저 열팽창 주철의 진동감쇠능에 미치는 흑연 및 탄화물의 영향

문병문,홍준표 ( Byung Moon Moon,Chun Pyo Hong ) 한국주조공학회 1997 한국주조공학회지 Vol.17 No.1

N/A Effects of the amount of flake type graphite, morphology and (V,Mo)carbides on the specific damping capacity of austenitic low thermal expansion cast irons were investigated. Specific damping capacity(SDC) of low thermal expansion cast irons increased with the increased amount of graphite. Specific damping capacity of low thermal expansion cast iron decreased with the increased Young`s modulus. In the case of V and Mo addition, SDC decreased with the increased amount of carbides. Specific damping capacity increased about 2% by the movement of magnetic domains which appeared in ferromagnetic materials.

SOLA-VOF 법에 의한 정밀 주형내 용탕흐름의 수치 모델링

조인성,홍준표 ( In Sung Cho,Chun Pyo Hong ) 한국주조공학회 1992 한국주조공학회지 Vol.12 No.5

N/A A numerical model based on the SOLA-VOF method, which can calculate the transient free-surface configuration of the melt, has been developed in order to analyze melt flow in the investment mold. The computational results were compared with experimental results obtained from pure aluminum investment casting. Heat transfer analysis, with and without consideration of melt flow effect has been performed. It can be concluded that analysis of melt flow in the investment mold, provides the optimum conditions for gating design. It also enables more precise solidification simulation, since heat loss, while filling the thin and complex investment mold, plays an important role in determining the solidification sequence.

용탕단조시 Al-4.5wt%Cu 합금의 조직예측

조인성,홍준표,이호인 ( In Sung Cho,Chun Pyo Hong,Ho In Lee ) 한국주조공학회 1996 한국주조공학회지 Vol.16 No.6

N/A A stochastic model, based on the coupling of the finite volume(FV) method for macroscopic heat flow calculation and a two-dimensional cellular automaton(CA) model for treating microstructural evolution was applied-for the prediction of microstructural evolution in squeeze casting. The interfacial heat transfer coefficient at the casting/die interface was evaluated as a function of time using an inverse problem method in order to provide a quantitative simulation of solidification sequences under high pressure. The effects of casting process variables on the formation of solidification grain structures and on the columnar to equiaxed transition of an Al-4.5wt%Cu alloy in squeeze casting were investigated. The calculated solidification grain structures were in good agreement with those obtained experimentally.

경동식 중력주조법에 의한 주조결함 제어

염기동,홍준표 ( Ki Dong Yeom,Chun Pyo Hong ) 한국주조공학회 1998 한국주조공학회지 Vol.18 No.3

N/A Gravity tilt pour casting can effectively guarantee the reduction of various casting defects by controlling the rotation speed and the tilting angle of the mold during tilt pouring. The relationship between casting process parameters and the soundness of castings has been investigated in order to determine the optimum process variables in the gravity tilt pour casting process. In order to evaluate the effect of rotation speed on mold filling patterns, a video camera was employed to visualize the in-situ fluid flow behavior of the molten metal, and the relevant fluid velocity was also estimated. X-ray and mechanical tests were also performed to evaluate the effect of fluid velocity on casting quality. With the rotation speed lower than 0.5 r.p.m., which is nearly corresponding to the critical velocity of stability in the fluid flow, sound castings were obtained without having any casting defects. It can be concluded that the gravity tilt pour casting process is an effective process for manufacturing sound casting products with enhanced physical and mechanical properties. (Received February 5, 1998)

PFC 법에 의한 광폭 Al-Ni 다결정 리본의 제조 및 응고특성

이상목,홍준표 ( Sang Mok Lee,Chun Pyo Hong ) 한국주조공학회 1995 한국주조공학회지 Vol.15 No.1

N/A Wide Al-Ni polycrystalline ribbons were produced continuously via the planar flow casting(PFC) process. The influence of the process variables on the ribbon geometry has been investigated. The empirical correlation t_c=0.835^(0.32)/V_s^(0.76) was proposed for the variation of ribbon thickness with melt flow reate and wheel velocity. The propagation rate(V) of the solid/liquid interface varies with the ribbon thickness(t), i.e. decreased with increasing the distance from the chilled surface of the ribbon, as V=9.16t^(-1). In accordance with the absolute stability criterion, the solid/liquid interface stability decreases as the solidification rate decreases toward the top surface of the ribbon, leading to the observed morphological degeneration, cellular to branched dendrite.

