Investigation of Selective Oxidation and Reaction Wetting of Q&P Steel Under Different Dew Point During Continuous Galvanizing

The effect of different dew points (−30 °C/− 10 °C) on the reactive wetting and selective oxidation of alloying elements of quenching and partitioning steel during continuous galvanizing was investigated. Morphology of the inhibition layer, the type of surface oxides and the variation of surface alloying elements concentration after galvanizing were all characterized. The results indicated that the enrichment of Si and Mn on the surface is lower after annealing at higher dew point, forming a more compact inhibition layer with a higher aluminum interior. Finally, better wettability of the steel during galvanizing and less leakage plating has been obtained. With the increase in dew point from −30 to −10 °C, the transformation of Si and Mn from outer oxidation to inner oxidation has occurred at 32 nm and 29 nm below the surface, respectively. Meanwhile, the oxidation depth becomes deeper.