Abstract: A steel sheet includes: a predetermined chemical composition; and a steel structure represented by, in area %, first martensite in which two or more iron carbides each having a circle-equivalent diameter of 2 nm to 500 nm are contained in each lath: 20% to 95%, ferrite: 15% or less, retained austenite: 15% or less, and the balance: bainite, or second martensite in which less than two iron carbides each having a circle-equivalent diameter of 2 nm to 500 nm are contained in each lath, or the both of these, in which the total area fraction of ND//<111> orientation grains and ND//<100> orientation grains is 40% or less, and the content of solid-solution C is 0.44 ppm or more.

Abstract: A steel sheet according to an aspect of the present invention has predetermined chemical composition, in which a structure at a thickness ¼ portion includes, in terms of volume ratios, tempered martensite: 30% to 70% and one or both of ferrite and bainite: a total of 20% to 70%, in the structure at the thickness ¼ portion, a volume ratio of residual austenite is less than 10%, a volume ratio of fresh martensite is 10% or less, a volume ratio of pearlite is 10% or less, and a total volume ratio of the residual austenite, the fresh martensite, and the pearlite is 15% or less, a number density of iron-based carbides having a major axis of 5 nm or more in the tempered martensite at the thickness ¼ portion is 5×107 particles/mm2 or more, a ratio of the number of ?-type carbides in the number of the iron-based carbides having the major axis of 5 nm or more at the thickness ¼ portion is 20% or more, and a tensile strength is 780 MPa or higher.

Abstract: A high-strength cold-rolled steel sheet is provided that has a chemical composition that consists of, by mass %, C: 0.050 to 0.40%, Si: 0.01 to 3.0%, Mn: 1.0 to 5.0%, sol. Al: 0.001 to 1.0%, Ti: 0.005 to 0.20%, B: 0.0005 to 0.010%, P: 0.1% or less, S: 0.01% or less, O: 0.1% or less, N: 0.01% or less, Cr: 0 to 1.0%, Mo: 0 to 1.0%, Ni: 0 to 1.0%, Cu: 0 to 1.0%, Sn: 0 to 0.50%, Nb: 0 to 0.20%, V: 0 to 0.50%, W: 0 to 0.50%, Ca: 0 to 0.01%, Mg: 0 to 0.01%, Bi: 0 to 0.01%, Sb: 0 to 0.10%, Zr: 0 to 0.01%, and REM: 0 to 0.01%, with the balance being Fe and impurities, and that satisfies the formulas [sol. Bs/B?0.50] and [sol. Bq/B>0.50] (where, B: B amount in the steel; sol. Bs: soluble B amount in a surface layer portion of the steel; and sol. Bq: soluble B amount in the steel interior).

Abstract: A steel sheet according to an aspect of the present invention has predetermined chemical composition, in which a structure at a thickness ¼ portion includes, in terms of volume ratios, tempered martensite: 70% or more and one or both of ferrite and bainite: a total of less than 20%, in the structure at the thickness ¼ portion, a volume ratio of residual austenite is less than 10%, a volume ratio of fresh martensite is 10% or less, a volume ratio of pearlite is 10% or less, and a total volume ratio of the residual austenite, the fresh martensite, and the pearlite is 15% or less, a number density of iron-based carbides having a major axis of 5 nm or more in the tempered martensite at the thickness ¼ portion is 5×107 particles/mm2 or more, a ratio of the number of ?-type carbides in the number of the iron-based carbides having the major axis of 5 nm or more at the thickness ¼ portion is 20% or more, and a tensile strength is 780 MPa or higher.

Abstract: High strength steel plate with an ultimate tensile strength of 900 MPa or more which is excellent in hydrogen embrittlement resistance characterized in that, in the structure of the steel plate, (a) by volume fraction, ferrite is present in 10 to 50%, bainitic ferrite and/or bainite in 10 to 60%, and tempered martensite in 10 to 50%, and (b) iron-based carbides which contain Si or Si and Al in 0.1% or more are present in 4×108 (particles/mm3) or more.

Abstract: The present invention provides a high-strength steel sheet excellent in shape fixability. The high-strength steel sheet contains C, Si, Mn, P, S, Al, N, and O with predetermined contents, in which a retained austenite phase of 5 to 20% in volume fraction is contained, an amount of solid-solution C contained in the retained austenite phase is 0.80 to 1.00% in mass %, WSi? is 1.10 times or more WSi*, WMn? is 1.10 times or more WMn*, and when a frequency distribution is measured with respect to a sum of a ratio between WSi and WSi* and a ratio between WAl and WAl*, a mode value of the frequency distribution is 1.95 to 2.05, and a kurtosis is 2.00 or more.

