Abstract: A steel sheet has a predetermined chemical composition and a metal structure represented by, in area fraction, polygonal ferrite: 40% or less, martensite: 20% or less, bainitic ferrite: 50% to 95%, and retained austenite: 5% to 50%. In area fraction, 80% or more of the bainitic ferrite is composed of bainitic ferrite grains that have an aspect ratio of 0.1 to 1.0 and have a dislocation density of 8×102 (cm/cm3) or less in a region surrounded by a grain boundary with a misorientation angle of 15° or more. In area fraction, 80% or more of the retained austenite is composed of retained austenite grains that have an aspect ratio of 0.1 to 1.0, have a major axis length of 1.0 ?m to 28.0 ?m, and have a minor axis length of 0.1 ?m to 2.8 ?m.

Abstract: A steel sheet for hot stamping use used as a material for a hot stamped article excellent in strength or bending deformability, having a predetermined chemical composition, having a microstructure containing at least one of lower bainite, martensite, and tempered martensite in an area ratio of 90% or more, having an X-ray random intensity ratio of {112}<111> of the crystal grains forming the above lower bainite, martensite, or tempered martensite of 2.8 or more, having a number density of grain size 50 nm or less cementite or epsilon carbides in the microstructure of 1×1016/cm3 or more, and having a grain boundary solid solution ratio Z defined by Z=(mass % of one or both of Nb and Mo at grain boundaries)/(mass % of one or both of Nb and Mo at time of melting) of 0.4 or more.

Abstract: A steel sheet includes a predetermined chemical composition and a metal structure represented by, in area fraction, ferrite: 50% to 95%, granular bainite: 5% to 48%, tempered martensite: 2% to 30%, upper bainite, lower bainite, fresh martensite, retained austenite, and pearlite: 5% or less in total, and the product of the area fraction of the tempered martensite and a Vickers hardness of the tempered martensite: 800 to 10500.

Abstract: A hot-stamped article according to the present invention has a plating layer being attached to a single surface in an amount of 10 g/m2 or more and 90 g/m2 or less and having a Ni content of 10 mass % or more and 25 mass % or less with a remainder including Zn and impurities on a surface of a base steel sheet having a predetermined chemical composition, in a surface layer region, a metallographic structure includes 80.0% or more of martensite and 8.0% or more of residual austenite in terms of area percentage, and the concentration of Ni in the surface layer region is 8 mass % or more.

Abstract: A hot-stamped article according to the present invention has a plating layer being attached in an amount of 10 g/m2 or more and 90 g/m2 or less and having a Ni content of 10 mass % or more and 25 mass % or less with a remainder including Zn and an impurity on a surface of a base steel sheet having a predetermined chemical composition, a surface layer region includes 90.0 % or more of martensite in terms of area percentage, and a concentration of Ni in a prior austenite grain boundary in the surface layer region is 5.5 mass % or more.

Abstract: A steel sheet for hot stamping according to the present invention has a plating layer being attached in an amount of 10 g/m2 or more and 90 g/m2 or less and having a Ni content of 10 mass % or more and 25 mass % or less with a remainder including Zn and impurities on a surface of a base steel sheet having a predetermined chemical composition, in a surface layer region, 15.0% or more of the crystal grains of one or two kinds of unauto-tempered martensite and lower bainite are included in terms of area percentage, and the average dislocation density is 4×1015 m/m3.

Abstract: A hot-stamping formed body includes: a steel sheet having a predetermined chemical composition; and a plating layer provided on a surface of the steel sheet, the plating layer having an adhesion amount of 10 g/m2 to 90 g/m2 and a Ni content of 10 mass % to 25 mass %, and containing a remainder consisting of Zn and impurities. The hot-stamping formed body includes, in a surface layer region of the steel sheet, an average grain size of prior austenite grains to 10.0 ?m or less, a Ni concentration per unit area at grain boundaries having an average crystal orientation difference of 15° or more is 1.5 mass %/?m2 or more.

Abstract: A hot-stamping formed body includes: a steel sheet having a predetermined chemical composition; and a plating layer provided on a surface of the steel sheet, the plating layer having an adhesion amount of 10 g/m2 to 90 g/m2 and a Ni content of 10 mass % to 25 mass %, and containing a remainder consisting of Zn and impurities.

Abstract: A steel sheet for hot stamping includes: a steel sheet having a predetermined chemical composition; and a plating layer provided on a surface of the steel sheet, the plating layer having an adhesion amount of 10 g/m2 to 90 g/m2 and a Ni content of 10 mass % to 25 mass %, and containing a remainder consisting of Zn and impurities. The steel sheet for hot stamping includes, in a surface layer region of the steel sheet, 80% or more by area % of grains having an average crystal orientation difference of 0.4° to 3.0° inside grains surrounded by grain boundaries having an average crystal orientation difference of 5° or more.

Abstract: This frame member includes a corner section extending along the longitudinal direction; a first wall section extending from an end portion of the corner section in a direction orthogonal to the longitudinal direction; and a second wall section extending from an opposite end portion of the corner section, wherein the corner section is formed with a deformation starting portion from which a deformation starts when a load is input to the frame member in the longitudinal direction, the deformation starting portion having a shape protruding to an inner bending side or an outer bending side of the corner section, and an average hardness value H(K1) at a first region is equal to or greater than 330 Hv in Vickers hardness, and a 3-sigma range of a standard deviation ? in a frequency distribution of the hardness at the first region is equal to or greater than 60, the first region being located at a portion outwardly apart from an end portion of the deformation starting portion in the longitudinal direction by 10 mm in

Abstract: This vehicle body structure includes a frame member with a first top section, a corner section, a vertical wall section, and a second top section, and a first support section and a second support section provided at the second top section. L/h?6.7 is satisfied where the h represents a length between an outer surface of the first top section and an outer surface of the second top section, and the L represents a length between the first support section and the second support section.

