电阻焊管在混合硝酸盐溶液中的应力腐蚀破裂

Stress Corrosion Cracking of ERW Pipes in Mixed Nitrate Solution

试验采用了插销ＳＣＣ试验法，测定了四种管线钢及其焊缝在混合硝酸盐介质中的ＳＣＣ临界值（临界断裂应力σｉｍｐＳＣＣ和临界断裂功ＷＡＳＣＣ），并采用动电位快慢扫描技术，结合侧面金相观察及扫描断口分析，讨论了其ＳＣＣ的行为。结果表明，所研究材料在硝盐介质中具有较高的ＳＣＣ抗力。其中母材的ＳＣＣ抗力最佳，均超过母材抗拉强度σｂ的６０％，而相应的焊缝已接近４０％σｂ，所有应力腐蚀裂纹均沿固态相变组织的晶界扩展，断口呈典型的沿晶破裂。

The stress corrosion cracking (SCC) of ERW pipes was studied in mixed nitrate slotion (MNS) at 90℃ σ impSCC (the critical stress of SCC) and W ASCC (the critical fracture energy of SCC) of the four pipe line steels and their weld metals were measured by notched tension specimen. The anodic polarization behavior of the researched materials was investigated by potentiondynamic fast-slow scanning polarization technique. The crack tip morphology and fracture surface of SCC were analyzed by the optical microscope and SEM respectively. The resault shows the SCC-resistance of the researched materials in MNS was higher. σ impSCC of the four pipes line steels exceeded 60% σ b (σ b tensile strength of base metal). σ impSCC of the weld metals of four pipe line steels approached 40% σ b. The stress corrosion crack propagates generally along the grain boundaries of solid state transformation structure. The features of the fracture surface shows a typical intergranular cracking.