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윤의박,조순형 ( Eui Pak Yoon,Soon Hyoung Cho ) 한국주조공학회 1983 한국주조공학회지 Vol.3 No.2
In this paper analytical and numerical methods fur analysis of solidification of castings are described, and the matrix method, one of numerical method, where the nodal point is designated on the element boundary was adapted. The cooling curve obtained by experimental values, when cast steel (0.29%C. 0.62%Si) was poured into CO₂mold, is compared with that of computed values by exploiting computer (V77-600 Data Proceeding System, UNIVAC). The computed value is nearly approximation to the experimental. But the computed value shows a tendency that is a little higher than the experimental in solid-liquid coexisting temperature ranges and much lower than the experimental after solidification. It is considered to result from the lacks and difficulties of ultimately appropriate adaptation of various physical properties and also air cap between castings and mold.
2상혼합조직을 (相混合組織) 가진 구상흑연주철의 기계적 성질에 관한 연구
윤의박,이영호 ( Eui Pak Yoon,Young Ho Lee ) 한국주조공학회 1982 한국주조공학회지 Vol.2 No.2
N/A This paper is concerned with the improvement of impact and tensile Properties of spheroidal graphite cast iron of the following duplex matricess which were heat treated in the eutectic transformation temperature range (that is, (α+γ) coexisting range) ; ferrite-martensite, ferrite-bainite and ferrite-pearlite. The absorbed energy and maximum load was measured by recording the load-deflection curve with instrumented Charpy impact testing machine in the temperature range from +100℃ to -196℃. It was found the ferrite-bainite duplex matrix showed the highest toughness among the above matrices in the room temperature and the low temperature range. Comparison of this matrix to ferrite-pearlite matrix(that is, as east) showed a lowering of 27 ℃ in the nil-ductility transition temperature (NDT) and a lowering of 40 ℃ in the ductile-brittle transition temperature (TrE), Which seems to result from the finner dimple pattern observed using miorofractography.
전자기력을 이용한 알루미늄 합금중 개재물의 연속적 제거에 관한 연구
윤의박(Eui Pak Yoon) 한국주조공학회 2002 한국주조공학회지 Vol.22 No.3
N/A The growing use of aluminum for castings over the past decade has brought with it the increased scrutiny of component properties. One area that has received much attention is the effect of in inclusions - or impurities particles held in the metal - on casting properties. A new method of electromagnetic separation for removal of inclusions in aluminum alloy melts is proposed. The principle is that as the electromagnetic force induced in metal acts on inclusions due to low electric conductivity, they are moved to the direction opposite to electromagnetic force and can be separated and removed from the melt. Experiments were carried out on A356 melt mixed alumina particles and commercial Al alloys of ADC 10 and 12. In the experiment using A356, it was proved that Al-2O_3 particles was separated and removed continuously from matrix melt by electromagnetic force. Based on these results, the continuous separation experiment that used ADC 10, 12 was carried and the cleanliness of melt was assessed by the amount of porosity, hydrogen contents, PoDFA and mechanical properties through tensile test. As the results of analyses, the amount of porosity and hydrogen contents decreased without variation of chemical composition in the specimen that passed the electromagnetic continuous separator. In addition, tensile strength and elongation of this specimen increased by 20∼30% because of reduction of inclusions.
