Abstract: A high-strength cold rolled steel sheet has excellent formability and crashworthiness and includes, on a mass % basis, C: 0.05 to 0.3%, Si: 0.3 to 2.5%. Mn: 0.5 to 3.5%, P: 0.003 to 0.100%, 5: 0.02% or less, Al: 0.010 to 0.5%, the balance being iron and unavoidable impurities, the high-strength cold rolled steel sheet having a microstructure including 20% or more of ferrite on an area fraction basis, 10 to 60% of tempered martensite on an area fraction basis, 0 to 10% of martensite on an area fraction basis, and 3 to 15% of retained austenite on a volume fraction basis.

Abstract: A multi-phase hot-rolled steel sheet having improved strength in an intermediate strain rate region has a chemical composition comprising, in mass percent, C: 0.07-0.2%, Si+Al: 0.3-1.5%, Mn: 1.0-3.0%, P: at most 0.02%, S: at most 0.005%, Cr: 0.1-0.5%, N: 0.001-0.008%, at least one of Ti: 0.002-0.05% and Nb: 0.002-0.05%, and a remainder of Fe and impurities. The area fraction of ferrite is 7-35%, the grain diameter of ferrite is in the range of 0.5-3.0 ?m, and the nanohardness of ferrite is in the range of 3.5-4.5 GPa. A second phase which is the remainder other than ferrite contains martensite and bainitic ferrite and/or bainite. The average nanohardness of the second phase is 5-12 GPa, and the second phase contains a high-hardness phase of 8-12 GPa with an area fraction of 5-35% based on the overall structure.

Abstract: This invention relates to an ultra-high-strength steel bar and to a method of manufacturing the same, in which the steel bar includes C: 0.05 to 0.45 wt %, Si: 0.10 to 0.35 wt %, Mn: 0.1 to 0.85 wt %, Cr: 0.6 to 1.20 wt %, and Mo: 0.05 to 0.35 wt %, with the remainder being Fe, wherein a martensite structure is formed at a surface layer and a fine ferrite structure is formed at a center layer.

Abstract: A high strength steel sheet has tensile strength of at least 1470 MPa and (tensile strength×total elongation) of at least 29000 MPa·% with a composition including, by mass %, C: 0.30% to 0.73%, Si: 3.0% or less, Al: 3.0% or less, Si+Al: at least 0.7%, Cr: 0.2% to 8.0%, Mn: 10.0% or less, Cr+Mn: at least 1.0%, P: 0.1% or less, S: 0.07% or less, N: 0.010% or less, and remainder as Fe and incidental impurities; and processing the steel sheet such that microstructure satisfies area ratio of martensite with respect to the microstructure of 15% to 90%; content of retained austenite of 10% to 50%; at least 50% of the martensite is constituted of tempered martensite and area ratio of the tempered martensite with respect to the microstructure is at least 10%; and area ratio of polygonal ferrite with respect to the microstructure is 10% or less.

Abstract: A high-strength hot-rolled steel sheet has a composition including C: 0.005% or more and 0.050% or less, Si: 0.2% or less, Mn: 0.8% or less, P: 0.025% or less, S: 0.01% or less, N: 0.01% or less, Al: 0.06% or less, and Ti: 0.05% or more and 0.10% or less, on a mass percent basis, such that S, N, and Ti satisfy Ti?0.04+(N/14×48+S/32×48), the remainder being Fe and incidental impurities; a matrix in which a ferrite phase constitutes 95% by area or more of the entire structure; and a structure in which Ti-containing fine carbide having an average grain size of less than 10 nm is dispersedly precipitated, and the volume ratio of the fine carbide to the entire structure is 0.0007 or more.

Abstract: A high-strength steel sheet is provided which, even when subjected to long-term stress-relief annealing after welding, decreases little in strength and which has satisfactory low-temperature HAZ toughness. The high-strength steel sheet has a chemical composition adequately regulated and has a CP value defined by the following equation (1) of 5.40% or higher and a carbon equivalent (Ceq) defined by the following equation (2) of 0.45% or lower. CP value=125[Ti]+111[Nb]+60[V]+15[Mo] (1) ([Ti], [Nb], [V], and [Mo] indicate the contents (mass %) of Ti, Nb, V, and Mo, respectively.) Ceq=[C]+[Mn]/6+([Cr]+[Mo]+[V])/5+([Cu]+[Ni])/15 (2) ([C], [Mn], [Cr], [Mo], [V], [Cu], and [Ni] indicate the contents (mass %) of C, Mn, Cr, Mo, V, Cu, and Ni, respectively.

