321不锈钢焊接波纹管失效分析

应用光学显微镜、扫描电镜和能谱仪等手段对321不锈钢焊接波纹管表面腐蚀物的化学成分、焊缝区域的显微组织、腐蚀裂纹的形态特征等方面进行检验和分析。结果表明，波纹管局部电镀端内壁腐蚀导致漏气失效，即加工应力、焊接残余应力与含Cl^-或含Cl^-和溶解氧的腐蚀性介质的联合作用使波纹管局部电镀端产生了点蚀和应力腐蚀开裂；退火工艺设计的不合理和钎焊工艺控制不恰当使焊缝热影响区敏化而出现了晶间腐蚀。据此提出了降低和避免321不锈钢焊接波纹管因腐蚀而漏气的措施。

FAILURE ANALYSIS OF 321 STAINLESS STEEL WELDED CORRUGATE PIPE

Chemical composition of surface corrosion products, microstructure of weld zone, characteristics of corrosion crack of the 321 stainless steel welded corrugate pipe were examined and analyzed by means of metallography, SEM and EDS. The results showed that the corrosion leakage in the inner wall of the localized electrodeposition end of corrugate pipe leaded to its failure. The main reasons were that the several stresses including making stress and weld residual stress combined with the corrosive medium containing Cl - and/or Cl - and dissolved oxygen caused pitting and stress corrosion cracking, and that the improper annealing processing and welding process control caused sensitization and intergranular corrosion in the heat affected zone of weld. Based upon the above analysis, the approaches to diminish or avoid the corrosion leakge were proposed.