HIGH STRENGTH THICK STEEL PLATE AND METHOD TO MANUFACTURE HIGH STRENGTH THICK STEEL PLATE

摘要

Disclosed are a high strength thick steel plate having excellent strain aging impact toughness, and a method to manufacture the same. According to the present invention, the method to manufacture the high strength thick steel plate comprises: a step of re-heating a slab plate, by weight%, including 0.07-0.12% of carbon (C), 0.05-0.3% of silicon (Si), 1.2-2.0% of manganese (Mn), 0.015% or less of phosphorus (P), 0.005% or less of sulfur (S), 0.01-0.04% of niobium (Nb), 0.003-0.02% of titanium (Ti), 0.005% or less of nitrogen (N), 0.4% or less of copper (Cu), 1.0% or less of nickel (Ni), 0.5% or less of molybdenum (Mo), 0.05% or less of calcium (Ca), and the remainder consisting of Fe and inevitable impurities at 1000-1200°C; a step of primary rolling the slab plate on the condition of the reduction rate of 40% or more in an austenite recrystallization area; a step of forming a plate whose thickness is 70-120 mm by secondary rolling the primary rolled plate at 650-900°C; and a step of cooling the secondary rolled plate to 200-500°C in an accelerated cooling method.;COPYRIGHT KIPO 2014