Abstract: A high strength hot-rolled steel sheet has a tensile strength of not less than 780 MPa and exhibits excellent stretch flangeability and excellent fatigue resistance. A steel has a composition containing C at 0.05 to 0.15%, Si at 0.2 to 1.2%, Mn at 1.0 to 2.0%, P at not more than 0.04%, S at not more than 0.005%, Ti at 0.05 to 0.15%, Al at 0.005 to 0.10% and N at not more than 0.007%.

Abstract: A high strength steel sheet contains, in percent by mass, 0.03 to 0.2% of C, 0.5 to 2.5% of Si, 1 to 3.0% of Mn, 0.01 to 0.5% of Cr, 0.01 to 0.5% of Mo, 0.02 to 0.15% of Al, 0.15% or less of Ti, 0.15% or less of No, and 0.15% or less of V; wherein the remainder includes Fe and inevitable impurities, and the content of Si satisfies the following formula (1), ??4.1?[Si]??2.4??(1), provided, ?=6.9×([C]+[Mn]/6+[Cr]/5+[Mo]/4+[Ti]/15+[Nb]/17+[V]/14)1/2 is given, wherein [ ] shows the quantity (mass percent) of each element contained in the steel sheet. The high strength steel sheet is improved in formability (particularly, elongation), and excellent in balance between strength and elongation.

Abstract: Disclosed is high strength spring steel that can limit the depth of pitting occurring when corroded and therefore possesses high strength as well as excellent pitting corrosion resistance and corrosion fatigue property, with a composition containing: C: greater than 0.35 mass % and less than 0.50 mass %; Si: greater than L75 mass % and less than or equal to 3.00 mass %; Mn: 0.2 mass % to 1.0 mass %; Cr: 0.01 mass % to 0.04 mass %; P: 0.025 mass % or less; S: 0.025 mass % or less; Mo: 0.1 mass % to 1.0 mass %; and 0: 0.0015 mass % or less, under a condition that a PC value calculated by PC=4.2×([C]+[Mn])+0.1×(1/[Si]+1/[Mo])+20.3×[Cr]+0.001×(1/[N]) is greater than 3.3 and equal to or less than 8.0. Also disclosed is a preferred method for manufacturing the same.

Abstract: A cold rolled steel sheet with excellent bendability contains C at 0.15 to 0.30%, Si at 0.01 to 1.8%, Mn at 1.5 to 3.0%, P at not more than 0.05%, S at not more than 0.005%, Al at 0.005 to 0.05% and N at not more than 0.005%, the balance being Fe and inevitable impurities, and has a steel sheet superficial soft portion satisfying: Hv(S)/Hv(C)?0.8??(1) wherein Hv(S) is hardness of the steel sheet superficial soft portion, and Hv(C) is hardness of a steel sheet core portion, 0.10?t(S)/t?0.30??(2) wherein t(S) is thickness of the steel sheet superficial soft portion, and t is the sheet thickness.

Abstract: A high strength press-formed member includes a steel sheet constituting the member including a composition including by mass %, C: 0.12% to 0.69%, Si: 3.0% or less, Mn: 0.5% to 3.0%, P: 0.1% or less, S: 0.07% or less, Al: 3.0% or less, N: 0.010% or less, Si+Al: at least 0.

Abstract: The steel wire material for a spring of the invention contains; C: 0.37-0.54%, Si: 1.7-2.30%, Mn: 0.1-1.30%, Cr: 0.15-1.1%, Cu: 0.15-0.6%, Ti: 0.010-0.1%, Al: 0.003-0.05%, and the balance including iron with inevitable impurities, wherein ferrite decarburized layer depth is 0.01 mm or less, whole decarburized layer depth is 0.20 mm or less, and fracture reduction of area is 25% or more. It alternately may contain; C: 0.38-0.47%, Si: 1.9-2.5%, Mn: 0.6-1.3%, Ti: 0.05-0.15%, Al: 0.003-0.1%, and the balance including iron with inevitable impurities, wherein ferrite decarburized layer depth is 0.01 mm or less.

Abstract: A high-strength cold-rolled steel sheet includes, by mass %, C: 0.10% to 0.40%, Mn: 0.5% to 4.0%, Si: 0.005% to 2.5%, Al: 0.005% to 2.5%, Cr: 0% to 1.0%, and a balance of iron and inevitable impurities, in which an amount of P is limited to 0.05% or less, an amount of S is limited to 0.02% or less, an amount of N is limited to 0.006% or less, the microstructure includes 2% to 30% of retained austenite by area percentage, martensite is limited to 20% or less by area percentage in the microstructure, an average particle size of cementite is 0.01 ?m to 1 ?m, and 30% to 100% of the cementite has an aspect ratio of 1 to 3.

