Abstract: The effect of ternary thermal cycle on microstructure of 2.25Cr1Mo steel was analyzed by SEM and EDS. The results show that ternary thermal cycle results in the formation of bainite. Grain size does not grow larger obviously after subjected ternary thermal cycle of maximum peak temperature 1 195 ℃, total t8/5 more than 97 s of ternary thermal cycle. Because phase transformation does not occur upon cooling of first thermal cycle, effect of peak temperature of second thermal cycle on grain size, which may result in grain finer does happen. EDS analyses of specimen after thermal cycle indicate that micro zone compositions of precipitated phase are similar and Fe element in the majority. It is assumed that precipitated phases formed are Fe, Cr, Mo carbides.

Key words: 2.25Cr1Mo steel, Thermal cycle, Microstructure, Peak temperature, Grain size

摘要： 通过扫描电镜（ＳＥＭ）、能谱（ＥＤＳ）分析方法，对２．２５Ｃｒ１Ｍｏ钢经受三次热循环后的组织进行了分析。结果表明，经过三次热循环作用，获得贝氏体组织。经三次热循环—三次热循环中最高峰值温度１　１９５℃，三次热循环总的ｔ８／５达９７ｓ以上的作用时，晶粒尺寸并未发生明显长大。由于第一次热循环冷却过程中没有发生相变，没能产生第二次热循环峰值温度的晶粒细化作用使晶粒尺寸细化。试样热循环作用后，对试样的能谱分析结果表明，析出相微区成分相近，以Ｆｅ元素为主要成分，可推测形成了Ｆｅ，Ｃｒ，Ｍｏ碳化物析出向。

关键词: ２．２５Ｃｒ１Ｍｏ钢 , 热循环 , 组织 , 峰值温度 , 晶粒尺寸