Fracture properties of multipass submerged are weld of HSLA steel producedby using flux cored filler wire

Multi pass submerged are welding of 25 mm thick structural steel plates has been carried out at different energy input using flux cored filler wire an d basic agglomerated flux resulting the weld deposit having chemical compos ition confirming that of a high strength low alloy (HSLA) steel. Microstruc ture and hardness of different microstructural regions of the multipass wel d has been studied. Tensile properties of the weld deposit has been found o ut by carrying out tensile test of the weld joint being fractured from the weld. Fracture toughness (Ka) and fatigue crack growth properties of the we ld are studied and correlated with the welding energy input, microstructure and ultimate tensile strength of the weld. The increase in energy input ha s been found to reduce the hardness, ultimate tensile strength and yield st rength, but to enhance the ductility and K-Q of the weld primarily due to i ts influence on microstructure of the weld deposit. However, the increase i n energy input has been found to reduce the da/dN at higher Delta K but, it has been found to enhance the same at lower Delta K. The K-Q and da/dN of the weld are found to be well correlated with its tensile strength, where a n increase in tensile strength reduces the K-Q but enhances the da/dN at De lta K higher than 30 MPa root m.