A Criterion for Unstable Crack Propagation in Welded Line Pipe Steel

The Modern Fracture Mechnics Concept is used in determining the acceptable defect level in line pipe steel. The toughness properties of the Heat Affected Zone (H. A. Z.) and Weld/Parent metal has been measured in terms of critical crack opening displacement (c.o.d.) values which are found to be more realistic and acceptable compared to other conventional tests. Crack arrest phenomena have been discussed by making use of Charpy V-notch absorbtion energy for the X-52 grade pipe steel. Besides, the development of different lest procedures for evaluating the performance of a line pipe has been outlined. The influence of different variables, such as weld flux, heat input and alloying elements on the toughness property of Heat Affected Zone are also incorporated in the present study.