Abstract: A clad steel plate having tensile strength (TS) of 780 MPa or more, excellent bendability, collision resistance, and LME resistance. The clad steel plate having a base metal and a cladding metal on front and back surfaces of the base metal, and the chemical composition and microstructure of the base metal and the cladding metal being appropriately controlled so that the average Vickers hardness (HVL) of the cladding metal is 260 or less, the average Vickers hardness (HVL) of the cladding metal divided by the average Vickers hardness (HVB) of the base metal is 0.80 or less, the boundary roughness between the base metal and the cladding metal is 50 ?m or less at the maximum height Ry, and the number of voids at the boundary between the base metal and the cladding metal is controlled to 20 or fewer per 10 mm length of the boundary.

Abstract: The present invention includes: an identification code generation unit that generates, from information of a company code including a first code that uniquely identifies a management target in a part of a company in the part of the company and a second code that identifies the part of the company, an identification code including a history of the management target; a hash processing unit that hashes the identification code generated by the identification code generation unit according to a hash function and converts the hashed identification code into a meaningless code; and a reference code generation unit that generates a reference code unified for the entire company based on the meaningless code converted by the hash processing unit.

Abstract: Provided is a galvanized steel sheet having a TS of 980 MPa or more, high YS, excellent ductility, strain hardenability, and hole expansion formability. A base steel sheet has a defined chemical composition and a steel microstructure as follows: area ratio of ferrite: 65.0% or less (including 0%), area ratio of bainitic ferrite: 5.0% or more and 40.0% or less, area ratio of tempered martensite: 0.5% or more and 80.0% or less, area ratio of retained austenite: 3.0% or more, area ratio of fresh martensite: 20.0% or less (including 0%), SBF+STM+2×SMA: 65.0% or more, SMA1/SMA: 0.80 or less, and SMA2/SMA: 0.20 or more.

Abstract: A high strength steel sheet has a yield-point elongation of 1% or greater and a tensile strength of 980 MPa or greater. The high strength steel sheet has a specific chemical composition and microstructure. A ratio of retained austenite grains adjoining a retained austenite grain having a different crystal orientation to total retained austenite grains is 0.60 or greater, the ferrite has an average grain size of 5.0 ?m or less, and the retained austenite has an average grain size of 2.0 ?m or less. A value obtained by dividing a volume fraction V?a by a volume fraction V?b is 0.40 or greater, where the volume fraction V?a is a volume fraction of retained austenite in a fractured portion of a tensile test specimen after a warm tensile test at 150° C., and the volume fraction V?b is a volume fraction of retained austenite before the warm tensile test at 150° C.

Abstract: A high strength steel sheet has a yield-point elongation of 1.0% or greater and a tensile strength of 980 MPa or greater. The high strength steel sheet has a specific chemical composition and microstructure. The ferrite has an average grain size of 5.0 ?m or less, the retained austenite has an average grain size of 2.0 ?m or less, a value obtained by dividing a Mn content of the retained austenite by a Mn content of steel is 1.50 or greater, 15% or more of all retained austenite grains in the retained austenite have an aspect ratio of 3.0 or greater, and 15% or more of all the retained austenite grains in the retained austenite have an aspect ratio of less than 2.0.

Abstract: A high-strength galvanized steel sheet is disclosed which has a specified chemical composition, has a steel microstructure including, in terms of area fraction, 35% or more and 80% or less of ferrite, 0.1% or more and less than 5.0% of as-quenched martensite, 3.0% or more and 35% or less of tempered martensite, and 8% or more of retained austenite, in which an average grain diameter of the ferrite is 6 ?m or less, in which an average grain diameter of the retained austenite is 3 ?m or less, in which a value calculated by dividing an average Mn content (mass %) in the retained austenite by an average Mn content (mass %) in the ferrite is 1.5 or more.

Abstract: A high-strength galvanized steel sheet and a method for producing the steel sheet. The steel sheet has a composition that includes C: 0.030% to 0.250%, Si: 0.01% to 3.00%, Mn: 2.00% to 10.00%, P: 0.001% to 0.100%, S: 0.0001% to 0.0200%, N: 0.0005% to 0.0100%, Ti: 0.005% to 0.200%, on a mass basis, and Fe and inevitable impurities. Additionally, the steel sheet has concentration of solute Mn at a depth of 5 ?m or less from a surface of the steel sheet that is 1.50% by mass or less, and a value obtained by dividing the average mass percentage of Mn in retained austenite by the average mass percentage of Mn in ferrite is 2.0 or more.

