溶融Znめっき鋼板のFe/Zn固液界面反応に及ぼす鋼板組織の影響

抄録

We have examined the growth kinetics of Fe-Zn intermetallics layers formed on Fe-1.5Mn (α-Fe single phase) and Fe-3.5Mn-0.1C (γ-Fe+α-Fe two phase) steel sheets dipped in pure Zn melt at 460 ºC. In an early stage of dipping, FeZn₁₃-ζ phase layer is initially formed and its thickness slightly increases with increasing dipping time till about 10 s, and then all Fe-Zn intermetallics layers (ζ, δ₁, Γ) grow following a parabolic law. The growth kinetics can be recognized in both steels. This result demonstrates a slight effect of steel microstructure on the formation of Fe-Zn intermetallics layers. The composition analysis revealed a significant Fe dissolution into pure Zn melt in an early stage of dipping. The supersaturated Fe in Zn melt would provide the driving force for the crystallization of ζ phase layer on steel sheets. The continuous layer of ζ phase would control Fe diffusion for the following growth of the other Fe-Zn intermetallics layers.