Abstract: A high strength, high toughness steel alloy is disclosed. The alloy has the following weight percent composition. Element C 0.30-0.47 Mn 0.8-1.3 Si 1.5-2.5 Cr 1.5-2.5 Ni 3.0-5.0 Mo + ½ W 0.7-0.9 Cu 0.70-0.90 Co ?0.01 max. V + ( 5/9) × Nb 0.10-0.25 Ti 0.005 max. Al 0.015 max. Fe Balance Included in the balance are the usual impurities found in commercial grades of steel alloys produced for similar use and properties including not more than about 0.01% phosphorus and not more than about 0.001% sulfur. Also disclosed is a hardened and tempered article that has very high strength and fracture toughness. The article is formed from the alloy having the broad weight percent composition set forth above. The alloy article according to this aspect of the invention is further characterized by being tempered at a temperature of about 500° F. to 600° F.

Abstract: A mechanical steel part in steel with high characteristics, characterized in that its composition, comprising in weight percentages, is 0.05%?C?0.25%; 1.2%?Mn?2%; 1%?Cr?2.5%; wherein the contents of C, Mn and Cr are such that (830-270C %-90 Mn %-70Cr %)?560; 0<Si?1.55; 0<Ni?1%; 0<Mo?0.5%; 0<Cu?1%; 0<V?0.3%; 0<Al?0.1%; 0<B?0.005%; 0<Ti?0.03%; 0<Nb?0.06%; 0<S?0.1%; 0<Ca?0.006%; 0<Te?0.03%; 0<Se?0.05%; 0<Bi?0.05%; 0<Pb?0.1%; the remainder of the steel part being iron and impurities resulting from processing, and wherein the in that its structure of the steel is bainitic and contains no more than a total of 20% of martensite and/or pro-eutectoid ferrite and/or pearlite.

Abstract: The present invention provides a high strength steel having unprecedentedly superior CTOD (fracture toughness) properties satisfying not only the CTOD properties of the FL zone at ?60° C., but also the CTOD properties of the ICHAZ zone in small and medium heat input multilayer welding, etc.; and a method of production of the same. The steel of the present invention is steel superior in CTOD properties of the heat-affected zone containing, by mass %, C: 0.015 to 0.045%, Si: 0.05 to 0.2%, Mn: 1.5 to 2.0%, Cu: 0.25 to 0.5%, Ni: 0.7 to 1.5%, P: 0.008% or less, S: 0.005% or less, Al: 0.004% or less, Ti: 0.005 to 0.015%, Nb: 0.005% or less, O: 0.0015 to 0.0035%, and N: 0.002 to 0.006%, PCTOD: 0.065 or less, CeqH: 0.235 or less and the balance consisting of Fe and unavoidable impurities.

Abstract: A pearlite rail contains, by mass %, 0.65 to 1.20% of C; 0.05 to 2.00% of Si; 0.05 to 2.00% of Mn; and the balance composed of Fe and inevitable impurities, wherein at least part of the head portion and at least part of the bottom portion has a pearlite structure, and the surface hardness of a portion of the pearlite structure is in a range of Hv320 to Hv500 and a maximum surface roughness of a portion of the pearlite structure is less than or equal to 180 ?m.

Abstract: Steel sheet having a composition of ingredients containing substantially, by mass %, C: 0.005 to 0.200%, Si: 2.50% or less, Mn: 0.10 to 3.00%, N: 0.0100% or less, Nb: 0.005 to 0.100%, and Ti: 0.002 to 0.150% and satisfying the relationship of Ti?48/14×N?0.0005, having a sum of the X-ray random intensity ratios of the {100}<001> orientation and the {110}<001> orientation of a ? sheet thickness part of 5 or less, having a sum of the maximum value of the X-ray random intensity ratios of the {110}<111> to {110}<112> orientation group and the X-ray random intensity ratios of the {211}<111> orientation of 5 or more, and having a high rolling direction Young's modulus measured by the static tension method and a method of production of the same are provided.

Abstract: Disclosed is an ultra high strength steel plate with at least 1100 MPa of tensile strength that has both an excellent strength-stretch balance and excellent bending workability, and a method for producing the same. The metal structure of the steel plate has martensite, and the soft phases of bainitic ferrite and polygonal ferrite. The area of the aforementioned martensite constitutes 50% or more, the area of the aforementioned bainitic ferrite constitutes 15% or more, and the area of the aforementioned polygonal ferrite constitutes 5% or less (including 0%). When the circle-equivalent diameter of the aforementioned soft phases is measured, the coefficient of variation (standard deviation/mean value) is less or equal to 1.0. The ultra high strength steel plate has at least 1100 MPa of tensile strength.

