Hot rolled steel sheet having excellent crashworthiness and method for manufacturing same

A method for manufacturing a high-strength hot rolled steel sheet having an excellent yield strength, the method comprising:

• heating a steel slab including, by weight:
• 0.05 to 0.13% of carbon (C), 0.2 to 2.0% of silicon (Si), 1.3 to 3.0% of manganese (Mn), 0.01 to 0.1% of aluminum (Al), 0.001 to 0.05% of phosphorus (P), 0.001 to 0.05% of sulfur(S), and 0.001 to 0.02% of nitrogen (N), with a balance of Fe and other inevitable impurities at 1100 to 1350° C.;
• finish hot rolling the heated steel slab while controlling the sum of reduction amounts of final two rolling passes to 10 to 40% in which FDT (° C.) which is a temperature of a hot rolled sheet immediately after the finish hot rolling satisfies the following Relations 1 and 2 at a temperature between 750° C. and 1150° C.;
• first cooling the hot rolled steel sheet to a temperature of T1 defined in the following Relation 3 or lower between Ms and 520° C. at a cooling rate of 50° C./s or more, and then, second cooling the steel sheet to a coiling temperature between T1 and Ms-50° C. at a cooling rate of 50° C./s or less;
• and
• finally cooling the hot rolled steel sheet coiled after the second cooling to room temperature:
• [Relation 1]
• FDT ≥Tnr−50° C.
• wherein Tnr is a temperature at which recrystallization delay starts with Tnr=795+88×[C]+45×[Mn]+23×[Cr]+760×[Ti]+480×[Nb]−80×[Si], and each element refers to % by weight thereof,
• [Relation 2]
• Du=3.7+0.36×[C]−1.21×[Si]−0.23×[Mn]+0.19×[Cr]−41.63×[Ti]−54.44×[Nb]+0.049×[FDT-773]≤10,
• wherein Du is an indicator showing an effective crystal grain size of austenite immediately before the first cooling after the finish hot rolling, and each element refers to % by weight thereof,
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• wherein TD=820−290×[C]−90×[Mn]−70×[Cr]−62×[Mo]−35×[Si], and each element refers to weight contents thereof,
• wherein Ms is a temperature at which martensite production starts by cooling with Ms=550−330×[C]−41×[Mn]−20×[Cr]−10×[Mo]+30×[A1]−20×[Si], in ° C., and each element refers to % by weight thereof.