Microstructures and mechanical properties of welded joints of novel 3Cr pipeline steel using an inhouse and two commercial welding wires

• Weldability of novel 3Cr pipeline steel was investigated using two commercial and an inhouse welding wires.
• Mechanical properties were measured and microstructure characteristics were observed.
• Fracture positions of tensile test just corresponded to the minimum hardness region of the joints.
• The inhouse wire R01 can provide the highest cost-performance ratio.

The welded joints of the novel 3Cr pipeline steel were fabricated via the gas tungsten arc welding (GTAW) technique using an inhouse welding wire labeled as R01 and two kinds of commercial wires (H08Cr3MoMnA and TGS-2CML). Microhardness, impact toughness and tensile properties of the joints were measured, and microstructure characteristics were observed by scanning electron microscopy (SEM). The results show that under selected welding procedure, the joints of R01 can achieve quite good mechanical properties without preheating and post weld heat treatment (PWHT). After thermal refining, elongation (15.2%) doubled and met the DNV-OS-F101 standard. For low carbon or super low carbon pipeline steels such as 3Cr steel, the revised formula with the carbon applicable coefficient (A(c)) was quite good for predicting the maximum hardness in heat affected zone (HAZ). Compared with these two selected commercial wires, the inhouse welding wire R01 can provide the highest cost-performance ratio.