| 摘要 |
Provided is a hot forging steel material with which increase of production cost due to V is limited and which has high strength and excellent normal temperature toughness and low temperature toughness even after hot forging. The hot forging steel of an embodiment contains, in mass%, C: greater than 0.30 to less than 0.40%, Si: 0.30-1.00%, Mn: 1.00-2.00%, Ti: 0.002-0.020%, P: 0.035% or less, S: 0.050-0.100%, Al: 0.050% or less, Cr: 0.02-1.49%, V: 0.02% or less, N: 0.003-0.030%, O: 0.0050% or less, and the balance Fe and impurities, and fn1 is at least 7.1, fn2 is not more than 0.264, and fn3 is at least 0.49. fn1=17C+Si+Mn+Cr (1) fn2=0.25Mn-14Ti (2) fn3=C+0.1Mn+0.28Cr (3) |
