Analysis of microstructure and corrosion resistance of X80 pipeline steel welded by shielded metal arc welding

X80 pipeline steel was welded by twin electrode arc welding technology, and the composition, microstructure, corrosion resistance of welded joint were studied and compared with those of traditional arc welding. The deposition efficiency of twin electrode arc welding is higher than that of the traditional electrode arc welding, however, the concentration of alloying elements in welding material is lower because of the gravity coefficient of coating and its special structure. In addition, the concentration of polygonal ferrite is higher in welding material. What's more, the microstructure of CGHAZ is much finer because of the lower heat input for base material, which is beneficial to the promotion of the properties. The corrosion resistance of weld metal and CGHAZ is inferior to that of base metal in 0.5 M Na₂CO₃-1 M NaHCO₃ solution and NACE A solution with saturated CO₂. However, the twin electrode arc welding facilitates the corrosion resistance of weld metal and CGHAZ compared with the traditional arc welding.