Abstract: A hot-stamping formed body has a predetermined chemical composition and a microstructure including, by area ratio, 90% to 100% of martensite and 0% to 10% of a remainder in the microstructure. In the microstructure, a region in which an average GAIQ value in a unit grain is 60,000 or more is 30 area % or more, and a number density of carbides having a circle equivalent diameter of 0.20 ?m or more is 50/mm2 or less.

Abstract: A hot-stamping formed body has a predetermined chemical composition, in which an average grain size of prior austenite grains in a microstructure is 5.0 ?m or less, and an average Mn concentration at grain boundaries of the prior austenite grains is 1.0 mass % or less. The hot-stamping formed body may be provided with a plating layer on the surface thereof, or may have a softened region in a portion thereof.

Abstract: The frame member has a flat sheet portion with a recessed portion having a pair of wall portions and a bottom portion extending between tip portions in an extending direction of the pair of wall portions, in which a Vickers hardness of a region of the flat sheet portion excluding the recessed portion is 330 Hv or more, a depth of the recessed portion is 5 mm or more, when a width of the recessed portion is L0 and a cross-sectional length of an inner peripheral wall of the recessed portion consisting of the pair of wall portions and the bottom portion is L1, a value of (L1?L0)/L0 is 0.18 or more and 2.8 or less, and a Vickers hardness of a ridgeline portion extending between the flat sheet portion and the recessed portion is 1.06 times or more and 1.20 times or less the Vickers hardness of the region of the flat sheet portion excluding the recessed portion.

Abstract: A high-strength cold-rolled steel sheet which is a steel sheet having a tensile strength of 980 MPa or more has a predetermined chemical component composition, a metallographic microstructure of the steel sheet contains, by area ratio, ferrite and granular bainite: 10% or more and 50% or less in total, one or both of upper bainite and lower bainite: 10% or more and 50% or less in total, tempered martensite: more than 0% and 30% or less, retained austenite: 5% or more, and one or more of pearlite, cementite, and martensite: 0% to 10% in total, and an area ratio of the ferrite with respect to a total area ratio of the ferrite and the granular bainite is 25% or less.

Abstract: A hot stamped article excellent in strength having a predetermined composition, having an average crystal grain size of prior austenite of 3 ?m or less, containing at least one of lower bainite, martensite, and tempered martensite in an area rate of 90% or more, and having a grain boundary solid solution ratio Z, defined by Z=(mass % of one or both of Nb and Mo at the grain boundaries)/(mass % of one or more of Nb and Mo at time of dissolution) of 0.3 or more.

Abstract: A hot stamped article of high strength steel sheet excellent in bending deformability having a predetermined chemical composition, having an area rate of 90% or more of the microstructures of the steel sheet comprised of one or more of lower bainite, martensite, and tempered martensite, and having a ratio of the length of grain boundaries with a rotational angle about a rotational axis of the <011> direction of the crystal grains of the lower bainite, martensite, and tempered martensite of 15° or more with respect to the length of grain boundaries with a rotational angle of 5° to 75° of 80% or more.

Abstract: [Object] To provide a steel sheet for carburizing having further improved formability and toughness after carburizing, and a method for manufacturing the same. [Solution] A steel sheet consisting of, in mass %, C: more than or equal to 0.02%, and less than 0.30%, Si: more than or equal to 0.005%, and less than or equal to 0.5%, Mn: more than or equal to 0.01%, and less than or equal to 3.0%, P: less than or equal to 0.1%, S: less than or equal to 0.1%, sol. Al: more than or equal to 0.0002%, and less than or equal to 3.0%, N: more than or equal to 0.0001, and less than or equal to 0.035%, and the balance: Fe and impurities, in which average crystal grain size of ferrite is smaller than 10 ?m, average equivalent circle diameter of carbide is 5.0 ?m or smaller, percentage of number of carbides with an aspect ratio of 2.

Abstract: When a zone surrounded by a grain boundary that is measured to be 5.0° or more by an EBSD analysis is assumed to be a grain, and when a K value is a value obtained by multiplying an average value of Image Qualities in a grain by 10?3, a Y value is an average crystal misorientation (°) in the grain, a metallic phase 1 is a metallic phase the K value of which is less than 4.000, a metallic phase 2 is a metallic phase the K value of which is 4.000 or more and the Y value of which is 0.5 to 1.0, a metallic phase 3 is a metallic phase the K value of which is 4.000 or more and the Y value of which is less than 0.5, and a metallic phase 4 is a metallic phase that falls under none of metallic phases 1 to 3, there is provided a steel sheet that has a predetermined chemical composition and includes a microstructure including, in area percent, a metallic phase 1: 1.0% or more and less than 35.0%, a metallic phase 2: 30.0% or more and 80.0% or less, a metallic phase 3: 5.0% or more and 50.

Abstract: A steel sheet for hot stamping use used as a material for a hot stamped article excellent in strength or bending deformability, having a predetermined chemical composition, having a microstructure containing at least one of lower bainite, martensite, and tempered martensite in an area ratio of 90% or more, having an X-ray random intensity ratio of {112}<111> of the crystal grains forming the above lower bainite, martensite, or tempered martensite of 2.8 or more, having a number density of grain size 50 nm or less cementite or epsilon carbides in the microstructure of 1×1016/cm3 or more, and having a grain boundary solid solution ratio Z defined by Z=(mass % of one or both of Nb and Mo at grain boundaries)/(mass % of one or both of Nb and Mo at time of melting) of 0.4 or more.