中文摘要：

对系列低碳、超高强度贝氏体钢（LCUHSBS），通过有效地控制相变温度、冷却速率与回火参数，贝氏体铁素体（BF）含碳量增加、组织细化、碳化物消除以及存在高稳定性、高体积分数的膜状残余奥氏体（AR）。利用AFM、SEM等分析并测试了贝氏体钢的显微组织与晶粒尺寸，结果表明，板条束内含有若干大致平行的BF板条，而每一板条由许多切变单元组成；切变单元进一步又分成大量超细亚结构．其直径约为18nm。如此细化的显微组织确保了贝氏体钢在超高强度条件下，冲击吸收能成倍提高。

英文摘要：

Through effectively controlling the transformation temperature, cooling rate and tempering parameters for a series of low carbon ultra-high strength bainite steels （LCUHSBS）. The carbon content in bainite ferrite is increased, the microstructure is refined, the carbides is eliminated and the films of AR with high stability and high volume fraction is obtained. The results of the analysis and measurement for the microstructure of bainite steels and the grain size by AFM and SEM show that there are several parallel ferrite lathes in a bainitic sheaf,and each lath is composed of a lot of shear units. Furthermore,every shear unit consists of a plenty of super-thin substructure （the diameter is less than 18nm）. This microstructure can not only ensure the bainitic steels possess ultra-high strength, but also play a very important role in enhancing the impact energy absorption.