80/ A method of manufacturing hot rolled steel for applying 80kgf/mm2 steel pipe

摘要

PURPOSE: A manufacture method of a hot rolled strip for steel tube with a tensile strength of 80 kgf/mm¬2 is provided to confirm high strength without quenching and tempering after steel tubing. CONSTITUTION: The method includes the steps of calcium treatment of a steel melt comprising C 0.25 to 0.45 wt.%, 0.35 wt.% or less of Si, Mn 1.20 to 1.80 wt.%, 0.020 wt.% or less of P, 0.010 wt.% or less of S, 0.030 wt.% or less of Al, V 0.070 to 0.15 wt.%, N 0.007 to 0.0120 wt.%, Ca 0.0005 to 0.006 wt.%, balance Fe and incidental impurities; continuous casting the steel melt into slab; hot rolling the slab; and winding the hot rolled steel sheet at 600 to 680C.