Abstract: 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 ?m or less.

Abstract: A seamless steel pipe for line pipe having high strength and high toughness contains, by mass percent, C: 0.02 to 0.10%, Si: at most 0.5%, Mn: 0.5 to 2.0%, Al: 0.01 to 0.1%, P: at most 0.03%, S: at most 0.005%, Ca: at most 0.005%, and N: at most 0.007%, and further contains at least one selected from a group consisting of Ti: at most 0.008%, V: less than 0.06%, and Nb: at most 0.05%, the balance being Fe and impurities. A carbon equivalent Ceq defined by Formula (1) is at least 0.38, a content of Ti, V and Nb satisfies Formula (2), and the size of carbo-nitride containing at least one of Ti, V, Nb and Al is at most 200 nm, Ceq=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15??(1) Ti+V+Nb<0.06??(2).

Abstract: On a cross section with a sheet width direction of a high-strength hot-rolled steel sheet set as a normal line, with regard to an inclusion having a major diameter of 3.0 ?m or more, a maximum of a major diameter/minor diameter ratio expressed by (a major diameter of the inclusion)/(a minor diameter of the inclusion) is 8.0 or less, and a sum total of a rolling direction length per 1 mm2 cross section of a predetermined inclusion group composed of plural inclusions each having a major diameter of 3.0 ?m or more and a predetermined extended inclusion having a length in a rolling direction of 30 ?m or more is 0.25 mm or less. The plural inclusions composing the predetermined inclusion group congregate in both the rolling direction and a direction perpendicular to the rolling direction 50 ?m or less apart from each other. The predetermined extended inclusion is spaced over 50 ?m apart from all the inclusions each having a major diameter of 3.

Abstract: A steel material has a composition of C: 0.02 to 0.2%, Si: 0.01 to 0.5%, Mn: 0.5 to 2.5%, P: 0.05% or lower, S: 0.05% or lower, Al: 0.1% or lower, and N: 0.01% or lower and, as required, one or two or more elements selected from Cu: 0.01 to 2%, Ni: 0.01 to 5%, Cr: 0.01 to 3%, Mo: 0.01 to 2%, Nb: 0.1% or lower, V: 0.1% or lower, Ti: 0.1% or lower, B: 0.01% or lower, Ca: 0.01% or lower, and REM: 0.1% or lower in terms of % by mass, and the balance Fe with inevitable impurities, in which the microstructure at the ¼ position of the plate thickness contains ferrite and a hard phase, the area fraction of the hard phase is 50 to 90%, and the average aspect ratio of the ferrite is 1.5 or more.

Abstract: Provided are the following cold-rolled steel sheets: 1) a cold-rolled steel sheet having higher stretch flangeability than conventional steels; 2) a cold-rolled steel sheet having a higher balance between elongation and stretch flangeability than conventional steels; and 3) a cold-rolled steel sheet heightened in all of yield stress, elongation, and stretch flangeability. The cold-rolled steel sheets are characterized by containing 0.03-0.30 mass % carbon, up to 3.0 mass % (including 0 mass %) silicon, 0.1-5.0 mass % manganese, up to 0.1 mass % phosphorus, less than 0.01 mass % sulfur, up to 0.01 mass % nitrogen, and 0.01-1.00 mass % aluminum and having a structure which comprises tempered martensite in an amount of 50% or more (including 100%) in terms of areal proportion and in which the remainder is ferrite.

Abstract: The present invention provides a spring steel that has superior hardenability, undergoes less pitting in a corrosive environment, and can achieve higher stress and toughness. More specifically, the present invention provides a high-strength and high-toughness spring steel with improved hardenability and pitting resistance, containing, in mass percent, 0.40 to 0.70% carbon, 0.05 to 0.50% silicon, 0.60 to 1.00% manganese, 1.00 to 2.00% chromium, 0.010 to 0.050% niobium, 0.005 to 0.050% aluminum, 0.0045 to 0.0100% nitrogen, 0.005 to 0.050% titanium, 0.0005 to 0.0060% boron, no more than 0.015% phosphorus and no more than 0.010% sulfur, the remainder being composed of iron and unavoidable impurities, the steel having a tensile strength of at least 1700 MPa in 400° C. tempering after quenching and a Charpy impact value of at least 40 J/cm2 for a 2 mm U-notched test piece of JIS Z 2202 and the parameter Fce being at least 1.70.

