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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.
Al-7wt%Si-0.3wt%Mg 합금의 응고 및 미세조직에 미치는 Sr 첨가와 금형예열온도의 영향
권일수,김경민,윤의박 ( Il Soo Kwon,Kyoung Min Kim,Eui Pak Yoon ) 한국주조공학회 1997 한국주조공학회지 Vol.17 No.6
N/A The effect of mold preheating temperature on the microstructure such as grain size, eutectic silicon morphology was investigated for the Al-7wt%Si-0.3wt%Mg alloy. Microstructural variations have been characterized as a function of Sr addition and cooling rate during solidification. Microstructures were correlated with cooling rate, local solidification time and eutectic nucleation temperature, etc. In this study, Sr addition caused increase of local solidification time, undercooling and reduction of eutectic plateau temperature. In logarithmic scale, local solidification time was in inverse proportion to cooling rate. Eutectic nucleation temperature was in inverse proportion to cooling rate of logarithmic scale. Increasing the cooling rate refined dendrite arm spacing; and eutectic silicon. Dendrite arm spacing was logarithmically in inverse proportion to cooling rate. Without modifier addition, eutectic silicon was modified at cooling rate of 7˚C/s or higher. (Received November 12, 1997)
전자기력을 이용한 알루미늄 스크랩 중의 Fe 제거에 관한 연구 : ( Part 1. Al-Si-Cu계 합금 스크랩에서 Mn 첨가에 따른 Fe 계 금속간화합물의 생성과 형상변화 )
김정호,박학수,김경민,윤의박 ( Jeong Ho Kim,Hak Soo Park,Kyoung Min Kim,Eui Pak Yoon ) 한국주조공학회 1998 한국주조공학회지 Vol.18 No.2
N/A In the view point of the environmental conservation and the energy reduction, the recycling of metal scrap is coming as one of the global subjects in the world. In this study, the formation and morphological change of the intermetallic compounds in the scrap of Al-Si-Cu alloy(JIS ADC12), which were widely used in diecasting process, was investigated in order to eliminate the Fe element, which was usually accumulated in the scrap. In accordance, the formation and morphological change of Fe-contained intermetallics by addition of Mn in Al-Si-Cu system alloy was investigated with the amount of Mn added, holding time and holding temperature. The formation temperature of the large angular intermetallic compound ascended with the amount of Mn added. The shape of needle-like Al_5FeSi compounds were completely changed to that of large angular Al_(15)(Fe,Mn)₃Si_5 intermetallics when Mn/Fe ratio was higher than 3/4. The higher Mn/Fe ratio was, the larger angular Al_(15)(Fe,Mn)₃Si_5 intermetallics were formed and the larger those were. Therefore, the content of Fe in matrix decreased from 1.64wt.% to 1.1wt.%. (Received November 29, 1997)
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)
Al-7wt%Si-0.3wt%Mg 합금의 응고시 미세조직에 미치는 Ca 및 P 의 영향에 관한 연구
권일수,김정호,김경민,윤의박 ( II Soo Kwon,Jeong Ho Kim,Kyoung Min Kim,Eui Pak Yoon ) 한국주조공학회 1998 한국주조공학회지 Vol.18 No.4
N/A In this study, the influence of impurity element Ca, P on solidification behavior and morphology of eutectic silicon was examined by observation of microstructure and by DSC analysis. In the case of 1.3 ppm P, eutectic Si was fine and fibrous when the added amount of Ca was 500 ppm, However, the modification of eutectic Si was depressed by formation of polygonal Ca-Si compounds when the addition amount of Ca was greater than 1000 ppm. The addition of Ca 500 ppm depressed the primary and eutectic temperature. The primary and eutectic temperature were depressed with Ca 500 ppm but rather ascended when the addition amount of Ca was more than 1000 ppm. When the content of P was 17.5 ppm, eutectic Si had modified morphology with Ca addition. DAS was increased, the primary temperature was ascended and eutectic temperature was depressed with Ca added. Eutectic Si appeared as coarse flake phase and DAS was decreased with the increase of P content. The existence of P in the melt depressed the primary temperature and ascended eutectic temperature. (Received January 9, 1998)
김기배,김경민,이재철,이호인,윤의박,조남돈 ( Ki Bae Kim,Kyoung Min Kim,Jae Chul Lee,Ho In Lee,Eui Pak Yoon,Nam Don Cho ) 한국주조공학회 1996 한국주조공학회지 Vol.16 No.3
N/A The effect of forced convection on the solute redistribution of the Al ingot is studied in an effort to fabricate high purity aluminum using a fractional solidification processing. Experimental setup is built in order for the Al melt to be solidified from the surface of the graphite cooling tube, which is rotated at a constant revolution rate to generate the forced convection environmental ahead of the solidification front. Based on the experimental results, Fe and Si concentrations, added as impurities within the Al ingot, decrease as the distance measured from the graphite tube and growth rate decreases and as revolution speed increases. In the case of Al melt with high initial solute concentration, spiral columnar grains tend to form along a direction of revolution. In the case of Al melt with low solute concentrations, however, grains tend to grow with planar geometry. In the fractional solidification process, the solute concentration within the solid phase tends to decrease at the early stage of solidification, reaches minimum concentration, and then increases gradually as solidification proceeds. The solute redistribution obtained based on the BPS model incorporated with the tangential flow component as well as the axial flow component within the melt, agree well with the measurements under sufficiently high revolution speed and low solidification rate.
