Nkk Corporation

Nkk Cororation

Akira Hiraya

Junichi Inagaki

Masaki Abe

Masaru Sagiyama

Masaya Morita

Toshio Ishii

Munehiro Ishioka

Hitoshi Oishi

Seishi Hatakeyama

Shinichi Tomonaga

Toshihiko Ooi

Nobuyuki Ishida

Kentaro Akashi

Teruhisa Kuwana

Kazumi Jiromaru

Hideyuki Suzuki

Takayuki Fukui

Masaaki Yamashita

Toyofumi Watanabe

Michitaka Sakurai

Takayuki Urakawa

Toru Imokawa

Satoshi Hashimoto

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.

Apparatus for hot-dip coating a steel strip

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.

Continuous hot-dip coating method and apparatus therefor

Zinciferous plated steel sheet and method for manufacturing same

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.

Process for manufacturing galvannealed steel sheet having excellent

Process for manufacturing galvannealed steel sheets having high

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 1.5 to the alloying-treated steel sheet, to level the numerous fine convexities on the surface of the alloying-treated iron-zinc alloy dip-plating layer, so as to form on the surface of the steel sheet the alloying-treated iron-zinc alloy dip-plating layer as a lower layer having the numerous fine concavities on the surface thereof; and then applying an iron-zinc alloy electroplating treatment to the temper rolling treated steel sheet to form, on the alloying-treated iron-zinc alloy dip-plating layer as the lower layer, an iron-zinc alloy electroplating layer as an upper layer. The above-mentioned iron-zinc alloy electroplating treatment is carried out with an electric current density of from 50 to 150 A/dm.sup. 2 in an acidic electroplating bath containing iron ions and zinc ions, and having a pH value of from 1.0 to 4.0 and a temperature of from 40.degree. to 70.degree. C.

Method for manufacturing iron-zinc alloy plated steel sheet having two

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.2 per surface of the steel sheet; then, passing the steel sheet through an acidic plating bath for 1 to 5 seconds without electrifying same to dissolve the surface portion of the alloying-treated iron-zinc alloy dip-plating layer, so as to form numerous fine jogs on the surface thereof; and then, electroplating the steel sheet in an iron alloy acidic electroplating bath to form an iron alloy electroplating layer as an upper layer, having a plating weight of 1 to 10 g/m.sup.2 per surface of the steel sheet, on the alloying-treated iron-zinc alloy dip-plating layer as the lower layer having the numerous fine jogs.

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Tokyo, Japan

Akira Hiraya