Abstract
The effect of final electromagnetic stirring parameters, with current intensity increasing from 300 A to 400 A and frequency increasing from 4 Hz to 12 Hz, on the electromagnetic forces and carbon concentration distribution of the central cross section of a 70 steel square billet have been studied. Along the center line of the liquid core zone, current intensity of 400 A and frequency of 8 Hz achieve the maximum electromagnetic force at the position 48 mm away from the billet edge among the 10 groups of stirring parameters. Nevertheless, along diagonal of the liquid core zone, the electromagnetic force near the diagonal center is the greatest and the current intensity of 280 A and frequency of 12 Hz obtain the maximum electromagnetic force. The optimal final electromagnetic stirring (F-EMS) parameter to uniform the central cross-sectional carbon concentration and minimize the center carbon segregation of 70 steel billet was obtained with a current intensity of 280 A and frequency of 12 Hz. Under this stirring parameter, the area ratios of carbon concentrations of 0.66 wt%, 0.70 wt% and 0.74 wt% in the middle of the billet cross section reached 28.5%, 56.9% and 10.9%, respectively. Moreover, the carbon segregation indexes for all sampling points were in the range of 0.92–1.05.
Highlights
The high carbon steel tends to solidify over a large solidification temperature range and long solidification time
The presence of proeutectoid cementite in the pearlite matrix of a high carbon steel billet has been attributed to the center carbon segregation
The morphology of cross and longitudinal sections was obtained by acid tech, and the concentration of solute element carbon at the central cross-section under different final electromagnetic stirring currents and frequencies were tested by the wet chemical and original position analyzer, and the optimal parameters of F-EMS for the continuously cast billet of 70 steel were determined
Summary
The high carbon steel tends to solidify over a large solidification temperature range and long solidification time. Many techniques have been proposed to minimize the detrimental center carbon segregation in high-carbon continuous casting, such as low temperature casting, intensive cooling at the solidification end, soft reduction, large reduction, and electromagnetic stirring (EMS) [9,10,11]. Among those techniques, the combination of mold and final electromagnetic stirring The morphology of cross and longitudinal sections was obtained by acid tech, and the concentration of solute element carbon at the central cross-section under different final electromagnetic stirring currents and frequencies were tested by the wet chemical and original position analyzer, and the optimal parameters of F-EMS for the continuously cast billet of 70 steel were determined
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