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测定了一种低C高Nb和一种低C高Nb加Mo X80级管线钢的动态连续冷却转变曲线,通过光学显微镜、扫描电镜和透射电镜观察两钢不同条件下的显微组织和细微组织的形貌特征。结果表明,随着冷速的增加,两钢的组织由多边形铁素体、准多边形铁素体转变为针状铁素体,同时晶粒得到细化;试验钢组织在低冷速时变化较明显,当冷速大于5℃/s时组织类型变化不明显,此时主要是组织均匀性及M-A岛发生变化,随冷速增加M-A岛更细小、弥散;Mo使CCT曲线中针状铁素体转变线右移,促进针状铁素体组织形成。
The dynamic continuous cooling transformation curve of a low C high Nb and a low C high Nb plus Mo X80 grade pipeline steel was measured. The microstructure and microstructure of the two steels under different conditions were observed by optical microscope, scanning electron microscope and transmission electron microscope The morphological features. The results show that with the increase of cooling rate, the microstructures of the two steels change from polygonal ferrite and quasi-polygonal ferrite to acicular ferrite, and the grains are refined. Obviously, when the cooling rate is more than 5 ℃ / s, the change of the tissue type is not obvious. At this time, the homogeneity of the tissue and the MA island change. The MA island is smaller and diffuse with the increase of the cooling rate. Mo makes the acicular ferrite Body shift right line to promote acicular ferrite formation.