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In continuous galvanizing line operations, the thickness and the uniformity of the zinc coating are governed by the gas jet wiping process; a complex multi-phase, multi-scale phenomenon. Though efficient, the process leads to the undesired top skimming formation. To better understand the intricate interactions among the moving strip, the unsteady turbulent jet, the falling excess liquid zinc and the local skimming generation, an efficient and accurate numerical model would be highly valuable. This work describes a modeling framework for top skimming formation, focusing on the coupling between the gas jet wiping process and the phenomenological model for local skimming formation., GALVATECH 2020: 12th International Conference on Zinc & Zinc Alloy Coated Steel Sheet, June 20-24, 2021, Vienna, Austria

International audience; The growth of faceted crystals occurs often in nature and industry, involving often the presence of flow. The growth of faceted crystals is the result of interface kinetics and diffusion phenomenon. The present paper presents a front tracking interface model based on a cellular automaton approach for the simulation of faceted crystal growth. The current model takes into account the interface kinetics and solute transport by diffusion and convection. The propagation of kinks is modelled by differentiating two growth velocities, one normal and one lateral at each face. The positions of the crystal corners are shifted according to growth of adjacent faces. The hydrodynamics is computed with a two-phase model using a penalty method to model the presence of growing obstacles (the crystals). This model was applied in 2D to the growth of hexagonal Fe 2 Al 5 crystals, so called top dross particles, in a saturated liquid at constant temperature. Qualitative comparison was made between simulation and experimental observation of crystal shape and size. The growth rate was found to be strongly influenced by the flow hydrodynamic induced kinetics.

Corrosion of steel reinforcing bar (rebar) is the most significant cause of concrete failure, resulting in expensive repairs and premature structure replacements across the country. This paper will discuss a new, low-cost, zinc coating process for rebar. The properties of this new coated rebar and its contribution to improvement of concrete performance will be presented together with the status of related national and international standards. The Continuous Galvanized Rebar (CGR) coating process is similar to galvanizing of sheet steel. The zinc coating is durable and resistant to abrasion that is routine during transport and construction, but is also highly ductile and can be bent without cracking to diameters of less than 4x the rebar diameter. This property ensures the bars can be coated pre-fabrication, reducing cost and speeding construction schedules. Once in the concrete, the zinc coating protects the rebar both as a barrier coating and with the well-known sacrificial properties of a galvanized coating.

This 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., 8th International Conference on Zinc and Zinc Alloy Coated Steel Sheet, GALVATECH 2011, June 21-24, 2011, Genova, Italy