| 摘要 |
PURPOSE: Non-normalized steel and a manufacturing method thereof are provided to obtain high strength and improve free-cutting characteristics by controlling the shapes of elongated MnS inclusions. CONSTITUTION: A method for manufacturing non-normalized steel comprises the steps of: reheating slab, which comprises 0.40-0.50 wt% of C, 1.0-1.8 wt% of Si, 0.9-1.3 wt% of Mn, 0.03 wt% or less of P, 0.08 wt% or less of S, 0.15-0.35 wt% of Cr, 0.01-0.03 wt% of Mo, 0.001-0.010 wt% of Al, 0.01-0.05 wt% of Nb, and the remaining amount of Fe and inevitable impurities(S110), hot-rolling the reheated slab(S120), and cooling the hot-rolled steel(S130). [Reference numerals] (AA) Start; (BB) End; (S110) Reheating; (S120) Hot rolling; (S130) Cooling |