Abstract: A high-strength steel sheet includes a steel structure with: ferrite being 35% to 80% and tempered martensite being greater than 5% and 20% or less in terms of area fraction; retained austenite being 8% or more in terms of volume fraction; an average grain size of: the ferrite being 6 ?m or less; and the retained austenite being 3 ?m or less; a value obtained by dividing an area fraction of blocky austenite by a sum of area fractions of lath-like austenite and the blocky austenite being 0.6 or more; a value obtained by dividing, by mass %, an average Mn content in the retained austenite by an average Mn content in the ferrite being 1.5 or more; and a value obtained by dividing, by mass %, an average C content in the retained austenite by an average C content in the ferrite being 3.0 or more.

Abstract: A high-strength steel sheet includes a steel structure with: ferrite being 35% to 80%, martensite being 5% to 35%, and tempered martensite being 0% to 5% in terms of area fraction; retained austenite being 8% or more in terms of volume fraction; an average grain size of: the ferrite being 6 ?m or less; and the retained austenite being 3 ?m or less; a value obtained by dividing an area fraction of blocky austenite by a sum of area fractions of lath-like austenite and the blocky austenite being 0.6 or more; a value obtained by dividing, by mass %, an average Mn content in the retained austenite by an average Mn content in the ferrite being 1.5 or more; and a value obtained by dividing, by mass %, an average C content in the retained austenite by an average C content in the ferrite being 3.0 or more.

Abstract: A steel sheet having a tensile strength (TS) of 780 MPa or more and less than 1180 MPa, high LME resistance, and good weld fatigue properties. The steel sheet has a specific chemical composition and a specific steel microstructure. Crystal grains containing an oxide of Si and/or Mn in a region within 4.9 ?m in a thickness direction from a surface of the steel sheet have an average grain size in the range of 3 to 10 ?m, the lowest Si concentration LSi and the lowest Mn concentration LMn in the region within 4.9 ?m in the thickness direction from the surface of the steel sheet and a Si concentration TSi and a Mn concentration TMn at a quarter thickness position of the steel sheet satisfy a specified formula.

Abstract: A steel sheet with a tensile strength (TS) of 1180 MPa or more, a member, and a method for producing them. In a region of the steel sheet within 4.9 ?m in the thickness direction, a region with a Si concentration not more than one-third of the Si concentration in the chemical composition of the steel sheet and with a Mn concentration not more than one-third of the Mn concentration in the chemical composition of the steel sheet has a thickness of 1.0 ?m or more. The lowest Si concentration LSi and the lowest Mn concentration LMn in the region within 4.9 ?m in the thickness direction from the surface of the steel sheet and a Si concentration TSi and a Mn concentration TMn at a quarter thickness position of the steel sheet satisfy the following formula (1): LSi+LMn?(TSi+TMn)/4??(1).

Abstract: A method for producing a high-strength hot-dip galvannealed steel sheet, in which a high-strength steel sheet is used as a base material, includes a rolling step (x) of rolling a hot-dip galvannealed steel sheet with a coating layer having an Fe concentration of 8% to 17% by mass, and a heat treatment step (y) of heating the coated steel sheet which has been subjected to the rolling step (x) under the conditions satisfying the following formulae (1) and (2): (273+T)×(20+2×log10(t))?8000??(1) 40?T?160??(2) where T: heating temperature (° C.) of the coated steel sheet, and t: holding time (hr) at the heating temperature T.

Abstract: A high-strength steel includes a steel structure with: in area fraction, 60.0% to less than 90.0% of ferrite, 0% to less than 5.0% of unrecrystallized ferrite, 2.0% to 25.0% of martensite, 0% to 5.0% of carbide, and 0% to 3.0% of bainite; in volume fraction, more than 7.0% of retained austenite; in a cross-sectional view of 100 ?m×100 ?m, a value obtained by dividing number of retained austenite that are not adjacent to retained austenite whose crystal orientations are different by a total number of retained austenite being less than 0.80, an average crystal grain size of the ferrite being 6.0 ?m or less, an average crystal grain size of the retained austenite being 3.0 ?m or less, and a value obtained by dividing, by mass %, an average content of Mn in the retained austenite by an average content of Mn in steel being 1.50 or more.

