论文部分内容阅读
采用慢应变速率试验(SSRT)、扫描电镜以及电化学测量技术研究了X70管线钢焊接接头在近中性模拟土壤溶液中的应力腐蚀开裂(SCC)行为。结果表明,断口和柱面SCC裂纹均发生在热影响区(HAZ)。在试验溶液中,随着外加极化电位降低管线钢SCC敏感性增强,电位负移到一定电位值后,SCC敏感性减弱;随着溶液pH值降低,腐蚀速率增大,敏感电位区间负移。施加阴极电位时,在试样断口观察到明显的准解理脆断特征,断口和柱面有穿晶SCC裂纹。分析了焊接接头试样HAZ的SCC机理,在试验介质中,管线钢应力腐蚀开裂主要受阳极溶解和氢致开裂两种机理的联合作用,适当的电位可以使阳极溶解和氢致开裂的联合作用达到最大,从而造成较严重的应力腐蚀开裂。
The stress corrosion cracking (SCC) behavior of X70 pipeline steel welded joints in near-neutral simulated soil solution was studied by slow strain rate test (SSRT), scanning electron microscopy and electrochemical measurement. The results show that the fracture and the cylindrical SCC crack occur in the heat affected zone (HAZ). In the test solution, the SCC sensitivity increased with the decrease of the applied potential and SCC decreased after the potential was negatively shifted to a certain potential. With the decrease of solution pH, the corrosion rate increased and the sensitive potential range shifted negatively . When the cathodic potential was applied, obvious quasi-cleavage brittle fracture was observed at the fracture surface of the sample, and the fracture and the cylinder surface had the transgranular SCC crack. The SCC mechanism of the welded joint sample HAZ is analyzed. In the test medium, the stress corrosion cracking of the pipeline steel is mainly caused by the combined action of anodic dissolution and hydrogen induced cracking. The appropriate potential can make the combination of anodic dissolution and hydrogen induced cracking Reaching the maximum, resulting in more serious stress corrosion cracking.