| 摘要 |
<p>Disclosed are high-strength hot-rolled steel plates having a tensile strength (TS) ; more than 600MPa and a yield strength (YS) ; more than 555MPa through adjustment of alloy compositions and control of process conditions while satisfying API(American Petroleum Institute) 5L X80 specification, and a manufacturing method thereof. The hot-rolled steel plates according to the present invention comprise in weight %; carbon (C) : 0.04 ~ 0.07%, silicon (Si) : 0.1 ~ 0.3%, manganese (Mn) : 1.5 ~ 1.8%, niobium (Nb) : 0.06 ~ 0.08%, titanium (Ti) : 0.01 ~ 0.03%, vanadium (V) : 0.03 ~ 0.06%, chromium (Cr) : 0.15 ~ 0.35%, calcium (Ca) : 0.001 ~ 0.004%, sulfur (S) : less than 0.003%, phosphor (P) : less than 0.018%, nitrogen (N) : less than 0.006% in addition to a balance of iron (Fe) and unavoidable impurities, and are characterized by having a composite microstructure containing ferrite, acicular ferrite and pearlite along with a tensile strength (TS) : more than 600MPa and a yield strength (YS) : more than 555MPa.</p> |
