Arcelormittal

Centre De Recherches Metallurgiques Asbl

Centre De Recherches Metallurgiques Asbl-centrum Voor Research in De Metallurgie Vzw

Michel Bordignon

Jonas Staudte

Marc Schyns

Xavier Vanden Eynde

Roger Franssen

A hot-dip coated steel substrate coated with a layer of Sn directly topped by a zinc or an aluminum based coating is provided, the steel substrate having the following chemical composition in weight percent:

Hot-dip coated steel substrate

A hot-dip coated steel substrate coated with a layer of Sn directly topped by a zinc or an aluminum based coating is provided, the steel substrate having the following chemical composition in weight percent:0.10&#x2264;C&#x2264;0.4%,1.2&#x2264;Mn&#x2264;6.0%,0.3&#x2264;Si&#x2264;2.5%,Al&#x2264;2.0%,and on a purely optional basis, one or more elements such asP&#x3c;0.1%,Nb&#x2264;0.5%, B&#x2264;0.005%,Cr&#x2264;1.0%,Mo&#x2264;0.50%,Ni&#x2264;1.0%,Ti&#x2264;0.5%,the remainder of the composition making up of iron and inevitable impurities resulting from the elaboration, the steel substrate further having between 0.0001 and 0.01% by weight of Sn in the region extending from the steel substrate surface up to 10 &#x3bc;m.

The present application relates to a method for continuously annealing and preparing a strip of high-strength steel for the purpose of hot-dip coating it in a bath of liquid metal, in which said steel strip is treated in at least two sections, comprising in succession, when considering the direction of advance of the strip: a section called the heating and holding section, in which the strip is heated and then held at a given annealing temperature in an oxidizing atmosphere; and a section called the cooling and transfer section, in which the annealed strip at least is cooled and undergoes complete reduction, in a reducing atmosphere, of the iron oxide present in the oxide layer formed in the previous section, in such a way that the oxidizing atmosphere is separated from the reducing atmosphere, a controlled oxygen content is maintained in the heating and holding section between 50 and 1000 ppm, and a controlled hydrogen content is maintained in the cooling and transfer section at a value of less than 4% and preferably less than 0.5%.

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Sprimont, Belgium

Michel Bordignon