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강훈철 ( H. C. Kang ),이승호 ( S. H. Lee ),김남수 ( N. S. Kim ),이경종 ( K. J. Lee ) 한국열처리공학회 2003 熱處理工學會誌 Vol.16 No.1
N/A In Nb, V and Ti added steels, carbo-nitrides are formed due to their strong interaction with C and N. The formation of carbo-nitrides has an important role to control the microstructure as well as mechanical properties by grain size refinement and precipitation hardening. However, the quantitative analysis of distribution of precipitates and the effect of precipitates on the phase transformation and mechanical properties are still far from satisfactory. In this study, the quantitative analysis of precipitates in austenite was investigated using the fact that the formation of precipitates in Nb, V and Ti added steels accelerates austenite/ferrite transformation. The formation of precipitates was controlled by adjusting holding temperature and time in austenite region. transformed Volume fractions were measured by dilatometer during slow cooling. Iso-precipitation kinetics were determined by comparing 5% and 50% volumes transformed at various conditions respectively. The result was compared with the calculated.
유한요소 해석과 동적 재결정 모델링을 이용한 열간단조 강의 오스테나이트 결정립 크기 예측
홍승찬,강훈철,안재천,황한섭,이상주,이경종,박종진,이경섭 대한금속재료학회 2004 대한금속·재료학회지 Vol.42 No.1
Austenite grain size of automotive forging steel was predicted by FEM analysis and dynamic recrystallization model. The hot forging process consisting of rolling, busting, blocking and finishing for lower arm connector was analyzed by commercial code DEFORM-3D. The flow curve and the dynamic recrystallization behavior of 0.43C steel were determined by hot compression test. The process parameters such as temperature, strain and strain rate obtained by the FEM analysis were coupled with the dynamic recrystallization model and they were applied to hot compression test. The variation of the grain size during the entire forging process was calculated by computer programming of the coupled model. The predicted final grain sizes agreed well with the experimentally observed.