316L不锈钢短接过早腐蚀开裂的机制与预防

摘要

分析了盐化工环境中316L不锈钢短接腐蚀裂纹的宏观特征、微观形貌及显微组织,研究了卤水介质参数及短接制造工艺对316L不锈钢腐蚀的影响.结果表明:短接过早失效的机制是点蚀和应力腐蚀开裂;短接点蚀主要由卤水高温以及高Cl-含量引起,焊接残余应力及卷曲加工应力的共同作用促进了短接的应力腐蚀开裂;用铸造成形代替焊接成形,并适当增加316L不锈钢的钼含量,有利于延长短接的使用寿命.%Macro characteristics,micro morphology and microstructure of the corrosion cracks of a 316L stainless steel short connection in the environment of salt chemical industry were analyzed.The influences of brine parameters and manufacturing processes on the corrosion of 316L stainless steel short connection were investigated.The results show that the premature failure of the short connection was due to pitting and stress corrosion cracking (SCC).The pitting of short connection was mainly caused by high temperature and high Cl-concentration of brine,and the combined action of welding residual stress and crimping stress promoted SCC of the short connection.Adopting casting instead of welding and appropriately increasing the content of molybdenum were helpful to extend the service life of the short connection.