Effects of Ti, C and N on Weld HAZ Toughness of High Strength Line Pipe

As pipeline construction projects seek to implement more efficient welding techniques in order to reduce construction costs, it is important to understand the factors that affect the tolerance of the steel to welding processes. This is particularly true in the case of welding high strength steels (X70 and greater) in which increased alloy content will promote the formation of low temperature phases with limited ductility in the heat affected zone (HAZ). In the present study, the effects of titanium (0.008 to 0.015 wt%), nitrogen (60 to 100 ppm) and carbon (0.035 versus 0.060 wt%) have been examined through welds produced by a robotic gas metal arc welder.