Method for continuously annealing and preparing strip of high-strength steel for the purpose of hot-dip galvanisating it

Abstract

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%.

Dependencies are inferred from the claim text.