The Analysis of Low Temperature Toughness on X80 Pipeline Steel Welded Joint

Aiming at the security problems of pipeline steel application, the different positions of the welded joints of circumferentially welding pipeline of X80 steel were investigated by microstructure observation, the hardness, Charpy impact toughness and crack tip opening displacement (CTOD) test at low temperature. The Vickers hardness test results show that there are local softened regions in heat-affected zone (HAZ). Charpy impact test indicate that the ductile–brittle transition temperature of weld is below − 60 °C, the ductile–brittle transition temperature of HAZ is around − 38 °C. CTOD test reveal that the fracture toughness of HAZ shows a large fluctuation since it is in the ductile–brittle transition temperature regime.