Abstract: A hot rolled steel sheet having a dual phase microstructure with a martensite phase of less than 35% by volume and a ferrite phase of more than 50% by volume and a composition containing by percent weight: 0.01?C?0.2; 0.3?Mn?3; 0.2?Si?2; 0.2?Cr+Ni?2; 0.01?Al?0.10; Mo less than about 0.2%, 0.0005?Ca?0.01, with the balance iron and incidental ingredients. Hot rolled sheet for cold rolling, the silicon range may be from about 0.05% to about 2%, and the amount of molybdenum may be up to 0.5%. Also, the hot rolled steel sheet has a tensile strength of at least 500 megapascals, a hole expansion ratio more than about 50%, and a yield strength/tensile strength ratio less than 70%.

Abstract: Regarding contents of C, Si, Mn and Cr, a value of parameter P represented by the following (equation 1) is 1000 or more. A metallic structure contains wire-drawn pearlite in an area ratio of 98% or more, a diameter is 0.05 mm to 0.18 mm, a tensile strength is 4000 MPa or more, and a twist number in a twist test in which a grip-to-grip distance is 100 mm, and a tension equal to a tensile strength×a cross-sectional area of wire×0.5 is applied, is 5 or more. P=1098×[C]+98×[Si]?20×[Mn]+167×[Cr]??(equation 1) (in the (equation 1), [C], [Si], [Mn] and [Cr] indicate contents (mass %) of C, Si, Mn and Cr, respectively.

Abstract: In an electric resistance welded steel pipe with excellent weld toughness for a line pipe, the area fraction of minute defects each having a maximum length of less than 50 ?m in a projection plane of an electric resistance welded seam is in the range of 0.000006 to 0.026, and the absorbed energy at ?40° C. measured by a method for an impact test of metallic materials is 315 J or more.

Abstract: The invention concerns an iron-nickel alloy strip comprising the following expressed in wt. %: 32?Co+Ni?45%, 0?Co?6.5%, 0?Cr=6.5%, Cu?3%, Si?0.5%, Mn?0.75%, the rest being made up of iron and unavoidable impurities resulting from production, whereof the microstructure has a recrystallized volume fraction ranging from 3 to 97%, whereof the thickness is less than 0.5 mm. The invention also concerns the use thereof in the manufacture of support grids for integrated circuits.

Abstract: A steel sheet, including: as chemical components, by mass %, 0.05% to 0.35% of C; 0.05% to 2.0% of Si; 0.8% to 3.0% of Mn; 0.01% to 2.0% of Al; equal to or less than 0.1% of P; equal to or less than 0.05% of S; equal to or less than 0.01% of N; and the balance including iron and inevitable impurities, wherein an area ratio of equal to or higher than 50% of a total of a ferrite phase, a bainite phase, and a tempered martensite phase is contained, an area ratio of equal to or higher than 3% of a retained austenite phase is contained, and crystal grains of the retained austenite phase having a number ratio of equal to or higher than 50% satisfy Expression 1, assuming carbon concentration at a position of center of gravity is Cgc and a carbon concentration at a grain boundary is Cgb.

Abstract: Disclosed is a steel plate having a specific chemical component composition. The steel plate has an F value defined by the following expression (1) and satisfying the following condition: 3.20?(F value)?4.50, has a tempered bainite microstructure having an average equivalent area diameter of grains surrounded by high-angle boundaries with a difference in orientation between two grains of 15° or more of 4 ?m or less, and has a tensile strength of 585 MPa or more: F value=9.4×[Mo]+8.1×[V]+4.7×[Cr]??(1) wherein [Mo], [V] and [Cr] represent contents (percent by mass) of Mo, V, and Cr, respectively. The steel plate having this configuration surely has satisfactory drop weight properties and high base metal toughness only by controlling the contents of necessary alloy elements.

Abstract: This steel plate for cold forging includes a hot-rolled steel plate, wherein the hot-rolled steel plate includes: in terms of percent by mass, C: 0.13% to 0.20%; Si: 0.01% to 0.8%; Mn: 0.1% to 2.5%; P: 0.003% to 0.030%; S: 0.0001% to 0.008%; Al: 0.01% to 0.07%; N: 0.0001% to 0.02%; and O: 0.0001% to 0.0030%, with a remainder being Fe and inevitable impurities, an A value represented by the following formula (1) is in a range of 0.0080 or less, a thickness of the hot-rolled steel plate is in a range of 2 mm to 25 mm, and an area percentage of pearlite bands having lengths of 1 mm or more in a region of 4/10t to 6/10t when a plate thickness is indicated by t in a cross section of a plate thickness that is parallel to a rolling direction of the hot-rolled steel plate is in a range of not more than a K value represented by the following formula (2), A value=O%+S%+0.033Al%??(1) K value=25.5×C%+4.5×Mn%?6??(2).

