FATIGUE CRACK .GROWTH AND FRACTURE TOUGHNESS. BEHAVIOUR OF MULTIPASS WELD PRODUCED BY SAW PROCESS

Abstract

Mild steel plates of thickness 25 mm was welded by • multipass submerged Arc welding Process at different welding currents (400 - 500 A) and welding speed .(30 -40 Cm/min), using a combination of flux and flux-cored wire (3.2 mm n diameter) suitable for welding of High Strength Steel. The specifications of the Flux-cored wire and the flux are oerlikon made basic agglomerated OP121TT and FLUXOCORD°45. The influence of welding parameters, affecting the energy input, on the microstructure, Tensile properties, Fracture Toughness, and fatigue crack growth behaviour of the weld have been studied. The change in welding parameter has been found to affect the microstructure of the weld consists of coarse and fine columnar dendrite and coarse and fine reheat regions. The variation in Energy input governed by the welding parameter has been found to affect the tensile properties, fracture toughness and fatigue crack growth behaviour of the weld.•The increase in energy input has been found to reduce tensile strength but to enhance the ductility of the weld. The increase in energy input has also been found to enhance the fracture toughness and reduce the fatigue crack growth rate of the weld. These behaviours are found to be correlated with the tensile properties of the weld where It is marked that the increase in fracture toughness and decrease in FGGR are characterised by decrease in tensile strength and increase in elongation.