| 摘要 |
<p>The present invention relates to a steel sheet manufacturing technique, and more specifically, to a cold rolled steel sheet suitable for an outer panel of a vehicle and a manufacturing method thereof. The manufacturing method for a cold rolled steel sheet comprises: (a) a step of reheating a slab sheet comprising 0.001-0.002 wt% of carbon (C), 0.03 wt% or lower of silicon (Si), 0.2-0.4 wt% of manganese (Mn), 0.02-0.04 wt% of phosphorus (P), 0.007 wt% or lower of sulfur (S), 0.005-0.015 wt% of niobium (Nb), 0.02-0.03 wt% of titanium (Ti), 0.02-0.06 wt% of aluminum (Al), 3-6 wt% of boron (B), 0.0024% or lower of nitrogen (N), and the remainder consisting of iron (Fe) and inevitable impurities, hot rolling the slab sheet at an Ar3 temperature or higher, and then cooling the slab sheet to roll the slab sheet at a temperature of 650°C or higher; (b) a step of pickling the rolled sheet and then cold rolling the sheet; (c) a step of annealing the cold rolled sheet and then cooling the sheet down to an Ms point temperature or lower; and (d) a step of temper-rolling the cooled sheet.</p> |
