Speaker
Description
Hot-dip galvanizing is a widely used method for protecting steel workpieces from corrosion, and controlling the coating thickness through wiping is crucial for ensuring both product quality and performance. Traditional gas wiping technology, though widely used, faces challenges, including air pollution, coating oxidation, uneven coating distribution, and difficulties in precise thickness control. Alternating-current electromagnetic wiping offers a non-contact and easily controllable solution. However, the single-phase electromagnetic wiping coil primarily generates large normal electromagnetic force with limited tangential force, which restricts wiping efficiency.
This study adopts three-phase coils structure to realize three-phase electromagnetic wiping (TPEW), where a traveling magnetic field is generated along the steel strip surface to increase tangential electromagnetic force and improve wiping effectiveness. The TPEW device employs three sets of plate-type coils energized by three-phase alternating current, interacting with the molten zinc layer to generate substantial tangential electromagnetic forces, which effectively remove excess liquid zinc. Adjustments to the frequency and amplitude of the TPEW coils currents enable precise modulation of the traveling magnetic field and electromagnetic forces, achieving accurate control over coating thickness and uniformity.
An analytical model is developed to identify key parameters affecting wiping performance. The model indicates that coils geometry, air gap distance, and power supply parameters significantly influence the magnitude of the electromagnetic forces. A multiphysics simulation model incorporating electromagnetic-fluid-thermal coupling and moving meshes is applied to analyze the interactions between the traveling magnetic field, the molten zinc layer, and thermal behavior. The results show that under appropriate current parameters, the zinc coating thickness is reduced to below 40 μm, with significant improvement in coating uniformity. Cooling channels integrated within the coil cores enable water circulation to reduce temperature rise. Compared to designs without cooling channels, this configuration reduces the temperature rise of the TPEW device from 120 K to less than 60 K. The simulation model also reveals the dynamic process of zinc liquid being wiped, forming distinct regions of thinning, fluctuation, and accumulation. This combined approach, incorporating analytical modeling, multiphysics simulation, and thermal management strategies, promotes the practical application of electromagnetic wiping technology in continuous galvanizing lines for steel strips.
