Ultra-high strength steel sheet having excellent shear workability and method for manufacturing same

A method for manufacturing an ultra-high strength steel sheet having excellent shear workability, the method comprising:

• heating a steel slab including, by weight %, carbon (C):
• 0.06 to 0.14%, silicon (Si):
• 0.1 to 0.8%, manganese (Mn):
• 1.6 to 2.2%, chromium (Cr):
• 0.005 to 0.8%, phosphorus (P):
• 0.001 to 0.05%, sulfur (S):
• 0.001 to 0.01%, aluminum (Al):
• 0.01 to 0.1%, nitrogen (N):
• 0.001 to 0.01%, titanium (Ti):
• 0.01 to 0.06%, niobium (Nb):
• 0.005 to 0.06%, boron (B):
• 0.0003 to 0.0050%, and a balance of iron (Fe) and unavoidable impurities;
• finish-rolling the heated steel slab within a temperature range of 800 to 1150° C. to manufacture a hot-rolled steel sheet;
• cooling the hot-rolled steel sheet, and then coiling the cooled hot-rolled steel sheet;
• and
• cold-rolling the coiled hot-rolled steel sheet to manufacture a cold-rolled steel sheet,
• wherein the cooling is performed at an average cooling rate CRMin, obtained by Relation Expression 1 below, or higher, and is performed to a temperature between CTMin and CTMax obtained by Relational Expression 2 below,
• CRMin=190−(105×[C])+(35×[Si])−(58×[Mn])−(46×[Cr])+(15×[Ti])+(50×[Nb])−(150×[B]) [Relational Expression 1]
• CTMax=510−(120×[C])+(30×[Si])−(25×[Mn])−(22×[Cr])+(8.5×[Ti])+(14×[Nb])+(805×[B])
• CTMin=420−(45.3×[C])+(16×[Si])−(21×[Mn])−(18×[Cr]) [Relational Expression 2]
• where each element denotes a content by weight %.