乙二醇装置蒸发器凝液罐封头腐蚀原因分析

摘要

A lots of cracks appeared on the internal and external surface of the straight flange in a condensate collector head of ethylene glycol device evaporation system. The composition, microstructure, corrosion situation and cracks of the head were analyzed by spectrometer, metallurgical microscopy, SEM and XRD. The results show that the material of the head is 0Cr18Ni9 stainless steel, and the cracks on the internal and external surface were attributed to the pitting caused by enriched C1- existing in the deformation martensite of the straight flange of the head. Subsequently, the Cl- pitting induced stress corrosion cracking of the material. In addition, the selective dissolution of martensite promoted the crack growth. According to the analyses, several reasonable suggestions about heat treatment and material selection were put forward.%某乙二醇厂乙二醇装置蒸发系统的封头直边处内、外表面出现大量裂纹。采用光谱仪、金相显微镜、扫描电镜和x射线衍射仪对该封头材料的成分、显微组织、腐蚀状况、裂纹进行了的分析。结果表明，封头材质为0Cr18Ni9不锈钢；内、外表面出现裂纹的原因是Cl-在封头直边处的形变马氏体组织中富集发生点蚀，进而引发材料的应力腐蚀开裂；马氏体的选择性溶解促进了裂纹扩展。据此提出了合理的热处理和选材建议。