Abstract: A high strength galvanized steel sheet has a composition including, C: 0.02% or more and 0.30% or less, Si: 0.01% or more and 2.5% or less, Mn: 0.1% or more and 3.0% or less, P: 0.003% or more and 0.08% or less, S: 0.01% or less, Al: 0.001% or more and 0.20% or less, Ti: 0.03% or more and 0.40% or less and the balance being Fe and inevitable impurities, and a zinc-coated layer having a coating weight per surface of 20 g/m2 or more and 120 g/m2 or less. The concentration ratio of C to Ti (C/Ti) in a portion within 10 ?m from the surface of the base steel sheet is 0.8 or more and 1.5 or less, and the total amount of oxides of one or more selected from Fe, Si, Mn, P, Al and Ti formed in a surface portion within 100 ?m from the surface of the base steel sheet is 0.05 g/m2 or less.

Abstract: Provided is a galvannealed steel sheet with excellent anti-powdering property when press forming is performed, without controlling the contents of chemical elements in steel which are effective for strengthening a steel sheet, such as Si and P, to be low in order to achieve required material properties and without increasing cost due to, for example, processes being complicated. A galvannealed steel sheet with excellent anti-powdering property has a coated layer taking in grains of a base steel sheet such that the grains constitute 2.0% or more and 15.0% or less of the coated layer in terms of cross section area ratio.

Abstract: A galvannealed steel sheet includes a zinc coating layer containing 7 to 15% Fe on the surface of steel sheet including, C: 0.02% to 0.30%, Si: 0.01% to 2.5%, Mn: 0.1% to 3.0%, P: 0.003% to 0.08%, S: not more than 0.01%, Al: 0.001% to 0.20%, one or more selected from Ti: 0.03% to 0.40%, Nb: 0.001% to 0.2%, V: 0.001% to 0.2%, Mo: 0.01% to 0.5% and W: 0.001% to 0.2%. In the zinc coating layer, carbides with average particle size of 1 nm to 20 nm including one or more selected from titanium, niobium, vanadium, molybdenum and tungsten are present with a density of five or more particles per segment that is defined by the thickness of the coating layer and also by dividing a cross section of the coating layer at intervals of 1 ?m in a direction perpendicular to the thickness of the coating layer.

Abstract: A high-strength galvanized steel sheet with high yield ratio having excellent ductility and stretch flange formability, the steel sheet having a chemical composition containing, by mass %, C: 0.04% or more and 0.13% or less, Si: 0.9% or more and 2.3% or less, Mn: 0.8% or more and 2.4% or less, P: 0.1% or less, S: 0.01% or less, Al: 0.01% or more and 0.1% or less, N: 0.008% or less, and the balance being Fe and inevitable impurities and a microstructure including, in terms of area ratio, 94% or more of a ferrite phase and 2% or less of a martensite ferrite phase, wherein mean grain size of ferrite is 10 ?m or less, Vickers hardness of ferrite is 140 or more, mean grain size of carbide particles existing at grain boundaries of ferrite is 0.5 ?m or less, and aspect ratio of carbide particles existing at the grain boundaries of ferrite is 2.0 or less.

Abstract: A high strength steel sheet including, by mass, C: 0.03% or more and 0.25% or less, Si: 0.4% or more and 2.5% or less, Mn: 3.5% or more and 10.0% or less, P: 0.1% or less, S: 0.01% or less, Al: 0.01% or more and 2.5% or less, N: 0.008% or less, Si+Al: 1.0% or more, the balance being Fe and inevitable impurities. The area ratio of ferrite is 30% or more and 80% or less, the area ratio of martensite is 0% or more and 17% or less, the volume fraction of retained austenite is 8% or more, and the average grain size of retained austenite is 2 ?m or less.

Abstract: Provided is a hot-rolled steel sheet having a composition containing 0.04 mass percent to 0.20 mass percent C, 0.7 mass percent to 2.3 mass percent Si, 0.8 mass percent to 2.8 mass percent Mn, 0.1 mass percent or less P, 0.01 mass percent or less S, 0.1 mass percent or less Al, and 0.008 mass percent or less N, the remainder being Fe and inevitable impurities. Internal oxides containing one or more selected from the group consisting of Si, Mn, and Fe are present at grain boundaries and in grains in a base metal. The internal oxides present at the grain boundaries in the base metal are located within 5 ?m from the surface of the base metal. The difference between the depths at which the internal oxides are formed in the cross direction of the steel sheet is 2 ?m or less.

Abstract: A high-strength hot-dip galvanized steel sheet excellent in formability includes, on the basis of mass percent, 0.05-0.3% C, 1.4% or less (including 0%) Si, 0.08%-3% Mn, 0.003-0.1% P, 0.07% or less S, 0.1-2.5% Al, 0.1-0.5% Cr, and 0.007% or less N, Si+Al?0.5%, and the balance being Fe and incidental impurities, wherein the steel sheet has a retained austenite content of 3% or more by volume fraction, a stretch-flange formability ?>50% and wherein the average aspect ratio (major axis/minor axis) of retained austenite grains is less than 2.5.

