| 摘要 |
PURPOSE: A high-strength cold-rolled steel sheet and a manufacturing method thereof are provided to obtain a desired strength of a cold-rolled steel sheet even at high annealing temperatures by putting the cold-rolled steel sheet into an annealing temperature changing section. CONSTITUTION: A method for manufacturing a high-strength cold-rolled steel sheets comprises the steps of: putting a first cold-rolled steel sheet in a continuous annealing line maintaining a first annealing temperature(S110), welding the front end of a second cold-rolled steel sheet to the rear end of the first cold-rolled steel sheet and putting the welded steel sheet in the continuous annealing line whose temperature gradually changes to a second annealing temperature difference from the first annealing temperature(S120), and welding the front end of a third cold-rolled steel sheet to the rear end of the second cold-rolled steel sheet and putting the welded steel sheet in a continuous annealing line being maintained at the second annealing temperature(S130), wherein an alloy component for delaying recrystallization is added at the first or second annealing temperature so that the second cold-rolled steel sheet obtains a target strength after passing through the continuous annealing line. [Reference numerals] (AA) Start; (BB) End; (S110) Inserting a first cold-rolled steel sheet(CAL: maintaining a first annealing temperature); (S120) Inserting a second cold-rolled steel sheet(Nb added steel)(CAL: the first annealing temperature→a second annealing temperature); (S130) Inserting a third cold-rolled steel sheet(CAL: maintaining the second annealing temperature) |
