Provided are a steel sheet having a predetermined chemical composition, and a steel microstructure comprising, by vol %, ferrite: 1 to 50%, ratio of nonrecrystallized ferrite in the ferrite: 0 to 50%, tempered martensite: 1% or more, retained austenite: 5% or more, fresh martensite: 0 to 10%, total of pearlite and cementite: 0 to 5%, and balance: bainite, and, when analyzing the surface by an EPMA, an area ratio of regions with an Al.sub.S/Si.sub.S ratio of 0.2 or less is 50% or less, and a tensile strength is 980 MPa or more, and a method for producing the same.

This cold-rolled steel sheet has a predetermined chemical composition, in which a metallographic structure of a t/4 portion, which is at a ? position of a sheet thickness t from a surface of the cold-rolled steel sheet in a sheet thickness direction has a predetermined structure, and in both an edge portion, which is at a position 50 mm away from an end portion of the cold-rolled steel sheet in a width direction, and a center portion of the cold-rolled steel sheet in the width direction, a metallographic structure of a 20 ?m portion, which is at a position 20 ?m away from the surface in the sheet thickness direction, includes, by volume percentage, ferrite and bainite: 75.0% or more and 100.0% or less in total, and martensite and tempered martensite: 0.0% or more and 25.0% or less in total, an average grain size of the martensite and the tempered martensite in the metallographic structure of the 20 ?m portion is 5.0 ?m or less, and a metallographic structure of a 75 ?m portion, which is at a position 75 ?m away from the surface in the sheet thickness direction, includes, by volume percentage, ferrite and bainite: 0.0% or more and 15.0% or less in total.

A galvanized steel sheet includes: a steel sheet having a chemical composition satisfying an equivalent carbon content Ceq of 0.35% or more and less than 0.60%, and a specified steel microstructure; and a galvanized layer on a surface of the steel sheet. The retained austenite has a solute C content of 0.6% or more by mass, and retained austenite grains with an aspect ratio of less than 2.0 constitute 50% or more of all retained austenite grains. In 90-degree bending at a curvature radius/thickness ratio of 4.2 in a rolling (L) direction with respect to an axis extending in a width (C) direction, an L cross section in a 0 to 50 ?m region from a surface of the steel sheet on a compression side has a number density of voids of 1000/mm.sup.2 or less, and the galvanized steel sheet has a tensile strength of 590 MPa or more.

Provided is a galvannealed steel sheet having high strength and excellent deep drawability, and being further excellent in slab cracking resistance and secondary working embrittlement resistance. A base metal steel sheet of the galvannealed steel sheet has a chemical composition containing, in mass %: C: 0.0080% or less; Si: 0.7% or less; Mn: 1.0 to 2.5%; P: more than 0.030 to 0.048%; S: 0.025% or less; Al: 0.005 to 0.20%; N: 0.010% or less; Ti: 0.005 to 0.040%; Nb: 0.005 to 0.060%; and B: 0.0005 to 0.0030%, with the balance being Fe and impurities, satisfying Formula (1) to (4). A galvannealed layer contains 7 to 15 mass % of Fe.

25P+4Si3.6(1)

BX10.0005(2)

C(12/93)NbX20.0035(3)

110Si+48Mn+550P120(4)

Provided is a method of manufacturing an HPF part comprising: preparing a steel sheet comprising C: 0.18% to 0.25%, Si: 0.1% to 1.0%, Mn: 0.9% to 1.5%, P: 0.03% or less, S: 0.01% or less, Al: 0.01% to 0.05%, Cr: 0.05% to 0.5%, Ti: 0.01% to 0.05%, B: 0.001% to 0.005%, N: 0.009% or less, and a balance of Fe and impurities; heating the steel sheet at 550 C. to 850 C. followed by maintaining at 640 C. to 680 C., and immersing the steel sheet in a hot dip aluminum plating bath, and a balance of Al and impurities; cooling the plated steel sheet at 15 C./s or faster; heating the cooled hot dip aluminum plated steel sheet at 880 C. to 930 C. followed by maintaining for a certain time; and hot forming the alloyed hot dip aluminum plated steel sheet and quenching at a range of 300 C. or lower at the same time.

