A steel welded member comprising a plurality of Zn-based plated steel materials, each having a Zn-based plating layer on a surface of a steel material, joined together through at least one spot weld, wherein the steel material contains, by mass %, C: 0.05 to 0.40%, Si: 0.2 to 3.0%, and Mn: 0.1 to 5.0%, the steel welded member includes, by area ratio, 20 to 80% of a ? phase (Fe.sub.3 Zn.sub.1 0) and at least one oxide with a long axis of 0.5 ?m or more in a region up to 0.5 mm from an end part of a pressure weld of the spot weld.

The present disclosure provides a hot-press formed part comprising a plated steel sheet and an aluminum alloy plated layer formed on the plated steel sheet, wherein the aluminum alloy plated layer comprises: an alloying layer (I) formed on the plated steel sheet and containing, by weight %, 5-30% of Al; an alloying layer (II) formed on the alloying layer (I) and containing, by weight %, 30 to 60% of Al; an alloying layer (III) formed on the alloying layer (II) and containing, by weight %, 20-50% of Al and 5-20% of Si; and an alloying layer (IV) formed continuously or discontinuously on at least a part of the surface of the alloying layer (III), and containing 30-60% of Al, wherein the rate of the alloying layer (III) exposed on the outermost surface of the aluminum alloy plated layer is 10% or more.

The present invention provides a deformed part created by forming a coated metal sheet into a part, the coated metal sheet comprising a steel substrate, at least one face of which is coated with a metal coating deposited by dipping the substrate in a bath, said coating comprising between 0.2 and 0.7% by weight of Al, the remainder of the metal coating being Zn and inevitable impurities, wherein an outer surface of a metal coating of the deformed part has a waviness Wa0.8 of less than or equal to 0.43 ?m.

The present invention provides a method for manufacturing a metal sheet. In this method, at least one of the following equations is satisfied: $\begin{array}{cc}\frac{Z}{d}+18\ln \left(\frac{Z}{d}\right)<8\ln \left(\frac{P}{V}\right)-27.52& \left(A\right)\\ {\mathrm{fO}}_2<\frac{2.304.Math.{10}^{-3}}{{(27.52+\frac{Z}{d}+8\ln (\frac{V}{P}}^{}}\end{array}$

A flat steel product for hot forming to a formed shaped sheet metal part and processes of making same. The flat steel product and the shaped sheet metal part have improved properties, especially in conjunction with an aluminum-based anticorrosion coating.

The steel sheet of the present invention has a steel microstructure containing, in area fraction, martensite: 20% to 100%, ferrite: 0% to 80%, and another metal phase: 5% or less, in which, on a surface of the steel sheet, a ratio of dislocation density in metal phases at a widthwise edge of the steel sheet to dislocation density in the metal phases at a widthwise center of the steel sheet is 100% to 140%, and, at a thicknesswise center of the steel sheet, a ratio of dislocation density in the metal phases at the widthwise edge of the steel sheet to dislocation density in the metal phases at the widthwise center of the steel sheet is 100% to 140%. The maximum amount of warpage of the steel sheet when the steel sheet is sheared to a length of 1 m in a rolling direction is 15 mm or less.

A high-strength steel sheet that has a predetermined component composition, that has a steel microstructure in which an area percentage of ferrite ranges from 5% to 50% in a thickness cross-section in a rolling direction, a total area percentage of fresh martensite and retained ranges from 2% to 30%, each of the fresh martensite and the retained has an average grain size of 5 m or less, and a ratio of the fresh martensite and the retained adjacent only to ferrite with respect to the fresh martensite and the retained from a surface to 200 m in the thickness direction is 30% or less in total area percentage, and that has a yield strength of 550 MPa or more.

The present invention provides a deformed part created by forming a coated metal sheet into a part, the coated metal sheet comprising a steel substrate, at least one face of which is coated with a metal coating deposited by dipping the substrate in a bath, said coating comprising between 0.2 and 0.7% by weight of Al, the remainder of the metal coating being Zn and inevitable impurities, wherein an outer surface of a metal coating of the deformed part has a waviness Wa0.8 of less than or equal to 0.43 m.

The present invention provides a method for manufacturing a metal sheet. In this method, at least one of the following equations is satisfied:

[00001]$\begin{array}{cc}\frac{Z}{d}+18.Math..Math.\ln \left(\frac{Z}{d}\right)<8.Math..Math.\ln \left(\frac{P}{V}\right)-27.52& \left(A\right)\\ f.Math..Math.O_2<\frac{2.304.Math.{\mathrm{.10}}^{-3}}{{\left(27.52+\frac{Z}{d}+8.Math..Math.\ln \left(\frac{V}{P}.Math.{\left(\frac{Z}{d}\right)}^{2.25}\right)\right)}^2}& \left(B\right)\end{array}$

wherein: Z is the distance between the metal sheet and the nozzle along the main ejection direction (E), Z being expressed in mm, d is the average height of the outlet of the nozzle along with the running direction of the metal sheet in front of the nozzle, d being expressed in mm, V is the running speed of the metal sheet in front of the nozzle, V being expressed in m.Math.s.sup.1, P is the pressure of the wiping gas in the nozzle, P being expressed in N.Math.m.sup.2, and fO.sub.2 is the volume fraction of oxygen in the wiping gas. A metal sheet, part and land motor vehicle are also provided.

According to an embodiment of the invention, a rolling equipment includes two coiler furnaces; a plurality of mill stands provided between the two coiler furnaces, the plurality of mill stands being for reverse rolling; and an induction heater provided between the plurality of mill stands, the induction heater implementing a heated temperature increase in a designated reverse rolling or in each reverse rolling, the heated temperature increase being in a hot strip longitudinal direction and width direction. Thus, the hot strip temperature distribution can be improved.