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FMC 법에서 모형 도형제가 순알루미늄 주물의 응고와 주형의 열적거동에 미치는 영향
조남돈,김용남 ( N . D . Cho,Y . N . Kim ) 한국주조공학회 1987 한국주조공학회지 Vol.7 No.2
Full mold casting process is a new technique offering numerous advantages and promising possibilities. The present study is aimed to bring out the results of experiments carried out to study the effect of pattern coatings on the solidification of 99.5% pure aluminum plate-shaped castings in the various sand molds and the thermal behavior of the molds. The results of the investigation indicate that (i) with increase in pattern coating thickness, the relative chilling power decreases gradually for silica and increases for zircon coating, and (ii) the application of a pattern coating significantly reduces the maximum interface temperature by the mold which is more pronounced in the case of thinner mold wall. The investigation also indicates that Chvorinov`s rule is not found to be valid for the casting in the full mold, with or without pattern coating. Therefore in full mold process, the pattern coating thickness will be a very important parameter in the study of thermal behavior.
큐폴라의 예열대영역과 (豫熱帶領域) 유사한 조건하에서 탄소강설의 (炭素鋼屑) 산화반응속도에 관한 연구 (2) - 비등온적 (非等溫的) 연구 -
조남돈,조성수,김호찬 ( N . D . Cho,S . S . Cho,H . C . Kim ) 한국주조공학회 1986 한국주조공학회지 Vol.6 No.3
Many of steel oxidations concerned with the iso-thermal oxidation, and few reports on the non -isothermal oxidation have been published. Then the auther investigated the oxidation of non-isothermal type: from 500℃ to 1070℃by CO-CO₂-N₂ mixed gases which approximate the distribution of gases in the preheating zone of the coke and the coke-gas cupola. The results obtained are as follows: 1) The effect of carbon on the oxidation rate of steels is to increase slightly as increasing temperature. 2) The observed rate of oxidation using cubic specimen is a little greater than cylindrical or spheric specimen. 3) Weigh gain of oxidation at the center of coke cupola is a little less than that of wall, but the center of coke-gas cupola it is more increased than above. 4) The rate of non-isothermal oxidation can be expressed by the following equation. 수식 5) The Al₂O₃-bentonite coating mixture for the oxidation resistance is more efficient than the cement or the CaO-bentonite mixture.
소실모형 주조법에서 도형제가 오스테나이트 스테인레스강 주물의 표면층조직에 미치는 영향
김지윤,조남돈 ( Ji Youn Kim,Nam Don Cho ) 한국주조공학회 1995 한국주조공학회지 Vol.15 No.6
N/A Austenitic stainless steel castings using expandable polystylene(referred to hereafter as EPS) patterns are often affected by distinctive defects associated with incomplete decomposition of the EPS as the molds are filled with metal. The quality of the castings, with particular reference to carbon pick-up in austenitic stainless steel is further influenced to a significant extent by such factors as reduced pressure, the additive by adding Na₂CO₃in coating. The steel composition and microstructure were examined at the surface layer of castings, at depths of 1mm, by taking successive layers of swarf and analysis. In experiments, the carburizing atmosphere was neutralized, showing that the coating performed efficiently by decomposing almost instantly on heating and liberating CO₂. The upper parts of castings obtained using EPS patterns were slightly higher in carbon pick-up than other parts. Comparing the 316L and 304 stainless steel castings, qualitative and quantative differences could be found between the carbon pick-up behaviours as influence of the carbon content and alloying elements. Carbide former such as Cr makes carbon more soluble in the steel. This must make carbon pick-up in the surface layer but at the same time richer in carbon especially in the 304 stainless steel castings.