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권오덕(O . D . Kwon),최주(J . Choi),임창희(C . H . Yim),이인열(I . R . Lee),신영길(Y . K . Shin),구경회(K . H . Ku) 대한금속재료학회(구 대한금속학회) 1992 대한금속·재료학회지 Vol.30 No.6
Through the microscopic observation of slab surface layer and the variation test of mold powder and Ar gas flow rate purged into submerged entry nozzle, the formation mechanism of pin hole in the surface layer of slab was verified. By changing casting variables, such as casting width, immersion depth, pouring angle of submerged entry nozzle and strand withdrawal speed, the effect of stream velocity on pin hole formation was investigated. Ar gas is the main source of pin hole, which is formed due to entrappment of Ar gas by solidifying meniscus hook. When the stream velocity in meniscus increases or exothermic mold powder is used, pin hole formation is reduced due to hotter meniscus, which retards the hook formation.
연속주조용 탄소강에서 상변화에 따른 열팽창 및 수축 거동
김현철,이재현,권오덕,임창희,Kim, H.C.,Lee, J.H.,Kwon, O.D.,Yim, C.H. 한국재료학회 2003 한국재료학회지 Vol.13 No.3
The air gap between the metal and mold, formed by shrinkage during solidification, causes surface and subsurface cracks in the continuous casting process. Molten crack on the surface might also occur due to improper heat transfer between them. In order to compensate the air gap in mold design, the thermal contraction is an essential factor. In this study, the thermal contraction and expansion behaviors were examined from the ($\alpha$ and pearlite)/${\gamma}$ to ${\gamma}$/$\delta$ transformations in continuous casting steels by the commercial dilatometer and the self- assembled dilatometer with laser distance measurement. It was found that the thermal contraction and expansion behaviors were very dependant on the phase transformation of the ${\gamma}$/$\delta$ as well as ($\alpha$ and pearlite)/${\gamma}$. The sudden volume change from $\delta$ to ${\gamma}$ which might cause cracks in the continuous casting process, was observed on cooling just below the melting temperature by the self-assembled dilatometer.