LINE PIPE STEEL PLATE HAVING EXCELLENT HYDROGEN INDUCED CRACKING RESISTANCE AND A METHOD FOR MANUFACTURING THE SAME THROUGH CONTROL OF COMPONENTS, FERRITE CRYSTAL SIZE, AND ROLLING AND COOLING CONDITIONS

摘要

PURPOSE: A line pipe steel plate having excellent hydrogen induced cracking resistance and a method for manufacturing the same are provided to achieve uniform acicular ferrite microstructure through single phase rolling and hard cooling and to reduce the heat loss of a furnace.;CONSTITUTION: A line pipe steel plate comprises C of 0.02-0.06%, Si of 0.1-0.5%, Mn of 1.0-1.5%, Ni of 0.1-0.3%, Nb of 0.01-0.08%, Al of 0.01-0.1%, Cu of 0.01-0.3%, P 0.015% or less, S 0.001% or less, Cr of 0.05-0.3%, H 0.00030% or less, N of 0.001-0.006%, and Fe and other inevitable impurities of the remaining amount, satisfying 1.0Ca/S4.0. The steel sheet includes acicular ferrite and bainite structure as main phase and martensite island as second phase.;COPYRIGHT KIPO 2011