Jfe Steel Corporation

Kawasaki Steel Corporation

Ntn Corporation

Jfe Steel Corporatin

Kazukuni Hase

Katsuyuki Ichimiya

Yusuke Terazawa

Shigeru Endo

Kenji Hayashi

Minoru Honjo

Hideto Kimura

Naoki Takayama

Takashi Iwamoto

Shigeki Kitsuya

Takaaki Toyooka

Keniti Amano

Tatsumi Kimura

Toshiyuki Hoshino

Yasuhiro Omori

Masao Yuga

Naoki Matsunaga

Tomoyuki Yokota

Tohru Hayashi

Akihiko Tanizawa

Ryuji Muraoka

Toshio Fujita

Nobuyuki Ishikawa

Kazuhiko Yoshida

Yuki Toji

Hideyuki Kimura

Isao Hirai

Kunikazu Tomita

Satoshi Ueoka

Junji Shimamura

Kiyoshi Uwai

Kyono Yasuda

Keisuke Ando

Takayasu Takubo

Akio Ohmori

Yoshiaki Murakami

Kimihiro Nishimura

Masayoshi Nakamura

Shinji Mitao

Yuta Tamura

Koichi Nakashima

Shusaku Ota

Kohei Yoshino

Yota Kuronuma

Daichi Izumi

Masayuki Horie

Hirofumi Ohtsubo

Yusaku Takemura

Yasuhiro Murota

Ryo Nagao

Keiji Ueda

Ryo Arao

Teruhisa Kinugawa

Yoshiko Takeuchi

Kazuya Tokunaga

A method for producing a steel material for line pipes including heating a steel having a specific composition to a temperature of 1000° C. to 1200° C.; performing hot rolling such that a cumulative rolling reduction ratio in a non-recrystallization temperature range is 60% or more, a cumulative rolling reduction ratio in a temperature range of (a rolling finish temperature +20° C.) or less is 50% or more, and a rolling finish temperature is the Artransformation point or more and 790° C. or less; subsequently performing accelerated cooling from a temperature of the Artransformation point or more, at a cooling rate of 10° C./s or more, to a cooling stop temperature of 200° C. to 450° C.; and then performing reheating such that the temperature of a surface of the steel plate is 350° C. to 550° C. and the temperature of the center of the steel plate is less than 550° C.

Steel material for line pipes, method for producing the same, and method for producing line pipe

A method for selecting a rail steel and a wheel steel comprising: selecting a rail steel and a wheel steel to be used as a rail and a wheel on an actual track, respectively, the rail steel and the wheel steel having a specific chemical composition, such that the rail comprises a head portion having a yield strength YSof 830 MPa or more, the wheel comprises a rim portion having a yield strength YSof 580 MPa or more, and a ratio YS/YSof the yield strength YSat the head portion of the rail to the yield strength YSat the rim portion of the wheel falls within a range of: 0.85&#x2264;YS/YS&#x2264;1.95 (1).

Method for selecting rail steel and wheel steel

A method for producing a steel material for line pipes which has a tensile strength of 570 MPa or more, a compressive strength of 440 MPa or more, and a thickness of 30 mm or more, the method including heating a steel having a specific composition to a temperature of 1000&#xb0; C. to 1200&#xb0; C.; performing hot rolling such that a cumulative rolling reduction ratio in a non-recrystallization temperature range is 60% or more, a cumulative rolling reduction ratio in a temperature range of (a rolling finish temperature +20&#xb0; C.) or less is 50% or more, and a rolling finish temperature is the Artransformation point or more and 790&#xb0; C. or less; and subsequently performing accelerated cooling from a cooling start temperature of the Artransformation point or more, at a cooling rate of 10&#xb0; C./s or more, until the temperature of a surface of a steel plate reaches 300&#xb0; C. to 500&#xb0; C.

Provided is a steel material for high heat input welding having excellent welding heat affected zone low-temperature toughness at &#x2212;55&#xb0; C. in the case that the steel material is welded by high heat input welding with a heat input of more than 80 kJ/cm. The steel material may be used in low-temperature storage tanks, for example. The steel material for high heat input welding includes, in mass %, C: 0.04 to 0.09%, Si: 0.15 to 0.25%, Mn: 1.40 to 2.00%, P: 0.015% or less, S: 0.0005 to 0.0040%, Al: 0.030 to 0.080%, Ti: 0.005 to 0.025%, B: 0.0003 to 0.0020%, Ca: 0.0005 to 0.0030%, N: 0.0030 to 0.0060%, O: 0.0040% or less, Nb: 0.005% or less, and Mo: 0.005% or less, the balance being Fe and incidental impurities.

