Challenges, innovation and designs in galvanising technologies for AHSS

Steel grades requiring galvanising have changed dramatically in the last 20 years, going from simple carbon grades for construction to ultra-high tensile strength dual phase grades and extra soft and deep drawing qualities for automotive applications. These new steels have required key modifications and improvements in galvanising lines. For instance, furnaces must accommodate new heat cycles, some with annealing temperatures over 900°C, fast cooling to various temperatures is sometimes followed by ageing sections in the line, and surface oxidation must be controlled to achieve good zinc wettability. Plant operating constraints, design changes, areas of investigation and thoughts about even newer steels are discussed.