STEEL MATERIAL

Claims

A steel material is provided that has high strength and excellent low-temperature toughness in an extremely low temperature environment of -80°C or below. A steel material according to this disclosure comprises C: 0.09% or less, Si: 0.60% or less, Mn: 1.0 to 2.5%, P: 0.05% or less, S: 0.005% or less, Ti: 0.005 to 0.050%, Al: 0.005 to 0.100%, N: 0.0050 to 0.0150%, O: 0.0050% or less, and the balance: Fe and impurities, with Fn1 defined by Formula (1) being 5.0 or more, Fn2 defined by Formula (2) being 1.80 or less, and the yield strength being 448 MPa or more. In the steel material, the number density of Ti-containing particles is 0.8 × 10 18 / mm 3 or more, and among the Ti-containing particles, the number ratio of Ti-containing particles with an equivalent circular diameter of 60 nm or less is 75% or more. Fn1 = Ti × N × 10 5 (1) Fn2 = Ti / N (2).