Steel material for high heat input welding

Excellent CTOD properties for multilayer welding joint is provided for a steel plate. The steel plate comprises a specific chemical composition with Ceq of 0.45% or less where Ceq (%)=[C]+[Mn]/6+([Cu]+[Ni])/15+([Cr]+[Mo]+[V])/5 . . . (1) and Pcm of 0.22% or less where Pcm (%)=[C]+[Si]/30+([Mn]+[Cu]+[Cr])/20+[Ni]/60+[Mo]/15+[V]/10+5 [B] . . . (2); an average effective grain size of 20 &#x3bc;m or less at a mid-thickness part of the steel plate; and porosities having an equivalent circular diameter of 200 &#x3bc;m or more, the number of the porosities per mmbeing 0.1/mmor less.

Steel plate and method of producing same

A steel plate for high-strength and high-toughness steel pipes has a chemical composition containing, by mass %, C: 0.03% or more and 0.08% or less, Si: more than 0.05% and 0.50% or less, Mn: 1.5% or more and 2.5% or less, P: 0.001% or more and 0.010% or less, S: 0.0030% or less, Al: 0.01% or more and 0.08% or less, Nb: 0.010% or more and 0.080% or less, Ti: 0.005% or more and 0.025% or less, and N: 0.001% or more and 0.006% or less, and further containing, by mass %, at least one selected from Cu: 0.01% or more and 1.00% or less, Ni: 0.01% or more and 1.00% or less, Cr: 0.01% or more and 1.00% or less, Mo: 0.01% or more and 1.00% or less, V: 0.01% or more and 0.10% or less, and B: 0.0005% or more and 0.0030% or less, with the balance being Fe and inevitable impurities. The steel plate has a microstructure in which an area fraction of ferrite at a &#xbd; position of a thickness of the steel plate is 20% or more and 80% or less and deformed ferrite constitutes 50% or more and 100% or less of the ferrite.

Steel plate for high-strength and high-toughness steel pipes and method for producing steel plate

A case hardening steel suitable as raw material for producing a mechanical structural part having high rotating bending fatigue strength and pitting fatigue strength at relatively low cost and a method of producing the case hardening steel are provided. A case hardening steel comprises a chemical composition containing, in mass %, C, Si, Mn, P, S, Cr, Mo, Al, N, and O in a predetermined relationship, with a balance being Fe and inevitable impurities, wherein &#x221a;I&#x2264;80 (where I denotes an area (&#x3bc;m) of an oxide-based inclusion located in a fish eye central portion at a fracture surface after subjecting the case hardening steel to carburizing-quenching and tempering and then performing a rotating bending fatigue test).

Case hardening steel, method of producing case hardening steel, and method of producing gear part

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.

A rail achieves a high 0.2% proof stress after straightening treatment, the high 0.2% proof stress being effective at improving rolling contact fatigue resistance of the rail, by hot rolling a steel raw material to obtain a rail, the steel raw material having a chemical composition containing C: 0.70% to 0.85%, Si: 0.1% to 1.5%, Mn: 0.4% to 1.5%, P: 0.035% or less, S: 0.010% or less, and Cr: 0.05% to 1.50% with the balance being Fe and inevitable impurities; straightening the rail with a load of 50 tf or more; and subsequently subjecting the rail to heat treatment in which the rail is held in a temperature range of 150&#xb0; C. or more and 400&#xb0; C. or less for 0.5 hours or more and 10 hours or less.

Method for producing rail

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.

A high manganese content deformed reinforcing bar having an austenite single phase microstructure has excellent bending workability. A deformed reinforcing bar includes a chemical composition containing, in mass %, C: 0.7% or more and 1.2% or less, Si: 1.0% or less, Mn: 9% or more and 15% or less, Cr: 1.0% or less, P: 0.03% or less, and S: 0.05% or less, the balance consisting of Fe and inevitable impurities; and a microstructure comprising an austenite single phase. The ratio of the difference between the maximum and minimum hardness at a periphery of a cross-section perpendicular to the longitudinal direction with respect to a central average hardness is 15% or less. Two or more ribs extend in the longitudinal direction at equal intervals in a cross-sectional circumferential direction. The ratio of the difference between the maximum and minimum width of the ribs to the minimum width is 50% or less.

Deformed reinforcing bar

A steel plate comprising, by mass %: C: 0.03% to 0.12%, Si: 0.5% or less, Mn: 1.0% to 2.0%, P: 0.015% or less, S: 0.0005% to 0.0050%, Al: 0.005% to 0.060%, Ni: 0.5% to 2.0%, Ti: 0.005% to 0.030%, N: 0.0015% to 0.0065%, O: 0.0010% to 0.0050%, Ca: 0.0005% to 0.0060%, and optionally one or two or more of Cu and the like. Ti/N, Ceq, Pcm, and ACR are in particular ranges, a base metal of the plate has an effective grain size of 20 &#x3bc;m or less at half the thickness of the plate, and the plate contains a particular number of complex inclusions at &#xbc; and &#xbd; of the thickness of the plate. The complex inclusions comprise a sulfide containing Ca and Mn and an oxide containing Al and having an equivalent circular diameter of 0.1 &#x3bc;m or more.

Thick steel plate having good multipass weld joint CTOD characteristics and method for manufacturing the same

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Tokyo, Japan

Kazukuni Hase