Hot-rolled steel sheet having excellent durability and method for manufacturing same

A hot-rolled steel sheet having excellent durability, comprising:

• by weight %, 0.05-0.14% of carbon (C), 0.1-1.0% of silicon (Si), 0.8-1.8% of manganese (Mn), 0.001-0.03% of phosphorous (P), 0.001-0.01% of sulfur (S), 0.1-0.5% of soluble aluminum (Sol.Al), 0.3-1.0% of chromium (Cr), 0.01-0.05% of titanium (Ti), 0.03-0.06% of niobium (Nb), 0.04-0.1% of vanadium (V), 0.001-0.01% of nitrogen (N), and a balance of Fe and inevitable impurities,
• wherein Mn and Si satisfy relational formula 1 as below,
• wherein a microstructure includes a hard phase including martensite and bainite phases mixed therein with a ferrite phase as a matrix structure,
• wherein in a total fracture (area fraction) of a hard phase, a fraction of grains in which a martensite phase and a bainite phase are mixed in a single grain is 60% or higher, and relational formula 2 as below is satisfied, and
• wherein the hot-rolled steel sheet has durability fatigue lifespan of 60×ten thousand cycles or higher
• 4<Mn/Si<12 [Relational Formula 1]
• where Mn and Si refer to weight contents of respective elements
• SSGM+B/(M+B+SSGM+B)≥0.6 [Relational Formula 2]
• where M refers to a martensite phase, B refers to a bainite phase, and SSGM+B refers to a hard phase in which B and M phases are mixed in a single grain, a structure in which an M phase is present around a grain boundary, and a B phase is present in a central region, each phase is represented by area fraction (%).