Flow and fluctuation of molten steel under permanent magnet flow control-mold in continuous casting process

Abstract

A new flow control technology in continuous casting process named permanent magnet flow control-mold (PMFC-Mold) was proposed, in which the permanent magnets are arranged in Halbach array near the narrow region of the mold. The behavior of molten steel flow and the fluctuation of molten steel/slag interface in the PMFC-Mold under different continuous casting speeds were investigated. Firstly, a physical experiment of liquid Ga–In–Sn alloy circulating flow was carried out in Perspex mold with Halbach’s permanent magnets (HPMs) to investigate the magnetic field distribution of HPMs and its impactful electromagnetic braking effect. The numerical simulation of 1450 mm × 230 mm slab shows that a stronger magnetic field over 0.3–0.625 T is formed at the wide surface and the narrow surface of the mold, which provides an effective electromagnetic braking for controlling the impingement of molten steel jet and suppressing the fluctuation of molten steel/slag interface. The numerical simulation results show that in the PMFC-Mold, the region with the turbulent kinetic energy greater than 0.01 and 0.04 m² s⁻² on the upper backflow zone and near the narrow surface of the mold are significantly reduced. The maximum turbulent kinetic energy of the submerged entry nozzle (SEN) jet in front of the narrow surface is significantly reduced, and the SEN jet moves downward before impacting the narrow surface of the mold. In the PMFC-Mold, the region with the surface velocity greater than 0.2 m s⁻¹ on the steel/slag interface is eliminated, the flow pattern and fluctuation profiles on the molten steel/slag interface become regular on both sides of SEN, and the vortex near SEN disappears. The maximum fluctuation height of molten steel/slag interface is controlled below 2.59 and 5.40 mm corresponding to the casting speed of 1.6 and 2.0 m min⁻¹, respectively.