Patent ID: 10844466

Abstract:
There is provided a hot forging steel including, by mass %, C: more than 0.30% and less than 0.60%, Si: 0.10% to 0.90%, Mn: 0.50% to 2.00%, S: 0.010% to 0.100%, Cr: 0.01% to 1.00%, Al: more than 0.005% and 0.100% or less, N: 0.0030% to 0.0200%, Bi: more than 0.0001% and 0.0050% or less, Ti: 0% or more and less than 0.040%, V: 0% to 0.30%, Ca: 0% to 0.0040%, Pb: 0% to 0.40%, and a remainder including Fe and impurities, in which P and O in the impurities are respectively P: 0.050% or less and O: 0.0050% or less, an expression d+3σ<20 is satisfied, and a presence density of MnS having an equivalent circle diameter of smaller than 2.0 μm is 300 pieces/mm2 or more in a cross section parallel to a rolling direction of a steel.