An experimental benchmark of vibratory strip feeding on grain formation and melt flow evolution under different vibration frequency

Feeding a vibratory strip into the mold has a positive effect on improving the homogeneity of a large continuous casting bloom. A visualized solidification benchmark experiment was designed to reveal the mechanism of grain formation promoted by vibratory strip feeding. The effect of cold strip vibration frequency (0, 50, 100, and 200 Hz) on melt flow dynamics and solidification structure evolution was investigated. The results show that the formation mechanism of fine equiaxed grains under vibratory strip feeding has been elucidated as a three-stage process involving dendritic separation, mixed formation, and melting fragmentation. Following the introduction of strip, the melt flow pattern transitions from a symmetric circulation pattern to a butterfly-shaped flow, with the maximum velocity increasing from 1.86 mm/s (before strip feeding) to 12.81 mm/s under 100 Hz vibration. The dispersed motion of grains induced by vibratory feeding promoted the uniform distribution of equiaxed crystals and increased the volume fraction of the equiaxed-dominant zone. Notably, under 100 Hz cold strip vibration, the solidification layer thickness at the bottom markers and reached maximum values, with the equiaxed-dominant zone achieving the highest volume fraction of 35.41% in the solidification structure. The research findings provide a theoretical foundation for applying vibratory strip feeding technology in continuous casting to achieve highly homogeneous production of large-section blooms.