Provided are a plated steel sheet and a method for manufacturing same, the plated steel sheet comprising: a base steel sheet; a ZnMgAl plating layer provided on at least one surface of the base steel sheet; and an FeAl inhibition layer provided between the base steel sheet and the ZnMgAl plating layer. The plating layer comprises, by weight %, 4 to 10% of Mg and 5.1-25% of Al and the remainder being Zn and unavoidable impurities with respect to components not including iron (Fe) diffused from the base steel sheet. The plating layer comprises a 24-50% MgZn.sub.2 phase in phase fraction. In the MgZn.sub.2 phase, an Al single phase is present in the ratio of 1-30% relative to the cross-sectional area of the total MgZn.sub.2 phase.

Provided is a hot press-formed (HPF) member with excellent powdering resistance at the time of press forming. The HPF member includes a hot-dip coating layer containing Al on a surface of a base steel sheet. The base steel sheet includes, based on wt %, 0.18-0.25% of C, 0.1-1.0% of Si, 0.9-1.5% of Mn, 0.03% or less of P, 0.01% or less of S, 0.01-0.05% of Al, 0.05-0.5% of Cr, 0.01-0.05% of Ti, 0.001-0.005% of B, 0.009% or less of N, the balance Fe, and the other impurities. The hot-dip coating layer comprises a soft diffusion layer and a hard alloy layer. The alloy layer has a Tau phase in the range of 10-30%, in terms of area percent.

Provided are a steel sheet; a related member; and methods for manufacturing the same.

The steel sheet has a chemical composition including, in mass %, C: 0.06 to 0.25%, Si: 0.4 to 2.5%, Mn: 1.5 to 3.5%, P: 0.02% or less, S: 0.01% or less, sol. Al: less than 1.0%, and N: less than 0.015%, the balance being Fe and incidental impurities, the steel sheet being such that the steel sheet includes a steel microstructure including, in area fraction, polygonal ferrite: 10% or less (including 0%), tempered martensite: 30% or more, fresh martensite: 20% or less (including 0%), lower bainite: 5 to 50%, and, in volume fraction, retained austenite: 5 to 20%, and the steel sheet has S.sub.C0.5/S.sub.C0.3100 of 15% or more.

Hot-stamped steel includes: a base metal that is steel including a tempered portion having hardness corresponding to 85% or less of the highest quenching hardness, the highest quenching hardness being defined as a Vickers hardness at a depth position spaced away from a surface by ? times a sheet thickness in a case of performing water quenching after heating at a temperature equal to or higher than an A.sub.c3 point and retention for 30 minutes; and a Zn coating layer that is formed on the tempered portion of the base metal. The Zn coating layer includes a solid-solution layer including a solid-solution phase that contains Fe and Zn that is solid-soluted in Fe, and a lamella layer that includes the solid-solution phase and a capital gamma phase. An area ratio of the lamella layer in the Zn coating layer is 20% or less.

A steel sheet for a container includes: a steel sheet; a coated layer which contains Ni and is provided as an upper layer of the steel sheet; and a chemical treatment layer which is provided as an upper layer of the coated layer, and contains a Zr compound in an amount of 3.0 to 30.0 mg/m.sup.2 in terms of Zr metal, and a Mg compound in an amount of 0.50 to 5.00 mg/m.sup.2 in terms of Mg metal, in which the coated layer is one of the group consisting of a Ni coated layer which contains Ni in amount of 10 to 1000 mg/m.sup.2 in terms of Ni metal, and a composite coated layer which contains Ni in an amount of 5 to 150 mg/m.sup.2 in terms of Ni metal and Sn in an amount of 300 to 3000 mg/m.sup.2 in terms of Sn metal, and has an island-shaped Sn coated layer formed on an FeNiSn alloy layer.