Abstract: A method for manufacturing a galvanized steel sheet includes heating a base steel sheet in a heating zone such that the surface of the base steel sheet is heated at a temperature of 600° C. or higher and 790° C. or lower while a furnace temperature T° C. in the heating zone of an annealing furnace is controlled based on the water vapor partial pressure PH2Oin Air of air fed into the heating zone, the base steel sheet having a chemical composition consisting of, by mass %, C: 0.05% or more and 0.25% or less, Si: 0.1% or more and 3.0% or less, Mn: 0.5% or more and 3.0% or less, P: 0.001% or more and 0.10% or less, Al: 0.01% or more and 3.00% or less, S: 0.200% or less, and the balance being Fe and inevitable impurities, heating the base steel sheet in the heating zone such that the surface of the base steel sheet is heated at a temperature of 630° C. or higher and 850° C.

Abstract: A galvanized steel sheet has formability and crashworthiness, consists of 0.03% to 0.13% C, 1.0% to 2.0% Si, 2.4% to 3.5% Mn, 0.001% to 0.05% P, 0.0001% to 0.01% S, 0.001% to 0.1% Al, 0.0005% to 0.01% N, and 0.0003% to 0.01% B on a mass basis; and optionally contains at least one selected from the following A-C: A: at least one selected from the group consisting of 0.0005% to 0.1% Ti and 0.0005% to 0.05% Nb on a mass basis; B: at least one selected from the group consisting of 0.01% to 1.0% Mo, 0.01% to 2.0% Ni, and 0.01% to 2.0% Cu on a mass basis; and C: 0.001% to 0.

Abstract: A method of manufacturing a high strength steel sheet having excellent formability suitable for the material of an automotive part has a tensile strength (TS) of 980 MPa or more and total elongation (EL) is 25% or more. A steel slab has a chemical composition containing C: 0.03% to 0.35%, Si: 0.5% to 3.0%, Mn: 3.5% to 10.0%, P: 0.100% or less, S: 0.02% or less, and the remainder includes Fe and incidental impurities on a percent by mass basis is hot-rolled, a heat treatment is performed, in which an achieved temperature of Ac1 to Ac1+100° C. is held for 3 minutes or more, subsequently, cold rolling is performed at a rolling reduction of 20% or more and, annealing is performed, in which an achieved temperature of Ac1?30° C. to Ac1+100° C. is held for 1 minute or more.

Abstract: A high-strength galvanized steel sheet having excellent formability and crashworthiness, including a component composition containing 0.03% to 0.13% C, 1.0% to 2.0% Si, 2.4% to 3.5% Mn, 0.001% to 0.05% P, 0.0001% to 0.01% S, 0.001% to 0.1% Al, 0.0005% to 0.01% N, and 0.0003% to 0.01% B on a mass basis, the remainder being Fe and unavoidable impurities, and a microstructure containing a tempered martensitic phase and a bainitic phase such that the sum of an area fraction of the tempered martensitic phase and an area fraction of the bainitic phase is 30% or more (the area fraction of the martensitic phase is 30% or more in the absence of the bainitic phase), wherein a distance of closest approach of the tempered martensitic phase is 10 ?m or less and the contents of C, Mn, and B satisfy (1): (% Mn)+1000×(% B)?35×(% C)??(1).

Abstract: A method for manufacturing the high strength steel sheet having excellent formability includes hot-rolling a steel slab having a chemical composition containing, by mass %, C: 0.03% or more and 0.35% or less, Si: 0.5% or more and 3.0% or less, Mn: 3.5% or more and 10.0% or less, P: 0.1% or less, S: 0.01% or less, N: 0.008% or less and the balance comprising Fe and inevitable impurities, coiling the hot-rolled steel sheet at a temperature range of the Ar1 transformation point to the Ar1 transformation point+(the Ar3 transformation point?the Ar1 transformation point)/2, cooling the coiled steel sheet down to 200° C. or lower, heating and holding the cooled steel sheet at a temperature range of the Ac1 transformation point?200° C.

Abstract: A hot dip galvanized steel sheet includes a steel sheet, a hot dip galvanizing layer, and an intermetallic compound, in which the steel sheet has a chemical composition containing, by mass %, C: 0.03% or more and 0.70% or less, Si: 0.10% or less, Mn: 0.5% or more and 0.9% or less, P: 0.020% or more and 0.050% or less, S: 0.010% or less, Nb: 0.010% or more and 0.035% or less, N: 0.005% or less, Al: 0.10% or less, and the balance being Fe and inevitable impurities, in which the hot dip galvanizing layer contains 0.3% or more and 0.6% or less of Al, and in which the intermetallic compound contains 0.12 gm?2 or more and 0.22 gm?2 or less of Al and Fe2Al5 having an average grain diameter of 1 ?m or less.