Abstract: An object of the present invention is to provide at a low cost a low-alloy steel having a high strength and excellent high-pressure hydrogen environment embrittlement resistance characteristics under a high-pressure hydrogen environment. The invention is a high-strength low-alloy steel excellent in high-pressure hydrogen environment embrittlement resistance characteristics, which is characterized in that the steel has a composition comprising C: 0.10 to 0.20%, Si: 0.10 to 0.40%, Mn: 0.50 to 1.20%, Cr: 0.20 to 0.80%, Cu: 0.10 to 0.50%, Mo: 0.10 to 1.00%, V: 0.01 to 0.10%, B: 0.0005 to 0.005% and N: 0.01% or less, by mass, with the balance consisting of Fe and unavoidable impurities.

Abstract: This high strength hot-rolled steel sheet includes: in terms of percent by mass, C: 0.05 to 0.12%; Si: 0.8 to 1.2%; Mn: 1.6 to 2.2%; Al: 0.30 to 0.6%; P: 0.05% or less; S: 0.005% or less; and N: 0.01% or less, with the remainder being Fe and unavoidable impurities, wherein a microstructure includes specific ranges (in area %) of ferrite phases as well as martensite phases, and a maximum concentration of Al detected by a glow discharge emission spectroscopic analysis is in a range of 0.75 mass % or less in a region from a surface of the steel sheet to a thickness of 500 nm after being acid-pickled.

Abstract: The present invention provides a high strength thick steel material excellent in toughness and weldability reduced in amount of C and amount of N, containing suitable amounts of Si, Mn, Nb, Ti, B, and O, having contents of C and Nb satisfying C—Nb/7.74?0.004, having a density of Ti-containing oxides of a particle size of 0.05 to 10 ?m of 30 to 300/mm2, and having a density of Ti-containing oxides of a particle size over 10 ?m of 10/mm2 or less, produced by treating steel by preliminary deoxidation to adjust the dissolved oxygen to 0.005 to 0.015 mass %, then adding Ti and, furthermore, vacuum degassing the steel for 30 minutes or more, smelting it, then continuously casting it to produce a steel slab or billet, heating the steel slab or billet to 1100 to 1350° C., hot rolling the slab or billet to a thickness of 40 to 150 mm, then cooling it.

Abstract: A transformation toughened, high-strength steel alloy useful in plate steel applications achieves extreme fracture toughness (Cv > 80 ft-lbs corresponding to KId=200 ksi.in ½) at strength levels of 150-180 ksi yield strength, is weldable and formable. The alloy is characterized by dispersed austenite stabilization for transformation toughening to a weldable, bainitic plate steel and is strengthened by precipitation of M2C carbides in combination with copper and nickel. The desired microstructure is a matrix containing a bainite-martensite mix, BCC copper and M2C carbide particles for strengthening with a fine dispersion of optimum stability austenite for transformation toughening. The bainite-martensite mix is formed by air-cooling from solution treatment temperature and subsequent aging at secondary hardening temperatures to precipitate the toughening and strengthening dispersions.

Abstract: There is provided a method for manufacturing a seamless steel pipe for line pipe, capable of improving the toughness of the seamless steel pipe for line pipe. A round billet having a chemical composition, by mass percent, of C: 0.02 to 0.15%, Si: at most 0.5%, and Mn: 0.5 to 2.5%, the balance being Fe and impurities, is heated. The heated round billet is piercing-rolled to produce a hollow shell. The hollow shell is elongated and rolled and sized to produce a seamless steel pipe. The seamless steel pipe is water cooled, and the water cooling is stopped when the temperature of the seamless steel pipe reaches at most 450° C. The water-cooled seamless steel pipe is quenched, and the quenched seamless steel pipe is tempered.

Abstract: A hot-pressed steel sheet member has a composition containing, by mass, C: 0.09% to 0.38%, Si: 0.05% to 2.0%, Mn: 0.5% to 3.0%, P: 0.05% or less, S: 0.05% or less, Al: 0.005% to 0.1%, N: 0.01% or less, Sb: 0.002% to 0.03%, and the balance being Fe and inevitable impurities, and having a tensile strength TS of 980 to 2,130 MPa.

