| 摘要 |
PURPOSE: A method for manufacturing a high tensile strength steel(58 kgf/mm¬2 class) for construction with excellent strength even at high temperature is provided. CONSTITUTION: The method includes the steps of heating a steel slab comprising C 0.05 to 0.15 wt.%, 0.55 wt.% or less of Si, 1.60 wt.% or less of Mn, 0.70 wt.%, or less of Cr, Mo 0.3 to 0.9 wt.%, 0.06 wt.% or less of Nb, 0.03 wt.% or less of P, 0.025 wt.% or less of S, Sol. Al 0.01 to 0.06 wt.%, a balance of Fe and incidental impurities up to 1150 to 1300 deg.C; hot rolling the steel slab, wherein the hot rolling finish temperature is adjusted greater than 820°C; water cooling the hot rolled steel sheet to ambient temperature at a cooling rate of 7 to 50 deg.C/sec; and tempering the cooled steel sheet in the temperature range of 500 to 650°C.
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