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유승목,이두호,김종기,소찬영,홍준표 ( Seung Mog Yoo,Doo Ho Lee,Jong Ki Kim,Chan Young So,Chun Pyo Hong ) 한국주조공학회 1991 한국주조공학회지 Vol.11 No.1
N/A A computer program which consists of pre-processor, main solidification simulator and post-processor has been developed for three dimensional solidification analysis of steel castings. The pre-processor is used for mesh generation in a small personal computing system. The modified finite difference method is adopted for the main solidification simulation algorithm. The post -processor graphically presents the simulation results and shows the formation of shrinkage defects. Several experiments on large steel castings in sand mold were carried out. The temperature variations in casting and mold with time are measured experimentally, and the results are compared with calculation results. Several numerical examples for the prediction of shrinkage cavity in large steel casting of SC42 and SCNCrM2 alloys are compared with experimental results. The effect of sleeve and chills on solidification patterns are also studied. Formation of shrinkage defects for the three cases of experimental castings are relatively well predicted by present model.
이영철,이두호,김종기,소찬영,최정길,홍준표 ( Young Chul Lee,Doo Ho Lee,Jong Ki Kim,Chan Young So,Jeong Kil Choi,Chun Pyo Hong ) 한국주조공학회 1997 한국주조공학회지 Vol.17 No.5
N/A An integrated computer program consisting of a pre-processor, main solver, and post-processor was developed for the design of large steel castings. The pre-processor, based on the AutoCAD, enables the user to produce approval drawings, casting design drawings and mesh diagrams in sequence using a personal computer. In the main solver, two numerical models were employed; one models the fluid flow during mold filling, and the other models the heat transfer and solidification. The post-processor can be used to present simulation results such as flow pattern, mold filling sequences, solidification times, temperature gradients and location of shrinkage defects by color graphics. In order to validate the applicability of the present integrated program, a series of experiments on simple-shaped steel castings were carried out. After the validation of the present model, it was applied to the casting design of the large steel anchor of an SC42 alloy. Various solidification parameters such as a temperature distribution and a solidification time in the casting and the mold were compared with those obtained experimentally. Simulated results predicting shrinkage defects were in good agreement with those obtained experimentally. It was found that the present method can be successfully applied to the quantitative casting design for complex-shaped large steel castings. (Received June 4, 1997)
이동희,소찬영 연세대학교 산업기술연구소 1980 논문집 Vol.12 No.2
本 硏究는 高逵素鋼材料인 Fe-Si混合壓粉體의 燒結現象에 관한 基礎硏究로서, 純 鐵粉에 융점이 낮은 Fe-Si合金粉을 혼합한 경우와 純Si粉을 혼합한 경우의 燒結擧動을 조사하고, 燒結方法에 의한 磁氣的 機械的 性質의 변화 양상을 定性的으로 고찰하였다. 硏究方法은 純 鐵粉에 Fe-Si合金粉 및 純 Si粉을 高硅素鋼의 組成範圍인 4%Si에서 8%Si까지의 여러 조성으로 혼합하여 6ton/㎠ 의 압력으로 成形한 후, 수소 분위기 중에서 燒結溫度(1100 ℃-1350℃)와 燒結時間(5分-240分)을 변화시켜 燒結을 행하였으며, 각각의 燒結擧動은 燒結體의 氣孔度, densification para meter, 微細組織을 토대로 검토하였다. 本 硏究結果에 의하면 Fe-Si合金粉을 液相으로 발생시킨 경우가 純粹 固相에 의한 것 보다 燒結이 다소 促進되었으나, 모두 短時間內(30分 이내)에만 效果가 있었다. 그 이유는 液相量이 너무 적고 또, 短時間內에 소멸되어 液相燒結現象의 지속이 오래가지 않았다는 것과, 급격한 結晶粒의 성장 등으로 燒結이 크게 促進되지 못하였다고 分析되며, Fe-Si合金粉의 混合壓粉體를 固相燒結할 경우 1시간 이상 長時間에서 Kirkendall效果에 의해 氣孔度가 다시 증가하는 경향을 보였으며 전체적으로 燒結이 沮害됨을 알 수 있었다. 또한 燒結에 따른 緻密化는 1200℃ 이하 固相燒結에서 純 Si粉의 混合壓粉體 보다 Fe-Si合金粉의 混合壓粉體가 양호한 것으로 나타난 반면, 1250℃ 이상에서는 純 Si粉의 混合壓粉體가 보다 더 緻密化 되었다. 