Jfe Steel Corporation

Nobuo Shikanai

Kenji Hayashi

Yoshinori Watanabe

Shinichi Suzuki

Makoto Suzuki

Nobuyuki Ishikawa

Tatsumi Kimura

Junji Shimamura

Minoru Honjo

Mitsuhiro Okatsu

Tomoyuki Yokota

Katsuyuki Ichimiya

Akihide Nagao

Kenji Oi

Kimihiro Nishimura

Shinji Mitao

Tomohiro Matsushima

Shinichi Kakihara

Akihiko Tanizawa

Hitoshi Sueyoshi

Masayuki Horie

Yutaka Awajiya

Yasumitsu Kiyoto

Yasuhiro Murota

Misao Ishikawa

Akiyoshi Tsuji

Hiroshi Awajiya

Provided is a steel pipe for a linepipe having high compressive strength, a heavy wall thickness and sour gas resistance. The steel pipe has the composition which contains by mass % 0.02 to 0.06% C, 0.01 to 0.5% Si, 0.8 to 1.6% Mn, 0.012% or less P, 0.0015% or less S, 0.01 to 0.08% Al, 0.005 to 0.050% Nb, 0.005 to 0.025% Ti, 0.0005 to 0.0035% Ca, 0.0020 to 0.0060% N, and Fe and unavoidable impurities as a balance. The steel pipe has metal microstructure where a fraction of bainite is 80% or more, a fraction of M-A constituent is 2% or less and an average grain size of bainite is 5 &#x3bc;m or less.

Welded steel pipe for linepipe having high compressive strength and excellent sour gas resistance and manufacturing method thereof

Provided is a low yield ratio, high strength and high uniform elongation steel plate having excellent strain ageing resistance equivalent to API 5L X70 Grade or lower and a method for manufacturing the same. In particular, the steel plate contains 0.06% to 0.12% C, 0.01% to 1.0% Si, 1.2% to 3.0% Mn, 0.015% or less P, 0.005% or less S, 0.08% or less Al, 0.005% to 0.07% Nb, 0.005% to 0.025% Ti, 0.010% or less N, and 0.005% or less O on a mass basis, the remainder being Fe and unavoidable impurities. The low yield ratio, high strength and high uniform elongation steel plate has a metallographic microstructure that is a two-phase microstructure consisting of bainite and M-A constituent, the area fraction of the M-A constituent being 3% to 20%, the equivalent circle diameter of the M-A constituent being 3.0 &#x3bc;m or less.

Low yield ratio, high strength and high uniform elongation steel plate and method for manufacturing the same

A steel plate for line pipes containing, in terms of % by weight, C: 0.02 to 0.06%, Si: 0.5% or less, Mn: 0.8 to 1.6%, P: 0.008% or less, S: 0.0008% or less, Al: 0.08% or less, Nb: 0.005 to 0.035%, Ti: 0.005 to 0.025%, and Ca: 0.0005 to 0.0035%, and optionally contains one or more of Cu: 0.5% or less, Ni: 1% or less, Cr: 0.5% or less, Mo: 0.5% or less and V: 0.1% or less, and has a CP value of 0.95 or less represented by CP=4.46C(%)+2.37Mn(%)/6+{1.18Cr(%)+1.95Mo(%)+1.74V(%)}/5+{1.74Cu(%)+1.7Ni(%)}/15+22.36P(%), and a Ceq value of 0.30 or more represented by Ceq=C(%)+Mn(%)/6+{Cr(%)+Mo(%)+V(%)}/5 +{Cu(%)+Ni(%)}/15.

Steel plate and steel pipe for line pipes

Provided is a low yield ratio, high strength and high toughness steel plate having excellent strain ageing resistance equivalent to API 5L X70 Grade or lower and a method for manufacturing the same. The steel plate has a metallographic microstructure that is a three-phase microstructure including bainite, M-A constituent, and quasi-polygonal ferrite, the area fraction of the bainite being 5% to 70%, the area fraction of the M-A constituent being 3% to 20%, the remainder being the quasi-polygonal ferrite, the equivalent circle diameter of the M-A constituent being 3.0 &#x3bc;m or less. The steel plate has a yield ratio of 85% or less and a Charpy impact test absorbed energy of 200 J or more at &#x2212;30&#xb0; C. before or after being subjected to strain ageing treatment at a temperature of 250&#xb0; C. or lower for 30 minutes or less.

