| 摘要 |
PURPOSE: A cold-rolled steel sheet and a manufacturing method thereof are provided to improve a yield-point elongation ratio without degradation of the materials and improve the harden baking by maintaining a high quantity of solid carbon. CONSTITUTION: A method for manufacturing a cold-rolled steel sheet comprises the steps of: reheating a slab panel(S110), finish hot-rolling the reheated panel at an FDT(Finishing Delivery Temperature) of 890-930°C(S120), cooling the hot-rolled panel and coiling the panel at a CT(Coiling Temperature) of 580-750°C(S130), pickling the coiled panel(S140), cold-rolling the pickled panel(S150), annealing the cold-rolled panel(S160), temper-rolling the annealed panel using the top and bottom rolls driven at different speeds(S170), and cooling the temper-rolled panel(S180). [Reference numerals] (AA) Start; (BB) End; (S110) Reheating slab(SRT:1150-1250°C); (S120) Hot rolling(FDT:890-930°C); (S130) Cooling/coiling(CT:580-750°C); (S140) Pickling; (S150) Cold rolling(reduction ratio: 60-80%); (S160) Annealing(annealing temperature: 800-880°C); (S170) Temper rolling(top/bottom roll speed ratio: 1:1.05-1:1.2); (S180) Cooling |
