Jfe Steel Corporation

Hitoshi Sueyoshi

Nobuyuki Ishikawa

Yoshihiro Yazawa

Tomoyuki Yokota

Shigeki Kitsuya

Kimihiro Nishimura

Nobuo Shikanai

Yota Kuronuma

Akihiko Tanizawa

Masayuki Horie

Keiichiro Kishi

Shunichi Tachibana

Toshiyuki Hoshino

Yasumitsu Kiyoto

Provided is an abrasion-resistant steel plate excellent in both abrasion resistance and wide bending workability. An abrasion-resistant steel plate comprises a specific chemical composition, wherein a volume fraction of martensite at a depth of 1 mm from a surface of the abrasion-resistant steel plate is 90% or more, hardness at a depth of 1 mm from the surface is 500 HBW 10/3000 to 650 HBW 10/3000 in Brinell hardness, and a transverse direction hardness difference is 30Hv10 or less in Vickers hardness, the transverse direction hardness difference being defined as a difference in the hardness at a depth of 1 mm from the surface between two points adjacent at intervals of 10 mm in a transverse direction of the abrasion-resistant steel plate.

Abrasion-resistant steel plate and method of producing abrasion-resistant steel plate

Provided is an abrasion-resistant steel plate excellent in both abrasion resistance and wide bending workability. An abrasion-resistant steel plate comprises a specific chemical composition, wherein a volume fraction of martensite at a depth of 1 mm from a surface of the abrasion-resistant steel plate is 90% or more, a number density of TiC precipitates of 0.5 μm or more in equivalent circular diameter at a depth of 1 mm from the surface is 400/mmor more, hardness at a depth of 1 mm from the surface is 360 HBW 10/3000 or more in Brinell hardness, and a transverse direction hardness difference is 30Hv10 or less in Vickers hardness, the transverse direction hardness difference being defined as a difference in the hardness at a depth of 1 mm from the surface between two points adjacent at intervals of 10 mm in a transverse direction of the abrasion-resistant steel plate.

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 are a steel pipe for a linepipe with high compressive strength and a heavy wall thickness, and a method of manufacturing the same. Lowering of yield stress caused by a Bauschinger effect can be suppressed by optimizing the metal microstructure of a steel plate without requiring particular forming conditions in forming the steel pipe, and without requiring heat treatment after pipe making. A steel pipe has the composition which contains by mass % 0.03 to 0.10% C, 0.30% or less Si, 1.00 to 2.00% Mn, 0.015% or less P, 0.003% or less S, 0.080% or less Al, 0.005 to 0.035% Nb, 0.005 to 0.020% Ti, and Fe and unavoidable impurities as a balance. The steel pipe has metal microstructure where a fraction of bainite is 60% or more, a fraction of rolled ferrite is 5% or less, and a fraction of M-A constituent (MA) is 3% or less.

Welded steel pipe for linepipe with high compressive strength and manufacturing method thereof

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Fukuyama, Japan

Hitoshi Sueyoshi