| 摘要 |
PURPOSE: A high-strength steel sheet with high formability for vehicles and a manufacturing method thereof are provided to improve strength and elongation ratio by increasing the concentration of Mn in ferrite to obtain high martensite fraction at a low content of Mn. CONSTITUTION: A method for manufacturing a high-strength steel sheet with high formability for vehicles comprises the steps of: heat-treating a hot-rolled coil at 700-800°C(S110), pickling and cold-rolling the hot-rolled coil to obtain a cold-rolled steel sheet(S140), and consecutively annealing the cold-rolled steel sheet(S150). The hot-rolled coil comprises 0.08-1.2 weight% of C, 0.2-0.4 weight% of Si, 2.2-2.8 weight% of Mn, 0.02-0.04 weight% of soluble Al, 0.04-0.07 weight% of Nb, 0.005 weight% or less of N, 0.02 weight% or less of P, 0.015 weight% or less of S, and the remaining amount of Fe and inevitable impurities. [Reference numerals] (AA) Start; (BB) End; (S110) Hot rolling step; (S120) Coiling step; (S130) Hot coil heat treatment step; (S140) Cold rolling step; (S150) Annealing step |
