材料科学
冶金
马氏体
焊接
储罐
脆化
微观结构
残余应力
光学显微镜
腐蚀
应力腐蚀开裂
复合材料
扫描电子显微镜
铁氧体(磁铁)
机械工程
工程类
作者
Tianfu Li,S. Qu,Qi Shan Zang,Dong Chen,Chen Fu,Zhefeng Zhang
标识
DOI:10.1016/j.engfailanal.2023.107591
摘要
This work aimed to analyze a leak that occurred in a 60 m3 LNG storage tank made of 304 stainless steel. Optical microscopy (OM), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), transmission electron microscope (TEM), and mechanical property and hardness tests were conducted to characterize the failed storage tank. The results show that the crack originates near the circumferential weld of the lower head and propagates perpendicular to the weld. There are dense corrosion pits near the crack paths, and high contents of Cl and S in the crack and pits. Besides this, deformation-induced martensite transformation occurs during the cold spinning process of the head, and the microstructure undergoes embrittlement. In service, the lower head subjected to greater internal pressure, plus the structural stress caused by martensite transformation and the welding residual stress, combined with the action of corrosive medium, stress corrosion cracking (SCC) occurs near the circumferential weld of the lower head. To prevent SCC on storage tank, it is suggested to utilize 304 stainless steel with a low content of δ-ferrite, and apply solution treatment after spin molding of the head of tank.
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