摘要
采用电化学测试和慢应变速率拉伸实验(SSRT)研究了X65和X80管线钢在高pH值溶液中的应力腐蚀开裂(SCC)行为及机理.结果表明,X65钢在高pH值溶液中的开裂方式是沿晶断裂(IGSCC);X80钢在高pH值溶液中的开裂方式是初期裂纹沿晶扩展与后期裂纹穿晶扩展断裂的混合模式,主要表现为穿晶断裂(TGSCC)特征.X80钢在高pH值溶液中的断裂方式与其组织及强度有关,其裂尖pH值降低是发生TGSCC的重要原因.X65钢在高pH值溶液中的SCC机理为阳极溶解(AD)机理;而X80钢为阳极溶解(AD)+氢脆(HE)机理.
X80 pipeline steel is a low carbon, micro alloyed high-grade steel and a fairly new steel used as pipeline material in worldwide. The materiM has the huge potentiM to be used widely for building the oil/gas transmission pipelines in the 21st century because of its high intensity and high toughness. XS0 steel has been adopted on the second west east gas transmission pipeline project in China. Whereas, there is a issue, stress corrosion cracking （SCC） is more likely to occur on XS0 pipeline steel, because of its high strength and fine microstructure, it will be a vital threat to safe operation of buried oil/gas pipelines. However, the related research about SCC behavior of X80 pipeline steel in high pH carbonate/bicarbonate solution is rarely reported at present. Comparing with X65 pipeline steel, X80 steel has higher strength and finer microstructure, because of these differences, it may have some certain influence on the SCC behavior of X80 steel, and even change the mechanism of high pH SCC. Consequently, it is necessary to study the SCC behavior and mechanism of XS0 steel in high pH solution. In this work, the SCC behavior and mechanism of X65 and X80 pipeline steels in high pH concentrated carbonate/bicarbonate solution are investigated by slow strain rate testing （SSRT）, electrochemical test and surface analysis technique. The results show that the cracking mode of X65 pipeline steel in carbonate/bicarbonate solution is intergranular SCC （IGSCC）. While the mixed cracking mode of X80 pipeline steel in high pH solution is that the crack is intergranular in the early stage of the crack propagation, and transgranular SCC （TGSCC） in the later stage, which is mainly transgranular. Tile cracking mode of X80 steel is associated with the microstructure and high strength of the steel. Tile key reason for TGSCC occurring of X80 steel is that the decrease of pH value of the crack tip during tile crack propagation process. Tile SCC mechanism of X65 steel in high pH carbonate/bicarbonate solution is anodic dissolution （AD） mechanism. While the SCC mechanism of X80 steel in high pH solution is mixed controlled by both AD and hydrogen embrittlement （HE） mechanisms, and the HE mechanism may play a significant role in the deep crack propagation at the later stage. The high strength X80 steel consisted of fine acieular ferrite and granular bainite has a higher susceptibility to SCC in high pH solution, comparing with low strength X65 steel composed of ferrite and pearlite.
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2013年第12期1590-1596,共7页
Acta Metallurgica Sinica
基金
国家自然科学基金项目51131001
国家高技术研究发展计划项目2012AA040105资助~~
关键词
管线钢
应力腐蚀开裂
高pH值溶液
pipeline steel, stress corrosion cracking, high pH solution
