| 摘要 |
<p>Disclosed are a steel sheet, capable of reducing the contents of high-priced alloy element and improving the property of hydrogen induced cracking and low temperature toughness by controlling the alloy component and process condition, and a manufacturing method thereof. According to the present invention, the steel sheet includes 0.02-0.04 wt% of C, 0.2-0.3 wt% of Si, 1.0-1.4 wt% of Mn, 0.008 wt% or less of P, 0.001 wt% or less of S, 0.02-0.05 wt% of Al, 0.2-0.5 wt% of Ni, 0.2-0.3 wt% of Cu, 0.2-0.3 wt% of Cr, 0.1-0.2 wt% of Mo, 0.01-0.03 wt% of Nb, 0.04-0.08 wt% of V, 0.01-0.02 wt% of Ti, 0.001-0.004 wt% of Ca, and the remainder consisting of iron (Fe) and inevitable impurities. The microstructure has a composite structure including accicular ferrite, ferrite, and pearlite. The fraction of accicular ferrite is equal to or greater than 70% as a cross-section area rate.</p> |
