A cold-rolled sheet is provided. The cold-rolled sheet includes a steel substrate with a carbon content C.sub.0 between 0.07% and 0.5%, expressed by weight, and a metal pre-coating on at least the two principal faces of the steel substrate. The substrate has a decarburized area on the surface of each of the two principal faces. The depth p.sub.50% of the decarburized area is between 6 and 30 micrometers, and p.sub.50% is the depth at which the carbon content is equal to 50% of the content C.sub.0. The sheet does not contain a layer of iron oxide between the substrate and the metal pre-coating.

A continuous annealing furnace for annealing steel strips that is a vertical-type annealing furnace is configured so that part of gas inside the furnace is drawn and introduced to a refiner disposed outside the furnace including an oxygen removing apparatus and a dehumidifying apparatus, oxygen and moisture contained in the gas are removed to lower the dew point of the gas, and the gas having a lowered dew point is put back into the furnace. At least one gas inlet through which gas is drawn from the furnace into the refiner is disposed in the vicinity of the entry side of the furnace at a distance of 6 m or less in the vertical direction and 3 m or less in the furnace-length direction from the steel-strip-introduction section located at the lower part of the heating zone.

A method for producing high-strength galvanized steel sheets having excellent coating adhesion, workability and appearance. The method comprises hot rolling a slab comprising, by mass %, C: 0.05 to 0.30%, Si: 0.1 to 2.0% and Mn: 1.0 to 4.0%, then coiling the steel sheet into a coil at a specific temperature T.sub.C, and pickling the steel sheet, cold rolling the hot-rolled steel sheet resulting from the hot rolling, annealing the cold-rolled steel sheet resulting from the cold rolling under specific conditions, and galvanizing the annealed sheet resulting from the annealing in a galvanizing bath containing 0.12 to 0.22 mass % Al.

Provided is a galvanized steel sheet having excellent spot weldability; and a method for producing same. The galvanized steel sheet includes a base steel sheet and a zinc-based plating layer formed on the base steel sheet, wherein the surface layer of the base steel sheet may have a decarburization rate of at least 30% as represented by equation 1. [Equation 1]: Decarburization rate (%) of surface layer=(1−average carbon concentration in surface layer/bulk carbon concentration)*100, where the surface layer refers to a region extending to a depth of 35 μm from the surface of the base steel sheet.

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.

Provided is a hot-dip plating method that achieves good plating wettability between a metal material and a hot-dip plating bath and that makes it possible to reduce the amount of consumed energy as compared to conventional techniques. In a plating step included in the hot-dip plating method, vibration is applied to a hot-dip plating bath such that the ratio of the average sound pressure level (excluding noise) over ranges each lying between sound pressure peaks at harmonic frequencies of a fundamental frequency to the average sound pressure level (excluding noise) over the measured frequency range in an acoustic spectrum is greater than 0.2.

A hot-dip galvanized steel sheet includes a plated layer formed on at least a part of a surface of a steel sheet, the plated layer containing: Al in a range from 10 mass % to 40 mass %; Si in a range from 0.05 mass % to 4 mass %; Mg in a range from 0.5 mass % to 4 mass %; and the balance consisting of Zn and inevitable impurities. The plated layer has a lamellar structure in which a layered Zn phase and a layered Al phase are alternately arranged in a cross section of the plated layer, the lamellar structure accounting for 5% or more by an area fraction in the cross section, and a total abundance ratio of an intermetallic compound containing at least one of Fe, Mn, Ti, Sn, In, Bi, Pb or B is regulated to 3% or less by the area fraction.

A zinc-plated steel sheet for hot stamping includes a steel sheet having a predetermined chemical composition and a zinc plating film disposed on the steel sheet. In the zinc plating film, the plating adhesion amount is 15.0 g/m.sup.2 or more and less than 40.0 g/m.sup.2, the Fe concentration is 1.5 mass % or more and 8.0 mass % or less, the Al content is 100 mg/m.sup.2 or more and 400 mg/m.sup.2 or less, the Al concentration is 0.50 mass % or more and 3.00 mass % or less, and the remainder consists of Zn and impurities.

A cold- or hot-rolled steel strip with a metallic coating, the steel strip having iron as the main constituent and, in addition to carbon, an Mn content of 8.1 to 25.0 wt. % and optionally one or more of the alloying elements Al, Si, Cr, B, Ti, V, Nb and/or Mo. The uncoated steel strip is first cleaned, a layer of pure iron is applied to the cleaned surface, an oxygen-containing, iron-based layer containing more than five mass percent of oxygen is applied to the layer of pure iron. The steel strip is then annealed and is reduction-treated in a reducing furnace atmosphere during the annealing treatment to obtain a surface consisting mainly of metallic iron. The steel strip is then hot-dip coated with the metallic coating. This creates uniform and reproducible bonding conditions for the coating on the steel strip surface.

A method for controlling surface reactions on a steel strip running through a furnace includes, successively, a first section, a second section, and a third section separated by a sealing element, an atmosphere in the second and third sections being oxidizing and reducing respectively, the method including: heating, in the first section, the steel strip to between 600 and 750° C., while causing the atmosphere therein to be slightly oxidizing and to include: an H.sub.2 content inferior to 2%; an O.sub.2 content inferior to 0.1%; an H.sub.2O or CO.sub.2, or H.sub.2O+CO.sub.2 content superior to 0.03%; a controlled dew point ranging from −50 to −15° C.; and a controlled concentration of CO+CO.sub.2 maintained below 2%. All percentages are expressed in terms of volume.