Low yield ratio, high strength and high toughness steel plate and method for manufacturing the same

An APIX100-grade high strength steel pipe includes a base material containing, in mass percentage, C: more than 0.03% and 0.08% or less, Si: 0.01% to 0.5%, Mn: 1.5% to 3.0%, P: 0.015% or less, S: 0.005% or less, Al: 0.01% to 0.08%, Nb: 0.005% to 0.025%, Ti: 0.005% to 0.025%, N: 0.001% to 0.010%, O: 0.005% or less, and B: 0.0003% to 0.0020%, further contains one or more of Cu, Ni, Cr, Mo, and V, satisfies 0.19&#x2266;P&#x2266;0.25, the balance being Fe and unavoidable impurities, and has a TS of 760 to 930 MPa, a uniform elongation of 5% or more, and a YR of 85% or less; the seam weld metal has a specific composition.

High strength steel pipe for low-temperature usage having excellent buckling resistance and toughness of welded heat affected zone and method for producing the same

The invention provides a high-strength pearlitic steel rail, which is inexpensive, and has a tensile strength of 1200 MPa or more, and is excellent in delayed fracture properties. Specifically, the rail contains, in mass percent, C of 0.6 to 1.0%, Si of 0.1 to 1.5%, Mn of 0.4 to 2.0%, P of 0.035% or less, S of 0.0005 to 0.010%, and the remainder is Fe and inevitable impurities, wherein tensile strength is 1200 MPa or more, and size of a long side of an A type inclusion is 250 mm or less in at least a cross-section in a longitudinal direction of a rail head, and the number of A type inclusions, each having a size of a long side of 1 mm to 250 mm, is less than 25 per observed area of 1 mmin the cross-section in the longitudinal direction of the rail head.

High-strength pearlitic steel rail having excellent delayed fracture properties

A steel rail including a composition of, in mass percent, C of 0.6% to 1.0%, Si of 0.1% to 1.5%, Mn of 0.4% to 2.0%, P of 0.035% or less, S of 0.010% or less, Ca of 0.0010% to 0.010%, and the remainder being Fe and inevitable impurities, wherein the tensile strength is 1200 MPa or more, and the size of a long side of a C type inclusion is 50 &#x3bc;m or less in at least a cross-section in a longitudinal direction of a rail head, and the number of Ca type inclusions, each having a size of a long side of 1 &#x3bc;m to 50 &#x3bc;m, is 0.2 to 10 per observed area of 1 mmin the cross-section in the longitudinal direction of the rail head.

High tensile strength steels that have both favorable delayed fracture resistance and a tensile strength of 600 MPa or higher and are suitably used in construction machinery, tanks, penstocks, and pipelines, as well as methods for manufacturing such steels are provided. The safety index of delayed fracture resistance (%) is 100&#xd7;(X/X), where X: reduction of area of a specimen substantially free from diffusible hydrogen, and X: reduction of area of a specimen containing diffusible hydrogen.

High tensile strength steel having favorable delayed fracture resistance and method for manufacturing the same

An internal high hardness type pearlitic rail that has a composition containing 0.73% to 0.85% by mass C, 0.5% to 0.75% by mass Si, 0.3% to 1.0% by mass Mn, 0.035% by mass or less P, 0.0005% to 0.012% by mass S, 0.2% to 1.3% by mass Cr, and the balance being Fe and incidental impurities, in which the value of [% Mn]/[% Cr] is greater than or equal to 0.3 and less than 1.0, where [% Mn] represents the Mn content, and [% Cr] represents the Cr content, and in which the internal hardness of a rail head that is defined by the Vickers hardness of a portion located from a surface layer of the rail head to a depth of at least 25 mm is greater than or equal to 380 Hv and less than 480 Hv.

Internal high hardness type pearlitic rail with excellent wear resistance and rolling contact fatigue resistance and method for producing same

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Tokyo, Japan

Nobuo Shikanai