Abstract: A base material (13) included in a plated steel sheet (1) includes a structure, at a ¼ sheet thickness position, represented by, in volume fraction: tempered martensite: 3.0% or more; ferrite: 4.0% or more; and retained austenite: 5.0% or more. An average hardness of the tempered martensite in the base material (13) is 5 GPa to 10 GPa, and a part or all of the tempered martensite and the retained austenite in the base material form an M-A. A volume fraction of ferrite in a decarburized ferrite layer (12) included in the plated steel sheet (1) is 120% or more of the volume fraction of the ferrite in the base material (13) at the ¼ sheet thickness position, an average grain diameter of the ferrite in the decarburized ferrite layer (12) is 20 ?m or less, a thickness of the decarburized ferrite layer (12) is 5 ?m to 200 ?m, a volume fraction of tempered martensite in the decarburized ferrite layer (12) is 1.

Abstract: A hot-rolled steel sheet according to the present embodiment has a chemical composition containing, in mass %: C: 0.07 to 0.30%, Si: more than 1.0 to 2.8%, Mn: 2.0 to 3.5%, P: 0.030% or less, S: 0.010% or less, Al: 0.01 to less than 1.0%, N: 0.01% or less, O: 0.01% or less, and one or more types selected from the group consisting of Sb, Sn and Te in a total amount of 0.03 to 0.30%, with a balance being Fe and impurities, and satisfying Formula (1). The micro-structure of the hot-rolled steel sheet includes ferrite and pearlite in a total amount of 50 area % or more. The tensile strength of the hot-rolled steel sheet is 900 MPa or less. Si+Mn?3.20??(1) Where, a content (mass %) of a corresponding element is substituted for each symbol of an element in Formula (1).

Abstract: A spot welding method able to simply prevent liquid metal embrittlement cracks in spot welding of plated steel sheets, comprising, before spot welding, removing the plating at least in a zone including the inside of a circle centered at a scheduled location where the center of the nugget is formed and having an outer circumference of the inside of the outer edge of a weld affected zone or a zone at the mated surfaces of the steel sheets to be welded at the inside of a circle sharing a center of a scheduled location becoming the center of the nugget formed at the mated surfaces of the steel sheets and having an outer circumference of the inside of the outer edge of a weld affected zone

Abstract: High strength steel sheet and high strength galvanized steel sheet which are excellent in shapeability which secure a tensile maximum strength 900 MPa or more high strength while obtaining excellent ductility and stretch flangeability, which sheets have predetermined compositions of ingredients, have steel sheet structures which contain volume fraction 1 to 20% of residual austenite phases, and which have martensite transformation points of the residual austenite phases of ?60° C. or less.

Abstract: A hot-dip galvanized steel sheet includes a base steel sheet and a hot-dip galvanized layer formed on at least one surface of the base steel sheet, in which the hot-dip galvanized layer includes Fe in a content of more than 0% to 5% or less, Al in a content of more than 0% to 1.0% or less, and columnar grains formed by a ? phase on the surface of the steel sheet, further, 20% or more of the entire interface between the hot-dip galvanized layer and the base steel sheet is coated with the ? phase, and a ratio of an interface formed between ? grains in which coarse oxides are present among ? grains and the base steel sheet with respect to the entire interface between the ? phase and the base steel sheet in the hot-dip galvanized layer is 50% or less, the base steel sheet has predetermined chemical components and a refined layer in direct contact with the interface between the base steel sheet and the hot-dip galvanized layer, an average thickness of the refined layer is 0.1 to 5.

Abstract: A hot-dip galvanized steel sheet wherein the hot-dip galvanized steel sheet comprises a base steel sheet and a hot-dip galvanized layer, a ferrite phase is, by volume fraction, 50% or less in a range of ? thickness to ? thickness centered at a position of ¼ thickness from the surface of the base steel sheet, a hard structure is 50% or more, wherein the hot-dip galvanized steel sheet has the hot-dip galvanized layer in which Fe is 5.0% or less and Al is 1.0% or less, and columnar grains formed of a ? phase is 20% or more in an entire interface between the plated layer and the base steel sheet, on the surface of the base steel sheet in which a volume fraction of a residual austenite is 3% or less and a ratio of a volume fraction of the hard structure is 0.10 times or more to 0.

Abstract: A hot-dip galvanized steel sheet wherein the hot-dip galvanized steel sheet comprises a base steel sheet and a hot-dip galvanized layer, a ferrite phase is, by volume fraction, 40% or more and 97% or less in a range of ? thickness to ? thickness centered at a position of ¼ thickness from the surface of the base steel sheet, a hard structure is 3% or more in total, wherein the hot-dip galvanized steel sheet has the hot-dip galvanized layer in which Fe is 5.0% or less and Al is 1.0% or less, and columnar grains formed of a ? phase is 20% or more in an entire interface between the plated layer and the base steel sheet on the surface of the base steel sheet in which a ratio of a volume fraction of the hard structure in a surface layer range of 20 ?m depth in a steel sheet direction from an interface between the hot-dip galvanized layer and the base steel sheet is 0.10 times or more to 0.

