STEEL AND METHOD OF MANUFACTURING THE SAME

摘要

According to the present invention, disclosed are a steel and a method to manufacture the same which secures excellent low temperature impact toughness and low yield ratio property through alloy component adjustment and process condition control. According to the present invention, the steel comprises: 0.15-0.20 wt% of C; 0.15-0.40 wt% of Si; 1.3-1.6 wt% of Mn; 0.001-0.025 wt% of P; 0.001-0.025 wt% of S; 0.001-0.055 wt% of Al; 0.03-0.05 wt% of Nb; 0.04-0.10 wt% of V; 0.001-0.025 wt% of Ti; 0.0001-0.0120 wt% of N; and the remaining of iron (Fe) and inevitable impurities. The steel has a tensile strength (TS) of 600-720 MPa; a yield strength (YS) of 490 MPa or more; and a yield ratio (YR) of 84% or less.