ESTIMATION OF FRACTURE TOUGHNESS AND CRACK GROWTH BEHAVIOUR OF C-Mn STEEL WELDMENT

Abstract

For this study work weld metal were deposited with the combination of Grade C-Mo wire and Automelt Grade iv Flux on C-Mn Steel using Submerged Are Welding process. Mechanical properties, Charpy V-notch energy, Hardness, Fatigue crack growth rate and fracture toughness (Jic ) tests were performed on weld metal as well as base metal. More Strength and less ductility was found in case of weld metal as compare to base metal. Toughness was assessed using the Charpy V -notch Impact test. Toughness of weld metal was found considerably high even at —30 °C temperature. The resistance of fatigue crack propagation of weld metal and base metal were evaluated at room temperature in Air. Fatigue crack growth rates were determined, as a function of the stress intensity factor range and value of Paris constants were determined for the stress ratio of 0.1 and 0.3. The crack propagation rate was higher in weld metal as compare to base metal which might be attributed to residual stress present in weld. Threshold stress intensity factor range was also found more in weld metal as compare to base metal. The weld metal had superior Fracture Toughness (Jig ) compare to base metal. This might be due to repeated re-heating, refining and tempering of the weld metal microstructure during the fabrication of weld