A method for manufacturing a hot-rolled steel sheet, comprising:
- a slab heating operation of heating a slab including by wt %, 0.1 to 0.25% of carbon (C), 0.2 to 2.0% of manganese (Mn), 0.3% or less of silicon (Si), 0.05% or less of aluminum (Al), 0.05% or less of phosphorous (P), 0.03% or less of sulfur (S), 0.01% or less of nitrogen (N), 0.005 to 0.05% of titanium (Ti), 0.0005 to 0.005% of boron (B), 0.01% or less of niobium (Nb), 0.1% or less of molybdenum (Mo), 0.1% or less of vanadium (V), and a balance of iron (Fe) and inevitable impurities;
- a hot rolling operation of hot rolling the heated slab at a rolling finish temperature (Tfm) satisfying the following Relational expression 3, to provide a steel sheet;
- a first cooling operation of cooling the hot-rolled steel sheet at a first cooling rate to a first cooling end temperature (T1) satisfying the following Relational expression 4;
- a second cooling operation of cooling the first-cooled steel sheet at a second cooling rate of 50 to 500° C./s, faster than the first cooling rate to a second cooling end temperature (T2) satisfying the following Relational expression 5;
- a third cooling operation of cooling the second-cooled steel sheet at a third cooling rate, slower than the second cooling rate to a third cooling end temperature (T3) satisfying the following Relational expression 6;
- a coiling operation of coiling the third-cooled hot-rolled steel sheet at the third cooling end temperature (T3);
- and
- a heat treatment operation of heat treating the coiled steel sheet in a temperature range of 450 to 720° C.,
- Tfm(° C.)≥800+3000*[Ti]+10000*[Nb]−20*t{circumflex over ( )}(½) [Relational expression 3]
- in Relational expression 3, [Ti] and [Nb] refer to contents (wt %) of titanium (Ti) and niobium (Nb) included in the slab, respectively, and t refers to a thickness (mm) of the hot-rolled steel sheet,
- Tfm(° C.)−80° C.≤T1(° C.)≤Tfm(° C.)−5° C. [Relational expression 4]
- in Relational expression 4, Tfm refers to a rolling finish temperature (Tfm) of the hot rolling operation,
- T2(° C.)≤750−270*[C]−90*[Mn] [Relational expression 5]
- in Relational expression 5, [C] and [Mn] refer to contents (wt %) of carbon (C) and manganese (Mn) included in the slab, respectively,
- 540−423*[C]−30.4*[Mn]≤T3(° C.)<T2(° C.) [Relational expression 6]
- in Relational expression 6, T2 refers to the second cooling end temperature (T2) of the second cooling operation, and [C] and [Mn] refer to contents of carbon (C) and manganese (Mn) included in the slab, respectively (by weight %).