Abstract: An apparatus for hot-dip coating a steel strip, comprising: (a) an annealing furnace for continuously annealing the steel strip, the annealing furnace having an entrance side and an exit side; (b) a coating pot having a molten metal coating bath for coating the annealed steel strip; (c) a snout through which the annealed steel strip is introduced into the molten metal coating bath, one end of the snout being connected to the annealing furnace and the other end being immersed into the molten metal coating bath; (d) a seal device for sealing between the annealing furnace and the snout, the seal device being disposed at the exit side of the annealing furnace; and (e) a discharge device for discharging a gas containing a metal vapor from the snout to outside of the snout, the metal vapor being evaporated from the molten metal coating bath in the snout.

Abstract: A method for hot-dip coating a steel strip comprises: (a) continuously annealing the steel strip in an annealing furnace; (b) introducing the annealed steel strip into a molten metal coating bath through a snout; (c) dipping the annealed steel strip into the molten metal coating bath; (d) controlling a pressure inside of the snout; and (e) discharging a gas containing a metal vapor from the snout to outside of the snout. An apparatus comprises an annealing furnace, a coating pot, a control device for controlling a pressure inside the snout and a gas discharging device.

Abstract: A zinciferous plated steel sheet which comprises a steel sheet, at least one zinciferous plating layer formed on at least one surface of the steel sheet, and an Fe--Ni--O film as an uppermost layer formed on the zinciferous plating layer. The total quantity of metallic elements in the Fe--Ni--O film is within a range of from 10 to 1,500 mg/m.sup.2, and the oxygen content in the Fe--Ni--O film is within a range of from 0.5 to under 30 wt. %. The ratio of the iron content (g/l) relative to the total quantity of the iron content (g/l) and the nickel content (g/l) in the Fe--Ni--O film is preferably within a range of from over 0 to under 1.0.

Abstract: It is an object to provide a process for manufacturing galvannealed steel sheets exhibiting excellent anti-powdering property when press formed, and uniform frictional properties in a coil. A steel strip is galvanized in a bath having a low aluminum content after entering it at a high temperature as defined in relation to the aluminum content of the both, so that the formation of a .zeta. phase may be promoted. Then, the strip is heated for alloying in a high-frequency induction heating furnace so as to have a temperature not exceeding 495.degree. C. when leaving the furnace to yield a plated steel strip having a coating containing a uniformly distributed .zeta. phase. After such heat treatment and cooling, the strip can be plated with an iron or iron-alloy top coating having an iron content of at least 50% and a coating weight of at least 1 g/m.sup.2 to achieve an improved press formability.

Abstract: It is an object to provide a process for manufacturing galvannealed steel sheets having high anti-powdering property as required when they are press formed, and stabilized frictional properties in a coil. Steel sheets are plated in a bath having a low aluminum content, while they have, when entering the bath, a low temperature as defined in relation to the aluminum content of the bath, so that an alloying reaction may be prevented. Then, the sheets are heated for alloying in a high-frequency induction heating furnace so that the sheets leaving the furnace may have a temperature of from over 495.degree. C. to 520.degree. C. to yield galvannealed consisting mainly of a .delta..sub.1 phase. An iron or iron-alloy top coating having an appropriate iron content can be applied onto the plated steel surface to improve its paintability.

Abstract: A method for manufacturing an iron-zinc alloy plated steel sheet having two plating layers and excellent in electropaintability and press-formability, which comprises the steps of: applying an alloying treatment under a temperature of from 420.degree. to 520.degree. C. to a zinc dip-plated steel sheet to form on the surface of the steel sheet an alloying-treated iron-zinc alloy dip-plating layer having on the surface thereof fine irregularities comprising numerous fine concavities and numerous fine convexities; then applying a temper rolling treatment at a reduction rate of from 0.3 to 1.

Abstract: A method for manufacturing an iron-zinc alloy plated steel sheet having two plating layers and excellent in electropaintability and press-formability, which comprises the steps of: passing a steel sheet through a zinc dip-plating bath to form a zinc dip-plating layer on at least one surface of the steel sheet; then, heating the steel sheet, on which the zinc dip-plating layer has been formed, to alloy the zinc dip-plating layer and the surface portion of the steel sheet, so as to form, on the surface thereof, an alloying-treated iron-zinc alloy dip-plating layer as a lower layer having a plating weight of from 30 to 120 g/m.sup.