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유위도,나영상,이종훈 한국주조공학회 2003 한국주조공학회지 Vol.23 No.1
Hot deformation behavior of GCD-50 cast has been investigated by employing the compressive test. Phenomenological deformation behaviors, which were modeled based on the dynamic materials model and the kinetic model, have been correlated with the microstructural change taken place during compression. Microstructrual investigation revealed that the adiabatic shear band caused by the localized deformation was taken place in low temperature and high strain rate. On the other hand, the wavy and curved grain boundaries, which represent the occurrence of dynamic microstructure change such as dynamic recovery and dynamic recrystallization, were observed in high temperature and low strain rate. Deformation model based on hyperbolic sine law has also been suggested.(Received August27, 2001)Kwyword: ductile cast iron, deformation, dynamic materials model, kinetic model
열처리 및 노출시간에 따른 17-4PH 스테인레스강의 미세조직 및 기계적 특성에 관한 연구
유위도,이종훈,임영목,윤국태,Yu, Wi-Do,Lee, Jong-Hun,Im, Yeong-Mok,Yun, Guk-Tae 한국기계연구원 2002 硏究論文集 Vol.32 No.-
A martensitic precipitation hardening stainless steel, 17-4PH has been widely used in the aircraft, chemical and nuclear industries for long time, owing to the excellent mechanical properties with corrosion resistance that can be achieved by simple heat treatment. The microstructure and mechanical properties of the 17-4PH stainless steel cast parts for aircraft, such as impeller, are largely affected by heat treatment condition. But the database of heat treatment has not been clearly established in the domestic investment casting industries because the domestic aerospace, industry lags behind the advanced countries. In this study, the microstructural evolution and mechanical properties of cast 17-4PH stainless steel depending on the heat treatment conditions and aging at $400^{\circ}C$ were investigated.
유위도(Wee Do Yoo),나영상(Young Sang Na),이종훈(Jong Hoon lee) 한국주조공학회 2002 한국주조공학회지 Vol.22 No.1
N/A Hot deformation behavior of GCD-50 cast iron has been investigated by employing the compressive test. Phenomenological deformation behaviors, which were modeled based on the dynamic materials model and the kinetic model, have been correlated with the microstructural change taken place during compression. Microstructural investigation revealed that the adiabatic shear band caused by the locallized deformation was taken place in low temperature and high strain rate. On the other hand, the wavy and curved grain boundaries, which repersent the occurrence of dynamic microstructure change such as dynamic recovery and dynamic recrystallization, were observed in high temperature and low strain rate. Deformation model based on hyperbolic sine law has also been suggested.
이종훈,유위도,임영목,권기현,Lee, Jong-Hun,Yu, Wi-Do,Im, Yeong-Mok,Gwon, Gi-Hyeon 한국기계연구원 2003 硏究論文集 Vol.33 No.-
In this study, the wear resistance of the complex powder diffusion treated KS STD 61 has been investigatived. KS STD 61 tool steel was pretreated in quenching and tempering processes to obtain the tempered martensitic microstructure. The samples were packed with complex powder in steel pot($\Phi$90x60mm) and heated in a box furnace. the complex powder diffusion treatment are carried out at $540^{\circ}C$, $520^{\circ}C$, $500^{\circ}C$ for 40min, 1.5hr and 2.5hr. The microstructure, microhardness, wear resistance, and coating layer thickness of the complex powder diffusion treated samples were investigation. The weight loss of as heat treated sample was 0.4mg and that of the complex powder treated at $540^{\circ}C$ for 2.5hr was 0.17mg. These result means that the wear resistance of tool steels can be easily improved by the powder diffusion process at conventional tempering treatment temperature.
이종훈,유위도,Lee, Jong-Hun,Yu, Wi-Do 한국기계연구원 2000 硏究論文集 Vol.30 No.-
The failed tube received for this study has been used for approximately 10 year at $330^{\circ}C$ in a steam production boiler tube was fractured in the transversed direction to tube length, and fracture mode was typically intergranulas type without the plastic deformation. The fracture surface was covered by the oxide scale formed from the intermal high pressure steam at high temperature. The microstructure was not nearly thermal-degraded during the service. From this result, we can conclude that the oxide film was proferentialy formed into the grainboundary and this grainboundary oxide film was brittle-fractured by the thermal stress in the longitudinal direction to the tube brittle intergranular fracture mode.