Determination of Fracture Toughness and K_(IC)‑CVN Correlations for BM, HAZ, and WB in API 5L X60 Pipeline

摘要

This paper presents a study to determine the fracture toughness for the API 5L X60 pipeline in the base metal (BM), theheat-affected zone (HAZ), and the welding bead (WB) by SE(B) specimens in the short transverse direction in an API 5LX60 pipeline. Also, a comparison of the K_(IC) results from SE(B) specimens and K_(IC)-CVN (Charpy V-notch) correlationequations using CVN energy values was done. SE(B) specimens were machined and tested according to ASTM E339.Standard Charpy specimens were machined and tested according to ASTM E23. The notch remained within the evaluationzone to obtain K_(IC) and Charpy specimens at the HAZ and WB. The K_(IC)and CVN values are higher for the BM, followedby the HAZ and the WB. These K_(IC) and CVN values are similar to those reported by other authors in API 5L pipelines.The decrease in K_(IC) and CVN values is due to the microstructure present in the temperature transformations. For BM, theferrite matrix with pearlite colonies could be presented, while for the WB zone, martensite and finer bainite are detected. Insome regions of the HAZ temperatures are reached that promote the transformation of the ferritic/pearlitic structure of theBM into austenite. K_(IC)-CVN correlation equations values should be used only to estimate K_(IC) values when K_(IC) data cannotbe obtained from standard specimens.