HIGH-STRENGTH STRUCTURAL STEEL SHEET HAVING EXCELLENT HEAT TREATMENT RESISTANCE AND MANUFACTURING METHOD THEREOF

摘要

The present invention relates to a high-strength structural steel sheet having excellent heat treatment resistance, comprising in percentage by weight: 0.03 to 0.07% of C; 0.05 to 0.2% of Si; 1.6 to 2.3% of Mn; 0.008% or less of P; 0.002% of less of S; 0.025% of less of Al; 0.1 to 0.4% of Cu; 1.4 to 2.3% of Ni; 0.08 to 0.2% of Mo; 0.01 to 0.025% of Nb; 0.008 to 0.02% of Ti; 0.001 to 0.008% of N; and the remainder being Fe and unavoidable impurities, wherein a microstructure within 10 mm or less from a surface comprises, by volume fraction, 80% or more of acicular ferrite and 20% or less of polygonal ferrite.