METHOD FOR MANUFACTURING HIGH STRENGTH STEEL PLATE EXCELLING IN BALANCE OF LOW-TEMPERATURE TOUGHNESS AND STRENGTH, AND CONTROL METHOD FOR THE SAME

摘要

PROBLEM TO BE SOLVED: To provide a method for manufacturing a high strength steel plate excelling in the balance of low-temperature toughness and strength, and a control method for manufacturing the steel plate with such characteristics with a high yield.;SOLUTION: The method for manufacturing the high strength steel plate includes heating, to 1,000-1,250°C, a steel piece containing 0.05-0.15% C, 0.05-0.5% Si, 1.0-2.0% Mn, at most 0.02% P, at most 0.01% S, 0.005-0.045% Al, and 0.005-0.08% Nb with a remaining portion consisting of iron and inevitable impurities, then subjecting the steel piece to hot rolling with a cumulative draft at 1,000°C or lower being 50% or more and with a rolling end temperature being an Ar₃ point or higher and 900°C or lower, and cooling the steel piece at an average cooling rate of 3-50°C/s from Ar₃-30°C or higher to a temperature range from a bainitic transformation end temperature +50°C to a bainitic transformation end temperature -50°C, wherein a bainitic area rate to the entire texture in a position of plate thickness 1/4 is 80% or more.;COPYRIGHT: (C)2013,JPO&INPIT