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采用动电位扫描技术和慢应变速率拉伸实验研究了X80钢及其焊缝在库尔勒土壤模拟溶液中的应力腐蚀行为,并利用扫描电镜观察了不同外加电位下的断口形貌.结果表明,X80管线钢及其焊缝在库尔勒土壤模拟溶液中的极化曲线具有典型的活性溶解特征.阳极极化及自腐蚀电位下,裂纹萌生于点蚀坑及夹杂物处,X80钢及其焊缝的开裂机制为阳极溶解;外加电位为-900 mV(vs SCE)时,母材处于阴极保护状态,应力腐蚀敏感性较低,而焊缝的应力腐蚀敏感性明显增加;当外加电位负移至-1200 mV(vs SCE),母材和焊缝均表现出较高的SCC敏感性,其开裂机制为氢和应力协同作用下的氢致开裂.相同电位下,焊缝的应力腐蚀敏感性高于母材,其断裂位置多在热影响区,这是由焊接过程中产生的冶金相变和残余应力造成的.
The stress corrosion behavior of X80 steel and its weld in Korla soil simulated solution was investigated by potentiodynamic scanning and slow strain rate tensile test. The fracture morphology under different applied potentials was observed by SEM. The results show that X80 Polarization curves of pipeline steel and its weld in Korla soil simulated solution have typical active dissolution characteristics. Under anodic polarization and self-corrosion potential, cracks originate in pits and inclusions. X80 steel and its weld The cracking mechanism is anodic dissolution. When the applied potential is -900 mV (vs SCE), the base metal is in cathodic protection, the stress corrosion sensitivity is low and the stress corrosion sensitivity of the weld is obviously increased. When the applied potential is negatively shifted to - At 1200 mV (vs SCE), both the base metal and the weld showed high SCC susceptibility, and the mechanism of cracking was hydrogen induced cracking under the synergistic effect of hydrogen and stress. Under the same potential, the stress corrosion resistance of the weld was higher than Base metal, the fracture location in the heat-affected zone and more, which is caused by the welding process of metallurgical transformation and residual stress caused.