| 摘要 |
<p>PURPOSE: A hot-rolled steel sheet, a manufacturing method thereof, and a method for manufacturing high-strength steel pipes are provided to obtain more than 930 MPa of tensile strength and 860-1,035MPa of yield strength by controlling QT(Quenching and Tempering) conditions. CONSTITUTION: A hot-rolled steel sheet manufacturing method is as follows. A slab sheet is composed of 0.2-0.3wt.% of C, 0.05-0.3wt.% of Si, 1.2-1.5wt.% of Mn, 0.02-0.04wt.% of Al, less than 0.03wt.% of Nb, 0.05-0.2wt.% of Ni, 0.01-0.2wt.% of Cu, 0.3-0.5wt.% of Cr, less than 0.03wt.% of Ti, less than 0.003wt.% of B, 0.001-0.004wt.% of Ca, and the rest of Fe and inevitable impurities. The slab sheet is finally rolled at 750-850°C of FDT(Finishing Delivery Temperature). A hot rolled sheet is cooled and coiled to 550-650°C of CT(Coiling Temperature).</p> |