Abstract: The present invention provides a product for enameling and an enameled product that achieve adhesion, bubble/black spot defect resistance and fishscale resistance, even when preprocessing and ground coating are omitted, which product comprise a steel sheet having on the surface thereof an oxide film of 0.10 ?m to 400 ?m thickness comprising oxides of components of the steel sheet, which steel sheet comprises, in mass %, C: 0.0001% to 0.040%, Si: 0.0001% to 0.50%, Mn: 0.001% to 2.00%, P: 0.0001% to 0.10%, S: 0.0001% to 0.060%, Al: 0.0001% to 0.10%, N: 0.0001% to 0.015%, and O: 0.0001% to 0.070%, further comprises one or more of Ni: 0.01% to 2.00%, Co: 0.0005% to 2.00%, Cr: 0.001% to 2.00%, Cu: 0.01% to 2.00%, Mo: 0.0001% to 2.00%, and Ti: 0.0005% to 0.50%, where Ni+Co+Cr/2+Cu+Mo+Ti: 0.010% to 8.0%, the balance being Fe and unavoidable impurities.

Abstract: A multiphase steel sheet has a steel composition containing, in percent by mass, more than 0.015% to less than 0.100% of carbon, less than 0.40% of silicon, 1.0% to 1.9% of manganese, more than 0.015% to 0.05% of phosphorus, 0.03% or less of sulfur, 0.01% to 0.3% of soluble aluminum, 0.005% or less of nitrogen, less than 0.30% of chromium, 0.0050% or less of boron, less than 0.15% of molybdenum, 0.4% or less of vanadium, 0.02% or less of titanium, wherein [Mneq] is 2.0 to 2.8, the balance being iron and incidental impurities.

Abstract: A high strength steel sheet has a tensile strength of 980 MPa or higher includes a composition including, on a mass% basis, C: 0.1% or more and 0.3% or less, Si: 2.0% or less, Mn: 0.5% or more and 3.0% or less, P: 0.1% or less, S: 0.07% or less, Al: 1.0% or less, and N: 0.008% or less, with the balance being Fe and incidental impurities, wherein a steel micro-structure includes, on an area ratio basis, martensite: 50% or more, ferrite: 50% or less, bainite: 10% or less, and retained austenite: 10% or less; and the full-width at half maximum in a frequency distribution of nano-hardness, which is obtained by measuring a hardness distribution of the martensite, is 2.0 GPa or more.

Abstract: A low-carbon martensitic armour steel comprises at least Fe, C, Si and Ni and has a ratio of yield strength to ultimate tensile strength of less than 0.7. The steel includes retained austenite at a volume fraction of at least 1%. The low-carbon martensitic armour steel can be prepared by subjecting a steel which comprises at least Fe, C, Si and Ni and which has a martensite start temperature of less than 210° C. to an austenisation heat treatment step at a temperature of at least 800° C., quenching the steel, and subjecting the steel to a tempering step at a temperature of less than 300° C.

Abstract: The present invention aims at providing a method for production of a steel product which surely retains scale during cooling, storage, and transportation and permits scale to scale off easily at the time of mechanical descaling and pickling that precede the secondary fabrication. The steel product is produced by heating and hot rolling a steel billet and spraying the hot-rolled steel product with steam and/or water mist having a particle diameter no larger than 100 ?m, for surface oxidation.

Abstract: A high-strength steel plate includes the following composition: 0.18 to 0.23 mass % of C; 0.1 to 0.5 mass % of Si; 1.0 to 2.0 mass % of Mn; 0.020 mass % or less of P; 0.010 mass % or less of S; 0.5 to 3.0 mass % of Ni; 0.003 to 0.10 mass % of Nb; 0.05 to 0.15 mass % of Al; 0.0003 to 0.0030 mass % of B; 0.006 mass % or less of N; and a balance composed of Fe and inevitable impurities. A weld crack sensitivity index Pcm of the high-strength steel plate is 0.36 mass % or less. The Ac3 transformation point is equal to or less than 830° C., the percentage value of a martensite structure is equal to or greater than 90%, the yield strength is equal to or greater than 1300 MPa, and the tensile strength is equal to or greater than 1400 MPa and equal to or less than 1650 MPa. A prior austenite grain size number N? is calculated by N?=?3+log2m using an average number m of crystal grains per 1 mm2 in a cross section of a sample piece of the high-strength steel plate.

