Deformations during jet-stripping in the galvanizing process

Abstract

The problem of coating steel by passing it through a molten alloy and then stripping off excess coating using an air jet is considered. The work revisits the analysis of Tuck (Phys Fluids 26:2352, 1983) with the addition of extra shear terms and a consideration of the effect of increased air-jet speeds. A first-order partial differential equation is derived and solved both to obtain the steady-state coating shape and to determine the evolution of any defects that may form.

Investigation of the Gas‐Jet Wiping Process − Two‐Phase Large Eddy Simulations Elucidate Impingement Dynamics and Wave Formation on Zinc Coatings

“…Hocking et al derived an analytic model to examine the evolution of small perturbations in liquid films . Unsteady phenomena within plane gas jets impinging on flat walls were experimentally investigated at moderate Reynolds numbers by Maurel et al and Senter et al, analyzing the jet and the instantaneous behavior of vortices in the impinging zone using the particle image velocimetry technique (PIV) .…”

Deformation and dewetting of thin liquid films induced by moving gas jets

“…In the galvanization of steel, for example, so-called jet stripping is a common technique [1][2][3][4][5][6][7][8], where the thickness and uniformity of a metallic coating on a moving sheet of steel is adjusted by the pressure and shear stress of an impinging slot jet. The analogous effect is also relevant in smaller scale systems, such as ultrathin films of hard disk lubricant [9].…”

Coating Film Profiles Generated by Fluctuating Location of the Wiping Pressure and Shear Stress

“…In developing the analytic model we have sourced an approximate mathematical model for the thin viscous coating in the jet-wiping problem from the literature 17) and employed a numerical scheme to obtain the solution for the free-surface of the coating along the strip for the case of temporal variation in the vertical location of the pressure and shear stress acting on the coating. In the simulation cases discussed in this report the along-strip location of the pressure and shear stress profiles oscillate with a temporal sinusoidal pattern.…”

“…The mathematical model that forms the basis of the present work is as formulated in the earlier work of other authors. 17,19,20) Overall, the general conditions of the model are that the coating is mathematically treated using the thin film assumptions and is assumed to be two-dimensional. Following the application of the usual boundary conditions for the jet wiping problem to the equations governing the flow, a PDE that specifies the coating surface h as a function of strip location x and time t can be formulated, and we have sourced such an equation from an earlier study 17) for use as the basis of the model reported herein, specifically (with the surface tension term omitted), using,…”