This study investigates the effects of alternating final electromagnetic stirring (F-EMS) on molten steel flow and the internal quality of large-size round blooms. Numerical simulations and plant trials were conducted to evaluate the influence of current intensity, frequency, and stirring direction on flow behaviour, final solidification feeding, and centreline cracking. Reversing the stirring direction after a pause enlarged the rotating fluid volume and axial range, enhancing feeding during final solidification. Flow field analysis indicated that the current parameters in the second half should be equal to or slightly higher than those in the first half. Meanwhile, using the Niyama criterion revealed threshold values for current parameters. Alternating stirring induced asynchronous flow between upper and lower regions, with the effective stirring zone located above the stirrer. Plant trials confirmed that alternating stirring improves both shrinkage feeding and crack control, offering practical guidance for optimizing stirring strategies to reduce casting defects.
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