SMS Group (Düsseldorf, Germany):

F. Brühl, Dr., Head of Direction “Strip Processing and Thermal Technological Equipment“
H. Behrens

H. G. Hartung

C. Sasse, e-mail: caesar.sasse@sms-group.com

Drever International (Lüttich, Belgien):
J.-P. Crutzen

PrOBO_X technology has recommended itself as an ideal process for hot galvanizing of high-strength and special steels with increased content of Si and Mn. The accompanying problems of wetting in this process can be solved via special oxidation and reduction processes. Thereby the strip surface during annealing is specially oxidized at definite temperature with forming of uniform and very thin layer if iron oxide, which is reduced afterwards before galvanizing. When strip passes through galvanizing bath, very thin Fe–Al coating is forming on this layer; it plays the role of bonding acceleration and is necessary for hot galvanizing. During consequent strip processing the uniform layer is forming, it meets all requirements. It is shown that PrOBO_X process is a tested solution for coating application on the modern high-strength steel strip. This technology has been successfully realized in many lines and has essential advantages in comparison with other technical solutions in this field. The coating problems caused by silicon and manganese content in steels can be overcome via preliminary oxidation. This method is also expedient for several steel gardes with annealed zinc coating, because the layer of reduced iron oxide leads to lowering of the required temperature and better forming of Fe–Zn layer.