Numerical investigation of dross formation and minimization in continuous galvanizing baths

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Conference8th International Conference on Zinc and Zinc Alloy Coated Steel Sheet, GALVATECH 2011, June 21-24, 2011, Genova, Italy
SubjectContinuous galvanizing; dross formation; oxidation; dross minimization; numerical simulation; bench scale experiment
AbstractThis contribution presents numerical investigations into some aspects affecting the formation of dross during continuous galvanizing. It is well known that dross formation depends on the bath composition, temperature and flow dynamics. However, experimental observation indicates that top dross formation is affected by oxidation at the surface of the bath as the use of an inert gas in air knifes greatly reduces dross generation. In this work numerical simulations are used to investigate the flow dynamics of the gas in the vicinity of the bath surface in order to obtain correlations between the gas velocity and the propensity for oxidation and dross formation. Simulations are first shown for a bench scale experiment simulating top dross formation for which experimental data are available. The experiment consists of a crucible containing liquid zinc with various aluminum and iron contents. The flow in the crucible is generated by the rotation of a propeller immersed into the liquid zinc and then air or inert gas is projected to the surface of the liquid metal to determine the effect on oxidation and dross formation. Dross formation is then correlated to the size of the exposed surface and to the relative velocity between the liquid zinc and the gas. Numerical results are also shown for the gas flow dynamics inside air knifes and in the vicinity of the bath surface. This provides a map of the relative gas/liquid velocity at bath surface which then can be used to estimate the propensity for oxidation and top dross formation.
Publication date
AffiliationNRC Industrial Materials Institute; National Research Council Canada
Peer reviewedNo
NRC number54269
NPARC number18371422
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Record identifier9a377019-7b4f-439e-b4cd-c2093799da9f
Record created2011-08-03
Record modified2016-05-09
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