| 摘要 |
PURPOSE: A method for manufacturing a hot rolled steel sheet with a tensile strength of 36 to 49 kg/mm¬2 and elongation ratio of higher than 22 % for steel pipes by mini mill process is provided. CONSTITUTION: The method for manufacturing a hot rolled steel sheet for steel pipes includes the steps of (a) melting scraps in electric furnace to prepare a molten steel comprising 0.07 wt.% or less of C, Mn 0.2 to 0.50 wt.%, 0.03 wt.% or less of Si, 0.03 wt.% or less of P, 0.015 wt.% or less of S, Soluble Al 0.01 to 0.10 wt.%, 0.010 wt.% or less of N and 0.30 wt.% or less of total amount of tramp elements including Cu, Ni, Cr, Mo, Sn, Sb and Zn, wherein the tramp elements includes 0.2 wt.% or less of Cu, 0.05 wt.% or less of Sn and 0.05 wt.% or less of Sb; (b) continuous casting the molten steel into a thin slab with a thickness of less than 70mm; (c) finish hot rolling the thin slab in austenite single phase region at higher than 830 deg.C by mini mill process; and (d) coiling the hot rolled steel sheet in the temperature range of 550 to 700°C.
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