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- 저자 : Su Jeong Shur ) (검색결과 4 건)
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急速凝固한 高純度 Fe―C―Si合金중의 Carbide共晶의 過冷却凝固 시뮬레이션
김영직,서수정,안현모 成均館大學校 科學技術硏究所 1991 論文集 Vol.42 No.1
This paper decribes a study of the solidification simulation with supercooling of levitation melted and rapidly solidified high purity Fe--C-Si alloys with emphasis on carbide eutectic. Newly designed growth model of carbide eutectic is proposed. From the simulation model, calculated cooling curves are derived by means of a personal computer, and compared with experimental data. The results calculated are influenced remarkably by coefficient of heat tranfer(h), latent heat of solidification(L), growth rate constant(n) and range of temperature of mushy zone. After suitable choice of h, L, n and especially temperature range of mushy zone as 100K, experimental cooling curves are duplicated by calculated. As the cooling rate exceed about l0^3K/s, graphite crystal is not formed in the high purity Fe -C-Si melts.
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Nd-Fe-B계 영구자석의 자기적 성질에 미치는 열처리의 영향
朴現錞,徐守正 成均館大學校 科學技術硏究所 1991 論文集 Vol.42 No.1
Alloys of 33%Nd-6.3%Fe-1.5%B-0.7%Al-0.6%Si were melted in vacuum induction furnace and quenched and ground to about 3㎛ sizes. After pressing these fine powders in magnetic field, sintering and annealing processes were performed in various temperatures. The measurement of magnetic properties of the processed alloys leads to the following conclusions. When the sintering temperatures were increased, the remanence of the alloys were increased slightly between 1060 and 1080℃ arid then were remained to be constant value of 10.3KG up to 1120℃. This is due to the effects of the presence of more Nd-rich phases as well as the presence of Al and Si in Nd-rich phase compared with the standard composition of Nd_15Fe_77B_8 which has a lower Nd-rich phase and contain no Al and Si. The optimum sintering temperature of the alloys was found to be 1080℃ and when the grains were hexagonal shaped and grain boundaries were linearly formed, the best magnetic property were obtained. When the alloys were annealed at about 520℃, the intrinsic coercivities were rapidly increased from 9 KOe to 12-14 KOe. Such increase was pronounced in the alloys sintered at 1060℃. But at the higher annealing temperatures the intrinsic coercivity was decreased in all the sintering temperatures. When the annealing were performed between 520 and 720℃, (BH)_max decreased in the lower temperature region but increased gradually as the annealing temperature increases. The is due to change of squarness and remanence.
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Levitation 법에 의한 고순도 Fe-C-Si 합금중의 흑연결정의 핵생성 및 성장
김영직,서수정 ( Young Jig Kim,Su Jeong Shur ) 한국주조공학회 1991 한국주조공학회지 Vol.11 No.3
N/A This paper describes a study of the nucleation and growth of graphite crystal of levitation melted high purity Fe-C-Si alloys with emphasis on hypereutectic composition. Spherulitic graphite was observed to form at high purity alloy and converted to compacted by changing the starting iron from ultra-pure zone refined iron to 99.95 pct electrolitic iron. Residual C-C clusters might be acting as an effective nucleation site for graphite, and sulphur was the element to prevent graphite from nucleating. The graphite morphology changed from compacted to spherulitic as the sulphur content decreased.
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Cu-Sn(P) 합금의 용질재분배에 (溶質再分配) 관한 연구
서수정,조순형,김익수,윤의박,최정철 ( Su Jeong Shur,Soon Hyung Cho,Ik Soo Kim,Eui Pak Yoon,Jeong Cheol Choi ) 한국주조공학회 1990 한국주조공학회지 Vol.10 No.3
N/A In this, we have investigated the solute behavior in front of solid-liquid interface according to the change of the cooling rate in bronze alloy and phosphor bronze alloy. The conclusive summary is as follows: 1) The secondary dendrite arm spacing was decreased with increasing the cooling rate. 2) The minimum solute concentration happened to along centerline of primary arm, and the maximum solute concentration was found at the boundary of arm or between the arms the minimum solute concentration was increased with the cooling rate. 3) Segregation Index S was decreased with increasing the cooling rate and content of P. 4) The degree of the microsegregation was decreased with increasing the cooling rate. The effective distribution coefficient, Ke was increased with addition of P in Cu-Sn.
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