力学与电化学作用下X80钢焊接接头SCC行为分析

SCC behavior of X80 steel welded joint in mechanical and electrochemical effects

摘要: 采用动电位扫描技术及慢应变速率拉伸试验(slow strain rate test, SSRT)研究了X80钢焊接接头在库尔勒模拟溶液中应力腐蚀开裂(stress corrosion cracking, SCC)行为,并利用扫描电镜(scanning electron microscope, SEM)对不同应变速率下试样断口形貌进行表征.结果表明,随着应变速率的增加,X80钢焊接接头的腐蚀速率则呈现持续增大的趋势.当应变速率为1×10^-5/s时,试样的腐蚀情况最为严重. X80钢焊接接头在不同应变速率下的腐蚀机制是由电化学-力学交互作用共同决定的.试样发生应力腐蚀后断裂于焊缝处,这是由于焊接过程导致焊缝晶格存在大量的缺陷,使得晶格活性较高所致.

Abstract: Potentiondynamic polarization curves and slow strain rate testing(SSRT) were used to study the stress corrosion cracking(SCC) behavior of welded joint for X80 pipeline steel in Ku'erle soil simulated solution. Fracture appearances at different strain rate were analyzed by SEM. The results showed that the corrosion rate of welded joint increases persistently with the increase of strain rate. When the strain rate is 1×10^-5/s, the corrosion of welded joint is the most serious. The influence of stress on electrochemical corrosion plays a decisive role of welded joint. The specimen fractures at the welded joint after SCC, which is caused by lattice defects in the welded joint.