Provided are a steel sheet having a tensile strength of 950 MPa or more and good toughness and a method for manufacturing the same. The steel sheet has a specific composition and a metallographic structure containing: a ferrite area fraction of 30% or less (including 0%), a tempered martensite area fraction of 70% or more (including 100%), and a retained austenite area fraction of 4.5% or less (including 0%), wherein the average aspect ratio of an iron based carbide, precipitated in tempered martensite grains, having a grain size in the largest 10% is 3.5 or more.

A hot-pressed member is formed using a tailored blank material obtained by butt joining respective ends of two or more coated steel sheets. The hot-pressed member has two or more sites formed by the respective coated steel sheets and at least one joining portion between the sites. Depending on a type of a coated layer of each of the coated steel sheets, t.sub.w/t.sub.0 is appropriately controlled where t.sub.w is a thickness of a thinnest portion in the joining portion and t.sub.0 is a thickness of a thinnest site of the sites. A tensile strength of each of the sites is 1180 MPa or more.

A hot-pressed member is formed using a tailored blank material obtained by butt joining respective ends of two or more coated steel sheets. The hot-pressed member has two or more sites formed by the respective coated steel sheets and at least one joining portion between the sites. Depending on a type of a coated layer of each of the coated steel sheets, t.sub.w/t.sub.0 is appropriately controlled where t.sub.w is a thickness of a thinnest portion in the joining portion and t.sub.0 is a thickness of a thinnest site of the sites. A tensile strength of each of the sites is 1180 MPa or more.

Provided is a galvanized steel sheet plated by vacuum deposition and, more specifically, to a galvanized steel sheet having excellent hardness and galling resistance, and a method for manufacturing same. The zinc coated steel sheet includes: a base steel sheet; and a zinc coated layer formed on the base steel sheet. The zinc coated layer is formed of a columnar structure, and a content of Mn included in the zinc coated layer is 0.1 to 0.4 wt %.

Provided is a galvanized steel sheet plated by vacuum deposition and, more specifically, to a galvanized steel sheet having excellent hardness and galling resistance, and a method for manufacturing same. The zinc coated steel sheet includes: a base steel sheet; and a zinc coated layer formed on the base steel sheet. The zinc coated layer is formed of a columnar structure, and a content of Mn included in the zinc coated layer is 0.1 to 0.4 wt %.

A coated steel product including a base steel, and a coating layer containing a Zn—Al—Mg alloy layer disposed on a surface of the base steel, in which the coating layer has a predetermined chemical composition, the coated steel product including dendrite-shaped MgZn.sub.2 phase having a surface roughness Sa of 50 nm or less on a surface of the Zn—Al—Mg alloy layer, an area ratio of the dendrite-shaped MgZn.sub.2 phase having a surface roughness Sa of 50 nm or less being from 30% to 80% within a region of an observable field of view of 5 mm.sup.2, and among the dendrite-shaped MgZn.sub.2 phase having a surface roughness Sa of 50 nm or less, a number of dendrite-shaped MgZn.sub.2 phase having an area of 0.1 mm.sup.2 or more being from 5 to 100 within a region of an observable field of view of 25 mm.sup.2.

A coated steel material including: a base steel, and a coating layer containing a Zn—Al—Mg alloy layer disposed on a surface of the base steel, wherein the coating layer has a predetermined chemical composition, and, in a backscattered electron image of the Zn—Al—Mg alloy layer that is obtained at a time of observing the surface of the Zn—Al—Mg alloy layer after polishing to ½ of the layer thickness, under a scanning electron microscope at a magnification of 100×, Al crystals are present, and the average value of the cumulative circumferential length of the Al crystals is 88 to 195 mm/mm.sup.2.

A coated steel material including: a base steel, and a coating layer containing a Zn—Al—Mg alloy layer disposed on a surface of the base steel, wherein the coating layer has a predetermined chemical composition, and, in a backscattered electron image of the Zn—Al—Mg alloy layer that is obtained at a time of observing the surface of the Zn—Al—Mg alloy layer after polishing to ½ of the layer thickness, under a scanning electron microscope at a magnification of 100×, Al crystals are present, and the average value of the cumulative circumferential length of the Al crystals is 88 to 195 mm/mm.sup.2.

This hot-dip galvanized steel sheet includes: a steel sheet; a boundary layer provided on the steel sheet; and a hot-dip galvanized layer provided on the boundary layer, in which the steel sheet has a predetermined chemical composition, in a region between a surface of the steel sheet and a depth of 25 μm from the surface of the steel sheet, an average grain size exceeds 4.0 μm, in a region between a position of 50 μm from the surface of the steel sheet and a position of 100 μm from the surface of the steel sheet, an area ratio of unrecrystallized ferrite is 50% or more, and in the hot-dip galvanized layer, a maximum value of a U concentration is 0.05 mass % or more.

Provided are a hot-dipped galvanized steel material and a method for manufacturing the same. The hot-dipped galvanized steel material comprises an iron substrate and a hot-dipped galvanizing layer formed on the iron substrate, wherein the hot-dipped galvanizing layer comprises, by wt %, 0.01 to 0.5% of Al, 0.01 to 1.5% of Mg, 0.05 to 1.5% of Mn, 0.1 to 6% of Fe, and the balance of Zn and inevitable impurities, with a Zn—Fe—Mn based alloy phase present at the interface between the iron substrate and the hot-dipped galvanizing layer, and an area ratio of the Zn—Fe—Mn-based alloy phase to the hot-dipped galvanizing layer ranging from 1 to 60%.