Abstract: A hot-dip galvanized steel sheet includes a base steel sheet and a hot-dip galvanized layer formed on at least one surface of the base steel sheet, in which the hot-dip galvanized layer includes Fe in a content of more than 0% to 5% or less, Al in a content of more than 0% to 1.0% or less, and columnar grains formed by a ? phase on the surface of the steel sheet, further, 20% or more of the entire interface between the hot-dip galvanized layer and the base steel sheet is coated with the ? phase, and a ratio of an interface formed between grains in which coarse oxides are present among grains and the base steel sheet with respect to the entire interface between the ? phase and the base steel sheet in the hot-dip galvanized layer is 50% or less, the base steel sheet has predetermined chemical components and a refined layer in direct contact with the interface between the base steel sheet and the hot-dip galvanized layer, an average thickness of the refined layer is 0.1 to 5.

Abstract: There is provided a high-strength hot-dip galvanized steel sheet and the like excellent in mechanical cutting property, which are capable of obtaining high ductility while ensuring high strength with maximum tensile strength of 900 MPa or more. The high-strength hot-dip galvanized steel sheet has a sheet thickness of 0.6 to 5.0 mm and has a plating layer on a surface of a steel sheet with component compositions being set in appropriate ranges, in which the steel sheet structure contains a 40 to 90% ferrite phase and a 3% or more retained austenite phase by volume fraction. In the retained austenite phase, a solid solution carbon amount is 0.70 to 1.00%, an average grain diameter is 2.0 ?m or less, an average distance between grains is 0.1 to 5.0 ?m, a thickness of a decarburized layer in a steel sheet surface layer portion is 0.01 to 10.0 ?m, an average grain diameter of oxides contained in the steel, sheet surface layer portion is 30 to 120 nm and an average density thereof is 1.

Abstract: A base steel sheet has a hot-dip galvanized layer formed on a surface thereof, in which, in a steel sheet structure in a range of ? thickness to ? thickness centered around ¼ thickness of a sheet thickness from a surface, a volume fraction of a retained austenite phase is 5% or less, and a total volume fraction of phases of bainite, bainitic ferrite, fresh martensite, and tempered martensite is 40% or more, an average effective crystal grain diameter is 5.0 ?m or less, a maximum effective crystal grain diameter is 20 ?m or less, and a decarburized layer with a thickness of 0.01 ?m to 10.0 ?m is formed on a surface layer portion, in which a density of oxides dispersed in the decarburized layer is 1.0×1012 to 1.0×1016 oxides/m2, and an average grain diameter of the oxides is 500 nm or less.

Abstract: High strength steel sheet which secures tensile maximum strength 900 MPa or more high strength while having excellent shapeability, which high strength steel sheet which is excellent in shapeability characterized by having a predetermined composition of ingredients, by the steel sheet structure including a ferrite phase and martensite phase, by the ratio of Cu particles incoherent with the bcc iron being 15% or more with respect to the Cu particles as a whole, by a density of Cu particles in the ferrite phase being 1.0×1018/m3 or more, and by an average particle size of Cu particles in the ferrite phase being 2.0 nm or more.

Abstract: Provided is a spot welded joint (10) which includes at least one thin steel plate with a tensile strength of 750 MPa to 1850 MPa and a carbon equivalent Ceq of equal to or more than 0.22 mass % to 0.55 mass % and in which a nugget (3) is formed in an interface of the thin steel plates (1A, 1B). In a nugget outer layer zone, a microstructure consists of a dendrite structure in which an average value of arm intervals is equal to or less than 12 ?m, an average grain diameter of carbides contained in the microstructure is 5 nm to 100 nm, and a number density of carbides is equal to or more than 2×106/mm2.

Abstract: Provided are: a galvannealed steel sheet, improved in the adhesiveness of a plated layer with a base steel sheet, as a galvannealed steel sheet, prepared by using a high-strength steel sheet as a base material; and a method for producing the galvannealed steel sheet. A galvannealed layer is formed on the base steel sheet including a high-strength steel having a predetermined composition. The average amount of Fe in the galvannealed layer is 8.0 to 12.0%. The absolute value of a difference (?Fe) between the amount of Fe in the vicinity of an interface with the base steel sheet and the amount of Fe in the vicinity of the external surface of the plated layer in the plated layer is 0.0 to 3.0%.

Abstract: A drive device includes a rotating electric machine, a substrate, a first drive element, a second drive element, a first extension line, and a second extension line. The rotating electric machine including a stator with a first winding group and a second winding group wound on the stator in at least three phases. The first extension line and the first drive element, as well as the second extension line and the second drive element have respectively reversed phase orders in an arrangement of the phase orders from an end close to a reference position toward an other end of the arrangement. In such manner, variation of wiring lengths from an electric power supply region among different phases is reduced.