초고탄소강의 제어압연에 의한 세멘타이트의 구상화와 냉각중 마르텐사이트의 핵발생과 성장의 현상론적 고찰

Study on the Spheroidization of Cementite by Controlled-Rolling and Martensitic Nucleation and its Growth during Cooling in Ultra High Carbon Steel

Ultra high carbon steel (Fe-1.4%C) was prepared by means of a high frequency induction furnace. The preferred nucleation site of martensite was observed. The changes of hardness and impact thoughness due to tempering temperatures, and the spheroidization of cementite by controlled -rolling were also studied for the steel. The preferred nucleation site of martensite in the ultra high carbon steel is prior austenite grain boundary. The hardness of the steel is slightly increased up to about $300^{\circ}C$, and then decreased with further tempering temperature. However, the impact energy keeps a almost constant value, independent of the tempering temperature. The spheroidization of cementite is accelerated as the reduction in thickness per rolling pass is increased and the number of the rolling passes becomes greater.