| 摘要 |
PURPOSE: An ultrahigh strength and high carbon hot-rolled steel sheet and a manufacturing method thereof are provided to have excellent material uniformity and dimensional accuracy. CONSTITUTION: An ultrahigh strength and high carbon hot-rolled steel sheet with excellent formability and material uniformity is composed of 0.3-0.6 wt.% of C, 0.5 wt.% or less of Si (not including 0), 0.2-1.5 wt.% of Mn, 1.0 wt.% or less of Cr ( not including 0), 0.05 wt.% or less of Al (not including 0), 0.0005-0.005 wt.% of B, 0.005-0.05 wt.% of Ti, 0.01 wt.% or less of N (not including 0), 0.03 wt.% or less of P, 0.015 wt.% or less of S, and the rest of Fe and other inevitable impurities; and satisfies an equation 1 (Mn + 1.3×Cr + 2.5×C > 1.5). A microstructure contains 95% or more of bainite as area fraction. 60% or more of the bainite is transformed before winding. |
