| 摘要 |
<p>Disclosed are a cold-rolled steel sheet and a manufacturing method thereof, wherein the cold-rolled steel sheet can secure a high surface quality through an alloy element control and a process condition control without an electromagnetic stirring apparatus or controlling casting cooling speed. The cold-rolled steel sheet according to the present invention comprises 0.0005 to 0.0050 wt% of C, at most 0.03 wt% of Si, 0.1 to 1.0 wt% of Mn, 0.01 to 0.06 wt% of Al, 0.01 to 0.10 wt% of P, at most 0.006 wt% of S, at most 0.03 wt% of Nb, at most 0.03 wt% of Ti, 0.0001 to 0.0030 wt% of B, at most 0.003 wt% of N, and remnants consisting of Fe and inevitable impurities, and has a tensile strength (TS) of at least 340 MPa, a yield point (YP) of at least 200 MPa, and an elongation (EL) of at least 36%. [Reference numerals] (AA) Start; (BB) End; (S110) Reheat a slab; (S120) Hot-roll; (S130) Cool/coil; (S140) Cold-roll; (S150) Apply annealing heat treatment; (S160) Apply hot-dip galvanizing and alloying heat treatment; (S170) Temper-roll</p> |
