500 MPa YIELD STRENGTH THICK STEEL PLATE EXCELLENT IN TOUGHNESS IN MULTILAYER WELD ZONE AND PRODUCTION METHOD THEREOF

摘要

PROBLEM TO BE SOLVED: To provide a thick steel plate having ≥500 MPa yield strength (YS) excellent in toughness in multilayer weld zone, which is suitably applied to shipbuilding, marine structure, steel pipe, tank, bridge, civil engineering, building, construction/industry machine, etc.;SOLUTION: The thick steel plate having ≥500 MPa yield strength (YS), contains, by mass, 0.03-0.20% C, 0.1-1.0% Si, 0.50-1.8% Mn, ≤0.020% P, ≤0.005% S, 0.1-1.8% Al, 0.25-3.0% Cr and if necessary, 0.005-0.030% Ti, 0.0010-0.0070% N and further, one or two or more kinds of Cu, Ni, Mo, Nb, V, REM, Ca, Mg. In the thick steel plate, constituent structure of ICCGHAZ (Inter Critically-reheated Coarse Grain HAZ) of the multilayer weld zone includes ≥4% of retained austenite and the balance comprising ferrite, pearlite, bainite and martensite.;COPYRIGHT: (C)2013,JPO&INPIT