Numerical Simulations and Modal Analysis to Investigate the Defects in a Coating Process

This work investigates the hydrodynamics of jet wiping, a coating process in which a thin slot gas jet impinges on a coating film dragged by a moving strip; thus, reducing the coating thickness and developing a run-back flow. The interaction between the liquid film and the gas jet is highly unsteady, producing long-wavelength defects on the final product known as undulations. We perform Computational Fluid Dynamics (CFD) simulations of the process using High-Performance Computing (HPC) resources. A multi-scale modal analysis is then applied to decrypt the mechanism of wave formation. The main undulation pattern features two-dimensional waves and is correlated with a large-scale motion of the gas jet.

Air jet impingement to reduce hot strip wave on a run-out table

Traveling stability is necessary for a hot rolled strip on a run-out table before coiling in steel mills because it affects the process efficiency and the quality of the rolled products. This study proposes an air jet impingement system to reduce the hot strip wave that occurs during tensionless travel in a run-out table before the top end of the strip reaches the coiler mandrel. The finite element method was used to examine the pressure distributions on the moving strip associated with the parameters in the air jet systems. Experiments were carried out on a pilot-scale air jet impingement system to investigate the performance. The results show that the air impingement in the moving direction effectively reduces the strip wave, and the simulated results agree with the actual measurements and observations.

Nonlinear Vibration Analysis of Moving Strip with Inertial Boundary Condition

According to the movement mechanism of strip and rollers in tandem mill, the strip between two stands was simplified to axially moving Euler beam and the rollers were simplified to the inertial component on the fixed axis rotation, namely, inertial boundary. Nonlinear vibration mechanical model of Euler beam with inertial boundary conditions was established. The transverse and longitudinal motion equations were derived based on Hamilton’s principle. Kantorovich averaging method was employed to discretize the motion equations and the inertial boundary equations, and the solutions were obtained using the modified iteration method. Depending on numerical calculation, the amplitude-frequency responses of Euler beam were determined. The axial velocity, tension, and rotational inertia have strong influences on the vibration characteristics. The results would provide an important theoretical reference to control and analyze the vertical vibration of moving strip in continuous rolling process.