ALLOYING REACTION CONTROL IN PRODUCTION OF GALVANNEALED STEEL

Alloying reaction in production of galvannealed steel was studied in unsteady-state diffusion conditions analogous to the industrial galvannealing process along with varying aluminum concentrations in the molten zinc bath. High bath aluminum concentration and rapid heating rate suppress the growth of not only the ζ phase, but also the Γ1 phase. The alloying temperature should be chosen in the vicinity of 773K in order to provide a coating predominantly composed of the δ1 phase. These results are discussed in accordance with the concept that the galvannealing process proceeds as a nonequilibrium zinc-iron reaction in an unsteady-state diffusion condition.