Abstract:The morphology of dendrite is an important factor affecting the solute distribution, shrinkage porosity and properties of cast bloom, and dendrite refinement can effectively improve the quality of bloom. The effect of PMO treatment on dendrite morphology of ø300 mm continuous casting round bloom of 42CrMoA steel was studied. It was found that the columnar dendritic growth direction of PMO treated bloom was deflected, and the dendrite arm spacing was significantly reduced. The primary dendrite arm spacing decreased by 10%-35%, and the secondary dendrite arm spacing decreased by 25%-35%. It is believed that the heat flow direction and solute field at the solidification front changed by PMO leads to the re-competitive growth of dendrites, so the primary dendrite growth direction changes, and the primary dendrite arm spacing decreases. In addition, PMO forms induced current at the front of solidification, and the difference of solid-liquid conductivity leads to the current accumulation at the tip of dendrite, which increases the radius of curvature, and then reduces the dissolution rate of fine dendrites, inhibits the secondary dendrite ripening process, so the secondary dendrite arm spacing decreases. The results provide guidance for improving the dendrite structure of the bloom by PMO in the future.
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