某公司输气管项目使用的0Cr18Ni9奥氏体不锈钢管,采用焊接方式连接,焊接工艺为手工电弧焊,钢管内输送介质为含硫化氢等腐蚀介质的富氨液,管内介质压力0.5 MPa,介质温度35～45℃,运行半年后停产半年,复产时即在钢管焊接接头附近发现横向裂纹.通过宏观低倍、微观金相、化学成分分析以及扫描电镜分析等一系列方法,对该0Cr18Ni9奥氏体不锈钢裂纹形成原因进行分析.结果表明:该0Cr18Ni9奥氏体不锈钢管的破裂原因为连多硫酸应力腐蚀破裂,通过向该0Cr18Ni9奥氏体不锈钢管内吹扫氩气,密封两端口,可避免连多硫酸应力腐蚀破裂.焊接时降低焊接电流,加快焊接速率,减小焊接热影响区的范围,也可降低连多硫酸应力腐蚀破裂的可能性.%0Cr18Ni9 austenite stainless steel has been used for the gas piping project in a certain corporation,the pipes were joined together with welding and the manual arc welding procedure was carried out.The transmission medium in the pipeline was enriched ammonia liquor containing hydrogen sulphide and other corrosive media,the medium pressure was 0.5 MPa and temperature was 35～45 ℃.Transverse crack was found nearby the welding joint when the production was resumed after one year,including half a year of operation and half a year of suspend production.Cracking causes of 0Cr18Ni9 austenite stainless steel pipe were analyzed by a series of examinations,such as macroscopic test,metallographic test and chemical compositions analysis as well as SEM analysis.The results showed that the crack of 0Cr18Ni9 austenite stainless steel pipe was polythionic acid stress corrosion cracking.By purging 0Cr18Ni9 austenite stainless steel pipe with argon and sealing pipe ports at opposite ends,polythionic acid stress corrosion cracking could be prevented.The possibility of polythionic acid stress corrosion cracking could also be decreased by reducing welding current,increasing welding rate and reduction in scope of heat effective zone during welding.
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