| 摘要 |
An H-section steel has a predetermined chemical composition in which a thickness of a flange is 100 mm to 150 mm, at a strength evaluation position an area fraction of bainite in a steel structure is 80% or more, yield strength or 0.2% proof strength is 450 MPa or more, tensile strength is 550 MPa or more and 680 MPa or less, at a toughness evaluation position an average austenite grain size in the steel structure is 150 µm or less, and (Mg, Mn)S having a particle size of 0.005 µm to 0.5 µm is included at a density of 1.0×10 5 pieces/mm 2 to 1.0×10 7 pieces/mm 2 . |
