Provided are a steel sheet with excellent weldability, and a production method therefor.

The steel sheet is characterized by having a specific composition and a metallographic structure containing, in terms of an area ratio, ferrite of 25% or more and 65% or less, martensite having iron-based carbides precipitated in the grains of 35% or more and 75% or less, and the balance structure other than the ferrite and the martensite of 20% or less (including 0%) in total, the average grain diameters of the ferrite and the martensite being respectively 5 m or lower, the total of concentration of Si and Mn at interface between the ferrite and the martensite being, in terms of an atomic concentration, 5% or more, and having a tensile strength of 900 MPa or higher.

A process for manufacturing corrosion resistant metal components is disclosed. The process comprises abrasive blasting of a silicon-containing steel substrate followed by hot dip galvanizing, a second abrasive blasting process, treating with a mineral acid, and coating with a polymeric coating. The resulting corrosion resistance is enhanced.

A pin comprising a conical body having a central axis and a cross-sectional area that decreases with distance from a first end to a second end. A coating applied to the conical body has a melting temperature that is lower than a melting temperature of the conical body. The coating melting temperature is lower than a friction temperature and the body melting temperature is higher than the friction temperature. The friction temperature is achieved at an interface of the pin and a component when the pin is forcibly positioned into the component to repair a defect. The coating comprises a material having a first tensile strength value of a bond formed between the conical body and the component in response to softening and rehardening of the coating.

A method for producing a coated steel sheet having a tensile strength of at least 1450 MPa and a total elongation of at least 17% is provided. The method includes providing a cold rolled steel sheet having a chemical composition in weight %: 0.34%C0.45%, 1.50%Mn2.30%, 1.50%Si2.40%, 0%<Cr0.7%, 0%Mo0.3%, 0.10%Al0.7%, optionally 0%Nb0.05%, and a remainder of Fe and unavoidable impurities. The sheet is annealed at an annealing temperature higher than the Ac3 transformation point of the steel, quenched to a quenching temperature lower than the Ms transformation point of the steel and between 150 C. and 250 C., reheated to a partitioning temperature between 350 C. and 450 C., maintained at the partitioning temperature for at least 80 s, then coated by galvannealing, with an alloying temperature between 470 C. and 520 C. A steel sheet is also provided.

A high strength galvannealed steel sheet having, a) a composition consisting of the following elements (in wt. %): C 0.10-0.2 Mn 2.0-3.0 Si 0.2-0.5 Cr 0.1-0.7 Ti 0.01-0.07 Al0.2 Nb<0.05 Mo<0.1 optionally B 0.001-0.005 balance Fe apart from impurities, b) a multiphase microstructure comprising (in vol. %) retained austenite 4-20 martensite 5-25 bainitic ferrite10 polygonal ferrite10 balance bainite+tempered martensite 50-90, c) at least one of the following mechanical properties a tensile strength (Rm) 1180-1300 MPa a yield strength (Rp0.2) 800-970 MPa an elongation (A50)8% an elongation (A80)6%, and d) a bendability according to a 90 V Bend test value Ri/t of 4 for a sample having the size of 35 mm100 mm, wherein Ri is the bending radius in mm and t is the thickness in mm of the steel sheet.

Disclosed herein is a high-strength galvannealed steel sheet having a galvannealed layer on a surface of a base steel sheet and containing predetermined steel components. The steel sheet sequentially has, from the interface of the base steel sheet and the galvannealed layer, towards the base steel sheet: an internal oxide layer and containing at least one oxide selected from the group consisting of Si and Mn; a soft layer including the internal oxide layer, and satisfying a predetermined Vickers hardness; and a hard layer made up of a structure mainly composed of martensite. The average depth D of the soft layer is 20 m or greater, and the average depth d of the internal oxide layer is 4 m or greater and smaller than D. A coefficient of variation of KAM of the base steel sheet at the portion t/4 is 0.66 or less.

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.

A high-strength hot-dip galvanized steel sheet including a hot-dip galvanized plating layer on a steel sheet base material whose tensile strength is 590 MPa or more, wherein the plating layer includes projecting alloy layers being in contact with the steel sheet base material, a number density of the projecting alloy layers is 4 pieces/mm or more per unit length of an interface between the steel sheet base material and the plating layer when seen from a sectional direction, and a maximum diameter of the projecting alloy layers at the interface is 100 m or less, wherein the steel sheet base material includes: a miniaturized layer being directly in contact with the interface between the steel sheet base material and the plating layer; a decarburized layer being in contact with the miniaturized layer and existing on an inward side of the steel sheet base material; and an inner layer other than the miniaturized layer and the decarburized layer, and one kind or two kinds or more of oxides of Si and Mn are contained in layers of the miniaturized layer, the decarburized layer, and the projecting alloy layers.

In some examples, an article including a substrate and a multi-layered coating on at least a portion of the substrate. The multi-layered coating including at least one nano-crystalline layer comprising a metal or a metal alloy and a corrosion resistant layer on the at least one nano-crystalline layer. The nano-crystalline layer defining an average grain size of less than 50 nanometers (nm) and the corrosion resistant layer including at least one of nickel metal, tin metal, zinc metal, cadmium metal, chromium metal, nickel-phosphorus alloy, nickel-sulfur alloy, nickel-boron alloy, nickel-cadmium alloy, nickel-zinc alloy, and tin-zinc alloy.

A high-strength steel sheet having high yield ratio, excellent stretch flange formability, and resistance to secondary working embrittlement. The steel sheet has a composition containing C: 0.02% to less than 0.10%, Si: less than 0.3%, Mn: less than 1.0%, P: 0.10% or less, S: 0.020% or less, Al: 0.01% to 0.10%, N: 0.010% or less, and Nb: 0.003% to less than 0.070% on a mass basis, the remainder being Fe and inevitable impurities. A steel microstructure of the steel sheet contains ferrite: 90% or more and a total of pearlite, martensite, retained austenite, and cementite: 0% to 10% on an area fraction basis, in which the average grain size of the ferrite is 15.0 m or less, and in which the average aspect ratio of the ferrite is 1.2 or more; and a tensile strength of 500 MPa or less.