Analysis of the Effects of Fabrication Flaws on Crack Initiation and Arrest Properties of 9% Nickel Steel Used in LNG (Liquefied Natural Gas) Storage Tanks. Final Report June 1982-March 1986

摘要

The purpose of the project, which was carried out in three phases, was to evaluate the crack resistance of LNG storage tanks. The first phase consisted of characterizing the mechanical behavior of seven different heats of 9% Ni steels using small test specimens. On the basis of these results three heats having two different toughnesses and two thicknesses were selected for the crack resistance study. Since weld defects are the most likely crack initiators, CTOD specimens were fabricated with lack-of-fusion (LOF) defects. It was found that the crack initiation toughness of austenitic welds exceeded that of the base-plate, while the toughness of ferritic welds was about equal to the base-plates. Further, fatigue sharpened defects were no more damaging than 'as-weld' defects. The major portion of the project consisted of defining the crack arrest capability of 9% Ni steel storage tanks. A specimen was developed for measuring full-thickness, non-plane strain crack arrest toughness.