Effect of heat input on the corrosion resistance of the cold worked 2304 lean duplex stainless steel GMAW welded joint

The effect of the welding GMAW, with heat input of 1.4 kJ/mm, on the microstructure and corrosion resistance of the steel UNS S32304 prior cold worked (0, 10, 30, and 30% thickness reduction) was evaluated. The welding process generated, in the weld joint, the regions: fusion zone (FZ), heat-affected zone (HAZ), an annealed region around the HAZ, and the metal base zone (BM) deformed by cold working. Excessive ferritization and high precipitation of chromium nitrides in the HAZ were identified. The corrosion resistance of the welded joints was not significantly changed for low deformation levels by cold work (up to 30% thickness reduction). However, for 50% thickness reduction a decrease in the corrosion resistance of the welded joint was observed. The annealing of the BM around the HAZ increased its corrosion resistance, making this region immune to localized corrosion. The heat input used in this study promoted higher ferritization and precipitation of chromium nitrides, lower annealing of the base metal near the HAZ and lower corrosion resistance when compared with the higher heat input used in our previous work (about 2.5 kJ/mm).