Scaling Physical Model Study on Dynamic Accumulation of Bottom Dross in a Molten Zinc Pot

In a continuous hot-dip galvanizing line the strip submerged in the Zn pot moves around a sink roll and a pair of support rolls.1) Dross is generated due to metallic compounds and chemical reactions occurring in the zinc bath2) and sorted into top dross, free dross and bottom dross according to the density ratio of dross to liquid zinc. Dross, especially the bottom dross, pick-up on steel strip is a common coating defect in hot dip galvanizing and therefore lowers the surface quality of steel sheets.3) For purpose of development of bottom dross control technologies, research on the dynamic accumulation behaviors of bottom dross in the zinc pot, including dispersion, transport and deposition, should be carried out. This is the main content of this paper. Physical model experiments are usually employed to observe as well as measure complex systems directly. Several experimental devices were designed and used to determine the circulation patterns of molten metal in the zinc pot.4,5) In the lab, a reduced scale model made of transparent material was generally used to facilitate measurements. The flow pattern, mean flow velocity components, root-meansquare values of turbulence components and Reynolds shear Scaling Physical Model Study on Dynamic Accumulation of Bottom Dross in a Molten Zinc Pot