Abstract: According to one embodiment, a high-strength stabilizer steel for vehicles having excellent corrosion resistance and low-temperature toughness, containing 0.07 to 0.20% C, more than 0.6% and 1.5% or less Si, 1 to 3% Mn, 0.1 to 1.0% Cr, 0.005 to 0.080% sAl, 0.005 to 0.060% Ti, 0.005 to 0.060% Nb, 0.070% or less Ti+Nb, 150 ppm or less N, 0.035% or less P, 0.035% or less S, 0.01 to 1.00% Cu, 0.01 to 1.00% Ni, the remainder being Fe, and unavoidable impurities, wherein a structure before molding a stabilizer is any one of a bainite, a martensite, and a mixed structure of bainite/martensite and an original austenitic crystal grain size number after a heat treatment of the stabilizer is Gh 9 or more.

Abstract: The present invention provides a spring steel that has superior hardenability, undergoes less pitting in a corrosive environment, and can achieve higher stress and toughness. More specifically, the present invention provides a high-strength and high-toughness spring steel with improved hardenability and pitting resistance, containing, in mass percent, 0.40 to 0.70% carbon, 0.05 to 0.50% silicon, 0.60 to 1.00% manganese, 1.00 to 2.00% chromium, 0.010 to 0.050% niobium, 0.005 to 0.050% aluminum, 0.0045 to 0.0100% nitrogen, 0.005 to 0.050% titanium, 0.0005 to 0.0060% boron, no more than 0.015% phosphorus and no more than 0.010% sulfur, the remainder being composed of iron and unavoidable impurities, the steel having a tensile strength of at least 1700 MPa in 400° C. tempering after quenching and a Charpy impact value of at least 40 J/cm2 for a 2 mm U-notched test piece of JIS Z 2202 and the parameter Fce being at least 1.70.

Abstract: The present invention provides a steel for machine and structural use which is capable of maintaining mechanical characteristics such as strength by reducing a S content as well as of exhibiting excellent machinability (particularly tool life) in intermittent cutting (such as hobbing) with the high speed tool, and a method useful for producing the steel for machine and structural use. The steel for machine and structural use according to the invention secures 0.002% or more of solute N in the steel and has a chemical composition which is appropriately adjusted and satisfies a relationship of the following expression (1): (0.1×[Cr]+[Al])/[O]?150 . . . (1), in which [Cr], [Al], and [0] represent a Cr content (mass %), an Al content (mass %), and an O content (mass %), respectively.

Abstract: An abrasion resistant steel consisting essentially of, in weight %: 0.20-0.30% carbon, 0.40-1.25% manganese, 0.05% maximum phosphorous, 0.01% maximum sulfur, 0.20-0.60% silicon, 0.50-1.70% chromium, 0.20-2.00% nickel, 0.07-0.60% molybdenum, 0.010-0.10% titanium, 0.001-0.10% boron, 0.015-0.10% aluminum, balance iron, and incidental impurities. The steel may be melted and cast into a steel ingot or slab, hot rolled to a desired plate thickness; austenitized at 1650-1700° F.; water quenched; and tempered at 350-450° F. The resulting steel plate may have a surface hardness of at least 440 HBW, a mid-thickness hardness of at least 90% of the surface hardness, and toughness in the transverse direction at ?60° F. of at least 20 ft-lbs and at room temperature of at least 40 ft-lbs.

Abstract: Disclosed is a high strength steel sheet having excellent hydrogen embrittlement resistance. The steel sheet has a tensile strength of 1180 MPa or more, and satisfies the following conditions: with respect to an entire metallographic structure thereof, bainite, bainitic ferrite and tempered martensite account for 85 area % or more in total; retained austenite accounts for 1 area % or more; and fresh martensite accounts for 5 area % or less (including 0 area %).

Abstract: In a high-tensile steel plate according to the invention, the carbon equivalent Pcm represented in Expression (1) is from 0.180% to 0.220%, the surface hardness is a Vicker's hardness of 285 or less, the ratio of a Martensite Austenite constituent in the surface layer is not more than 10%, the ratio of a mixed structure of ferrite and bainite inside beyond the surface layer is not less than 90%, the ratio of the bainite in the mixed structure is not less than 10%, the thickness of the lath of bainite is not more than 1 ?m, the length of the lath is not more than 20 ?m, and the segregation ratio as the ratio of the Mn concentration in the center segregation part relative to the Mn concentration at a part in a depth equal to ¼ of the thickness of the plate from the surface is not more than 1.3. Pcm=C+Si/30+(Mn+Cu+Cr)/20+Ni/60+Mo/15+V/10+5B . . . (1) where the element symbols in Expression (1) represent the % by mass of the respective elements.