SCC Propagation Behaviour of X70 Pipeline Steel under Cyclic Loading in Near-neutral Solution

SCC propagation behavior of X70 pipeline steel specimens with V-shape and linear shape notches under cyclic loading in near-neutral solution was studied. The results show that linear shape notch made the cracks propagate easier than V-shape notch because the stress concentration factor of linear shape notch specimen was larger than that of V-shape notch specimen. And the crack propagation rate increased with the decrease of stress ratio. The environment was dominant affecting foctor of crack propagation at the beginning,and the mechanical role was enhanced gradually with the continuous propagation of cracks. When stress intensity factor amplitude ΔK reached a certain value,the propagation of cracks transferred from a stable stage to an unstable quick period.