Salzgitter Flachstahl Gmbh

Nils Köpper

Marc Debeaux

Michael Braun

Ingwer Denks

Christian Pelz

Maik Habermann

Stefan Mecke

Ansgar Geffert

A method for producing a steel strip containing, in addition to iron as the main component and unavoidable impurities, one or more of the following oxygen-affine elements in wt. %: Al: more than 0.02, Cr: more than 0.1, Mn: more than 1.3 or Si: more than 0.1, where the surface of the steel strip is cleaned, oxidation-treated and annealed. The treated and annealed steel strip is subsequently coated with a hot-dip coat. In order to be less cost-intensive and to achieve uniform, reproducible adhesion conditions for the coat, the steel strip is oxidation-treated prior to the annealing at temperatures below 200&#xb0; C., where on the surface of the steel strip, with the formation of oxides with iron from the steel strip, an oxide layer is formed, which contains iron oxide and is reduction-treated during the course of the annealing under a reducing atmosphere to achieve a surface consisting substantially of metallic iron.

Method for producing a steel strip with improved bonding of metallic hot-dip coatings

The invention relates to a method for producing a hot-rolled strip composed of a bainitic multi-phase steel and having a Zn&#x2014;Mg&#x2014;Al coating, comprising the following steps: melting a steel melt containing (in weight percent): C: 0.04-0.11, Si: &#x3c;=0.7, Mn: 1.4-2.2, Mo: 0.05-0.5, Al: 0.015-0.1, P: up to 0.02, S: up to 0.01, B: up to 0.006, and at least one element from the group Nb, V, Ti in accordance with the following condition: 0.02&#x3c;=Nb+V+Ti&#x3c;=0.20, the remainder being iron including unavoidable steel-accompanying elements resulting from the melting process, casting the steel melt into a preliminary material, in particular a slab or a block or a thin slab, hot rolling the preliminary material into a hot-rolled strip having a final rolling temperature in the range of 800 to 950&#xb0; C., cooling the hot-rolled strip to a winding temperature less than 650&#xb0; C., winding the hot-rolled strip at a winding temperature less than 650&#xb0; C., cooling the wound hot-rolled strip to room temperature in still air, wherein the microstructure of the wound hot-rolled strip then has a bainite fraction greater than 50% after the hot rolling, heating the hot-rolled strip to a temperature greater than 650&#xb0; C. and less than Ac3, in particular less than Ac1+50&#xb0; C., cooling the hot-rolled strip to zinc bath temperature, hot-dip coating the heated hot-rolled strip in a zinc alloy molten bath containing (in weight percent): Al: 1.0-2.0, Mg: 1.0-2.0, the remainder being zinc and unavoidable impurities. The invention further relates to the hot-rolled strip produced in accordance with the method above and to shaped, dynamically highly loadable components, in particular motor vehicle parts, that are produced from said hot-roiled strip and that are resistant to corrosive and abrasive influences.

Method for producing a hot strip of a bainitic multi-phase steel having a Zn&#x2014;Mg&#x2014;Al coating, and a corresponding hot strip

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Harsum, Germany

Nils Köpper