| 摘要 |
<p>Disclosed are a non-heated type high strength hot-rolled steel sheet and a manufacturing method thereof which enables the hot-rolled steel sheet to satisfy the standard of an American petroleum institute (API) 5CT N80 by controlling alloy elements and process conditions without a quenching and tempering (QT) process. The non-heated type high strength hot-rolled steel sheet according to the present invention is composed of 0.06-0.10 wt% of C, 0.15-0.25 wt% of Si, 1.5-1.8 wt% of Mn, 0.05-0.10 wt% of Nb, 0.01-0.03 wt% of Ti, 0.1-0.3 wt% of Ni, 0.1-0.2 wt% of Cr, 0.1-0.2 wt% of Mo, 0.001-0.004 wt% of Ca, and the rest of Fe and inevitable impurities. A microstructure is formed of a bainite structure as a main phase. The tensile strength (TS) is over 689 MPa and the yield strength (YS) is within 552-758 MPa.</p> |
