Nippon Steel Corporation

Motomichi Hara

Kazutoshi Ichikawa

Masaki Mizoguchi

Shunsuke Yamagishi

In an H-section steel, which has a predetermined chemical composition, a thickness of the flange is from 25 to 140 mm; an average crystal grain diameter is 38 &#x3bc;m or less and the area fraction of a martensite-austenite constituent is 1.2% or less, in a plane orthogonal to the width direction of the flange, centering on a measurement positionthat is a position separated, in the width direction of the flange, from the end face in the width direction of the flange by (&#x2159;)F, and separated, in the thickness direction of the flange, from the outer face in the thickness direction of the flange by (&#xbc;)t, when the width direction length of the flange is F and the thickness of the flange is t; a yield strength or 0.2% proof stress is 385 MPa or more and a tensile strength is 490 MPa or more, in the rolling direction of the flange, when measured with respect to the entire thickness in the thickness direction of the flange at a position separated in the width direction of the flange from the end face in the width direction of the flange by (&#x2159;)F; and the absorbed energy in a Charpy test at the measurement positionat &#x2212;20&#xb0; C. is 200 J or more.

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Tokyo, Japan

Motomichi Hara