Abstract:Galvalume coatings on steel strips have a superior performance, it combines the good durability of an aluminum coating and the sacrificial characteristics of a zinc coating, which has excellent corrosion resistance. In recent years in the construction sector is rapid development. Galvalume bath by adding alloying elements have a greater impact on the growth and performance of steel plate coating.
This paper investigated the effects of adding different content of Si and Ti to Galvalume bath on the structure and thickness of hot-dip coating. Zinc-aluminum bath temperature control in 600 5℃ ,then pure iron samples were hot-dipped in the alloy bath containing additives, observation of molten pool and coating surface morphology by adding alloying elements. Coating cross-section morphology were observed using scanning electron microscopy, while using energy dispersive analysis of the composition of each phase in the coating metal intermetallic compound layer, And growth kinetics of intermetallic compounds in the coating were analyzed.
The results show that a large number of zinc-containing Fe-Al phase in the alloy layer due to a violent exothermic reaction occurs between the iron and aluminum when the 55%Al-Zn bath did not add Si. Fe2Al5-Znx phase appears only in the vicinity of the iron substrate, while large number of the layered FeAl3-Znx phase was appeared more distant from the substrate. A lot of liquid zinc-aluminum phase layer between FeAl3-Znx.The reaction is inhibited between the Fe-Al when Si is added to the bath, only 1.0% of the addition even with the intermetallic compound layer thinning, straight state can be maintained at the appropriate dipping time. The inhibitory effect is more obvious when the Si content to 3.0%.Adding a small amount of Ti element makes the surface of the strip coating is shiny and smooth in the Galvalume bath, simultaneously intermetallic compounds significantly thinning. Its thickness at a lower value as the Ti content is added to 0.2%.Followed by Ti content further increase has little effect on the growth of the coating.
Keywords: Si; Ti; Galvalume; hot-dipping Zn-Al; intermetallics