Effect of peak value and discharge frequency of electric current pulse on solidification structure of Fe–1C–1·5Cr bearing steel

Abstract

An experimental study with respect to the influence of an electric current pulse (ECP) on the solidification structure of Fe–1C–1·5Cr bearing steel is reported. Without ECP, the steel solidifies in the form of coarse columnar dendrites. In contrast, the primary dendritic arm was shortened as well as the equiaxed dendrites increased and hence the columnar to equiaxed transition was observed after the ingot was exposed to an ECP. As the peak value and discharge frequency of the ECP increased, the region of the equiaxed dendrites expanded. In particular, equiaxed dendrites nearly dominated the structure when the pulse parameters of 300 K _i A, 10 L _i Hz and 100 K _i A, 50 L_i Hz were employed (where K _i and L _i are known constants). In addition, the improvement of shrinkage porosity of the specimen with pulse parameters of 100 K _i A, 50 L _i Hz was better than that of 300 K _i A, 10 L _i Hz.