Ni-CONTAINING STEEL HAVING EXCELLENT TOUGHNESS IN WELD ZONE AFTER STRESS RELIEF ANNEALING

摘要

PROBLEM TO BE SOLVED: To provide a technique for improving toughness in weld zone after stress relief annealing (abbreviated as SR) of Ni-containing steel used, e.g. for liquefaction equipment for LPG, LEG, LNG, etc.;SOLUTION: The Ni-containing steel having excellent toughness in weld zone after SR has a composition consisting of, by weight, 0.02-0.15% C, 0.05-0.15% Si, 0.2-1.0% Mn, ≤0.01% P, 0.0005-0.003% S, 1.0-7.5% Ni, 0.01-0.08% Al, 0.002-0.006% N, 0.0005-0.0050% Ca, either or both of 0.05-0.5% Mo and 0.05-0.5% Cr, and the balance iron with inevitable impurities. Further, ≥40×103 pieces/mm2, in total, of CaO, calcium aluminate and CaS having ≤0.5 μm average particle size exist dispersedly in the steel.;COPYRIGHT: (C)2002,JPO