Abstract: A steel sheet with a tensile strength (TS) of 780 MPa or more and less than 1180 MPa, a member, and a method for producing them. In a region of the steel sheet within 4.9 ?m in the thickness direction, a region with a Si concentration not more than one-third of the Si concentration in the chemical composition of the steel sheet and with a Mn concentration not more than one-third of the Mn concentration in the chemical composition of the steel sheet has a thickness of 1.0 ?m or more. The lowest Si concentration LSi and the lowest Mn concentration LMn in the region within 4.9 ?m from the surface of the steel sheet and a Si concentration TSi and a Mn concentration TMn at a quarter thickness position of the steel sheet satisfy the following formula (1): LSi+LMn?(TSi+TMn)/4??(1).

Abstract: A steel sheet having a tensile strength (TS) of 1180 MPa or more, high LME resistance, and good weld fatigue properties. The steel sheet has a specific chemical composition and a specific steel microstructure. Crystal grains containing an oxide of Si and/or Mn in a region within 4.9 ?m in a thickness direction from a surface of the steel sheet have an average grain size in the range of 3 to 10 ?m, the lowest Si concentration LSi and the lowest Mn concentration LMn in the region within 4.9 ?m in the thickness direction from the surface of the steel sheet and a Si concentration TSi and a Mn concentration TMn at a quarter thickness position of the steel sheet satisfy a specified formula.

Abstract: To obtain a high-strength hot-dip galvanized steel sheet having excellent surface appearance even in the case where a steel strip containing Mn at a predetermined ratio or more to Si is subjected to hot-dip galvanizing treatment, a method of producing a hot-dip galvanized steel sheet using a continuous hot-dip galvanizing apparatus comprises: subjecting a steel strip to annealing, by conveying it in an annealing furnace; and subjecting the steel strip discharged from a cooling zone to hot-dip galvanizing using a hot-dip galvanizing line, to obtain a hot-dip galvanized steel sheet. The steel strip has a chemical composition containing, in mass %, Mn: 1.7% or more and 3.5% or less and Si: 0.2% or more and 1.05% or less and satisfying [Si]/[Mn]?0.30. The chemical composition, a dew point of an atmosphere in the soaking zone, and a delivery temperature of the heating zone satisfy Formula (1).

Abstract: A method for producing a high-strength hot-dip galvannealed steel sheet, in which a high-strength steel sheet is used as a base material, includes a rolling step (x) of rolling a hot-dip galvannealed steel sheet with a coating layer having an Fe concentration of 8% to 17% by mass, and a heat treatment step (y) of heating the coated steel sheet which has been subjected to the rolling step (x) under the conditions satisfying the following formulae (1) and (2): (273+T)×(20+2×log10(t))?8000??(1) 40?T?160??(2) where T: heating temperature (° C.) of the coated steel sheet, and t: holding time (hr) at the heating temperature T.

Abstract: Provided is a high strength steel sheet that has a predetermined chemical composition and is manufactured under optimum conditions, the high strength steel sheet having a steel microstructure including, by area, ferrite: 30% or more and 80% or less, martensite: 5% or more and 35% or less, and retained austenite: 8% or more, wherein the quotient of the area fraction of grains of the retained austenite, the grains having an aspect ratio of 2.0 or more and a minor axis length of 1 ?m or less, divided by the total area fraction of the retained austenite is 0.3 or more, wherein the quotient of the average Mn content (mass %) in the retained austenite divided by the average Mn content (mass %) in the ferrite is 1.5 or more.

Abstract: Provided is a high strength steel sheet that has a predetermined chemical composition and is manufactured under optimum conditions, the high strength steel sheet having a steel microstructure including, by area, ferrite: 30% or more and 80% or less, tempered martensite: 3.0% or more and 35% or less, and retained austenite: 8% or more, wherein the quotient of the area fraction of grains of the retained austenite, the grains having an aspect ratio of 2.0 or more and a minor axis length of 1 ?m or less, divided by the total area fraction of the retained austenite is 0.3 or more, wherein the quotient of the average Mn content (mass %) in the retained austenite divided by the average Mn content (mass %) in the ferrite is 1.5 or more.

Abstract: Provided is a high strength steel sheet that has a predetermined chemical composition and is manufactured under optimum conditions, the high strength steel sheet having a steel microstructure including, by area, ferrite: 30% or more and 80% or less, tempered martensite: 3.0% or more and 35% or less, and retained austenite: 8% or more, wherein the quotient of the area fraction of grains of the retained austenite, the grains having an aspect ratio of 2.0 or more and a minor axis length of 1 ?m or less, divided by the total area fraction of the retained austenite is 0.3 or more, wherein the quotient of the average Mn content (mass %) in the retained austenite divided by the average Mn content (mass %) in the ferrite is 1.5 or more.