Investigation of Impact Toughness of SMAW, GMAW and FCAW of API X60 Pipeline Steel.

This research work investigates the impact of different welding processes i.e., Shield metal arc welding (SMAW), Gas metal arc welding (GMAW), and Flux core arc welding (FCAW) technique on the fracture toughness of API X60 pipeline steel. Utilizing Charpy V-notch (CVN) testing, the impact toughness of the base metal (BM), heat-affected zone (HAZ), and weld zone (WZ) was measured across a range of temperatures from -196°C to 20°C. The analysis reveals that different welding methods and the heat input associated with each significantly affect the fracture properties of the steel. The SMAW process shows the most considerable decrease in energy absorption in the HAZ, especially at lower temperatures, indicating a significant impact on the material's toughness. Conversely, GMAW demonstrates the lowest reduction and the highest increase in toughness in the HAZ and WZ, respectively, making it a superior method in maintaining material integrity during welding. The FCAW method exhibited a moderate and variable behavior in toughness changes, suggesting its intermediate effectiveness. The study further identifies that the chemical composition of the welding electrodes, particularly those containing nickel has a crucial part in enhancing the toughness of the welded zones. Additionally, it underscores the importance of understanding the microstructural changes induced by varying heat inputs, which directly influence the fracture behavior and lifespan of pipeline steels under low-temperature conditions. These findings are essential for improving welding practices and material selection in an ensuring safer, and economical transportation solutions for hydrocarbons over long distances. [ABSTRACT FROM AUTHOR]