25Cr2Mo1VA钢奥氏体晶粒长大规律探讨

Austenite grain growth behavior in 25Cr2Mo1VA steel

为了研究不同加热温度和保温时间下25Cr2Mo1VA钢奥氏体晶粒长大规律,利用金相显微镜、TEM、EDS以及截距法分析了不同状态下奥氏体晶粒大小、形貌,析出相类型及其大小分布等。结果表明,当加热温度在900℃以下,试验钢的奥氏体晶粒长大缓慢且细小;随着温度加热至950℃,奥氏体晶粒出现了"混晶"现象,再加热超过1000℃后,奥氏体晶粒异常长大。随保温时间的延长,奥氏体晶粒也会长大,但保温时间对奥氏体晶粒尺寸的影响没有加热温度显著。试验钢中出现近似球形状的析出相,即为富钒的非计量化合物M8C7析出相。根据Anelli改进模型和回归分析,建立了试验钢奥氏体晶粒长大的热力学模型,并结合析出相粒子对奥氏体晶粒钉扎作用,探讨了25Cr2Mo1VA钢的奥氏体晶粒长大规律及成因。

The austenite grain growth behavior of 25Cr2Mo1VA steel was investigated at different heating temperatures and holding time,then the grain size,distribution,precipitate type and its size distribution of austenite were adopted to study the effects of different heating temperature and holding time by metallographic microscopy,TEM,EDS and intercept method.The results shows that the austenite grain size increases with heating temperature,and the austenite grain size grows slowly under 900℃;but"mixed crystal"phenomenon is appeared at 950℃,subsequently the grain size of austenite grows quickly at over 1000℃.In addition,it is also found that the austenite grain size slowly increases with the prolonging of holding time,but the effect is not much obvious than temperatures.And connecting with the scanning electron microscope analysis,it confirmes that the similar ball precipitation in the test steel is V-rich M8 C7 precipitated phase.According to the existing model of Anelli correction,relationship between the pinning force and the second phase particles on austenite grains,the behavior and causes of the 25Cr2Mo1VA steel grain growth are analyzed.