Thyssenkrupp Steel Europe Ag

Thyssenkrupp Steel Ag

Gernot Nothacker

Norbert Schaffrath

Sabine Zeizinger

Manfred Meurer

Wilhelm Warnecke

Ronny Leuschner

Michael Ullmann

Michael Peters

Friedhelm Macherey

Klaus Josef Peters

Tim Rübenstrunk

Thorsten Muller

Thorsten Müller

Tim Rubenstrunk

The invention relates to an apparatus for the continuous hot-dip coating of metal strip, preferably steel strip, comprising a melting bath vessel, a snout, which opens in the melting bath vessel, for introducing a metal strip, which is heated in a continuous furnace, into the melting bath in protective gas, and a deflecting roller, which is arranged in the melting bath vessel, for deflecting the metal strip, which is entering the melting bath, in a direction pointing out of the melting bath, wherein that end of the snout which is dipped into the melting bath has at least one runoff chamber which is bounded inward by an overflow wall, downward by a floor and outward by the wall of the snout, wherein the overflow edge of the overflow wall lies at least in sections below the melting bath surface, and wherein a suction line with a pump is connected to the runoff chamber, characterized in that the runoff chamber is provided with at least one through opening through which liquid molten metal can flow out of the melting bath into the runoff chamber, wherein the at least one through opening is arranged lower than the overflow edge.

Apparatus for the continuous hot-dip coating of metal strip

The invention relates to a method and to an apparatus for avoiding surface defects, which are caused by zinc dust, on galvanized metal strip in continuous strip galvanization, in which metal strip which is to be galvanized and is heated in a continuous annealing furnace is moved through a furnace pipe in protective furnace gas and is immersed into a zinc bath, wherein the furnace pipe is provided with injection openings via which the front side and the rear side of the metal strip can be acted upon with protective furnace gas, and wherein extraction openings for extracting protective furnace gas loaded with zinc vapor are arranged adjacent to the injection openings. The apparatus according to the invention is characterized in that a multiplicity of the injection openings are configured and arranged in the furnace pipe in such a manner that the protective furnace gas streaming out of said injection openings is directed onto that surface of the metal strip which faces the respective injection opening with an angle of impact within the range of 70&#xb0; to 110&#xb0;, wherein the distance between the respective injection opening and at least one extraction opening assigned thereto is selected in such a manner that, at a predetermined or predeterminable flow velocity of the protective furnace gas emerging from the respective injection opening, an entraining of protective furnace gas, which occurs during movement of the metal strip, in the direction of the zinc bath is opposed.

Method and device for avoiding surface defects caused by zinc dust in a continuous strip galvanising process

A process for melt dip coating a strip of high-tensile steel with alloy constituents including zinc and/or aluminum includes the following steps. The strip is heated in a continuous furnace initially in a reductive atmosphere to a temperature of approximately 650&#xb0; C., at which the alloy constituents diffuse to the surface in small amounts. The surface, consisting predominantly of pure iron, is converted into an iron oxide layer by a short heat treatment at a temperature of up to 750&#xb0; C. in a reaction chamber which is integrated in a continuous furnace and has an oxidizing atmosphere. In a subsequent annealing treatment at a higher temperature in a reductive atmosphere, this iron oxide layer prevents the alloy constituents from diffusing to the surface. In the reductive atmosphere, the iron oxide layer is converted into a pure iron layer to which the zinc and/or aluminum are applied in the molten bath with optimum adhesion.

Process for melt dip coating a strip of high-tensile steel

A method for coating a flat steel product manufactured from a high strength steel with a metallic coating, wherein the flat steel product is initially subjected to a heat treatment, in order then, in the heated state, to be hot-dip galvanized with the metallic coating in a melting bath containing overall at least 85% zinc and/or aluminum. The heat treatment includes heating the steel product in a reducing atmosphere, followed by converting a surface of the flat product to an iron oxide layer by a heat treatment lasting 1 to 10 secs in an oxidizing atmosphere, followed by annealing in a reducing atmosphere over a period of time which is longer than the duration of the formation of the iron oxide layer such that the iron oxide layer is reduced at least on its surface to pure iron, followed by cooling the product to a melting bath temperature.

Method for melt immersion coating of a flat steel product made of high strength steel

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Dortmund, Germany

Gernot Nothacker