Nippon Steel Sumitomo Metal Corporation

Nippon Steel Corporation

Kazutoshi Ichikawa

Masaki Mizoguchi

Hirokazu Sugiyama

Kazuaki Mitsuyasu

Tadashi Ishikawa

Ryuichi Honma

Hidetoshi Ito

Noriaki Onodera

Manabu Hoshino

Teruyuki Wakatsuki

Shunsuke Yamagishi

Motomichi Hara

Kohichi Yamamoto

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

Provided is a steel H-shape for low temperature service including a predetermined chemical composition. A CEV obtained by CEV=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15 is 0.40 or less. A sum of an area ratio of one or both of ferrite and bainite at a 1/4 position from an outer side across a thickness of a flange and a 1/6 position from an outer side across a flange width is 90% or more, and an area ratio of a hard phase is 10% or less. An effective grain size is 20.0 &#x3bc;m or less, and a grain size of the hard phase is 10.0 &#x3bc;m or less. 30 pieces/mmor more Ti oxides having an equivalent circle diameter ranging from 0.01 to 3.0 &#x3bc;m are included. The thickness of the flange ranges from 12 to 50 mm.

Steel H-shape for low temperature service and manufacturing method therefor

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.

In a steel sheet pile according to the present invention, a carbon equivalent CEis 0.260 to 0.500, a structure includes a ferrite, a pearlite, a Widmanst&#xe4;tten ferrite, and a precipitate, the precipitate is one or both of Nb carbonitride and V carbonitride, a total number density of the precipitate is 0.10 to 0.30 pieces/&#x3bc;m, a total area ratio of the ferrite and the pearlite is 70% or more, an area ratio of the Widmanst&#xe4;tten ferrite is 1% or more, an average grain size of the ferrite and the pearlite is 10 to 80 &#x3bc;m, and a yield strength is 460 MPa or more.

Steel sheet pile and method for manufacturing the same

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.

This H-beam steel contains, in mass %, C, Si, Mn, Al, Ti, N, O, Nb, and B. The H-beam steel has composition in which the amount of Nb and the amount of B satisfy, in mass %, 0.070&#x2266;Nb+125B&#x2266;0.155, and has a metal structure in which, in a microstructure, an area fraction of bainite is not less than 70%, a total of an area fraction of pearlite and an area fraction of cementite is not more than 15%, and the remainder is at least one of ferrite and island martensite. The effective crystalline-grain size of the bainite is not more than 40 &#x3bc;m, and the thickness of a flange falls in a range of 12 to 40 mm.

High-strength H-beam steel exhibiting excellent low-temperature toughness and method of manufacturing same

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

A welding joint comprises a pair of steel materials, and a welding metal that is formed with a high-energy density beam at a butt welding portion between the pair of steel materials, wherein a transformation starting temperature Ms that is calculated by a following formula: Ms(&#xb0; C.)=371&#x2212;353C&#x2212;22Si&#x2212;24.3Mn&#x2212;7.7Cu&#x2212;17.3Ni&#x2212;17.7Cr&#x2212;25.8Mo, using a composition of mass % of the welding metal is 250&#xb0; C. or less.

Butt welding joint using high-energy density beam

A butt-welded joint of a welded structure which includes a pair of target metals; a weld bead formed by irradiating a high-energy density beam to a butt portion between the pair of the target metals and has a width W on the irradiated side surface; and a pair of altered zones consisting of heat-affected zones formed by irradiating another high-energy density beam to both sides of the center of the weld bead in the weld bead width direction such that the pair of the altered zones are located on respective sides of the center of the weld bead and each has a band shape extending in the weld bead length direction and a method for manufacturing the butt-welded joint of the welded structure.

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Tokyo, Japan

Kazutoshi Ichikawa