王晶^1，*， 苗伟^1，， 张亦良^1，， 李书瑞^2，

（  1、北京工业大学机电学院，北京 100124；       2、武汉钢铁集团公司，武汉 430083；  ）

摘要： 本文研究了硫化氢腐蚀环境中X70管线钢母材及热影响区的疲劳裂纹扩展速率。首先应用X射线衍射法测量了母材及热影响区的残余应力。其次，应用改进型WOL试样，参考实际工况，在饱和硫化氢环境中，低频率（f=0.01Hz）和三个应力比（R=0.7，0.8，0.9）下进行了裂纹扩展速率实验。结果显示：热影响区处存在明显的残余拉应力；硫化氢腐蚀的存在极大的加速了裂纹扩展速率；随着应力比的上升，裂纹闭合效应减弱，平均应力增大，裂尖氢脆程度增加，从而导致FCGR加快；热影响区处的组织不均匀、夹杂物及高残余拉应力使得该处的FCGR高于母材处FCGR。断口SEM扫描结果显示：X70材料腐蚀疲劳的断裂形式属于脆性断裂，断口以解理特征为主，母材和热影响区试样断口形貌差别不大，热影响区试样断口的浮凸更大，裂纹更长。
关键词： 腐蚀疲劳；裂纹扩展速率；X70管线钢；热影响区

WANG Jing^1,*， MIAO Wei^1,， ZHANG Yiliang^1,， LI Shurui^2,

（  1、College of Mechanical Engineering and Applied Electronics Technology, Beijing University of Technology, Beijing 100124；       2、Wuhan Iron and Steel Group Corporation, Wuhan 430083；  ）

Abstract： Fatigue crack growth rates (FCGRs) of X70 pipeline steel base metal (BM) and heat affected zone (HAZ) were studied in the hydrogen sulfide environment. X-ray diffraction method was used to measure the residual stress of BM and HAZ. Modified WOL specimen was selected for the test in the simulated actual working conditions. In the saturated H2S environment, the crack growth experiments were carried out under low frequency (f = 0.01 Hz) and three stress ratios (R = 0.7, 0.8, 0.9). Results showed there was obvious residual tensile stress in HAZ. The presence of H2S greatly accelerated the FCGR. With rising stress ratio, crack closure effect weakened, and then the increasing degree of hydrogen embrittlement of the crack tip leads to FCGR acceleration. Microstructure defects, inclusions, and high residual tensile stress of HAZ made the FCGR of this area higher than the FCGR of BM. SEM scans of the fracture suggested that the fracture mode of the corrosion fatigue of the X70 material belonged to brittle fracture. Cleavage fracture was the dominant form. The differences between corrosion fatigue fracture morphologies of BM and HAZ were not very large, and the relief of the fracture of HAZ was larger and the cracks longer.

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