled to ambient temperature, and then reheated at 900-1200 ℃ for different holding time to study the influence of the difference of hot deformation microstructure on the austenite grain growth behavior in reheating. The results show that under different strain rates (0.01-10 s^-1), deformation temperatures (900-1150 ℃) and 60% engineering strain, the hot deformed microstructure can be roughly divided into three types: the microstructure with obvious deformation characteristics, the fully recrystallized uniform fine microstructure, and the coarsened recrystallized microstructure. The grain growth trend of the three types of microstructure is basically the same during reheating. The larger the initial grain size, the larger the final austenite grain size is, and when reheated at 950 ℃, the austenite grains of deformed specimens with the first type of deformation microstructure grow slowly at first and then coarsen rapidly. After evaluation and verification, the Sellars model, Beck model andHillert model grain growth kinetics equation have a relatively satisfactory prediction effect on the austenite grain growth behavior of the test steel. The activation energy of austenite growth in Hillert model and Sellars model corresponding to the three types of deformed microstructure is basically the same, indicating that the difference of initial structure of the same composition steel does not have an essential influence on the grain growth mechanism.