| 摘要 |
A steel material superior in high temperature characteristics and toughness is provided, that is, a steel material containing, by mass%, C: 0.005% to 0.03%, Si: 0.05% to 0.40%, Mn: 0.40% to 1.70%, Nb: 0.02% to 0.25%, Ti: 0.005% to 0.025%, N: 0.0008% to 0.0045%, B: 0.0003% to 0.0030%, restricting P: 0,030% or less, S: 0.020% or less, Al: 0.03% or less, and having a balance of Fe and unavoidable impurities, where the contents of C and Nb satisfy C - Nb / 7.74 ‰¤ 0.02 and Ti-based oxides of a grain size of 0.05 to 10 µm are present in a density of 30 to 300/mm 2 . |
