The present invention relates to an apparatus and a method of manufacturing a hot dipped galvanized steel sheet that is excellent in corrosion resistance and has no linear defects, thereby being available for automobile bodies, household appliances, construction materials, and the like which need aesthetic surfaces. The apparatus for manufacturing a hot dipped galvanized steel sheet includes: a plating pot filled with a galvanizing bath for coating of a steel sheet; a sink roll; a wiping device adjusting the thickness of the coating on the steel sheet; a top roll; an oxidation process chamber; and an air cooling device. According to the present invention, after an excess molten coating solution attached to the steel sheet is evenly removed, an oxide film is made to be 0.1 μm to 0.3 μm thick before a coating layer starts to solidify. Thus, linear defects can be prevented.

Provided is a hot-dip galvanized steel sheet to be used for home appliances, vehicles, and the like, and having excellent surface appearance and low-temperature bonding brittleness. The hot-dip galvanized steel sheet includes: a base steel sheet; and a hot-dip galvanized layer formed on the base steel sheet. A surface of the base steel sheet has a centerline average roughness (Ra) of 0.3 or more, a roughness skewness (Rsk) of −1 or less, and a roughness kurtosis (Rku) of 6 or more.

Disclosed is a steel sheet for hot press forming, which includes: a base steel sheet; and a plating layer disposed on the base steel sheet and including a diffusion layer and a surface layer that are sequentially laminated, wherein the diffusion layer includes an Fe—Al alloy layer and an Fe—Al intermetallic compound layer that are sequentially disposed on the base steel sheet and each include silicon, and an area fraction of the Fe—Al intermetallic compound layer with respect to the diffusion layer is 84.5% to 98.0%.

An apparatus for controlling coating weight coated on a strip by using an air knife disposed in a travelling direction of the strip in a continuous plating process in which the strip is dipped in a molten metal pot and is coated includes: a prediction model unit including a prediction model in which a neural network is trained with accumulated operation conditions; and an optimum air knife condition calculation unit configured to derive an absolute value of at least one of an air knife gap and an air knife pressure by using the prediction model based on an input operation condition.

A method manufacturing a steel strip, including the subsequent steps of hot rolling the strip into a hot rolled strip, cold rolling the hot rolled strip and hot dip coating the cold rolled strip with a Zn based coating by leading the strip through a bath including molten zinc and wiping the strip after the coating using a gas knife having a knife slot from which a wiping gas is projected and the steel strip is cold rolled to a final cold rolled thickness of between 0.40 mm and 1.00 mm in a multi-stand cold rolling mill, and the coated steel sheet includes a steel substrate provided with a hot dip metal coating.

Provided is a highly corrosion-resistant plated steel sheet having plating adhesion and resistance to liquid metal embrittlement. A highly corrosion-resistant plated steel sheet comprises a base steel sheet and a plated layer, which sequentially comprises an Fe—Al alloy layer and an MgZn.sub.2 layer from an interface with the base steel sheet.

A method for manufacturing a gas wiping nozzle provided with a pair of lip parts facing each other and a slit formed as a gas ejection port between the pair of lip parts and blowing gas from the slit against a steel strip pulled up from a plating bath to adjust a thickness of a molten metal film deposited on a surface of the steel strip, which method includes fitting fitting projections provided at one lip part with fitting holes provided at another slip part and fastening the pair of lip parts together in the fitted state, the fitting projections fitted with the fitting holes, two pairs of the fitting projections and the fitting holes provided separated by a distance in a width direction of the steel strip, relative movement between the pair of lip parts in a thickness direction of the steel strip restricted in the fitted state.

Provided is a low-density clad steel sheet having excellent formability and fatigue properties, including a base material; and cladding materials provided on both side surfaces of the base material, wherein the base material is a lightweight steel sheet including, by weight, C: 0.3 to 1.0%, Mn: 4.0 to 16.0%, Al: 4.5 to 9.0%, and a remainder of Fe and inevitable impurities, and each of the cladding materials is martensitic carbon steel including, by weight, C: 0.1 to 0.45%, Mn: 1.0 to 3.0%, and a remainder of Fe and inevitable impurities.

Provided is a low-density clad steel sheet having excellent formability and fatigue properties, including a base material; and cladding materials provided on both side surfaces of the base material, wherein the base material is a lightweight steel sheet including, by weight, C: 0.3 to 1.0%, Mn: 4.0 to 16.0%, Al: 4.5 to 9.0%, and a remainder of Fe and inevitable impurities, and each of the cladding materials is martensitic carbon steel including, by weight, C: 0.1 to 0.45%, Mn: 1.0 to 3.0%, and a remainder of Fe and inevitable impurities.

A cooling method of a travelling coated steel strip, exiting a hot-dip coating bath, including the steps of A) sucking a gas into a cooling device, B) filtering the sucked gas by a filtering system capturing at least 50% of the particles having a size of at least 2.5 .Math.m, C) blowing, at a velocity comprised from 1 to 80 m.s.sup.-1, the sucked and filtered gas onto the coated steel strip.