A cold-rolled or hot-rolled steel strip having a metal coating, the steel strip having iron as the main constituent and, in addition to carbon, an Mn content of 4.1 to 8.0 wt. % and optionally one or more of the alloy elements Al, Si, Cr, B, Ti, V, Nb and/or Mo. The surface of the uncoated steel strip is cleaned, a layer of pure iron is applied to the cleaned surface, an oxygen-containing iron-based layer is applied to the layer of pure iron and contains more than five mass percent oxygen. The steel strip is then annealed and, to attain a surface consisting substantially of metallic iron, is subjected to a reduction treatment in a reducing furnace while being annealed. The steel strip is then coated with the metallic coating by hot dipping. Uniform and reproducible adhesion conditions are hereby achieved for the metallic coating on the steel strip surface.

The present invention is a production method of a hot-dip galvanized steel sheet including annealing a belt-shaped steel sheet having a Si content of greater than or equal to 0.2% by mass, wherein the annealing is continuously carried out using an annealing furnace having an oxidation heating zone and a reduction heating zone in this order, while the steel sheet is fed using rollers. The annealing includes oxidizing a surface of the steel sheet in the oxidation heating zone at a temperature at which roll pickup does not occur and reducing an iron oxide layer, formed by the oxidizing, in the reduction heating zone before the iron oxide layer reaches an initial roller in the reduction heating zone.

Provided are a hot-dip zinc plated steel material and a method for preparing same, the hot-dip zinc plated steel material comprising: base iron comprising 0.01-1.6 wt % of Si and 1.2-3.1 wt % of Mn; a Zn—Al—Mg alloy plating layer; and an Al-rich layer formed on the interface of the base iron and Zn—Al—Mg alloy plating layer, wherein the rate of occupied surface area of the Al-rich layer is 70% or higher (including 100%).

A plated steel sheet having excellent post-coating corrosion resistance includes: a steel; and a plating layer that is provided on a surface of the steel, in which the plating layer includes, by mass %, Al: 5.00% to 35.00%, Mg: 2.50% to 13.00%, Fe: 5.00% to 35.00%, Si: 0% to 2.00%, Ca: 0% to 2.00%, and a remainder consisting of Zn and impurities, and in a cross section of the plating layer, the area fraction of a Fe.sub.2Al.sub.5 phase is 5.0% to 60.0%, the area fraction of an eutectic structure of Zn and MgZn.sub.2 is 10.0% to 80.0%, the area fraction of a massive MgZn.sub.2 phase is 5.0% to 40.0%, and the area fraction of a remainder is 10.0% or less.

A hot-dip galvanized steel sheet including: a hot-dip galvanizing layer on at least one side of a base steel sheet. The hot-dip galvanizing layer has a Fe content of more than 0% to 3.0% and an Al content of more than 0% to 1.0%. The hot-dip galvanized steel sheet includes a Fe—Al alloy layer provided on an interface between the hot-dip galvanizing layer and the base steel sheet and a fine-grain layer provided in the base steel sheet and directly in contact with the Fe—Al alloy layer. The Fe—Al alloy layer has a thickness of 0.1-2.0 μm. The fine-grain layer has an average thickness of 0.1-5.0 μm, includes a ferrite phase with an average grain diameter of 0.1-3.0 μm, and contains oxides of one or more out of Si and Mn, a maximum diameter of the oxides being 0.01-0.4 μm.

A method of forming an Al—Zn—Si—Mg alloy coating on a steel strip includes dipping steel strip into a bath of molten Al—Zn—Si—Mg 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 Al—Zn—Mg—Si coated steel strip includes a uniform Al/Zn ratio on the surface or the outermost 1-2 μm of the Al—Zn—Si—Mg alloy coating.

There is provided a high-strength hot-dipped steel sheet having excellent coating adhesion and a method for manufacturing the steel sheet. The steel sheet has a chemical composition, and a coating layer is disposed on the steel sheet. The chemical composition includes, by mass %, C: 0.02% or greater and 0.30% or less, Si: 0.01% or greater and 2.0% or less, Mn: 0.2% or greater and 3.0% or less, P: 0.08% or less, S: 0.02% or less, and Al: 0.001% or greater and 0.40% or less, with the balance being Fe and incidental impurities. The coating layer has a coating weight per side of 30 to 90 g/m.sup.2 and contains exfoliated base steel in an amount of 0.3 to 1.5 g/m.sup.2.

High-strength galvannealed steel sheet including any of a) an oxide containing Fe and Mn, b) an oxide containing Fe and Mn and an Fe oxide, c) an oxide containing Fe and Mn and a Mn oxide, d) an oxide containing Fe and Mn, an Fe oxide, and a Mn oxide, and e) an Fe oxide and a Mn oxide is present in a zinc coated layer. The total amount of oxide is 0.01 to 0.100 g/m.sup.2; the ratio by mass % of Mn to Fe, e.g., Mn/Fe, contained in the oxide is 0.10 to 10.00; an oxide of at least one selected from Fe and Mn is present in an amount of 60% or more; and an oxide of at least one selected from Fe and Mn is present in a surface layer portion of a steel sheet in an amount of 0.040 g/m.sup.2 or less (not including zero).

A method for producing a metallic coated steel sheet is provided. The method includes continuously annealing a steel sheet in a continuous annealing furnace and hot dip coating the steel sheet.

A steel sheet includes a hot-dip galvanized layer or a galvannealed layer on a surface of the steel sheet, the steel sheet including: in mass %, C: 0.06% or more and 0.22% or less; Si: 0.50% or more and 2.00% or less; Mn: 1.50% or more and 2.80% or less; Al: 0.02% or more and 1.00% or less; P: 0.001% or more and 0.100% or less; S: 0.0005% or more and 0.0100% or less; N: 0.0005% or more and 0.0100% or less; and a balance: Fe and impurities.