铁素体晶界结构对管线钢HIC敏感性的影响

摘要：铁素体作为酸性环境用管线钢的主要组织类型之一，探究其晶界结构与管线钢氢致开裂（HIC）敏感性之间关系，可为进一步优化管线钢的抗HIC性能提供指导。对热轧态管线钢进行不同工艺热处理，采用扫描电子显微镜（SEM）、电子背散射衍射（EBSD）、透射电子显微镜（TEM）观察了试样的晶界、位错结构及氢鼓泡、氢致裂纹形貌，用电化学充氢及动态充氢方法对试样的HIC敏感性及氢致塑性损失进行了测试，用电化学氢渗透及氢微印实验对试样的氢捕获效率及氢原子分布进行了观察与分析，探索了铁素体晶界结构与HIC敏感性之间内在关联。其结果表明：当材料中以小角度晶界占主导或大小角度晶界比例约为1∶1时，对氢原子的捕获效率较高，HIC敏感性也相对较大；大小角度晶界均能捕获氢原子，但与氢的作用机制不同，大角度晶界主要促进氢致裂纹萌生，而小角度晶界主要促进氢致裂纹扩展。

Effect of grain boundary structure of ferrite on HIC susceptibility of pipeline steel

Ferrite is one of the main structure types of pipeline steel used in acidic environment, the relationship between grain boundary structure of ferrite and hydrogen induced cracking (HIC) susceptibility of pipeline steel was explored, which can provide guidance for further optimizing the HIC resistance of pipeline steel. The hot rolled pipeline steel was heat treated in different processes. Scanning electron microscope (SEM), electron backscatter diffraction (EBSD), and transmission electron microscope (TEM) were used to observe the grain boundary, dislocation structure, hydrogen bubbling, and hydrogen induced crack morphology of the sample. The HIC susceptibility and hydrogen induced ductility loss of the samples were measured by electrochemical hydrogen charging and dynamic hydrogen charging methods. The hydrogen trapping efficiency and hydrogen distribution of the samples were observed and analyzed by electrochemical hydrogen permeation test and silver decoration technique, and the relationship between grain boundary structure of ferrite and HIC susceptibility was explored. The results show that when the material is dominated by low angle grain boundaries or the ratio of high and low angle grain boundaries is about 1∶1, its trapping efficiency for hydrogen atoms and HIC susceptibility is high; both high and low grain boundaries can trap hydrogen atoms, but the mechanism of action on hydrogen atoms is different. High angle grain boundaries mainly promote hydrogen induced crack initiation, while low angle grain boundaries mainly promote hydrogen induced crack propagation.