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17-4 PH Stainless Steel의 최적 정밀주조공정기술 개발
이경환,류성곤,나태엽 계명대학교 산업기술 연구소 1992 産業技術硏究所 論文報告集 Vol.15 No.2
In order to esteblish the manufacturing process of compressor wheel used in gas turbine engine it was studied as base step that Ceramic Shell forming condition, melting condition by Rollover Furnace, Riser design condition, It was benefit to use Zircon Flour as Filler to increase the green strength of shell, and to use Fused Silica to reduce the retained strength. It was suitable to use Rollover Furnace to melt 17-4PH Stainless Steel for high quality casting. The Computer Simulation technology was used in studying the riser design on Investment casting process, the satisfiable results were not gained because of the lack of mold properties informations. It was recommended that to use 1.5 as riser multiplier factor.
구상흑연주철의 파괴특성에 미치는 Cu 및 열처리의 영향
김원용,나태엽,강인찬,곽창섭 ( Won Yong Kim,Tae Youb Ra,In Chan Kang,Chang Sub Kwak ) 한국주조공학회 1993 한국주조공학회지 Vol.13 No.6
N/A A study was investigated the relationship between fracture characteristics and microstructure changes according to Cu addition and heat treatment methods on the ductile cast iron. According to increment of Cu addition pearlite volume fraction was increased due to the deflect of anti-ferritizing of Cu. At the case of austempering heat treatment, fracture toughness of Cu contained specimen was decreased. The reason for the results seems to be responsible for decrement of plastic zone size at the crack tip. It was observed that the excellent fracture toughness can be obtained at the condition of normalizing and the specimen was not contained Cu. Under the such conditions, fractographs is composed of dimple pattern and fracture toughness 71.6㎫ √m, tensile strength determined as the value of 961.6㎫, respectively.
용체화처리 및 시효처리가 17-4 석출경화형 스테인레스강 정밀주조품의 미세조직 및 기계적 성질에 미치는 영향
유성곤,이경환,나태엽 ( Sung Kon Yu,Kyong Whoan Lee,Tae Yeob Ra ) 한국주조공학회 1992 한국주조공학회지 Vol.12 No.5
N/A The effect of the solution & aging treatment on the tensile strength, yield strength, elongation, reduction of area, hardness was studied in the 17-4 PH stainless steel. SEM pictures were also taken in order to examine the fracture surfaces and precipitated particles. X-ray diffraction patterns for the heat treated samples were also observed. Mechanical properties of the heat treated samples were superior to those of as cast samples. Tensile strength, yield strength, hardeness decreased with the increase of aging temperature. On the other hand, elongation and reduction of area increased as the aging temperature increased.
김현승(H. S. Kim),이준상(J. S. Lee),조동현(D. H. Cho),강성웅(S. W. Kang),나태엽(T. Y. Na),장호(H. Jang) 한국트라이볼로지학회 2014 한국윤활학회지(윤활학회지) Vol.30 No.1
The temperature-dependent tribological properties of brake discs for a train were examined in this study. The discs were produced using heat-resistant alloy steel, which showed different thermal conductivity after the heat treatments. A commercial brake friction material was used to evaluate the friction effectiveness, and the friction tests were carried out using a 1/5 scale dynamometer under various initial braking temperature conditions. The results showed that the tribological property of the disc was strongly affected by the heat treatment schedule. At low temperatures (below 250℃), the friction coefficient increased as a function of disc temperature, indicating that frictional heat increased the adhesion between the disc and pad. In addition, fade was observed at high temperatures (above 250℃); it was pronounced in the case of the disc with low thermal conductivity. The different fade resistances observed in the discs with different heat treatment schedules appear to be influenced by microstructural changes such as carbide redistribution occurring during the heat treatments, which affected the thermal conductivity.