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알루미늄 합금 소실모형주조 시의 주형충전재에 따른 특성변화
김기영(Ki Young Kim),이경환(Kyung Whoan Lee),임경화(Kyung Hwa Rim) 한국주조공학회 2002 한국주조공학회지 Vol.22 No.3
N/A Silica sand, zircon sand, and steel shots were used as mold packing materials in lost foam casting of the aluminum alloy bar. Vibration acceleration in three directions and temperatures in the casting and mold were measured, and packing and cooling characteristics of these materials were investigated. Packing densities increased with increase in vibration magnitude and time, and were 1.41∼1.49g/㎠ for silica sand, 2.54∼2.86g/㎠ for zircon sand, and 3.92∼4.52g/㎠ for steel shots. Sound castings were obtained only without evacuation of the flask during pouring. Solidification time became faster in order of silica sand, zircon sand and steel shot packing because steel shot has the highest cooling capacity of them. Solidification time of steel shot packing was shortened to about 1/2 of silica sand packing. Cooling capacity of sand mold was generally evaluated by heat diffusivity of the mold, however could be simply evaluated with specific heat per unit volume of the packing material in lost foam casting.
고크롬 백주철재 소실모형 주조시 표면 결함 발생에 미치는 모형밀도 및 감압의 영향
이규희 ( Kue Hee Lee ),유국종 ( Kook Jong Yoo ),백응률 ( Eung Ryul Baek ),최현진 ( Hyun Jin Choi ),이경환 ( Kyung Whoan Lee ) 한국주조공학회 2002 한국주조공학회지 Vol.22 No.6
N/A The effect of mold density and evacuation on surface defect of high chromium cast iron upon EPC process was investigated. Under evacuation of 0.1~0.3 atm, surface defects were carbon defect, burn on and misrun. Carbon defect was augmented by increasing mold density from 0.011 g/㎤ to 0.03 g/㎤ under evacuation of 0.1~0.3 atm, but carbon defect was decreased by increasing evacuation from 0.1 to 0.3 atm. Burn-on wasn`t found under evacuation of 0.1 atm regardless of mold density, but burn-on was augmented by increasing evacuation from 0.2 to 0.3 atm and decreased by reducing mold density. Misrun was only found under 0.1 atm evacuation and 0.011 g/㎤ mold density.
이강래 ( Kang Rae Lee ),최경환 ( Kyeong Hwan Choe ),조규섭 ( Gue Serb Cho ),이경환 ( Kyong Whoan Lee ),김명호 ( Myung Ho Kim ),임경화 ( Kyung Hwa Rim ),김기영 ( Ki Young Kim ) 한국주조공학회 2004 한국주조공학회지 Vol.24 No.5
N/A Vibrational motions of the compaction table were investigated to select the optimal operation conditions of sand filling and compaction for the EPC process. Their modes were measured at the nine points of the table with changing the relative rotation angles between the two eccentric mass vibrators which were attached parallel beneath the table. Well-defined vibration modes were measured at the center of the table but those of left and right sides of the table were distorted regardless of rotational angle differences. The distortion of vibration modes at both sides of the table were caused by the moment generated by offset positions of two eccentric masses. It was found that the uniform vibration modes would be gathered by controlling the relative distances between the rotating axis and the center of gravity in the compaction system at the various conditions of vibration modes and rotational angle differences.
소실모형구조법에 의한 탄소강주강 제조시의 Carbon Pick-up 현상
박익민 ( Ik Min Park ),박희상 ( Hee Sang Park ),이동렬 ( Dong Ryol Lee ),이경환 ( Kyung Whoan Lee ),이진형 ( Zin Hyoung Lee ) 한국주조공학회 2003 한국주조공학회지 Vol.23 No.2
N/A It has been a major concern in the foundry that steel castings manufactured by the evaporative pattern casting process encounter the carbon pick-up problem. A carbon rich layer at the evaporative pattern cast surface is a result of interactions between the gaseous products from foamed polystyrene and the molten metal. The carburized layer with a high hardness makes it difficult to machine the casting. In this study, the influence of the density of EPS pattern and coatings on carbon pick-up phenomena of S25C and S45C commercial carbon cast steel were investigated. As the density of EPS pattern is increased, the carbon concentration of decomposed pattern is increased and the thickness of carburized layer at the surface of steel castings is increased. Also as the density of coatings is increased, the permeability of coatings is decreased and the thickness of carburized layer at the surface of steel castings is increased. S25C steel which has lower original carbon content compared to S45C steel exhibited severe carburization.
김기영 ( Ki Young Kim ),오돈석 ( Don Suk Oh ),최경환 ( Kyeong Hwan Choe ),조규섭 ( Gue Serb Cho ),이경환 ( Kyung Whoan Lee ) 한국주조공학회 2004 한국주조공학회지 Vol.24 No.2
N/A Gas porosity which is a common defect in aluminum alloy casting, is also thought to be severer in aluminum alloy castings produced by lost foam process due to the pyrolysis of the polystyrene foam pattern during pouring. Fundamental experiments were carried out to evaluate the effect of process variables such as the melt treatment, the cooling rate and pouring temperature on the density and mechanical properties in A356.2 castings with simple bar shape. The density of grain refined specimen was slightly lower than that of degassed one, but was higher than that of no treated one and that of shot ball packed specimen was higher than the other specimens. The tensile strength and elongation were in the ranges of 200∼230MPa and 0.5∼1.5% respectively. The density and hardness of lost foam cast specimens decreased with increase in pouring temperature.