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연속주조법에 의한 Sn-38%Pb 공정합금의 초소성특성
송태석,조형호,최재하,지태구,김명한 ( Tae Seok Song,Hyung Ho Jo,Jae Ha Choi,Tae Gu Ji,Myung Han Kim ) 한국주조공학회 1997 한국주조공학회지 Vol.17 No.3
N/A The 8㎜ dia: Sn-38%Pb eutectic alloy rods were produced by use of the horizontal continuous casting process with the heated mold and chill cast process. The cast rods were rolled into 2.0∼0.5㎜ thick plates and structural and mechanical properties were examined. The results revealed that the plates produced by the continuous casting process with the heated mold show much higher superplasticity at ambient temperature (1550% elongation at 0.5㎜ thick plate and 0.5㎜/min strain rate) than the plates procured by chill cast process (630% elongation). Such a high superplasticity of the continuous cast plates is due to the high-quality plates free from any inside and surface defects with fine and uniform distribution of eutectic phases.
수평식 연속주조법에 의한 순 Al 및 Al-5wt%Si 합금 주괴제조시 주조변수에 관한 고찰
김상동,조형호,김명한 ( Sang Dong Kim,Hyung Ho Jo,Myung Han Kim ) 한국주조공학회 1993 한국주조공학회지 Vol.13 No.6
N/A The effect of casting variables for making pure Al and Al-5wt%Si alloy rods free from any surface and inside defects was studied by adopting the horizontal continuous casting method with heated mold. The rods were cast under the casting conditions such as the mold temperature of 670∼690℃, water flow rate of 0.2∼0.6ℓ/min, and rod diameter of 4∼8㎜, when the melt temperature and mold to cooler distance was fixed at 700℃ and 20㎜, respectively. The results represented that the casting speed for good quality rod increased as the water flow rate increased, whereas, the casting speed decreased as the rod diameter or mold temperature increased. The statistical analysis of 2³factorial design was also applied and the results represented that the averaged optimum casting speed for pure Al(302㎜/min) was higher than that of Al-5wt%Si alloy(273㎜/min) resulting from the difference of superheat applied. The effect of rod diameter on the optimum casting speed was the highest for pure Al as well as Al-5wt%Si alloy. The effect of water flow rate and mold temperature on the optimum casting speed was in decreasing order.
그래핀이 코팅된 스테인리스강의 고분자전해질 연료전지 분리판 적용을 위한 표면 특성
이수형(Su-Hyung Lee),김정수(Jungsoo Kim),강남현(Namhyun Kang),조형호(Hyung-Ho Jo),남대근(Dae-Guen Nam) 한국표면공학회 2011 한국표면공학회지 Vol.44 No.5
Graphene was coated on STS 316L by electro spray coating method to improve its properties of corrosion resistance and contact resistance. Exfoliated graphite (graphene) was made of the graphite by chemical treatment. Graphene is distributed using dispersing agent, and STS 316L was coated with diffuse graphene solution by electro spray coating method. The structure of the exfoliated graphite was analyzed using XRD and the coating layer of surface was analyzed by using SEM. Analysis showed that multi-layered graphite structure was destroyed and it was transformed into fine layers graphene structure. And the result of SEM analysis on the surface and the cross section, graphene layer was uniformly formed with 3∼5 μm thickness on the surface of substrate. Corrosion resistance test was applied in the corrosive solution which is similar to the PEM fuel cell stack inside. And interfacial contact resistance test was measured to simulate the internal operating conditions of PEM fuel cell stack. The results of measurements show that stainless steel coated with graphene was improved in corrosion resistance and surface contact resistance than stainless steel without graphene coating layer.
Squeeze Casting 에 의한 Al-SiCp 복합재료의 제조에 있어서 가압력의 영향
문정탁,김명한,조형호 ( Jeong Tak Moon,Myung Han Kim,Hyung Ho Jo ) 한국주조공학회 1995 한국주조공학회지 Vol.15 No.1
N/A The Al-SiC_p composite was fabricated by the liquid mixing and squeeze casting method. The effects of squeezing pressure in the fabrication of the Al-SiC_p composite were studied by analysing microstructure and mechanical properties. The results could be summarized as follows; 1) The tensile strength and hardness of Al-SiC_p composite were increased as the squeezing pressure was increased. However, the elongation and amount of wear were decreased as the squeezing pressure was increased. 2) When the high squeezing pressure at the high molten temperature was applied in fabrication, the mechanical properties of Al-SiC_p composite were declined, which resulted from the deterioration of SiC_p particles in the matrix alloy. 3) The wear mechanism at the matrix alloy only was changed from adhesive wear to oxidation wear and from oxidation wear to fusion wear. However, the Al-SiC_p composite represented sliding wear mechanism resulting from the sliding action of SiC_p particles in the matrix alloy.
수평식 연속주조법에 제조된 무산소동의 방향성 응고에 관한 연구
김명한,이유재,조형호 ( Myung Han Kim,You Jae Lee,Hyung Ho Jo ) 한국주조공학회 1994 한국주조공학회지 Vol.14 No.6
N/A The horizontal continuous casting process with the heated mold was applied to obtain the unidirectionally solidified rods(4∼8㎜ dia.) of pure copper with good surface quality. The results could be summarized as follows. 1. The unidirectional solidification of pure copper rods with good surface(mirror surface) quality could be obtained by placing the S/L interface inside the heated mold cavity even though the cast copper rods were covered with thin copper oxide layer. 2. The casting speed for 4mm dia. rods with mirror surfaces was affected significantly by the mold-cooler distance rather than the cooling flow rate when other casting conditions were fixed. 3. The casting speed was the main factor affecting the oxidation of copper during the continuous casting and the thickness of copper oxide layer decreased almost linearly as the casting speed increased.
연속주조법에 의한 Al-11.3wt%Si 합금의 미세조직 변화에 미치는 Ti 및 Sr 의 영향
정찬회,김명한,조형호 ( Chan Hoi Jung,Myung Han Kim,Hyung Ho Jo ) 한국주조공학회 1996 한국주조공학회지 Vol.16 No.5
N/A The horizontal continuous casting process with the heated mold has been applied to study the effect of grain refiner or modifier such as Ti or Sr, respectively, in Al-11.3wt%Si alloy. The results represented that the addition of 0.02%Sr or 0.2∼0.4%Ti promoted the directionality of primary α dendrite, whereas the addition of 0.6%Ti suppressed the directionality. Also, the addition of 0.02%Sr suppressed the occurrence of feathery grains, while the addition of 0.2%Ti promoted the occurrence of feathery grain. The addition of Ti over 0.4% suppressed the occurrence of feathery grain, resulting from the in creasing grain-refining effect. The addition of Ti also increased the coarsening effect of eutectic silicon phase in Al-11.3%Si alloy.