Ti-Al 금속간화합물의 미세조직 및 기계적 성질에 미치는 제3원소의 영향

최창우,홍준표 ( Chang Woo Choi,Chun Pyo Hong ) 한국주조공학회 1992 한국주조공학회지 Vol.12 No.2

N/A The mechanical properties of Ti-Al intermetallic compounds which contain Mn, Zr, or Cr as the third element have been evaluated by means of hardness and compression tests. Microstructures have also been examined using an optical microscope. The cast structures of Ti-Al alloys are coarsened and the lamellar volume fraction is increased by the additions of Mn or V, but the cast structures are refined by the addition of Zr. Hardness tests of room temperature and compression tests at 600℃ showed that the mechanical properties of Ti-Al alloys were mainly dependent on the volume fraction of the α₂phase, grain size and solid solution hardening. However according to the compression test at 1000℃, the yield strength of Ti-Al alloys decreased with an increase in Mn or Cr content, but increased with an increase in the Zr content.

인바형 저열팽창 주조재의 절삭성

문병문,홍준표 ( Byung Moon Moon,Chun Pyo Hong ) 한국주조공학회 1997 한국주조공학회지 Vol.17 No.2

N/A The relative machinability of the invar-type cast alloys, such as invar cast steel, invar-type cast iron, Meehanite cast iron, and the modified Invar-type cast iron containing Mo and V was evaluated based on the tool life test, the surface roughness test and the chipping test. Tool life and surface roughness were measured under various rotting conditions. The tool lives of Invar cast steel, Meehanite cast iron, the modified Invar cast iron and Invar cast iron was 12min, 8min, 1min, 41min, respectively. The surface finish of Invar cast steel and the modified Invar cast iron was better than that of Meehanite cast iron, and the chip breakability of invar cast iron and Meehanite cast iron was better than that of invar cast steel. The Taylor`s equations of invar cast steel and the modified invar cast iron were VT^(0.3076)=154.479 and VT^(0.3880)=102.326, respectively. As the cutting speed increases, the surface finish of the modified invar cast iron was improved.

고압하에서의 Al-4.5wt.%Cu 합금의 응고현상

조인성,홍준표 ( In Sung Cho,Chun Pyo Hong ) 한국주조공학회 1995 한국주조공학회지 Vol.15 No.2

N/A Solidification of aluminum alloys under moderate pressures has been investigated. Interfacial heat transfer coefficient at the casting/mold interface varies with time after pouring the molten metal into the die cavity, and therefore plays an important role in determining solidification sequence. The heat transfer coefficients were evaluated by using an inverse problem method, based on the measured temperature distribution. The calculated heat transfer coefficients were used for solidification simulation in the squeeze casting process. The effects of applied pressure and positions of insulation in the mold have also been investigated on solidification microstructures and on the formation of macrosegregation of Al-4.5wt.%Cu alloys.

일방향 응고법에 의한 다결정 Si 의 결정성장 및 특성평가에 관한 연구

김계수,홍준표 ( Kye Soo Kim,Chun Pyo Hong ) 한국주조공학회 1994 한국주조공학회지 Vol.14 No.4

N/A Czochralski off-grade polycrystalline silicon was directionally solidified at a growth rate of 0.2∼1.0㎜/min using split reusable graphite molds, coated with Si₃N₄powder. The impurity concentration and grain size of the silicon wafers which affect the conversion efficiency of the solar cell were measured and compared with the reference values reported for high efficiency solar cells. The resultant grain diameter was above 1.0㎜. X-ray diffraction analysis has been performed to examine the preferred orientation in each of the silicon ingots. According to the X-ray diffraction analysis, preferred orientation was(111). The carrier concentration increases, while the resistivity decreases with increasing growth rate and fraction solidified.

저 열팽창 주철의 경도향상 및 선팽창계수에 미치는 탄화물 형성원소의 영향

문병문,홍준표 ( Byung Moon Moon,Chun Pyo Hong ) 한국주조공학회 1997 한국주조공학회지 Vol.17 No.1

N/A Invar-type austenitic cast irons are being used as low thermal expansive materials because of its good low thermal expansion characteristics and castability despite its low hardness. The effects of alloying elements such as Cr, Ti, V, and Mo on hardness and linear thermal expansion coefficient of the invar-type austenitic cast irons were investigated. A combined use of V and Mo addition was found to be the most effective for the improvement of hardness without causing an increase in the thermal expansion coefficient. With a combined addition of 4.6wt%V and 3.8wt%Mo, the hardness increased up to 180HB and the thermal expansion coefficient was kept at a relatively low value of 4.6×10^(-6)/℃ in the temperature range from room to 250℃.