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윤의박,조순형 ( Eui Pak Yoon,Soon Hyoung Cho ) 한국주조공학회 1983 한국주조공학회지 Vol.3 No.2
In this paper analytical and numerical methods fur analysis of solidification of castings are described, and the matrix method, one of numerical method, where the nodal point is designated on the element boundary was adapted. The cooling curve obtained by experimental values, when cast steel (0.29%C. 0.62%Si) was poured into CO₂mold, is compared with that of computed values by exploiting computer (V77-600 Data Proceeding System, UNIVAC). The computed value is nearly approximation to the experimental. But the computed value shows a tendency that is a little higher than the experimental in solid-liquid coexisting temperature ranges and much lower than the experimental after solidification. It is considered to result from the lacks and difficulties of ultimately appropriate adaptation of various physical properties and also air cap between castings and mold.
2상혼합조직을 (相混合組織) 가진 구상흑연주철의 기계적 성질에 관한 연구
윤의박,이영호 ( Eui Pak Yoon,Young Ho Lee ) 한국주조공학회 1982 한국주조공학회지 Vol.2 No.2
N/A This paper is concerned with the improvement of impact and tensile Properties of spheroidal graphite cast iron of the following duplex matricess which were heat treated in the eutectic transformation temperature range (that is, (α+γ) coexisting range) ; ferrite-martensite, ferrite-bainite and ferrite-pearlite. The absorbed energy and maximum load was measured by recording the load-deflection curve with instrumented Charpy impact testing machine in the temperature range from +100℃ to -196℃. It was found the ferrite-bainite duplex matrix showed the highest toughness among the above matrices in the room temperature and the low temperature range. Comparison of this matrix to ferrite-pearlite matrix(that is, as east) showed a lowering of 27 ℃ in the nil-ductility transition temperature (NDT) and a lowering of 40 ℃ in the ductile-brittle transition temperature (TrE), Which seems to result from the finner dimple pattern observed using miorofractography.
계장화 충격시험에 의한 구상흑연 주철의 동적파괴인성의 고찰
윤의박,김기철,고광필 ( Eui Park Yoon,Ki Chol Kim,Kwang Pill Ko ) 한국주조공학회 1989 한국주조공학회지 Vol.9 No.2
N/A Microstructures and fracture toughness of the weld heat-affected zone of the ductile cast iron have been investigated. With increasing the cooling time from 800℃ to 500℃, the matrix structure of the heat-affected zone was transformed to martensite, martensitet pearlite, pearlite and pearlite including small amount of ferrite. The use of a proper preheat temperatures prevented the formation of martensite. These welding conditions corresponded to the preheat temperature of 200℃, heat input of 30KJ/㎝. And the instrumented charpy impact test has been carried out on a welded ductile cast iron. Result showed that the dynamic fracture toughness, K_(Id) was increased slightly with preheat temperature and heat input. In this work, it was shown that apparent impact energy includes contributions other than that of the true deflection of specimen. We found that a compliance energy correction was always needed to determine the true specimen energy. For this purpose, elastic compliance value of testing machine was measured dynamically by the low blow test to correct the apparent impact energy. From these results, the true specimen energy was nearly 62 percent of an apparent impact energy value. There, in instrumented impact testing, machine compliance corrections must be adapted to load-deflection curve.
전자기력을 이용한 알루미늄 합금중 개재물의 연속적 제거에 관한 연구
윤의박(Eui Pak Yoon) 한국주조공학회 2002 한국주조공학회지 Vol.22 No.3
N/A The growing use of aluminum for castings over the past decade has brought with it the increased scrutiny of component properties. One area that has received much attention is the effect of in inclusions - or impurities particles held in the metal - on casting properties. A new method of electromagnetic separation for removal of inclusions in aluminum alloy melts is proposed. The principle is that as the electromagnetic force induced in metal acts on inclusions due to low electric conductivity, they are moved to the direction opposite to electromagnetic force and can be separated and removed from the melt. Experiments were carried out on A356 melt mixed alumina particles and commercial Al alloys of ADC 10 and 12. In the experiment using A356, it was proved that Al-2O_3 particles was separated and removed continuously from matrix melt by electromagnetic force. Based on these results, the continuous separation experiment that used ADC 10, 12 was carried and the cleanliness of melt was assessed by the amount of porosity, hydrogen contents, PoDFA and mechanical properties through tensile test. As the results of analyses, the amount of porosity and hydrogen contents decreased without variation of chemical composition in the specimen that passed the electromagnetic continuous separator. In addition, tensile strength and elongation of this specimen increased by 20∼30% because of reduction of inclusions.
