X70管线钢在硫酸盐还原菌作用下的应力腐蚀开裂行为

目的油气管输中X70钢的应力腐蚀开裂问题日趋严重,而且土壤环境中微生物腐蚀现象备受关注,因此拟通过实验室模拟土壤环境下X70管线钢的腐蚀,获得高强度管线钢在硫酸盐还原菌作用下的应力腐蚀开裂规律。方法采用自制的应力电化学测试装置,通过慢应变速率拉伸试验(SSRT)对材料的应力腐蚀敏感性进行分析,利用交流阻抗以及扫描电镜(SEM)对断口形貌以及生物膜的成分进行研究。结果当应变速率为5×10~(-7)s~(-1)时,无菌模拟溶液中试样的应力腐蚀敏感性远大于含SRB模拟溶液中试样的应力腐蚀敏感性,SRB的存在对X70管线钢应力腐蚀起到很大程度的促进作用。当应变速率为1×10~(-6)s~(-1)时,SRB对于X70管线钢应力腐蚀敏感性的影响较小,断裂主要由力学因素主导,SRB起辅助作用。结论 X70管线钢在沈阳土壤模拟溶液中具有一定的应力腐蚀敏感性。SRB对于X70管线钢在沈阳土壤模拟溶液中的应力腐蚀起到一定程度的促进作用。

Stress Corrosion Cracking Behavior of X70 Pipeline Steel Under the Action of Sulfate Reducing Bacteria

Nowadays the problem of stress corrosion cracking of X70 steel in oil gas pipeline is increasingly serious, and the microbial corrosion in soil environment is attracting attention. Stress corrosion cracking law of high strength pipeline steel under the action of sulfate reducing bacteria was obtained by simulating corrosion of X70 pipeline steel in soil environment. Stress corrosion susceptibility of the material was analyzed by performing slow strain rate tensile test (SSRT) with self-made stress electrochemical test device. Fracture morphology and biofilm composition were studied by using AC impedance and scanning electron microscopy (SEM). When the strain rate was 5×10-7 s-1, the stress corrosion susceptibility of the sample in aseptic si- mulated solution was much greater than that in SRB simulated solution. The existence played a significant role in promoting stress corrosion of X70 pipeline steel. When the strain rate was 1×10-6 s-1, SRB had minor effect on the stress corrosion suscep-tibility of X70 pipeline steel. Mechanical factors mainly dominated the fracture while SRB played a helping role. X70 pipeline steel exhibits certain stress corrosion sensitivity in Shenyang soil simulation solution. SRB plays a certain role in promoting the stress corrosion of X70 pipeline steel in Shenyang soil simulation solution.