THICK STEEL PLATE FOR WELDED STRUCTURE HAVING HIGH STRENGTH AND EXCELLENT TOUGHNESS AT THE CENTER OF THICKNESS AND SMALL VARIATION OF PROPERTIES ALONG WITH THROUGH-THICKNESS AND METHOD OF PRODUCING THE SAME

摘要

An ultra-thick low alloy steel plate for welded structure which has a thickness of 50 mm or more, has 530 MPa or more of tensile strength and 390 MPa or more of yield strength at the center of thickness, has a ductile-brittle transition temperature of -50 deg.C or less, and has a hardness deviation of 50 Hv or less in the thickness direction, and a method of manufacturing the same are provided. An ultra-thick steel plate for welded structure having excellent strength and toughness at the center of thickness and small property deviation in the thickness direction comprises, by weight percent, 0.05 to 0.10% of C, 0.10 to 0.5% of Si, 1.3 to 1.7% of Mn, 0.0005 to 0.0025% of B, 0.005 to 0.03% of Ti, 0.010% or less of N, 0.005 to 0.03% of Nb, 0.005 to 0.055% of soluble Al, and the balance of Fe and unavoidable impurities, wherein a content ratio of the Ti and N(Ti/N) is 2.0 or more, and a component percentage(CP) represented by a relational expression, CP=165Î%C+6.8Î%Si+10.2Î%Mn+80.6Î%Nb+9.5Î%Cu+3.5Î%Ni+12.5Î%Cr+14.4Î%Mo, is between 40 and 50.