Thyssenkrupp Steel Ag

Thyssen Krupp Ag

Thyssenkrupp Steel Europe Ag

Michael Ullmann

Marc Blumenau

Manfred Meurer

Wilhelm Warnecke

Sabine Zeizinger

Norbert Schaffrath

Gernot Nothacker

Ronny Leuschner

Udo Zocher

Oliver Moll

Sahin Cengiz

Erhard Klemm

Roger Nüssen

Christian Schmidt

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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Bochum, Germany

Michael Ullmann