A METHOD FOR PRODUCING A HIGH TENSILE STEEL WITH 125kgf/㎟ TENSILE STRENGTH GRADE

摘要

PURPOSE: A method for manufacturing high tension steel having a tensile strength of 125 kgf/mm2 is provided to manufacture high tension steel for armature in which not only strength-ductility combination properties are superior but also resistance for formation of adiabatic shear band is improved 25 or more compared to existing steel by controlling alloy constituents and heat treatment. CONSTITUTION: The method for manufacturing high tension steel having a tensile strength of 125 kgf/mm2 comprises the processes of hot rolling the steel slab by sufficiently heating a steel slab comprising 0.14 to 0.19 wt.% of C, 0.2 to 1.5 wt.% of Mn, 0.15 to 0.35 wt.% of Si, 0.02 wt.% or less of P, 0.008 wt.% or less of S, 2.5 to 5.5 wt.% of Ni, 0.5 to 1.5 wt.% of Cr, 0.15 to 0.75 wt.% of Mo, 0.02 to 0.07 wt.% of Nb, 0.005 to 0.025 wt.% of Ti, 0.01 to 0.04 wt.% of sol.Al (an acid soluble aluminum), and a balance of Fe and other inevitable impurities at a temperature of 1200 to 1350 deg.C, air cooling the hot rolled steel slab, quenching the steel slab by reheating the air cooled steel slab at a temperature of 850 to 950 deg.C, and tempering the quenched steel slab at a temperature of 300 to 550 deg.C.