论文部分内容阅读
采用动电位极化技术、慢应变速率拉伸试验和扫描电镜观察研究了有、无硫酸盐还原菌(SRB)情况下X70管线钢及焊缝在近中性p H溶液(NS4)中的应力腐蚀行为。电化学实验结果表明:X70管线钢母材和焊缝在NS4溶液中的极化曲线都表现出典型的活性溶解特征,且有菌介质中管线钢表面能生成一层具有保护性的生物膜。SSRT曲线和SEM结果表明:在无菌NS4溶液中,X70钢母材和焊缝的SCC机理为氢致开裂机理。在有SRB的NS4溶液中,由于SRB生命代谢释放大量代谢产物H2S,促进H原子进入管线钢,将破坏其基体的连续性,从而导致氢损伤,使X70钢母材和焊缝的SCC敏感性都大于其在无菌介质中,其开裂机理表现为硫化物应力开裂和氢致开裂共同作用。在有菌和无菌介质中,焊缝的应力腐蚀敏感性均高于母材,这是由于焊缝处组织不均匀、存在残余应力造成的。
The stress of X70 pipeline steel and weld in near-neutral p H solution (NS4) with and without sulfate-reducing bacteria (SRB) was investigated by potentiodynamic polarization, slow strain rate tensile test and scanning electron microscopy. Corrosion behavior. The results of electrochemical experiments show that the polarization curves of the parent material and the weld of X70 pipeline steel in NS4 solution all show typical active dissolution characteristics, and the biofilm with protective properties can be formed on the surface of the pipeline steel in the bacteria medium. The SSRT curves and SEM results showed that the SCC mechanism of the base metal and weld of X70 steel was hydrogen induced cracking in sterile NS4 solution. In NS4 solution with SRB, due to release of a large amount of metabolite H2S by SRB’s life metabolism, H atom will be promoted into the pipeline steel, which will destroy the continuity of the matrix, resulting in hydrogen damage and SCC sensitivity of X70 steel base metal and weld Are greater than their in aseptic medium, the cracking mechanism manifested as sulfide stress cracking and hydrogen induced cracking together. In both bacteria and sterile medium, the stress corrosion resistance of the weld is higher than that of the base metal, which is due to the uneven microstructure and the residual stress in the weld.