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Ni-Fe-Co 합금의 고온 변형 공정 변수와 미세조직 및 열물리적 특성의 상관 관계
이광석(K.S. Lee),정중은(J.E. Jung),장영원(Y.W. Chang),이정환(J.H. Lee) 한국소성가공학회 2011 한국소성가공학회 학술대회 논문집 Vol.2011 No.5
High temperature deformation behavior of a Ni30Fe53Co17 alloy was investigated by conducting a series of compression tests. After constructing empirical process map, the appropriate working temperature-strain rate combination for optimum forming was deduced to be~1423 K, 10<SUP>-2</SUP> s<SUP>-1</SUP> region having relatively high power dissipation efficiency greater than 0.36. Furthermore, open die forging for the 100 mm diameter billets was performed to confirm the variation of thermo-physical properties in relation to microstructure. The coefficient of thermal expansion was found to increase considerably with increasing the open die forging temperature and decreasing the cooling rate, which in turn provides a drastic increase of average grain size.
Cu<SUB>47.5</SUB>Zr<SUB>47.5</SUB>Al₅ 벌크 비정질 합금의 고온 변형 및 성형 특성
이수은(S. E. Lee),이광석(K. S. Lee),전현준(H. J. Jun),장영원(Y. W. Chang) 한국소성가공학회 2010 한국소성가공학회 학술대회 논문집 Vol.2010 No.10
Plastic deformation of a CU47.5Zr47.5Al? ternary bulk metallic glass in the supercooled liquid region was investigated. The appropriate working temperature-strain rate combination for optimum solid-to-solid forming was deduced to be between (710 K, 3×10?⁴ s?¹) and (735 K, 3×10?² s?¹) by constructing a processing map superimposed with the time-temperature transformation curve indicating crystallization. Furthermore, the actual formability around this processing window was not only confirmed by overlapping the laboratory-scale extrusion deformability but also estimated by applying finite element analysis.
공압식 폐쇄다이세트 적용 정밀단조공정 설계 및 해석기술
이광석(K. S. Lee),엄득하(D. H. Eom),강성훈(S. H. Kang),이정환(J. H. Lee) 한국소성가공학회 2009 한국소성가공학회 학술대회 논문집 Vol.2009 No.10
This paper describes design and analysis techniques of cold forging process for precise producing of T-200 type spider made of SCr420H by utilizing pneumatically operated enclosed die set. Since deducing feasible closing force is an important factor to optimize entire pneumatically operated cold forging system, a series of FE analyses with varying the number of gas cylinders has been carried out to investigate the influence of closing force upon the direction of applied load at die surfaces. It also reveals the optimum distribution of the gas cylinders in terms of the flatness of upper/lower plates.
이광석(K.S. Lee),김상우(S.W. Kim),신민철(M.C. Shin),이정환(J.H. Lee) 한국소성가공학회 2009 한국소성가공학회 학술대회 논문집 Vol.2009 No.5
When the metal sheet is subjected to the housing surface for fitting and insulating from harsh surroundings like fluid ingression or hot steam, both strength and formability have to be equally considered. In this regard, the main aim of this study is to design an apparatus of cost-effectively producing flexible fluted band with increasing the formability of embossed stainless steel sheet, which is utilized as a thermal insulation metal for housing ship engine exhauster. Designed to fabricate a maximum sheet width of 700 mm. this new apparatus consists of upper roll made of hard urethane and the female-etched lower roll made of SKD11, have a producing capacity up to 1-meter homogeneously embossed sheet for just 60 seconds. This machine is devised for the maximum operating efficiency from original sheet handling to machine setting. The embossing properties are characterized by 3-D PROFILING. After embossing plain metal sheet, both yield strength and elongation properties are improved simultaneously, indicating the effectiveness of the newly designed apparatus.