Selective Oxidation Behaviors of a DP780 Steel during Hot-Dip Galvanizing Process

The selective oxidation behaviors of a DP780 steel during recrystallization under different annealing atmospheres have been investigated in a hot dip process simulator (HDPS). The surface chemistry and morphology were analyzed by glow discharge optical emission spectroscopy (GDOES) and scanning electron microscopy (SEM) respectively. The results indicate that the dew point and hydrogen content in the annealing atmosphere have great effects on selective oxidation, and the influence of dew point is slightly stronger than that of hydrogen content. Under the higher dew point and lower hydrogen content, resulting from the increased tendency of internal oxidization of Mn and Cr, the amount and size of oxides dispersed on the external surface decrease, which finally improves the wetting between the annealed substrate and the Zn bath.