材料期刊网

采用慢速率拉伸试验（ＳＳＲＴ）方法及电化学测量技术，研究了阴极电位下Ｘ７０钢在某种近中性介质中的应力腐蚀开裂（ＳＣＣ）机理。试验表明，在近中性介质中，随着电位的降低，管线钢的ＳＣＣ敏感性增强，但当电位低于某一范围后，ＳＣＣ敏感性减弱；随着溶液ｐＨ值的降低，管线钢的腐蚀速率增大，敏感电位区间负移。分析表明，在近中性介质中，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，氢的渗入可能与氢的还原过程及管线钢阳极溶解密切相关。适宜的电位可以使阳极溶解和氢的联合作用增强，增强应力腐蚀开裂倾向。

Stress corrosion cracking (SCC) mechanism of pipeline steel X70 has been investigated in a solution of near-neutral pH by means of slow strain rate test and electrochemical test technology. The experiments showed that SCC susceptibility increased as the applied potential shifted in the cathodic direction, but when the potential was lower than the extent of susceptive potential, SCC susceptibility depressed. Besides, the susceptive potential became more negative as the pH value decreased and corrosion rate increased. The analysis showed that hydrogen-induced cracking together with anode dissolution played an important role in the SCC of pipeline steel X70. However, anode dissolution and hydrogen-induced cracking did not work separately. Hydrogen permeation was related to the process of hydrogen deoxidization and the anode dissolution at specimen surface. Relevant potential was able to make the two mechanisms combined to cause much more serious SCC.