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Studies on nine percent nickel steel for liquefied natural gas carriers

Conference · · Am. Soc. Test. Mater., Spec. Tech. Publ.; (United States)
OSTI ID:7354100

The spherical tanks for the Moss-Rosenberg type of liquefied natural gas (LNG) carriers are to be fabricated from rolled and forged nine percent nickel (9Ni) steels, with the former steel being used as tank shell-plate material and the latter as tank equator-ring material. A series of experimental studies was conducted to evaluate the fatigue strength, resistance to fatigue crack propagation, fracture toughness, etc., of these tank steels having due regards to the ''leak-before-failure'' premise of the Moss-Rosenberg LNG containment system. Various forms of plain and welded test specimens were prepared from shell-plate and equator-ring materials for fatigue tests; and, the effects of stress ratio and surface finish of reinforcement weld on the tank-steel fatigue strength were closely studied. Wide-plate test specimens were fatigue tested under repeated tensile and bending loads, and configurations of through cracks immediately after penetration and crack propagation rates were examined. Notched plain and welded wide-plate test specimens of different thicknesses were prepared from tank steel plates produced from different heats and submitted for tension tests to determine the critical stress intensity factor (K/sub c/ value) at the cryogenic temperature of LNG. Using data obtained on material properties of the rolled and forged /sup 9/Ni steels, the structural safety of the spherical LNG tank was evaluated confirming that the /sup 9/Ni steel LNG tank completely satisfied the leak-before-failure criterion.

OSTI ID:
7354100
Journal Information:
Am. Soc. Test. Mater., Spec. Tech. Publ.; (United States), Journal Name: Am. Soc. Test. Mater., Spec. Tech. Publ.; (United States) Vol. 579; ISSN ASTTA
Country of Publication:
United States
Language:
English