Principle and simulation of three-phase electromagnetic wiping technique for hot-dip galvanizing of steel pipes

Abstract

Electromagnetic wiping offers the advantages of non-contact operation and ease of control compared to the gas wiping. However, the single-phase electromagnetic wiping technique predominantly generates an axially oriented magnetic flux, resulting in limited axial electromagnetic force and reduced wiping efficiency. This paper introduces a three-phase electromagnetic wiping (TPEW) method for hot-dip galvanizing pipes. Compared to single-phase coils, the three-phase coils in the TPEW create a traveling magnetic field along the pipe axis, generating stronger axial electromagnetic forces on the surface of the galvanized coating, thereby achieving more effective removal of excess liquid zinc. Furthermore, the frequency and amplitude of the TPEW coil currents can be easily adjusted, enabling precise modulation of the traveling magnetic field and the electromagnetic forces acting on the liquid zinc. This ultimately allows for accurate control over the thickness and uniformity of the coating. Experimental results show that at a current amplitude of 70 A and a frequency of 50 Hz or lower, the TPEW technique effectively reduces the average coating thickness to below 40 μm. The modeling, simulation, and experimental results of the prototype demonstrate the feasibility of the TPEW approach, which effectively reduces the coating thickness and enhances its uniformity.