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采用XRD物相分析、金相组织观察及TEM精细组织分析研究了奥氏体组织结构状态对Fe-0.88C-1.35Si-1.03Cr-0.43Mn钢中温等温相变鼻温和孕育期的影响,以及不同温度奥氏体化后240℃等温20 min试样的组织结构特征。试验发现,随着奥氏体化温度的升高,中温等温开始转变的鼻温移向更低温度并且相变孕育期缩短;不同温度奥氏体化后同为240℃等温20 min处理,虽然均形成由贝氏体铁素体亚条平行排列构成的束状贝氏体组织,但贝氏体组织的精细结构状态不同,突出的差别在于对应低温奥氏体化贝氏体亚条端部边界具有凸起结构,而对应高温奥氏体化贝氏体亚条端部边界较为平齐且呈现楔形结构。不能简单地以马氏体切变机制认识试验钢中贝氏体组织的形成。
The effects of austenite structure and structure on the moderate temperature and phase transition of Fe-0.88C-1.35Si-1.03Cr-0.43Mn steel were studied by means of XRD, phase observation and microstructure analysis. Tissue structure characteristics of isothermal 20 min specimens at 240 ℃ after austenitizing at different temperatures. The results showed that as the austenitizing temperature increased, the nasal temperature at which the mesophilic isothermal transformation started to shift to a lower temperature and the gestation period of the phase transition was shortened. After being austenitized at different temperatures, the same temperatures of 240 ° C for 20 min were treated, The bainitic bainite structure formed by parallel arrangement of bainitic ferrite sub-billets is formed. However, the fine structural state of the bainite structure differs from that of the bainite sub-bainite, The boundary has a convex structure, while the end boundary corresponding to the high-temperature austenitic bainite sub-strip is relatively homogeneous and has a wedge-shaped structure. The formation of bainitic tissue in the test steel can not be simply understood by the martensitic shear mechanism.