Revealing the effect of travelling-wave magnetic field on dendrite growth of high-strength steel slab: Industrial trials and numerical simulation

The dendrite growth behaviours of high-strength steel during slab continuous casting with travelling-wave magnetic field was studied in this paper. The morphology of solidification structure and composition distribution were analysed in detail. The results showed that the columnar crystals could deflect and break when travelling-wave magnetic field worked with low current intensity. With the increase of current intensity, the secondary dendrite arm spacing and solute permeability decreased, and the columnar crystal transformed to equiaxed crystal. Electromagnetic force caused by travelling-wave magnetic field changed the temperature gradient and velocity magnitude, and promoted the breaking and fusing of dendrites. The order of dendrite compactness and composition uniformity from good to bad was columnar-to-equiaxed transition (high current intensity), columnar crystal zone (low current intensity), columnar-to-equiaxed transition (low current intensity) and equiaxed crystal zone (high current intensity). Additionally, combined with the verified numerical simulation results, as well as the boundary layer theory of solidification front and the dendrite breaking-fusing model, the dendrite deflection mechanism and growth process are revealed. When thermal stress is not considered and there is no obvious narrow segment in dendrite, the velocity magnitude on the solidification front of liquid steel need to reach 0.041 m/s before dendrites can break.