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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.
과공정 Al-Si 합금의 열팽창 특성에 미치는 Si 입자 크기의 영향
김철현 ( Kim Cheol Hyeon ),주대헌 ( Ju Dae Heon ),김명호 ( Kim Myeong Ho ),윤의박 ( Yun Ui Bag ),윤우영 ( Yun U Yeong ),김권희 ( Kim Gwon Hui ) 한국주조공학회 2003 한국주조공학회지 Vol.23 No.4
N/A Hyper-eutectic Al-Si alloy is used much to automatic parts and material for the electronic parts because of the low coefficient of thermal expansion, superior thermal stability and superior wear resistance. In this work, A390 alloy specimens were fabricated for control of the Si particle size by various processes, such as spray-casting, permanent mold-casting and squeeze-casting. To minimize the effect of microporosity of the specimen, hot extrusion was carried out under equal condition. Each specimens were evaluated tensile properties at room temperature and thermal expansion properties in the range from room temperature to 400℃. Ultimate tensile strength and elongation of the spray-cast and extruded specimens which have fine and well distributed Si particles were improved greatly compare to the permanent mold-cast and extruded ones. Specimens which have finer Si particles showed higher ultimate tensile strength and elongation than those having large Si particle size, and coefficient of thermal expansion of the specimens increased linearly with Si particle size. In case of the repeated high temperature exposures, thermal expansion properties of the spray-cast and extruded specimens were found to be more stable than those of the others due to the effect of fine and well distributed Si particles.
알루미늄 chip 의 용해시 산화피막 제거에 미치는 Flux 혼합물의 영향
송상우,김정호,김경민,김정식,윤의박 ( Sang Woo Song,Jeong Ho Kim,Kyoung Min Kim,Jung Sik Kim,Eui Pak Yoon ) 한국주조공학회 1998 한국주조공학회지 Vol.18 No.1
N/A Aluminum alloy forms rapidly a layer of oxide on surfaces exposed to an oxygen-containing atmosphere and absorbs hydrogen gas by reaction with water vapor. Oxidation accelerates as time and temperature increase. Also hydrogen content increase with time and temperature. In this experiment, A356.2 aluminum chip was used. The ability of oxidation protection of covering fluxes and oxide removal ability of flux additives were evaluated. Recovery and hydrogen content of Al melt was measured with various NaCl/KCl ratio. And recovery was measured with various flux additives such as chlorides and fluorides. The optimal ratio of NaCl/KCl for protection of oxidation was 5:5. Fluorides were more effective in removal of oxide than chlorides. (Received July 23, 1997)
알루미늄 Droplets 합체거동에 미치는 Salt Flux 및 합금원소 첨가의 영향
김예식 ( Ye Sik Kim ),윤의박 ( Eui Pak Yoon ),김기태 ( Ki Tae Kim ),정운재 ( Woon Jae Jung ),조덕호 ( Duk Ho Jo ) 한국주조공학회 2000 한국주조공학회지 Vol.20 No.1
The remelting for recycling of thin aluminum scrap, such as aluminum chip generally involves melting of these pieces sub-merged in molten salt flux. In this study, the effects of salt flux compositions and alloying elements on the aluminum dropletscoa-lescence and oxide film removal were studied in 99.8%A1, Al-1.01%Cu, Al-1.03%Si, and Al-1.38%Mg alloys as a function of holding time at 740℃ Salt fluxes based on NaC1-KCl(1:1) with addition of 5wt.% fluorides(NaF, Na3AlF6, CaF2) or 5 Wt.% chloride(MgCl2, AlCl3) were used. The experimental results show that NaCl-KCl(1:1)with addition of 5 wt.% fluorides exhibits better coalescence ability than that with chlorides. The oxide film is not removed by NaCl-KCl(1:1) with addition of 5 wt.% chlorides, while it is removed by NaCl-KCl(1:1) with addition of 5 wt.% fluorides. The aluminum droplets coalescence and oxide film removal by salt fluxes are related to interfacial tension between metal and salt flux.
편석법에 의한 Al 정련시 불순물농도의 정량적계산에 관한 연구
김경민,윤의박 ( Kyoung Min Kim,Eui Pak Yoon ) 한국주조공학회 1995 한국주조공학회지 Vol.15 No.5
N/A The effect of forced convention on the solute redistribution of the Al ingot was studied quantitatively in an effort to fabricate high purity aluminum using a segregation method. Based on the experimental results, the solute concentration in the solid phase tended to decrease at the early state of solidification, and then increased gradually as solidification proceeded. Fe and Si concentrations decreased as growth rate decreased and as revolution speed increased. The solute redistribution obtained from the BPS model incorporated with the tangential flow component as well as the axial flow component within the melt, agreed well with the measurements.
공정복합재료의 일방향응고시 용질편석에 미치는 자연대류의 영향
김기배,윤의박,Kim, Gi-Bae,Yun, Ui-Park 한국재료학회 1995 한국재료학회지 Vol.5 No.1
비공정조성 공정복합재료의 일방향응고시 나타나는 액상내의 자연대류가 응고후 공정복합재료의 조성에 미치는 영향을 조사하였다. 이를 위해 Al-Cu합금을 선택하여 액상내에서 발생되는 애류의 형태를 변화시키기 위하여 상향 및 하향 일방향응고를 실시하여 각 응고조건에 따른 공정복합재료의 Cu 용질농도를 측정하였으며, 일방향응고 중에 급냉응고하여 고액계면 전방의 용질농도분포와 열분석을 통해 온도분포를 실측하였다. 그 결과로 비공정조성 공정복합재료의 일방향응고시 나타나는 대류는 공정복합재료의 용질편석에 커다란 영향을 주었으며, 고액계면 전방에서 thermal convection과 solutal convection이 모두 발생하는 하향 일방향응고된 아공정 Al-Cu합금에서 용질편석이 가장 크게 나타났다. 과공정 Al-Cu합금에서 상향 일방향응고한 경우가 하향 일방향응고한 경우보다도 용질편석이 증가한 것으로 나타났다. 이것은 본 연구조건에서는 solutal convection이 thermal convection보다 용질편석에 더 커다란 영향을 주는 것으로 생각되었다. 공정복합조직으로 성장시 고액계면은 평활계면으로 성장하였으며, 고액계면에서 액상 쪽의 용질농도는 아공정이나 과공정합금에 관계없이 공정조성의 용질농도를 가지며, 고액계면에서의 온도는 커다란 과냉도 없이 거의 공정온도 부근이었다. Natural convection in bridgman growth and it's effect on macrosegregation in unidirectionally solidified off-eutectic alloys were examined in this study. AlCu off-eutectic alloys(27.5wt% ~35. 6wt% ) were solidified upward or downward for producing a different natural convection and then Cu concentrations of off-eutectic composites were measured as a function of solidified fraction. Solutal and temperature distributions ahead of the solid/liquid interface were measured on quenched specimen. When hypo-utectic AlCu alloys are directionally solidified with downward growth, considerable macrosegregation occurs due to flow induced by thermal and solutal convection in melt. Soultal convection affects the macrosegregation of hyper-eutectic AlCu alloys more severely than thermal convection. Solute composition at solid/liquid interface of offkutectic composites was eutectic and also temperature was near eutectic point without large undercooling.
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)