| 摘要 |
<p>Disclosed are a cold-rolled steel sheet and a manufacturing method thereof, wherein the cold-rolled steel sheet with a high moldability can satisfy a plastic anisotropy coefficient (r-value) of at least 2.0. The manufacturing method of the cold-rolled steel sheet according to the present invention comprises: a step of reheating a slab sheet under the condition of a slab reheating temperature (SRT) of 1150 to 1200°C; a hot-rolling the reheated sheet under the condition of a finishing delivery temperature (FDT) of 900 to 940°C; a step of coiling the hot-rolled sheet at a coiling temperature (CT) of 700 to 760°C while cooling the hot-rolled sheet under the condition of an average cooling speed of 40 to 60°C/sec; a step of cold-rolling the coiled steel sheet after acid-pickling the coiled steel sheet; and a step of annealing the cold-rolled steel sheet by raising temperature to a temperature of 680 to 700°C under the condition of an initial temperature raising speed of 10 to 15°C/sec, wherein the slab sheet comprises 0.0003 to 0.0018 wt% of C, at most 0.02 wt% of Si, at most 0.15 wt% of Mn, at most 0.018 wt% of P, at most 0.010 wt% of S, 0.02 to 0.06 wt% of Al, at most 0.004 wt% of N, 0.0025 to 0.0035 wt% of Ti, 0.005 to 0.012 wt% of Nb, and remnants Fe and inevitable impurities. [Reference numerals] (AA) Start; (BB) End; (S110) Reheat a slab (SRT: 1150 to 1200°C); (S120) Hot-roll (FDT: 900 to 940°C); (S130) Cool/coil (cooling speed: 40~60°C/sec); (S140) Acid-pickle/cold-roll; (S150) Anneal (initial temperature raising speed: 10~15°C/sec)</p> |
