POSCO Holdings Inc.
STRUCTURAL STEEL HAVING EXCELLENT BRITTLE FRACTURE RESISTANCE AND METHOD FOR MANUFACTURING SAME

Abstract:

A structural steel having excellent brittle fracture resistance according to an aspect of the present invention comprises, by weight %, 0.02-0.12% of C, 0.01-0.8% of Si, 1.5-2.5% of Mn, 0.005-0.5% of Al, 0.02% or less of P, 0.01% or less of S, 0.0015-0.015% of N, and the remainder of Fe and unavoidable impurities, wherein an outer surface layer portion and an inner central portion are microstructurally divided along the thickness direction, the surface layer portion comprises tempered bainite as a matrix structure, the central portion comprises bainitic ferrite as a matrix structure, and the NDT temperature by the NRL drop-weight test may be -70.degree. C. or lower.