| 摘要 |
PURPOSE: A method for manufacturing a cold rolled steel sheet with a tensile strength of greater than 60 kg/mm¬2 and high ductility of greater than 35 % for use in the manufacture of automobile inner panel requiring both high formability and strength is provided. CONSTITUTION: The method includes the steps of adding C 0.07 to 0.13 wt.%, Mn 1.4 to 1.8 wt.%, Si 0.2 to 0.4 wt.%, Ti 0.05 to 0.08 wt.%, 0.03 wt.% or less of P, 0.015 wt.% or less of S, 0.01 wt.% or less of N to low carbon aluminum killed steel to prepare a slab; soaking the slab at higher than 1100 deg.C; hot rolling the soaked slab at a finish rolling temperature of higher than 870 deg.C; coiling the hot rolled steel sheet; and continuous annealing the hot coil, wherein hot coiling is conducted at 650 to 750 deg.C in case of £Ti|>=3x3.42£N| followed by continuous annealing at 800 to 830 deg.C, or hot coiling is conducted at 550 to 650 deg.C in case of £Ti|<3x(3.42£N|) followed by continuous annealing at 750 to 800 deg.C.
|
