P92钢的过冷奥氏体等温转变

Isothermal transformation of undercooled austenite in P92 steel

对P92钢进行了TTT图测定,观察分析了过冷奥氏体的等温转变的类型及组织形貌。结果表明,经1050℃奥氏体化,在650-800℃之间进行等温转变,奥氏体中首先析出碳化物（Cr23C6）,接着发生F＋P转变;在170-400℃区间存在马氏体的变温转变和贝氏体相变。在400-650℃区间存在宽广的海湾区,且贝氏体相变的孕育期比共析分解短得多。同时发现了两种特殊的组织形态：珠光体组织为纤维状,下贝氏体中的碳化物为颗粒状。

TTT diagram of P92 steel was examined and determined and microstructure of undercooled austenite transformation of the P92 steel was observed and analyzed.The results show that when austenitized at 1050 ℃ and then isothermal transformed at 650-800 ℃,the carbide（ Cr23C6） precipitates from austenite first,and then the transformation of ferrite and pearlite consequently occurs.When isothermal transformed at 170-400 ℃,the athermal martensite transformation and bainite transformation happens.There is a broad bay area from 650 ℃to 400 ℃,however the incubation period of bainite transformation is much shorter than that of the eutectoid decomposition.In the mean time,two kinds of special microstructure in P92 steel are observed that the pearlitic is fibrous and the lower bainite is granular.