Jfe Steel Corporation

Nisshin Flour Milling Co., Ltd.

Nkk Corporation

Bridgestone Corporation

Kobe Steel, Ltd.

Exxonmobil Upstream Research Company

Nhk Spring Co., Ltd.

Kabushiki Kaisha Kobe Seiko Sho

Sumihatsu Co., Ltd.

Ministry of Agriculture, Forestry and Fisheries Tohoku National

Shigeru Endo

Nobuyuki Ishikawa

Kazukuni Hase

Katsuyuki Ichimiya

Junji Shimamura

Toyohisa Shinmiya

Shusaku Ota

Moriyasu Nagae

Shigeki Kitsuya

Yusuke Terazawa

Minoru Suwa

Kenji Tanaka

Masao Yuga

Mitsuhiro Okatsu

Naoki Matsunaga

Kiyoshi Uwai

Shinji Ishigami

Sadao Nagata

Keiichi Kishi

Kenji Hayashi

Akira Tange

Narasimha-Rao Venkata Bangaru

Jayoung Koo

Hyun-Woo Jin

Tatsumi Kimura

Douglas Paul Fairchild

Adnan Ozekcin

Minoru Honjo

Raghavan Ayer

Seishi Tsuyama

Kyono Yasuda

Motokiyo Itoh

Toshiki Nakamura

Shinichi Kakihara

Ryuji Muraoka

Moriyasu Yamaguchi

Satoshi Nomura

Masayuki Horie

Kiwamu Shiiba

Danny Lee Beeson

Hajime Akashi

Tsuguhiro Hoshino

Seiji Ito

Koichi Hatta

Ryo Yoshikawa

Makoto Yamamori

Seiji Tago

Keiko Tanaka

Katsuyuki Hayakawa

Yoshie Negishi

Shouzou Naruse

Takeshi Sugino

Toshihiko Nakano

Douglas S Hoyt

James B LeBleu, Jr

Sonoko Karibe

Teruhisa Kinugawa

Shusaku Ohta

Katsutoshi Yamashita

Koei Tsuru

Keiichi Fujie

Masato Konishi

Osamu Hirano

Kazuyoshi Ume

Yoshibumi Yamaguchi

Toshifumi Doda

Narasimha V Bangaru

Danny L Beeson

Disclosed is, as a high-strength steel plate of API X80 grade or higher with a thickness of 38 mm or more, a thick steel plate for structural pipes or tubes that exhibits high strength in the rolling direction and excellent Charpy properties at its mid-thickness part without addition of large amounts of alloying elements. The thick steel plate for structural pipes or tubes disclosed herein has: a specific chemical composition; a microstructure at its mid-thickness part that is a dual-phase microstructure of ferrite and bainite with an area fraction of the ferrite being less than 50%, and that contains ferrite grains with a grain size of 15 &#x3bc;m or less in an area fraction of 80% or more with respect to the whole area of the ferrite; a tensile strength of 620 MPa or more; and a Charpy absorption energy vEat &#x2212;20&#xb0; C. at the mid-thickness part of 100 J or more.

Thick steel plate for structural pipes or tubes, method of producing thick steel plate for structural pipes or tubes, and structural pipes and tubes

A high-strength steel having a specified chemical composition, wherein parameter Pis 0.050% or more, the relationship (TS&#x2212;TS)/TS&#x2264;0.050 is satisfied, wherein TS is defined as tensile strength determined at a temperature of 350&#xb0; C. after aging has been performed under the condition of a Larson-Miller Parameter (LMP) of 15700, and wherein TSis defined as tensile strength determined at a temperature of 350&#xb0; C. before the aging is performed, and having a toughness represented by a vEof 100 J or more in a weld heat-affected zone, which is formed when welding is performed.

High-strength steel, method for manufacturing high-strength steel, steel pipe, and method for manufacturing steel pipe

Disclosed is, as a high-strength steel plate of API X80 grade or higher with a thickness of 38 mm or more, a thick steel plate for structural pipes or tubes that exhibits high strength in the rolling direction, excellent Charpy properties at its mid-thickness part, and high material homogeneity without addition of large amounts of alloying elements. The thick steel plate for structural pipes or tubes disclosed herein has: a specific chemical composition; a microstructure mainly composed of bainite; a tensile strength of 620 MPa or more; a Charpy absorption energy vEat &#x2212;20&#xb0; C. at the mid-thickness part of 100 J or more; a variation of Vickers hardness in a plate thickness direction &#x394;HVof 50 or less; and a variation of Vickers hardness in a plate widthwise direction &#x394;HVof 50 or less.

