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Fe-Co-W 소결체와 탄소강의 레이저 용융부 결함형성에 미치는 공정변수의 영향
김성욱(S. W. Kim),윤병현(B. H. Yoon),정우광(W. G. Jung),이창희(C. H. Lee) 한국레이저가공학회 2004 한국레이저가공학회지 Vol.7 No.3
This study was performed to clarification of the formation of weld discontinuities in the dissimilar laser fusion zone. Welding parameters were beam power of 1300, 1430, 1560, and 1700 W and travel speed of 1, 1.3, and 1.7 m/min. Most cavities in the fusion zone were observed near the tip. Cavities in the fusion zone observed to be formed and grown from pores in the tip. More cavities were formed as the beam position moves to the tip side. Small cavities were decreased but large cavities were increased when the energy input increased. W content in the fusion zone was increased with heat input and as the beam position close to the tip. In the fusion zone, W content in the dendrite boundary was increased with heat input. Considering the propagation path and fracture morphology, cracks were solidification cracking, and were initiated and propagated along the dendrite boundaries. The formation of cracks might be related with the W rich μ phase which was formed in the grain boundaries and dendrite boundaries.
용융아연 도금욕중 Al농도 센서의 기준전극에 대한 연구
정우광,정세혁,Jung, W.G.,Jung, S.H. 한국재료학회 2006 한국재료학회지 Vol.16 No.2
In order to get basic information on the reference electrode material for the long life Al concentration sensor in zinc galvanizing melt, the workability and stability of fluorine potential cell with $CaF_2$ single crystal electrolyte were examined carefully at constant temperature for six kinds of reference materials (Zn, Sn, Cd, Bi, Pb, Al-Sn alloy + fluorides). Good workability and stability of the sensor were found in sensor with $Bi+BiF_3$ reference electrode. The Al sensor with $Bi+BiF_3$ reference electrode was assembled and was tested in Zn-Al melt with different Al concentration. The EMF was changed rapidly with the change of Al concentration and was stabilized in a short time. Thus the response of EMF was satisfactory for $CaF_2$ sensor. The correlationship between EMF from the sensor and logarithm of Al concentration has been derived from the least square regression method. E/mV=57.515log[wt% Al]+1883.3 R=0.9717 ($0.013{\leq}[wt% Al]{\leq}0.984$) The EMF from Al sensor was increased linearly against logarithm of [wt% Al]. The fluorine potential of Zn-Al melt was also calculated to be in the range of $10^{-60}{\sim}10^{-61}$ Pa for the present experiemental condition.
유병돈,손봉상,최현수,정우광 대한금속재료학회(대한금속학회) 1997 대한금속·재료학회지 Vol.35 No.12
A new hot metal pretreatment process has been developed at Pohang Works to produce low phosphorus steel economically. A new process could be characterized by simultaneous dephosphorization and desiliconization with oxygen and lime based flux after desulfurizing hot metal. In this study, the influence of the operational conditions such as hot metal and slag compositions and blowing condition was investigated. Dephosphorization ratio of hot metal was increased with the [Si] and [Mn] oxidation ratio. On the other hand, hot metal dephosphorization ratio was decreased with (%T.Fe) and basicity in slag. By the use of dephosphorized hot metal in a converter, the phosphorus content at blowing end was less than 0.01wt%.
무가압 침투법에 의한 BN/Al(-Mg) 복합재료 제조시의 반응기구
권훈,진창훈,정우광 대한금속재료학회(대한금속학회) 2000 대한금속·재료학회지 Vol.38 No.12
BN/Al(-Mg) metal matrix composite(MMC) was fabricated using pressureless infiltration technique, in order to clarify the reaction mechanism. The phase characterizations of the composite were analysed using the scanning electron microscopy, energy dispersive X-ray spectroscopy, Auger electron spectroscopy and electron probe micro analysis on reaction products after the electrochemical dissolution of the matrix. It is confirmed that aluminum nitride (AlN) was formed by the reaction of Mg₃N₂ and Al alloy melt. Plate type AlN and polyhedral type Mg(-Al) boride were formed by the reaction between Mg₃N₂, BN and molten Al in the BN reinforced metal matrix composite. The reaction mechanism in the fabrication of BN/Al(-Mg) metal matrix composite was derived from the phase analysis results and thermodynamic investigation.