Effects of Heat-Affected Zones on the Fracture Toughness of 9% Nickel Steel Used in LNG (Liquefied Natural Gas) Storage Tanks. Volume 1. Final Report September 1982-January 1986

摘要

An extensive experimental and analytical study of the crack arrest capability of 9% Ni steel weldments at cryogenic temperatures (-162 C and -196 C) has been carried out. Five heats of parent steel, with varying levels of Charpy properties and thicknesses in the range 16-28mm, have been examined in detail, with limited testing also being performed on two other heats. Welded panels, using two types of Ni-base consumable and 2 levels of heat input, were prepared, using the shielded metal arc (SMA) process. A wide range of mechanical tests, including Charpy, CTOD, DWT, DWTT, compact crack arrest and wide plate crack arrest tests, were carried out on parent steels and weldments. The results showed that all the commercially obtained steels could arrest cracks with a half length of 100mm under the conditions present in an LNG tank. The exception was one specially produced steel which had rather worse Charpy properties. When welded with Ni-base consumables, cracks were arrested in all the welded panels under these conditions, thus demonstrating the benefits for crack arrest of an under matching weld metal. Dynamic finite element analysis assisted with the interpretation of the wide plate crack arrest tests. Requirements for the specification of parent steels with good crack arrest capability are proposed.