機械的 性質(硬度)은 Si의 組成이 높을수록 증가되었으며, 磁氣的 性質은 예상과는 달리 Si의 組成이 낮은 경우가 양호한 것으로 나타났다. SINTERING OF Fe-(4∼8wt%) Si POWER COMPACTS. The sintering behaviour and the varation of related properties for Fe-Si powder compacts containing various composition of Si from 4%, to 8% have been investigated with mixture of pure iron and pure silicon powders,and mixture of pure iron and Fe-75% Si alloy powders The results obtained in these experiments can be summarized as follows. (1) The enhanced densification for the compacts sintered at high temperatures above 1250℃, where liquid phase of Fe-Si alloy powder begins to occur, was not so high as what could be expected from the conventional liquid phase sintering concepts. The reasons for this can be attributed to the little amount of the liquid phase and its rapid disappearance in compacts during sintering, and the fast grain growth due to the high sintering temperatures. (2) Under the sintering condition of solid state only, the compacts of Fe-Si alloy powder mixtures showed that the densification rate decreased slowly due to the Kirkendall effect for long sintering time over 1 hour. (3) Sintering of the compacts prepared from pure iorn and Fe-Si alloy powder mixture showed an improved densification as compared to that of pure iron/pure Si power mixed compacts under the temperature of 1200℃, but above 1250℃ an opposite result was observed. (4) Magnetic susceptibility of the sintered compacts containing lower Si contents(4.5%) was higher than those of higher Si compacts. This fact is not consistent with the expectation, but it may be attributed to the observed high values of porosity for 6.5% and 7.5% Si compacts in these experiements. Hardness values, however, increased with Si content.
소찬영,오명석,정선광,김성우 대한금속재료학회(대한금속학회) 1992 대한금속·재료학회지 Vol.30 No.2
For the production of the clean steels, liquid steel transfer in practice from electric furnace through tundish to continuous casting mold has been studied. Samples of the slag and liquid steel were taken simultaneously from each sequential step especially including the tundish at three different times and their chemical compositions were analyzed. The metal specimens were examined under an optical microscope and the electron optics and their nonmetallic inclusions were investigated in terms of area fractions of the inclusions by an image analyzer. The results are as follows : Open stream transfers of the liquid steel from ladle to tundish and presumably from tundish to mold were found to be contributed greatly to reoxidation of metal by air. So was the reoxidation of the metal in the tundish particularly at early stage without protection by the synthetic slag. The slag carryover from the ladie to tundish towards the end of metal transfer was found to be obviously detrimental to the cleanliness of the steel.
블룸 연속주조에 있어서 경계밀착좌표계를 이용한 용강유동과 열전달의 연결해석
윤종규,소찬영,이중의,한승호,석윤종 대한금속재료학회(대한금속학회) 1996 대한금속·재료학회지 Vol.34 No.1
A 2-D coupled analysis of heat transfer and fluid flow was conducted in continuously cast bloom. Latent heat of fusion was considered by modifying the heat capacity/temperature relation, which is so called the effective heat capacity method. To consider the curved type geometry, boundary-fitted coordinate(BFC) system was employed. Water cooling in the mold was simulated by considering the known heat flux and the secondary cooling by considering air cooling and air-mist spray. In this study, the fluid flow and the temperature profile in the continuous casting system of bloom were simulated with the variation of casting speed, tundish superheat. Thus, the effects of casting variables on the distribution of surface temperature, shell thickness, metallurgical length were predicted.
이동희,소찬영 대한금속재료학회(대한금속학회) 1985 대한금속·재료학회지 Vol.23 No.2
A kinetic investigation was carried out on the development of ferromagnetic γ phase in Mn-Al-C alloys of three different carbon contents (O, 0.18 and 0.27 wt.% at a fixed Mn of 70 wt.%) by means of the isothermal heat-treatment at temperatures ranging 425∼600℃. The results obtained can be summarized as follows; 1) The transformation kinetics was interpreted as an autocatalystic reaction in which the induced stress developed during the growth of ε' phase from the high temperature εphase was believed to be responsible for the reaction. 2) The addition of carbon to Mn-Al binary alloy decreased the rate of transformation. The activation energy for the transformation from εto τphase was calculated to be 58.0, 59.1 and 60.1㎉/㏖ respectively for Mn-Al and Mn-Al-C specimens.