HIGH-STRENGTH STEEL PLATE AND PRODUCING METHOD THEREFOR

摘要

The present invention relates to a high strength thick steel plate with excellent heat straightening part properties and a manufacturing method thereof and, more specifically, relates to a high strength thick steel plate with heat straightening part properties to satisfy a demanded strength and a toughness of impact even under a local heating in an abnormal area of approximately 870°C or less in a straightening process; and a manufacturing method thereof. An embodiment of the present invention comprises: 0.05-0.10 wt% of C; 1.45-1.55 wt% of Mn; 0.15-0.25 wt% of Cu; 0.20-0.70 wt% of Ni; 0.10-0.15 wt% of Si; 0.008-0.012 wt% of Nb; 0.008-0.012 wt% of Ti; 0-0.012 wt% of P; and 0-0.003 wt% of S; and includes: a step of preparing a thick steel plate wherein a residual part is formed with Fe and extra inevitable impurities; a step of reheating the thick steel plate to reach a temperature of 1100-1200°C at a rate of 14-16 °C/min per thickness; a step of finishing a hot rolling of the reheated thick steel plate on a platform area right above Ar3; and a step of air-cooling the hot rolled thick steel plate after performing an accelerated cooling up to 400°C or below at a cooling rate of 25-40 °C/min.