Jfe Steel Corporation

Jfe Steel Corporatin

Hitachi, Ltd.

Naoki Takayama

Kazukuni Hase

Yusuke Terazawa

Kenji Hayashi

Yoshiaki Murakami

Yuji Tanaka

Hidekazu Minami

Takako Yamashita

Shigeki Kitsuya

Shinichi Miura

Shinsuke Inoue

Yusaku Takemura

Yasuhiro Murota

Keiji Ueda

Tomoaki Terunuma

Gorou Satou

The steel plate has a specific chemical composition, and a microstructure where a volume fraction of martensite at a depth of 1 mm from a surface of the steel plate is 95% or more, and at a depth of 1 mm from a surface of the steel plate, a Vickers hardness at 400° C. is 288 or more, and a Brinell hardness at 25° C. is 360 HBW10/3000 to 490 HBW10/3000.

Wear-resistant steel plate and method for producing same

A high-strength cold-rolled steel sheet having a high yield ratio and excellent stretch flangeability and a method for manufacturing the steel sheet. The high-strength cold-rolled steel sheet has a chemical composition including, by mass %, C: 0.10 to 0.30%, Si: 0.50 to 2.00%, Mn: 2.5 to 4.0%, P: 0.050% or less, S: 0.020% or less, Al: 0.10% or less, N: 0.01% or less, Ti: 0.100% or less, and B: 0.0003 to 0.0030%, with the balance being Fe and incidental impurities. N and Ti satisfy a specified formula, and the total area fraction of martensite and bainite is 95% or more. The number density of bainite grains having an area of 3 μmor more and a carbon concentration of less than 0.7C is 1200 grains/mmor less.

High-strength cold-rolled steel sheet and method for manufacturing the same

An abrasion-resistant steel plate comprises: a chemical composition containing, in mass %, C: 0.20% to 0.45%, Si: 0.01% to 1.0%, Mn: 0.3% to 2.5%, P: 0.020% or less, S: 0.01% or less, Cr: 0.01% to 2.0%, Ti: 0.10% to 1.00%, B: 0.0001% to 0.0100%, Al: 0.1% or less, N: 0.01% or less, and a balance consisting of Fe and inevitable impurities; and a microstructure in which a volume fraction of martensite is 90% or more, and a prior austenite grain size is 80 &#x3bc;m or less, wherein a number density of TiC precipitate having a size of 0.5 &#x3bc;m or more is 400 particles/mmor more, and a Mn content [Mn] and a P content [P] in a plate thickness central segregation area satisfy 0.04[Mn]+[P]&#x3c;0.50.

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

An abrasion-resistant steel plate comprises: a specific chemical composition; and a microstructure in which a volume fraction of martensite at a depth of 1 mm from a surface of the abrasion-resistant steel plate is 90% or more, and a prior austenite grain size in a plate thickness central part at the mid-thickness of the abrasion-resistant steel plate is 80 &#x3bc;m or less, wherein hardness at a depth of 1 mm from the surface of the abrasion-resistant steel plate is 460 to 590 HBW 10/3000 in Brinell hardness, and a concentration [Mn] of Mn in mass % and a concentration [P] of P in mass % in a plate thickness central segregation area satisfy 0.04[Mn]+[P]&#x3c;0.50.

Provided is an abrasion-resistant steel plate which has high hardness up to the mid-thickness part thereof although the steel plate is 50 mm or more, and can be manufactured at low cost. The abrasion-resistant steel plate has a specific chemical composition having DI* of 120 or more, where DI* is defined by the following Formula (1): DI*=33.85&#xd7;(0.1&#xd7;C)&#xd7;(0.7&#xd7;Si+1)&#xd7;(3.33&#xd7;Mn+1)&#xd7;(0.35&#xd7;Cu+1)&#xd7;(0.36&#xd7;Ni+1)&#xd7;(2.16&#xd7;Cr+1)&#xd7;(3&#xd7;Mo+1)&#xd7;(1.75&#xd7;V+1)&#xd7;(1.5&#xd7;W+1) . . . (1), has HBof 360 HBW10/3000 to 490 HBW10/3000, HBbeing a Brinell hardness at a depth of 1 mm from a surface, has a hardness ratio, HBto HB, of 75% or more, HBbeing a Brinell hardness at a mid-thickness position, and has a plate thickness of 50 mm or more.

Abrasion-resistant steel plate and method of manufacturing same

An abrasion-resistant steel plate that can achieve both gas cutting cracking resistance and abrasion resistance at low cost is provided. An abrasion-resistant steel plate comprises: a chemical composition containing, in mass %, C: more than 0.34% and 0.50% or less, Si: 0.01% to 1.0%, Mn: 0.30% to 2.00%, P: 0.015% or less, S: 0.005% or less, Cr: 0.01% to 2.00%, Al: 0.001% to 0.100%, N: 0.01% or less, and a balance consisting of Fe and inevitable impurities; and a microstructure in which a volume fraction of martensite at a depth of 1 mm from a surface of the abrasion-resistant steel plate is 90% or more, and a prior austenite grain size at the mid-thickness of the abrasion-resistant steel plate is 80 &#x3bc;m or less, wherein hardness at a depth of 1 mm from the surface of the abrasion-resistant steel plate is 560 HBW 10/3000 or more in Brinell hardness, and a concentration [Mn] of Mn in mass % and a concentration [P] of P in mass % in a plate thickness central segregation area satisfy 0.04[Mn]+[P]&#x3c;0.45.

An abrasion-resistant steel plate comprises: a specific chemical composition; and a microstructure in which a volume fraction of martensite at a depth of 1 mm from a surface of the abrasion-resistant steel plate is 90% or more, and a prior austenite grain size at the mid-thickness of the abrasion-resistant steel plate is 80 &#x3bc;m or less, wherein hardness at a depth of 1 mm from the surface of the abrasion-resistant steel plate is 360 to 490 HBW 10/3000 in Brinell hardness, and a concentration [Mn] of Mn in mass % and a concentration [P] of P in mass % in a plate thickness central segregation area satisfy 0.04[Mn]+[P]&#x3c;0.55.

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Tokyo, Japan

Naoki Takayama