Effect of the welding process and heat input on the fracture toughness of welded joints in high strength low alloy steel

Abstract

Fracture toughness studies were conducted in high strength, low alloy steel weldments obtained by using two different welding techniques namely CO 2 welding and manual metal arc welding. The heat input was varied in order to study its effect on the fracture toughness of the weld zone (WZ) and the heat-affected zone (HAZ). The crack-tip-opening displacement and the J integral were used as the characterizing toughness parameters. The tensile properties of the weldments were obtained and the hardness profiles through the various zones were determined. The fracture toughness values for the HAZ and the WZ were compared under different welding conditions. Microstructural studies and fractographic studies were also conducted to correlate the micromechanism of fracture with the fracture toughness values. The effect of heat input was found to be predominant in the WZ toughness and the HAZ toughness for CO 2 welding. Also, manual metal arc welding provided a higher fracture toughness than did CO 2 welding for a similar heat input. The microvoid coalescence mode of fracture led to higher fracture toughness values for the WZs than for the HAZs which exhibited a cleavage mode of fracture mixed with microvoid coalescence. In all conditions the WZs exhibited higher fracture toughness values than the HAZs.