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从断口形貌观察、金相组织的检验、腐蚀产物成分分析等方面对液化气原料罐法兰与入口管线接头的失效原因进行了分析,认为是16Mn钢在含有H2S的腐蚀介质中,在焊接残余应力和工作载荷的共同作用下,由于应力腐蚀而产生的沿晶脆性开裂。裂纹起始于内表面法兰侧焊缝热影响区熔合线附近(马氏体区),裂纹源起始于该区域的蚀坑或焊缝根部余高应力集中部位,同时出现多处裂纹源,每个微小裂纹在该区域内沿焊缝纵向扩展最终连接成大裂纹,并向纵深扩展,直至穿透。并提出了相应的措施防止此类事故的发生。
From the fracture surface morphology, metallographic examination, analysis of the composition of corrosion products and other aspects of the liquefied gas tank flange and inlet pipe joints failure analysis was that 16Mn steel in H2S containing corrosion medium, the welding Residual stress and working load under the joint action, due to stress corrosion and brittle cracking along the crystal. The cracks originate in the vicinity of the weld line (martensite) in the heat affected zone of the weld on the flange side of the inner surface. The source of the crack originates from the site of excess stress at the root of the pits or welds in the area, and multiple crack sources , Each tiny crack in the region along the weld longitudinal expansion eventually connected into a large crack, and extended to the depth until penetration. And put forward the corresponding measures to prevent such accidents.