THICK WALL 9 Ni STEEL SUPERIOR IN WELDED ZONE TOUGHNESS AFTER STRESS RELIEF ANNEALING

摘要

PROBLEM TO BE SOLVED: To provide a technology for improving toughness of welded zone after a stress-relief annealing of a 9% Ni steel with a thickness of 50 mm or more used for a liquefier of liquefied natural gas, and the like.;SOLUTION: A 9% Ni steel superior in welded zone toughness after a stress relief annealing is characterized by including, by weight, C: 0.02-0.10%, Si: less than 0.10%, Mn: 0.2-1.0%, P≤0.01%, S: 0.0005-0.003%, Ni: 7.5-10.0%, Al: 0.01-0.08%, N: 0.002-0.006%, and Ca: 0.0005-0.0050%, and besides, Mo: 0.05-0.5% and/or Cr: 0.05-0.5%, and the balance iron with inevitable impurities, and by that 35×103 particles in terms of total particles of CaO, calcium aluminate, and CaS with mean particle size of 0.5 μm or less exist dispersedly per square mm or more of the steel.;COPYRIGHT: (C)2002,JPO