实验室制备了一种新型超低碳X120管线钢, 采用光学显微镜、透射电镜、扫描电镜和电子背散射衍射分析技术对其显微组织进行了分析。结果表明: 该管线钢的显微组织以板条贝氏体和针状铁素体为主, 单个贝氏体小板条长2~5 μm, 宽0.2~0.5 μm; 若干小板条紧密结合在一起组成一组板条束, 宽度为2~5 μm; 在板条束内部可以观察到不规则的(Nb, Ti)(C, N)和CuxS(x=1, 2)颗粒, 且存在高密度位错; 同一板条束的晶体学取向基本一致, 各板条束之间取向无规律, 板条束的各细小板条之间存在大量的大、小角度晶界。

A new kind of ultra-low carbon X120 pipeline steel was prepared in laboratory. Optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron backscattered diffraction (EBSD) were used to observe the microstructure of X120 pipeline steel. The results show that the microstructure of the steel was primarily characterized by lath-bainite and acicular ferrite. The size of the single lath-bainite was 2-5 μm in length and 0.2-0.5 μm in width. A group of bainite laths in the size 2-5 μm was composed of a number of single lath-bainite. Particles of (Nb, Ti)(C, N) and CuxS(x=1, 2) were observed, and there were high density of dislocations in bainite laths. The crystallographic orientation in a whole bainite laths was uniform, but distributed with random in different bainite laths. There were a large number of high angle boundaries and low angle boundaries among the fine bainite laths.