The Galvatech 2021 session entitled “Furnace pre-treatments for Hot Dip Galvanizing lines” contained 14 excellent contributions from renowned experts in the field of galvanising and furnace control.
The continuing demand for new and stronger advanced high-strength and ultra-high strength steels, imposes challenges to combine desired substrate properties with stringent requirements on coating and surface quality. These new A/UHSS grades require more complex annealing cycles with increasingly lower thermal tolerances. This complexity entails a need for increased cooling rates and top temperatures, as well as the capability for intermediate cooling and reheating for quench & partitioning processes.
For the successful production of challenging A/UHSS grades, a well-balanced and controlled process starting from upstream processing down to continuous hot-dip galvanizing is crucial. Knowing the variations in the incoming product and anticipating accordingly with adjustments in furnace settings is good practice. For example, variations in emissivity along the coil length and width can affect the heating rate during the annealing cycle, potentially resulting in undesired inhomogeneities in mechanical properties and other product inconsistencies.
The new A/UHSS steels are harder to galvanize due to an increased alloy content, for which a tighter atmosphere control is required, with often an oxidation step or dew point control. External selective oxidation can – apart from resulting in a poor galvanized surface – also result in build-up on furnace rolls, which may lead to defects on the steel strip. Roll coatings can prevent or minimize this oxide pick-up. Furthermore, the challenging product mix for many galvanizing lines nowadays demands flexibility in terms of coil width and gauge and temperature cycle. This comes with the necessity for increased flexibility to adapt furnace settings accordingly, which may impact lifetime expectancy of the equipment and maintenance schedules.
In the presentation results will be given from flash oxidation in an annealing simulator, in which the growing Fe-oxide layer is being monitored by an in-situ RGB camera. This will be followed by selected highlights from the session, addressing some of the challenges mentioned above.
Best Paper Winner Marga Zuijderwijk, Tata Steel Europe Research and Development, will present highlights from her Galvatech 2021 paper "Evaluation of Iron-Oxide Layers During Flash Pre-Oxidation in an Annealing Simulator". Selected highlights from other Galvatech 2021 papers on furnace pretreatment advances will also be summarized.
Each session will start with the 20 minute lecture, followed by a 20 minute panel discussion. This will be followed by 10 minutes of general discussion and a short break before beginning the next session.
pre-oxidation, annealing simulator, in-situ measurement, AHSS galvanizing