Single Roller 법에 의한 Al-Cr 계 합금의 급냉응고 조직과 상분해
조순형,윤의박 ( Soon Hyoung Cho,Eui Pak Yoon ) 한국주조공학회 1987 한국주조공학회지 Vol.7 No.2
Al-Cr alloy with composition in the range from 1.5wt% to 10wt% Cr were rapidly solidified from the melt by the single roller method. The supersaturated solid solution was obtained up to 6wt% Cr in Al-Cr alloy for 20㎛ thickness. Lattice parameter decreased with increasing Cr content at the rate of 0.00456A perwt% Cr up to 6wt% Cr. Microhardness increased with increasing Cr content at the rate of 10㎏/㎟ per wt% Cr up to 6wt% Cr. Microhardness measurements on the Al-6wt% Cr supersaturated solid solution annealed isothermally showed no sign of age hardening. Decomposition temperature, determined by lattice parameter changes and microhardness changes, was 470℃ for Al-6wt% Cr supersaturated solid solution. Transmission electron microscopy showed that decomposition within one hour below 400℃ occurred at grain boundaries only, and also the additional decomposition within grains being evident at 450℃. The coarse precipitate structure showed at 500℃ and 550℃, respectively. The coarse precipitate structure is considered Al_7Cr.
주강계 저열팽창 주조합금의 열팽창 계수와 경도에 미치는 Mo , V 첨가의 영향
김영한,윤의박,문병문,홍영명 ( Young Han Kim,Eui Park Yoon,Byoung Moon Moon,Young Myung Hong ) 한국주조공학회 1998 한국주조공학회지 Vol.18 No.5
N/A For enhancing the mechanical properties of LTE (low thermal expansion) cast steel, systematic researches have been carried out. The effects of alloying elements such as vanadium, molybdenum and carbon on the hardness and linear thermal expansion coefficient were investigated. In the range of 0.5∼2.3 wt% carbon, addition of 1.73 wt% carbon caused hardness increase due to the formation of eutectic carbide having high hardness but over the range of 1.73 wt% carbon, hardness was decreased. Thermal expansion coefficient increases with carbon contents. In the LTE cast steel containing 0.6 wt% carbon, hardness increased up to 1.96 wt% vanadium addition. But over the range of 1.96 wt% vanadium hardness was decreased by coarse eutectic carbide. Thermal expansion coefficient of LTE cast steel containing 0.6 wt%carbon moderately increased with increasing vanadium contents. There was no significant variation of hardness and thermal expansion coefficient according to molybdenum content in LTE cast steel. (Received June 29, 1998)
분무성형법에 의한 Al 합금 (AA2014) 대형봉상성형체 제조시 기공발생에 관한 연구
신돈수,윤의박 ( Don Soo Shin,Eui Pak Yoon ) 한국주조공학회 1997 한국주조공학회지 Vol.17 No.5
N/A In order to manufacture large rod preforms of 2014 Al alloy with a good mechanical property by spray forming method, it was spray-formed at a droplet temperature of 715˚C, a droplet flight distance of 400㎜, and a spraying angle of 35˚. The rod preforms were extruded at 397˚C with the die temperature of 420˚C under the hot extrusion ratio 21:1 and T6 heat treatment was performed. The 2014 Al alloys cast by hot top process were also extruded and heat-treated at the same condition as a reference material. Microstructural observation and tensile test were carried out to investigate the effects of extrusion on microstructure and mechanical property of spray-formed Al alloy. Spray-formed Al alloys had many porosities due to inappropriate process conditions such as long droplet flight distance and low droplet temperature but have fine equiaxed grain. These porosities were reduced with decreasing in grain size by hot extrusion. Ultimate tensile strength and yield strength of spray formed-extruded 2014 Al alloy were inferior to those of the normal cast-extruded 2014 Al alloy, but elongations were superior. The control of porosity was important to get spray formed preform with a good mechanical property. (Received September 6, 1997)