발간논문

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Vol.37, No.7, 782 ~ 788, 1999
Title
Research Paper / Solidification : A Mechanism of Longitudinal Surface Crack Formation in the Continuously Cast Slab of the Medium Carbon Steel
유정희Chong Hee Yu, 이오연Oh Yeon Lee, 김동건Dong Kun Kim
Abstract
A mechanism of longitudinal surface crack formation in the continuous casting mold for the peritectic medium carbon steel was investigated by measurement of the fracture strength, the heat flux and the shrinkage of solidifying shell. The fracture strength of medium carbon steel shell is higher than that of other carbon steels and it exhibits an anomalous decrease of the heat flux on the mold surface due to the surface roughness of the solidifying shell caused by the δ→γ phase transformation just after solidification. Because of the larger shrinkage and higher strength, the peritectic medium carbon steel shell forms larger air gap between the shell surface and the mold wall, resulting decrease of the heat flux to the mold and hence higher recalescent shell temperature. The recalescence of the shell will induce the crack in the sub-surface at low ductile interdendritic area or grain boundary of the solidifying shell if combined with the stress due to the bending and frictional force. The sub-surface crack will propagate to the shell surface via grain boundraries at a later stage beacause of thermal and mechanical tensile stresses.
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