Nippon Steel Sumitomo Metal Corporation

Nippon Steel Corporation

Masaki Mizoguchi

Kazutoshi Ichikawa

Hirokazu Sugiyama

Kazuaki Mitsuyasu

Yoshiyuki Watanabe

Suguru Yoshida

Yasushi Hasegawa

Manabu Hoshino

Tadayoshi Okada

Motomichi Hara

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.

H-section steel and method of producing the same

An H-section steel has a predetermined chemical composition, in which a Mg-containing oxide having an equivalent circle diameter of 0.005 &#x3bc;m to 0.5 &#x3bc;m is contained at a total number density of 100 pieces/mmto 5000 pieces/mm, a thickness of a flange is 100 mm to 150 mm, at a strength evaluation portion which is at a &#x2159; position from a surface of the flange in a length direction and at a &#xbc; position from the surface in a thickness direction, a fraction of bainite in a steel structure is 80% or more, and the average prior austenite grain size is 70 &#x3bc;m or more, and at a toughness evaluation portion which is at a &#xbd; position from the surface of the flange in the length direction and at a &#xbe; position from the surface of the flange in the thickness direction, the average prior austenite grain size in a steel structure is 200 &#x3bc;m or less.

An H-section steel has a predetermined chemical composition in which Ti oxides having a grain size of 0.01 &#x3bc;m to 3.0 &#x3bc;m are included at a density of 30 pieces/mmor more, a thickness of a flange is 100 mm to 150 mm, an area fraction of bainite at a &#x2159; position from a surface of the flange in a length direction and at a &#xbc; position from the surface thereof in a thickness direction is 80% or more, a yield strength or 0.2% proof stress is 450 MPa or more, and a tensile strength is 550 MPa or more, a Charpy absorbed energy at 21&#xb0; C. at a &#xbd; position from the surface of the flange in the length direction and at a &#xbe; position from the surface thereof in the thickness direction is 100 J or more, and an average austenite grain size is 50 &#x3bc;m to 200 &#x3bc;m.

This H-beam steel has a composition including C, Si, Mn, Cu, Ni, V, Al, Ti, B, N, and O, and further including at least one of Mo and Nb, in which Ceq obtained in Equation 1 described below falls in a range of 0.37 to 0.50, the thickness of a flange falls in a range of 100 to 150 mm, and the area fraction of bainite at a depth of one quarter of the thickness of the flange from the external surface of the flange is 60% or more.Ceq=C+Mn/6+(Mo+V)/5+(Ni+Cu)/15&#x2003;&#x2003;Equation 1,where C, Mn, Mo, V, Ni, and Cu represent the amount of each element contained.

High-strength ultra-thick H-beam steel

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 &#x3bc;m or less, and (Mg, Mn)S having a particle size of 0.005 &#x3bc;m to 0.5 &#x3bc;m is included at a density of 1.0&#xd7;10pieces/mmto 1.0&#xd7;10pieces/mm.

There is provided an H-section steel in which a number density of oxide particles having an equivalent circle diameter of 0.005 &#x3bc;m to 2.0 &#x3bc;m per unit area is 100 pieces/mmto 5000 pieces/mm, the oxide particles includes Ca, Al, and O as a composition, the amount of Ca is 5% or more, the amount of Al is 5% or more, and a total amount of Ca and Al is 50% or more by mass ratio excluding O in the oxide particles, a thickness of the flange is 100 mm to 150 mm, a bainite fraction in a metallographic structure of the flange is 80% or more at a strength evaluation position, and an average prior austenite grain size in the metallographic structure of the flange is 200 &#x3bc;m or less at a toughness evaluation position.

H-Section steel

The present invention provides high temperature strength and fire-resistant steel superior in weld joint reheat embrittlement resistance and toughness which is produced using steel of a room temperature strength of the 400 to 600N/mmclass containing as main ingredients C: 0.010% to less than 0.05%, Si: 0.01 to 0.50%, Mn: 0.80 to 2.00%, Cr: 0.50% to less than 2.00%, V: 0.03 to 0.30%, Nb: 0.01 to 0.10%, N: 0.001 to 0.010%, and Al: 0.005 to 0.10%, limiting the contents of Ni, Cu, Mo, and B, and satisfying the relationship of 4Cr[%]-5Mo[%]-10Ni[%]-2Cu[%]-Mn[%]&#x3e;0.

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Tokyo, Japan

Masaki Mizoguchi