不锈钢硝酸输送管道焊缝的腐蚀失效原因

Corrosion Failure Reasons for Welded Joint of Stainless Steel Pipeline for Nitrate Transport

通过化学成分分析、扫描电镜观察、能谱分析等方法,研究了硝酸管道焊缝腐蚀失效的原因。结果表明:304不锈钢硝酸管道在焊缝的腐蚀失效主要发生在焊缝热影响区,出现晶间腐蚀,沿热影响区出现刀口状腐蚀沟槽。三通母材的含碳量高于标准值,导致三通侧的管材在焊接过程中,其热影响区更容易发生敏化,晶粒粗大,导致耐蚀性下降。碳含量是影响304不锈钢焊接接头在硝酸中耐蚀性的关键因素,碳含量越高,焊接过程中热影响区的不锈钢越容易发生敏化,导致其耐蚀性显著降低。

Chemical composition analysis, field emission scanning electron microscopy, energy spectrum analysis were used to study the corrosion failure reasons for nitric acid transportation pipeline welds. The results showed that intergranular corrosion occured mainly in the weld heat affected zone of 304 stainless steel pipe, and knife-line corrosion occured along the heat affected zone. Carbon content of the tee joint material was higher than the standard value, leading to the material in the heat affected zone more likely to be sensitized and to form coarse grains during the welding process, resulting in a decline of the material＇s corrosion resistance. Carbon content was the key factor influencing the nitric acid corrosion resistance of 304 stainless steel weld joint, high carbon content led to stainless steel sensitizing in heat affected zone during welding process, reducing the corrosion resistance of the material.