Welding HAZ Impact Toughness of X80 Mother Pipe for Bend and Relevant Influencing Actors

Studied here in the paper are the impact energy and its distribution characteristics in the HAZ of the X80 mother pipe for the bend. Comparing the HAZ impact energy of the said X80 mother pipe for the bend with that of the main line pipe,it is identified that HAZ impact energy of the said mother pipe is on the low side,and fluctuates obviously;and it is also revealed via comparison of the welding HAZ impact energy of the mother tube with that of the hot bend that after heat treatment,the HAZ impact energy of the bend is increased significantly. Finally it is pointed out that the alloy composition of the base metal,the welding heat input,the impact toughness of the base metal and the HAZ notch position are the main factors as affecting the HAZ impact. Accordingly some suggestions for improvement are put forward.