Al-Si 합금의 개량화에 미치는 각종 개량화제의 영향에 관한 연구
박준표,김경민,조순형,윤의박 ( Joon Peuo Park,Kyoung Min Kim,Soon Hyung Cho,Eui Park Yoon ) 한국주조공학회 1991 한국주조공학회지 Vol.11 No.4
N/A In this study, Na, Li, Sb, Sr were added as the modifiers to improve the mechanical proper ties of Al-Si alloys and their effects were compared one another Thermal analysis was carried out to measure the degree of undercooling, that is, the basic mechanism of modifying effect. The measurements of holding time and analyses of components of Al-Si alloys were carried out to compare the fading of the modifiers. Greater degree of undercooling was measured from the modified alloy than the normal alloys. In the modified alloy, the shape of Si was changed into a fine fiber phase or a lamellar phase from the coarse plate phase. There are not modifying effect of Sb below the 1.5℃/sec of cooling rate. As the cooling rate increases, similar effects appears in the non-modified alloys like the modified alloys. Na and Li were faded in short time and were difficult to control on the melt, but Sb and Sr were scarcely faded for 6 hours of holding and were easy to control on the melt. Na and Sr are the good modifiers in terms of microstructure. Sb is the best modifier, but Na, Li are the inadequate modifiers in terms of fading.
용탕단조법에 의한 AC8A / Al2O3 복합재료의 기계적 성질에 관한 연구
김기배,김경민,조순형,윤의박 ( Ki Bae Kim,Kyoung Min Kim,Soon Hyung Cho,Eui Park Yoon ) 한국주조공학회 1991 한국주조공학회지 Vol.11 No.6
N/A In this study the fabrication technology and mechanical properties of AC8A/Al₂O₃ Composites by squeeze casting process were investigated to develope for application as the piston materials that require good friction, wear resistance, and thermal stability. AC8A/Al₂O₃ composistes without a porosity and the break of preform were fabricated at the melt temperature of 740℃, the preform temperature of 500℃, and mold temperature of 400℃ under the applied pressure of 1200㎏/㎠ as the results of the observation of microstructures. As the results of this study, the tensile strength of AC8A /Al₂O₃composites was not increased linearly with Al₂O₃volume fraction and so it seemed not to agree with the rule of mixture, which had been used often in metal matrix composite. Also the tensile strength after thermal fatigue test was little different from that before the test. Consequently it was thought that AC8A /Al₂O₃composites fabricated under our experimental conditions had a good thermal stability and subsequently a good interface bonding. Wear rate(i.e., volume loss per unit sliding distance) of AC8A/Al₂O₃composites was decreased with Al₂O₃volume fraction and the sliding speed at both room temperature and 250℃ and so there was a good correlation between wear rate and hardness. Also the wear rate of AC /8A20% Al₂O₃composities was obtained the value of 1.65 ㎤/㎝ at sliding speed of 1.14m/sec as compared with about 3.0×10^(-8)㎤/㎝hyereutectie Al-Si alloy(Al-16%Si-2%Cu-1%Fe-1%Ni), which applied presently for piston materials. The wear behavior of Al₂O₃composites was observed to a type of abrasive wear by the SEM view of wear surface.
강제대류시 고순도 Al 괴의 응고조직에 미치는 유동의 영향
김경민,김헌주,하기윤,윤의박 ( Kyoung Min Kim,Heon Joo Kim,Ki Yun Ha,Eui Pak Yoon ) 한국주조공학회 1993 한국주조공학회지 Vol.13 No.6
N/A The effects of fluid flow on the purification of aluminum were studied. As the revolution rate(N) increased, the size of columnar grain decreased gradually. The concentration of solidified crystal was decreased with increasing distance from chill and revolution rate(N). Distribution boundary layer thickness(δ) was calculated from the solute distribution obtained in solid experimentally and by use of BPS equation. The value of δ changed from about 60㎛ at N value of 27rpm to about 15㎛ at N value of 1000rpm. From this result, high purification was obtained by decreasing the diffusion boundary layer under forced convection.
논문 : 응고 ; Al-7wt%Si-0.3wt%Mg합금의 공정 Si 개량화 처리에 미치는 P의 영향에 관한 연구
권일수 ( Il Soo Kwon ),김정호 ( Jeong Ho Kim ),김경민 ( Kyoung Min Kim ),윤의박 ( Eui Pak Yoon ) 대한금속재료학회 ( 구 대한금속학회 ) 1998 대한금속·재료학회지 Vol.36 No.7
In this study, the influence of impurity element P on modification of eutectic Si with Sr addition was examined by the observation of microstructures, DSC thermal analysis, tension test and fractographs observation. When the content of P was 1.3ppm, the eutectic morphology was the fine neeldle phase. In case of P 17.5ppm, eutectic Si appeared coarse flake phase. The increase of P in the melt deteriorated modification of eutectic Si and ascended eutectic temperature. UTS and elongation decreased with the increase of P content.