High-strength steel having a specified chemical composition, wherein X (%) calculated by using equation (1):=0.35Cr+0.9Mo+12.5Nb+8V&#x2003;&#x2003;(1)is 0.75% or more, wherein the symbols of chemical elements in equation (1) respectively denote the contents (mass %) of the corresponding chemical elements and wherein the symbol of a chemical element which is not included is assigned a value of 0, a microstructure having a bainite phase fraction of 50% or more, a dislocation density of 1.0&#xd7;10/mor more after aging has been performed under the condition of a Larson-Miller parameter (LMP) of 15000, and a yield strength of 550 MPa or more before and after the aging is performed, as well as methods of manufacturing such high-strength steel, is disclosed. The high-strength steel can be used as a raw material for manufacturing large diameter steel pipe having the strength properties required for its use in steam transportation.

A high toughness and high tensile strength thick steel plate has a plate thickness of 100 mm or more, wherein a reduction of area in a center of the plate thickness by tension in a plate thickness direction is 40% or more. Thus, a high tensile strength thick steel plate with excellent strength and toughness in a center of the plate thickness can be obtained with no need for a larger production line, even in the case of producing a high strength thick steel plate for which the addition amount of alloying element needs to be increased.

High toughness and high tensile strength thick steel plate and production method therefor

A steel plate has excellent strength and toughness in a mid-thickness part thereof, despite having a plate thickness of 100 mm or greater. The steel plate has a chemical composition containing specific amounts of C, Si, Mn, P, S, Cr, Ni, Al, N, B, and O, with the balance being Fe and incidental impurities, and having an equivalent carbon content Ceqof 0.65 or greater. The steel plate has a yield strength of 620 MPa or greater, a plate thickness of 100 mm or greater, and has a microstructure in which prior &#x3b3; grain size in a mid-thickness part of the steel plate has a maximum value, expressed as an equivalent circle diameter, of 150 &#x3bc;m or less, and a total area ratio of martensite and bainite in the mid-thickness part is 80% or greater.

Steel plate and method of producing same

A high-tensile-strength steel plate is provided with a new chemical composition design that guarantees the same properties as a 50 mm thick steel plate even in a steel plate with a thickness of 100 mm or greater, without the yield stress being affected by the plate thickness. By mass %, the chemical composition includes C: 0.02% to 0.08%, Si: 0.01% to 0.35%, Mn: 1.4% to 2.0%, P: 0.007% or less, S: 0.0035% or less, Al: 0.010% to 0.060%, Ni: 0.5% to 2.0%, Mo: 0.10% to 0.50%, Nb: 0.005% to 0.040%, Ti: 0.005% to 0.025%, B: less than 0.0003%, N: 0.002% to 0.005%, Ca: 0.0005% to 0.0050%, and O: 0.003% or less, with the components additionally satisfying a predetermined relationship.

High-tensile-strength steel plate and process for producing same

A weld joint with an excellent CTOD property is produced with a weld metal, using a steel plate as a base metal. The steel plate has a chemical composition including C: 0.03% to 0.09%, Si: 0.01% to 0.35%, Mn: 1.3% to 2.0%, P: 0.012% or less, S: 0.0035% or less, Al: 0.01% to 0.06%, Ni: less than 0.3%, Mo: less than 0.10%, Nb: 0.005% to 0.023%, Ti: 0.005% to 0.025%, B: less than 0.0003%, N: 0.002% to 0.005%, Ca: 0.0005% to 0.0050%, and O: 0.0030% or less, with the components additionally satisfying a predetermined relationship. The weld metal has a chemical composition including C: 0.040% to 0.090%, Si: 0.1% to 0.8%, Mn: 1.0% to 2.5%, Al: 0.020% or less, Ni: 0.1% to 1.0%, Mo: 0.05% to 0.50%, Ti: 0.005% to 0.050%, and B: 0.0015% or less, the balance being Fe and incidental impurities.

Weld joint

A pearlitic rail includes a composition including in % by mass: 0.70% to 0.90% of C; 0.1% to 1.5% of Si; 0.01% to 1.5% of Mn; 0.001% to 0.035% of P; 0.0005% to 0.030% of S; 0.1% to 2.0% of Cr, remainder of the composition consisting of Fe and inevitable impurities. Surface hardness of a rail top is not less than HB 430, and hardness at a depth of 25 mm from a surface of the rail top is not less than HB 410.

