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On the Formation of Macrosegregation and Interdendritic Cracks During Dendritic Solidication of Continuous Casting of Steel
MOSTAFA OMAR EL-BEALY
The aim of the current article is to elucidate the signicant eects of macrosegregation distribution and its level on the dierent stages of interdendritic crack formation during dendritic solidication in continuously cast steel slabs. Couple formations of macrosegregation and interdendritic crack phenomena during dendritic solidication of peritectic carbon steels have been investigated by metallographic study of collected slab samples and by performing a set of mathematical analyses. The metallographic study involved plant trails to measure slab surface temperature of dierent secondary spray cooling conditions. Also, macromicroexaminations, measurements of dendrite arm spacing, macrosegregation analysis, and interdendritic distance between the dendrites of collected samples from plant trials have been performed. The experimental results show a uctuation of carbon segregation with respect to distance from slab surface. These results also reveal that the interdendritic cracks vary with this uctuation in various nano, macro, and microscales based on the cooling conditions. A mathematical model of heat transfer, solidication, structure evolution, interdendritic strain, macrosegregation, and elementary interdendritic area EIA has been developed. This model takes also into account the calculating of interdendritic distance between the dendrites IDD to evaluate the inter-dendritic crack width. The model predictions of dierent thermal and solidication phenomena show a good agreement with measurements. The results pointed out also that the coupled eect of interdendritic strain and macrosegregation phenomena and their distributions can be considered as the most important tools to evaluate the surface and internal interdendritic cracks in continuously cast steel slabs. The formation mechanisms of dierent types of interdendritic crack with interdendritic strain patterns and uctuation of macrosegregation levels during various cooling zones have been explained, and the possible solutions to these problems have been discussed.
DOI: 10.1007/s11663-013-9911-z The Minerals, Metals & Materials Society and ASM International 2014
I. INTRODUCTION
INTERDENDRITIC cracking is particularly a serious problem in continuously cast steel slabs. It may form almost anywhere at the surface or in the interior of slabs. Surface cracks such as interdendritic longitudinal mid-face[13] or mid-side[4] and transverse cracks[58] are oxidized by the air and therefore cannot be rewelded during rolling processes. If they are not removed by scarng or grinding, then interdendritic surface cracks will...