Jfe Steel Corporation

Junji Shimamura

Nobuyuki Ishikawa

Shigeru Endo

Shusaku Ota

Nobuo Shikanai

Kenji Adachi

Kazukuni Hase

Mitsuhiro Okatsu

Kimihiro Nishimura

Yutaka Matsui

Takafumi Ozeki

Tomoyuki Yokota

Kazuki Terada

Hiroshi Nakata

Sota Goto

Ryosuke Sakai

Kyono Yasuda

Yuta Tamura

Seishi Tsuyama

Yota Kuronuma

Ryuji Muraoka

Daichi Izumi

Hiroki Imanaka

Shusaku Ohta

A steel material for line pipes has a specific composition. The metallic microstructure of the steel material at a ⅛-plate thickness position below the surface includes bainite of an area fraction of 85% or more, polygonal ferrite of an area fraction of 10% or less, and martensite-austenite constituent of an area fraction of 5% or less. The 0.23% compressive strength of a portion of the steel material which extends from the surface to the ⅛-plate thickness position in a transverse direction is 340 MPa or more. The temperature at which a percent ductile fracture of the steel material measured in a DWTT test becomes 85% or more is −10° C. or less.

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

Provided are: a mechanical property measuring apparatus and method that can accurately measure a mechanical property through physical quantities; a substance manufacturing equipment and method that can improve the production yield rate and high-quality substance. A mechanical property measuring apparatus () comprises: a physical quantity measuring unit () configured to measure a plurality of physical quantities of a measured object that includes a substance and a film on a surface of the substance; a mechanical property calculating unit () configured to calculate, using a plurality of calculation models each for calculating a mechanical property of the substance and at least two of the plurality of physical quantities measured, the mechanical property of the substance for each of the plurality of calculation models; and a selection processing unit () configured to select one mechanical property based on the at least two of the plurality of physical quantities.

Mechanical property measuring apparatus, mechanical property measuring method, substance manufacturing equipment, substance management method, and substance manufacturing method

A metal structure evaluator for rolled steel sheets includes: a magnetic property measuring unit configured to measure a magnetic property of an evaluation target point in at least two or more different magnetization directions by performing, in the at least two or more different magnetization directions, processing of: applying a magnetic field on a surface of a rolled steel sheet in one direction; and measuring a magnetic property of the evaluation target point on the surface of the rolled steel sheet; and a determination unit configured to determine a metal structure of the evaluation target point based on the magnetic property measured by the magnetic property measuring unit.

Metal structure evaluator for rolled steel sheets, method for evaluating metal structure of rolled steel sheet, production facility of steel product, method for manufacturing steel product, and method of quality management of steel product

Disclosed is a clad steel plate with further improved low temperature toughness along with excellent HIC resistance while ensuring a tensile strength of 535 MPa or more. A clad steel plate includes: a base steel; and a clad metal made of a corrosion resistant alloy bonded to one surface of the base steel, in which the base steel has: a chemical composition with appropriately controlled values of ACR and P; and a steel microstructure in which bainite is present in an area fraction of 94% or more at a &#xbd; thickness position in a thickness direction of the base steel, and with an average crystal grain size of 25 &#x3bc;m or less, and shear strength at a bonded interface between the base steel and the cladding metal is 300 MPa or more.

Clad steel plate and method of producing the same

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 hot-rolled steel sheet for a heavy-wall, high-strength line pipe, the steel sheet having a chemical composition including, in mass %, C: 0.02 to 0.20%, Mn: 0.80 to 2.10%, Si: 0.01 to 0.50%, P: 0.034% or less, S: 0.0050% or less, Nb: 0.01 to 0.15%, Ti: 0.001 to 0.030%, and Al: 0.001 to 0.080%, the balance being Fe and incidental impurities, the steel sheet having a microstructure in which a main phase is a continuous cooling transformation structure and in which {001}grains in a plane whose normal direction is the sheet width direction constitute an area fraction of 10% or less and have a combined size of 10 &#x3bc;m or less, wherein the steel sheet has a tensile strength of 520 MPa or greater, and, in a drop weight tear test, a temperature at which a percent ductile fracture reaches 85% is &#x2212;25&#xb0; C. or lower.

Hot-rolled steel sheet for heavy-wall, high-strength line pipe, welded steel pipe for heavy-wall, high-strength line pipe, and method for producing the welded steel pipe

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 steel plate has a chemical composition containing, by mass %, C: 0.03% or more and 0.08% or less, Si: 0.01% or more and 1.0% or less, Mn: 1.2% or more and 3.0% or less, P: 0.015% or less, S: 0.005% or less, Al: 0.08% or less, Nb: 0.005% or more and 0.07% or less, Ti: 0.005% or more and 0.025% or less, N: 0.010% or less, O: 0.005% or less and the balance being Fe and inevitable impurities, a structure being a dual-phase structure consisting of a bainite phase and island martensite, wherein the area fraction of the island martensite is 3% to 15%, the equivalent circle diameter of the island martensite is 3.0 &#x3bc;m or less, and the remainder of the structure is a bainite phase.

High strength steel plate having low yield ratio excellent in terms of strain ageing resistance, method of manufacturing the same and high strength welded steel pipe made of the same

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

A steel plate has a chemical composition containing, by mass %, C: 0.03% or more and 0.08% or less, Si: 0.01% or more and 1.0% or less, Mn: 1.2% or more and 3.0% or less, P: 0.015% or less, S: 0.005% or less, Al: 0.08% or less, Nb: 0.005% or more and 0.07% or less, Ti: 0.005% or more and 0.025% or less, N: 0.010% or less, O: 0.005% or less and the balance being Fe and inevitable impurities, a metallographic structure including a bainite phase and island martensite, and a polygonal ferrite in surface portions within 5 mm from the upper and lower surfaces, wherein the area fraction of the island martensite is 3% to 15%, the equivalent circle diameter of the island martensite is 3.0 &#x3bc;m or less, the area fraction of the polygonal ferrite in the surface portions is 10% to less than 80%.

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

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

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Tokyo, Japan

Junji Shimamura