| 摘要 |
<p>A hot-rolled steel sheet having weatherability, tensile strength of 800 to 875 MPa, and yield strength of 700 to 745 MPa by adding Cu, Cr and Ni to steel is provided. A high strength hot-rolled steel sheet having excellent weatherability comprises, by weight percent, 0.05 to 0.07% of C, 2.5% or less of Mn, 0.04 to 0.06% of Nb, 0.08 to 0.10% of Ti, 0.30 to 0.60% of Cu, 0.5 to 1.0% of Cr, and 0.15 to 0.30% of Ni with the balance being Fe and other inevitable impurities, and has an acicular ferrite structure. The high strength hot-rolled steel sheet comprises 2.0 to 2.5% of Mn. The steel sheet has material characteristics of tensile strength of 800 to 875 MPa and yield strength of 700 to 745 MPa. The steel sheet has a yield ratio(yield strength/tensile strength) of at least 80%.</p> |
