A method and arrangement for manufacturing hot dip galvanized rolled high strength steel product is presented. The method comprises providing a rolled steel product, heating and annealing the rolled steel product for creating a layer of iron oxide on the surface of the rolled steel product, cooling the rolled steel product, having the iron oxide layer, in a first cooling step to a temperature in a temperature range of 560-600 C. and holding for 3-10 seconds, quenching said rolled steel product, covered with the layer of iron oxide, in a second cooling step by immersing it into a zinc bath comprising aluminium and having a temperature between 440-450 C. for 1-5 seconds and cooling the rolled steel product in a third cooling step to room temperature. An arrangement for implementing the method is also presented.

The present invention relates to a plated steel sheet which can be used for automobiles, home appliances, building materials, etc. and a method for manufacturing same and, more particularly, to a zinc alloy plated steel sheet having excellent adhesion to an adhesive and a method for manufacturing same.

A hot-dip galvanized steel sheet according to one aspect of the present invention comprises a base steel sheet and a hot-dip galvanized layer formed on the surface of the base steel sheet, wherein the difference between the average of the Mn/Si values of surface oxides present on a surface portion, which is the region from the interface between the hot-dip galvanized layer and the base steel sheet to a depth of 15 nm, and the average of the Mn/Si values of internal oxides, which are present in the region from the interface to a depth of 50-100 nm, can be 0.5 or more. Mn and Si of each oxide mean the amounts (wt %) of Mn and Si components in the oxide, which are measured by EDS, and the average of Mn/Si values means the averaged value of the Mn/Si values measured for each oxide.

A plated steel material having a plating layer having an average chemical composition containing, in mass %, Zn: more than 50.00%, Al: more than 15.0% and less than 30.0%, Mg: more than 5.0% and less than 15.0%, and Si: 0.25% or more and less than 3.50%, and impurities, and wherein a total amount (?A) of at least one selected from the group consisting of Sn, Bi and In is less than 1.00%, a total amount (?B) of at least one selected from the group consisting of Ca, Y, La, Ce and Sr is 0.02% or more and less than 0.60%, 2.0?SMg/Si<20.0 (Formula 1), 3.0?Si/?B<24.0 (Formula 2), and 26.0?(Si/?B)?(Mg/Si)<375.0 (Formula 3) are satisfied, and in an X-ray diffraction pattern of the surface of the plating layer, a diffraction intensity ratio R1 defined by R1={I(16.18?)+I(32.69?)}/I(27.0?) (Formula 4) satisfies 2.5<R1 (Formula 5) is used.

A steel sheet has a chemical composition containing, by mass %, C: 0.20% or more and 0.40% or less, Si: more than 1.0% and 3.0% or less, Mn: 1.5% or more and 3.5% or less, P: 0.002% or more and 0.010% or less, S: 0.0002% or more and 0.0020% or less, sol. Al: 0.40% or less (not including 0%), and N: 0.0100% or less, with the balance being Fe and incidental impurities; and a steel microstructure containing, in area fraction, tempered martensite: 45% or more and 83% or less, bainite: 15% or more and 53% or less, and retained austenite: 2% or more. Carbides in the tempered martensite have an average particle size of 0.40 ?m or less, an average amount of C in the retained austenite is 0.5% by mass or more, and a tensile strength is 1,470 MPa or more.

A method for manufacturing a hot-dip galvanized steel sheet having a high Si content and good plating adhesion. The method for manufacturing a hot-dip galvanized steel sheet includes the following: hot-rolling a steel raw material having a Si content of 1.0 mass % or more and coiling a steel sheet at 500? C. to 700? C.; subjecting a surface of the steel sheet after the coiling to an oxidation treatment at a heating temperature of a steel sheet temperature of 750? C. or lower, and subsequently subjecting the surface to a reduction treatment; and subjecting the steel sheet after the reduction treatment to a hot-dip galvanizing treatment to form a Zn-plated layer on a surface of the steel sheet.

A zinc or zinc-alloy coated rolled steel strip or sheet includes (in wt. %) 0.08-0.28 C, 1.4-4.5 Mn, 0.01-0.5 Cr, 0.01-2.5 Si, 0.01-2.0 Al. The steel has a tensile strength of 950-1550 MPa, a yield strength of 350-1400 MPa, a yield ratio?0.35, and Ri/t?4. The microstructure includes ?40 tempered martensite+bainite, ?30 fresh martensite, 5-20 retained austenite, and ?35 polygonal ferrite. The hydrogen concentration is less than 0.2 ppm in the steel.

A method of forming an AlZnSiMg alloy coating on a steel strip includes dipping steel strip into a bath of molten AlZnSiMg alloy and forming a coating of the alloy on exposed surfaces of the steel strip. The method also includes controlling conditions in the molten coating bath and downstream of the coating bath so that there is a uniform Al/Zn ratio across the surface of the coating formed on the steel strip. An AlZnMgSi coated steel strip includes a uniform Al/Zn ratio on the surface or the outermost 1-2 ?m of the AlZnSiMg alloy coating.

A cold rolled and hot dip coated steel sheet presenting a tensile strength above 100050Al MPa, a uniform elongation above 15% and a low density is provided. The steel includes, by weight percent: 0.1C0.5%, 3.5Mn10.0%, 0Al9.0%, Si5.0%, Ti0.2%, V0.2%, Nb0.2%, S0.004%, P0.025%, 0.5Si+Al9.0%, B0.0035, Cr1%, The balance being Fe and impurities and the microstructure containing 25% to 90% of ferrite, 10% to 50% of austenite, kappa precipitates lower than 5% and martensite lower than 25%. The steel is able to be coated using total oxidation.

A method for producing a cold rolled and hot dip coated steel sheet is provided. The method includes casting a steel into a slab, reheating, hot rolling, cooling, coiling, descaling and cold rolling the slab. The cold rolled steel sheet is annealed so a layer of iron oxide forms on the surface with an internal oxidation underneath. The sheet is then heated so the surface is oxidized and the layer of iron oxide is fully reduced to obtain an internally oxidized depth between 200 nm and 100 m which includes one or more of Si, Mn, Al, Ti containing oxides. The sheet is then hot dip coated and cooled.