超低碳贝氏体钢的显微组织分析

Microstructure Analysis of Ultra Low Carbon Bainite Steel

对两阶段控轧控冷的超低碳贝氏体钢显微组织进行了光学显微镜和扫描电镜分析。结果表明:扫描电镜更能显示超低碳贝氏体钢的特点,纵向显微组织细小,奥氏体晶粒沿轧向被轧成扁平状,方向性明显,晶界清晰可见,奥氏体晶粒宽度在6～13μm之间;而横向显微组织、心部显微组织、表面显微组织以粒状贝氏体为主,没有明显的方向性,组织粗大,分布弥散、均匀;粒状贝氏体和板条贝氏体只有在两个极端的温度下才有明显的差异,而处于中间过渡温度时很难截然分开。

Optical rnicroscopy（OM） and scanning electron microscopy（SEM） were used to observe the rnicrostructure of ultra low carbon bainite steel（ULCB） that experienced controlled rolling and controlled cooling.Results show that it is more appropriate for SEM to reveal the characteristics of microstructure of the ULCB. The longitudinal rnicrostructure of ULCB is fine and austenite grain is fiat along the rolling direction and austenite grain boundary is very clear, the width of austenite grain is about 6-13 tan. Along the transverse direction, granular balnite is dominant at the center and surface of the sample, grain is coarse, equlaxed and even. There are distinct differences between granular bainite and lath bainite at the two extremity temperature and it is very difficult to distinguish them at the transitional temperature.