经济型铁素体不锈钢与耐候钢异种金属接头的耐蚀性能

采用ER-309焊丝焊接了T4003与Q450NQR1耐候钢、Nirosta 4003与Q450NQR1耐候钢两种异质接头,用金相方法分析了母材和接头的显微组织,通过盐雾腐蚀试验及电化学极化曲线测量对异种金属焊接接头的耐蚀性能进行了评价。结果表明,对T4003和Nirosta 4003铁素体不锈钢同种金属所形成的焊接接头而言,焊缝的耐蚀性能均优于对应的母材,但热影响区的耐蚀性能变差。对T4003和Nirosta 4003铁素体不锈钢与Q450NQR1耐候钢焊接形成的异质接头而言,焊缝的耐蚀性能下降。在盐雾状态下,同种金属焊接所形成的焊缝与母材的耐盐雾腐蚀性能水平相当,耐蚀性能较好;T4003和Nirosta 4003不锈钢与Q450NQR1耐候钢焊接而成的异质接头腐蚀较为明显,尤其是耐候钢一侧的腐蚀较为严重,出现了大量的腐蚀坑。在异种金属所形成的焊接接头中,不锈钢母材、热影响区、焊缝以及耐候钢母材由于腐蚀电位差的不同形成原电池,致使耐候钢母材的腐蚀加剧。

CORROSION RESISTANCE OF DISSIMILAR METAL JOINTS OF ECONOMIC FERRITIC STAINLESS STEEL AND WEATHERING STEEL

T4003 and Q450NQR1,as well as Nirosta 4003 and Q450NQR1 dissimilar metal joints were welded by ER-309 welding wire.The microstructure of their base metal and joint were analyzed by metallographic approach.The corrosion resistance of base metal and joints was evaluated by salt fog and electrochemical corrosion tests.The results demonstrated that as far as the similar metal joints of Nirosta 4003 and T4003 was concerned,the corrosion resistance of welding line was much better than that of base metal.However, the corrosion resistance of heat affected zone(HAZ) became worse.In the case of dissimilar metal joints of Nirosta 4003 and Q450NQR1,as well as T4003 and Q450NQR1,the corrosion resistance of welding line was reduced.Under salt spray condition,the corrosion resistance of welding line and base metal of similar metal joints was comparative.However,the dissimilar metal joints of Nirosta 4003 and Q450NQR1,as well as T4003 and Q450NQR1 exhibited obvious corrosion.Especially,abundant corrosion pits were found near the side of Q450NQR1.Due to the different corrosion voltages of stainless steel,weathering steel,HAZ,and welding line,a series of micro-batteries were formed in the dissimilar metal joints,which worsened the corrosion of weathering steel.