Pearlitic rail and method for manufacturing pearlitic rail

A steel plate has a chemical composition containing, by mass %, C: 0.03% or more and 0.10% or less, Si: 0.05% or more and 0.50% or less, Mn: 1.00% or more and 2.00% or less, P: 0.015% or less, S: 0.005% or less, Mo: 0.20% or less (including 0%), Nb: 0.01% or more and 0.05% or less, and the balance being Fe and inevitable impurities, and, if desired, containing, by mass %, one or more of Al: 0.005% or more and 0.1% or less, Cu: 1.00% or less, Ni: 1.00% or less, Cr: 0.50% or less, and V: 0.05% or less, in which Pcm* (%) (=C+Si/30+(Mn+Cu+Cr)/20+Ni/60+Mo/2+V/10) is 0.20 or less. The steel plate has a volume fraction of bainite in a base material of 50% or more, and has a volume fraction of island martensite (MA) in a coarse-grain region reheated in a dual-phase temperature range of 5.0% or less. A slab having the chemical composition described above that is cast using a continuous casting method is reheated at a specified temperature, hot-rolled, and then subjected to accelerated cooling to a temperature of 550&#xb0; C. or lower and 250&#xb0; C. or higher.

Steel plate for thick-walled steel pipe, method for manufacturing the same, and thick-walled high-strength steel pipe

Provided is high strength steel for springs that, compared to conventional high strength steel for springs, has excellent decarburization resistance and scale exfoliation property, by optimization of the added amounts of C, Si, Mn, and Cr as well as of Sb and Sn. The steel for springs contains C: more than 0.45 mass % and less than 0.65 mass %, Si: 0.15 mass % or more and 0.70 mass % or less, Mn: 0.10 mass % or more and 1.00 mass % or less, Cr: 0.20 mass % or more and 1.50 mass % or less, P: 0.025 mass % or less, S: 0.025 mass % or less, O: 0.0015 mass % or less, Sb: 0.010 mass % or more and less than 0.030 mass %, and Sn: 0.010 mass % or more and 0.030 mass % or less, under predetermined conditions.

Steel for spring, and method for producing spring

There is provided a thick steel plate having good multipass weld joint CTOD characteristics for low to medium heat input and a method for manufacturing the thick steel plate. A steel plate containing, on a mass percent basis, 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, wherein Ti/N, Ceq, Pcm, and ACR are in particular ranges, a base material 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 being composed of a sulfide containing Ca and Mn and an oxide containing Al and having an equivalent circular diameter of 0.1 &#x3bc;m or more. Steel having the composition described above is heated at a particular temperature, is then hot-rolled, and is cooled.

Thick steel sheet having excellent CTOD properties in multilayer welded joints, and manufacturing method for thick steel sheet

Provided are a thick steel plate with which a welded joint having good CTOD property is formed by low-to-medium heat input multipass welding and a method for producing the thick steel plate. The steel plate has a composition containing, by mass, C: 0.03% to 0.10%, 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, as needed, one or more elements such as Cu. Ti/N, Ceq, Pcm, and ACR each fall within the specific range. The effective crystal grain size of the base metal at the center of the plate in the thickness direction is 20 &#x3bc;m or less. A specific amount of a composite inclusion including a sulfide containing Ca and Mn and an oxide containing Al having an equivalent circular diameter of 0.1 &#x3bc;m or more is present at the &#xbc;-thickness position and the &#xbd;-thickness position of the plate. The steel having the above-described composition is heated to a specific temperature, hot rolled, and cooled.

A thick, high-toughness high-strength steel plate has excellent strength and toughness in the central area through the plate thickness. The thick steel plate has a specific chemical composition and includes a microstructure having, throughout an entire region in the plate thickness direction, an average prior austenite grain size of not more than 50 &#x3bc;m and a martensite and/or bainite phase area fraction of not less than 80%. A continuously cast slab having the specific chemical composition is heated to 1200&#xb0; C. to 1350&#xb0; C., hot worked with a strain rate of not more than 3/s and a cumulative working reduction of not less than 15%, and thereafter hot rolled and heat treated.

Thick, tough, high tensile strength steel plate and production method therefor

A steel composition and method from making a dual phase steel therefrom. The dual phase steel may have carbon of about 0.05% by weight to about 0.12 wt %; niobium of about 0.005 wt % to about 0.03 wt %; titanium of about 0.005 wt % to about 0.02 wt %; nitrogen of about 0.001 wt % to about 0.01 wt %; silicon of about 0.01 wt % to about 0.5 wt %; manganese of about 0.5 wt % to about 2.0 wt %; and a total of molybdenum, chromium, vanadium and copper less than about 0.15 wt %. The steel may have a first phase consisting of ferrite and a second phase having one or more of carbide, pearlite, martensite, lower bainite, granular bainite, upper bainite, and degenerate upper bainite. A solute carbon content in the first phase may be about 0.01 wt % or less.

Low yield ratio dual phase steel linepipe with superior strain aging resistance

Growing community of inventors

Tokyo, Japan

Shigeru Endo