Flow Field and Dross Behaviour in a Hot-Dip Round Coreless Galvanizing Bath

Abstract

This paper presents the results of fluid flow and dynamic behavior of dross in a hot-dip coreless galvanizing process by performing water modeling experiments and numerical simulations. NaCl aqueous solutions and plastic particles were employed as model fluid and top and bottom dross, respectively. The velocity distributions of the fluid were measured with the help of an Acoustic Doppler Velocimeter (ADV) for the strip speeds from 1.0 m/s to 2.7 m/s. The results from both water modeling experiments and numerical simulations showed that the flow in the bath is very complex and is determined by the strip speed, which is also a key factor for the distribution of top and bottom dross distribution in the bath. In the water modeling experiments applying the ADV at different strip speeds, some swirling flow which may drive the dross to the strip was observed on the surface of the bath, as well as inside the bath. And the swirling flow on the surface was disappeared when the strip speed was increased to 2.0 m/s. Consequently, high strip speed is favorable for the strip to avoid the dross adhering problem. In addition, bottom dross distribution was also investigated by using plastic particles. The results illustrate that bottom particles distribution is highly determined by the strip speed. Remarkably, more intensive flow driven by much higher strip speed (2.3 m/s) may roll up the bottom particles into the bath. This gives higher possibilities for the strip to cause surface quality problem.