Ultra high strength cold rolled steel sheet having excellent spot weldability and formability, ultra high strength plated steel sheet and manufacturing method therefor

Abstract

The present invention provides an ultra high strength cold rolled steel sheet having excellent spot weldability and formability. The ultra high strength cold rolled steel sheet, according to one embodiment of the present invention, comprises, in weight percent: 0.05% to 0.09% of carbon (C); 0.5% to 1.0% of silicon (Si); 2.0% to 2.8% of manganese (Mn); 0.2% to 0.5% of aluminum (Al); 0.8% to 1.2% of chromium (Cr); 0.05% to 0.10% of molybdenum (Mo); 0.03% to 0.06% of titanium (Ti); 0.001% to 0.003% of boron (B); 0.02% to 0.05% of antimony (Sb); 0.001% to 0.015% of phosphorus (P); more than 0% to 0.003% of sulfur (S); 0.004% to 0.006% of nitrogen (N); and a balance of iron (Fe) and other inevitable impurities, and the ultra high strength cold rolled steel sheet comprises a microstructure comprising ferrite and low hardness martensite.