Single Roller 법에 의한 Al-Cr 계 합금의 급냉응고 조직과 상분해
조순형,윤의박 ( Soon Hyoung Cho,Eui Pak Yoon ) 한국주조공학회 1987 한국주조공학회지 Vol.7 No.2
Al-Cr alloy with composition in the range from 1.5wt% to 10wt% Cr were rapidly solidified from the melt by the single roller method. The supersaturated solid solution was obtained up to 6wt% Cr in Al-Cr alloy for 20㎛ thickness. Lattice parameter decreased with increasing Cr content at the rate of 0.00456A perwt% Cr up to 6wt% Cr. Microhardness increased with increasing Cr content at the rate of 10㎏/㎟ per wt% Cr up to 6wt% Cr. Microhardness measurements on the Al-6wt% Cr supersaturated solid solution annealed isothermally showed no sign of age hardening. Decomposition temperature, determined by lattice parameter changes and microhardness changes, was 470℃ for Al-6wt% Cr supersaturated solid solution. Transmission electron microscopy showed that decomposition within one hour below 400℃ occurred at grain boundaries only, and also the additional decomposition within grains being evident at 450℃. The coarse precipitate structure showed at 500℃ and 550℃, respectively. The coarse precipitate structure is considered Al_7Cr.
전자교반시 미세화제첨가에 따른 Al-7wt%Si 합금의 미세조직변화
임성철,윤의박 ( Sung Chul Lim,Eui Pak Yoon ) 한국주조공학회 1996 한국주조공학회지 Vol.16 No.5
N/A To gain a semi-solid alloy the electromagnetic stirring by an induction motor of 3 phase and 2-poles was used. And it was also observed that the change of primary particle size, distribution and degree of sphericity by addition of a refiner, Al5Ti1B. The effect of refiner on the distribution and dimensions of primary particles prior to that electromagnetic refining on those was examined. In case of electromagnetic stirring with the refiner Al5Ti1B, the average size of primary solid particles increased as the fraction of solid increased. However it decreased as the amount of Al5Ti1B addition increased to 0.5% and then it was increased again as the addition amount of Al5Ti1B increased above 1.0%. The average size of primary solid particles was 31㎛ in case of melt temperature 600℃ when the fraction of solid was 0.3, input voltage 140V, cooling rate 2.5℃/s, and 0.5% Al5Ti1B. To use the electromagnetic stirring with the addition of a refiner was able to obtain more small primary solid particles than to use the electromagnetic stirring only.
전자교반시 Al-7wt%Si 합금의 초정입자에 미치는 유동의 영향
임성철,윤의박 ( Sung Chul Lim,Eui Pak Yoon ) 한국주조공학회 1996 한국주조공학회지 Vol.16 No.6
N/A In this study, to gain the semi-solid alloy we employed the electromagnetic rotation by a induction motor of 3-phases and 2-poles for Al-7wt%Si alloy and observed the size of primary solid particle, distribution state of primary solid particle, the degree of sphericity, and fraction of primary solid for the evaluation of its results. The size of primary solid particle increases from 98㎛ to 118㎛ as solid fraction increases from 0.2 to 0.5. The degree of sphericity increased as the solid fraction increased. Solid particles obtained from the microstructures of isothermally held sample were coarsened and the degree of sphericity was enhanced as isothermal holding time increased. However, when the sample was stirred for more than 40min, solid particles merged together and liquid phase was entrapped within the cluster of solid particles. The size of primary solid particle was not changed significantly with the variation of input voltages by 160V over which solid particles began to merge together to be a large cluster of about 170㎛ at 180V. The standard deviation and the degree of sphericity were not changed significantly with the variation of input voltage.
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.
전자교반에 의한 Al 합금의 초정입자 미세화에 관한 연구
임성철,윤의박 ( Sung Chul Lim,Eui Pak Yoon ) 한국주조공학회 1996 한국주조공학회지 Vol.16 No.5
N/A The change of microstructure of Al-7wt%Si alloy was examined by using a induction motor of 3-phases and 2-poles in semi-solid electromagnectically stirring process. The size and degree of sphericity of primary solid particles were observed by means of change of cooling rate. At a certain cooling rate, the size of primary solid particles increased and the sphericity became perfect, as the fraction of solid increased. The average size of primary solid particles was 43㎛ when the fraction of solid was 0.3 and at 600℃, input voltage 140V, cooling rate 2.5℃/s. It was shown that the size of primary solid particles was proportional to local solidification time.