This article describes the influence of an electric current pulse (ECP) on the microstructure of an Al-Si eutectic alloy during directional solidification. Experimental results demonstrate that the ECP has a significant effect on the microstructure of the directionally solidified Al-Si eutectic alloy. Application of ECP can increase the number and area percentage of the complex regular structure (CRS). Furthermore, the area of single CRS increases first and then declines with the increase of the ECP density. Analysis results suggest that the change of the CRS is a result of the forced convection caused by Lorentz force and change of temperature gradient induced by the ECP. The growth process of the CRS is discussed.
Pulsed Magneto-Oscillation (PMO) is a newly developed and effective homogenization technique, and has been successfully applied in rectangular continuous casting, but its processing parameters and effective stability in round billet continuous casting have not been investigated. In this paper, the effects of PMO on the solidification structure and the macrosegregation of Φ 178 mm continuous casting round billets for low carbon alloy steel were studied by industrial experiments. The results show that PMO can stably increase the equiaxed grain area, and reduce the macrosegregation of billets. Moreover, it has strong adaptability to steel grade and continuous casting process parameters. Compared with the billets without PMO treatment, for 93.8% of billets (15 billets) solidified with PMO, the equiaxed grain area ratio increased by an average of 5.8%, while for 87.5% of billets (14 billets), the carbon segregation index range decreased by an average of 0.06, though different steel grades, superheat and casting speed were used in the experiment. It is believed that convection caused by Lorentz force can accelerate the heat dissipation of steel liquid, and reduce the temperature of a liquid at the solidification front, while the magnetic oscillation effect is conducive to dendrite fragmentation. Both effects lead to refinement of the solidification structure and reduction of macrosegregation.
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