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

US8652275B2 · kind B2 · utility

Assignee

• Thyssenkrupp Steel AG · DE

Inventors

• Ronny Leuschner · Dresden, DE
• Manfred Meurer · Rheinberg, DE
• Wilhelm Warnecke · Hamminkeln, DE
• Sabine Zeizinger · Mülheim, DE
• Gernot Nothacker · Dortmund, DE
• Michael Ullmann · Bochum, DE
• Norbert Schaffrath · Hamm, DE

Key dates

• Filing date: Dec 2, 2005
• Grant date: Feb 18, 2014
• Expiry date: Oct 9, 2027

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C23C2/0224
• WIPO field: Surface technology, coating
• WIPO sector: Chemistry

Abstract

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° 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° 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.