Abstract: A hot-dip galvanized steel sheet having a good appearance and good adhesion to a coating, the hot-dip galvanized steel sheet having a composition containing, on a mass basis: C: 0.08% or more and less than 0.20%, Si: 0.1% to 3.0%, Mn: 0.5% to 3.0%, P: 0.001% to 0.10%, Al: 0.01% to 3.00%, and S: 0.200% or less, a remainder being Fe and incidental impurities, wherein the hot-dip galvanized steel sheet includes an internal oxidation layer and a decarburized layer, the internal oxidation layer having a thickness of 5 ?m or less, the decarburized layer having a thickness of 20 ?m or less, and 50% or more by area of the internal oxidation layer is composed of a Si oxide containing Fe and/or Mn represented by Fe2XMn2-2XSiOY, wherein X ranges from 0 to 1, and Y is 3 or 4.

Abstract: A hot-dip galvanized steel sheet having a good appearance and good adhesion to a coating, the hot-dip galvanized steel sheet having a composition including, on a mass basis: C: 0.20% to 0.50%, Si: 0.1% to 3.0%, Mn: 0.5% to 3.0%, P: 0.001% to 0.10%, Al: 0.01% to 3.00%, and S: 0.200% or less, a remainder being Fe and incidental impurities, wherein the hot-dip galvanized steel sheet includes an internal oxidation layer and a decarburized layer, the internal oxidation layer having a thickness of 4 ?m or less on a ferrite side from an interface between ferrite and a galvanized layer, the decarburized layer having a thickness of 16 ?m or less on the ferrite side from the interface between the ferrite and the galvanized layer, and 50% or more by area of the internal oxidation layer is composed of a Si oxide containing Fe and/or Mn represented by Fe2XMn2-2XSiOY, wherein X ranges from 0 to 1, and Y is 3 or 4.

Abstract: A high-strength hot-dip galvanized steel sheet is produced by a method that includes a first heating step of holding a steel sheet at a temperature for a time in an atmosphere having a H2 concentration and a dew point, a cooling step of cooling the steel sheet after the first heating step, an electrolytic treatment step of subjecting the steel sheet after the cooling step to electrolytic treatment under specific conditions, a second heating step of holding the steel sheet after the electrolytic treatment step at a temperature for a time in an atmosphere having a H2 concentration and a dew point, and a coating treatment step of subjecting the steel sheet after the second heating step to hot-dip galvanizing treatment.

Abstract: A method of manufacturing a galvanized steel sheet having a composition containing, by mass %, C: 0.05% or more and 0.5% or less, Si: 0.01% or more and 2.5% or less, Mn: 0.5% or more and 3.5% or less, P: 0.003% or more and 0.100% or less, S: 0.02% or less, Al: 0.010% or more and 0.5% or less, B: 0.0002% or more and 0.005% or less, Ti: 0.

Abstract: A method of manufacturing a high strength galvanized steel sheet has a first heating step including heating to 400° C. to 750° C. in an atmosphere containing O2: 0.1 to 20 percent and H2O: 1 to 50 percent and heating to 600° C. to 850° C. in an atmosphere containing O2: 0.01 to less than 0.1 percent and H2O: 1 to 20 percent is applied to a steel sheet, a second heating step includes holding the steel sheet in an atmosphere containing H2: 1 to 50 percent and having a dew point of 0° C. or lower at 750° C. to 900° C. for 15 to 600 s, cooling to a temperature of 450° C. to 550° C., and holding is performed at that temperature for 10 to 200 s, and a galvanization treatment is applied.

Abstract: There is provided a method for manufacturing a high-strength galvannealed steel sheet having excellent coating adhesiveness and corrosion resistance whose base material is a high-strength steel sheet containing Si and Mn. The method includes performing an oxidation treatment on a steel sheet including Si and Mn in a first zone having an atmosphere of an oxygen concentration, thereafter performing an oxidation treatment in a second zone having an atmosphere of an oxygen concentration, thereafter performing reduction annealing and galvanizing, and further performing an alloying treatment by heating the galvanized steel sheet.

Abstract: A high strength cold rolled steel sheet includes a chemical composition containing, by mass %, C: 0.010% or more and 0.060% or less, Si: more than 0.5% and 1.5% or less, Mn: 1.0% or more and 3.0% or less, P: 0.005% or more and 0.100% or less, S: 0.010% or less, sol.Al: 0.005% or more and 0.500% or less, N: 0.0100% or less, Nb: 0.010% or more and 0.100% or less, Ti: 0.015% or more and 0.150% or less and the balance comprising Fe and inevitable impurities. The microstructure includes, in area fraction, 70% or more of a ferrite phase and 3% or more of a martensite phase. The tensile strength is 440 MPa or more and an average r value is 1.20 or more.