L51624 Topical Report on Mechanical Behavior of Selected Line-Pipe Steels

Methods to characterize flaw growth in line pipe have evolved with the materials used in pipelines and the technology used to analyze flaw growth. Developments in steel processing and pipeline manufacture have given rise to steels that are very flaw tolerant. Recent steels sustain significant stable flaw growth accompanied by local inelastic straining prior to unstable crack growth. The need for an analysis that can account for the stable flaw growth and inelastic straining in line-pipe applications was recognized and PRCI Line Pipe Supervisory Committee initiated a combined analytical and experimental program to assess the effects of stable flaw growth during hydrotesting. The objective of this report is to present the mechanical properties needed to assess stable flaw growth. These properties involve the usual tensile properties obtained from flattened strap specimens, as well as some properties unique to the analysis of ductile flaw growth. Accordingly, these properties are presented following a brief introduction of the analysis method that has been developed to provide the gas industry with an accurate and validated model for predicting growth of a flaw due to the effects of a hydrostatic test or hydrostatic retesting.