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Pidgeon process를 통한 마그네슘 제련 공정에서의 열 환원 거동 해석
백의현 ( Ui Hyun Baek ),이병덕 ( Byeong Deok Lee ),이기우 ( Ki Woo Lee ),한길수 ( Gil Soo Han ),한정환 ( Jeong Whan Han ) 대한금속재료학회(구 대한금속학회) 2016 대한금속·재료학회지 Vol.54 No.2
This study examined methods to increase the production of Mg crown and minimize the amounts of solid impurities using the thermodynamic commercial package Factsage. A thermodynamic calculation was carried out to predict the degree of reduction of Mg vapor depending on the operating parameters through a single-stage calculation method involving the use of the CaO/MgO molar ratio, ferrosilicon/ dolime mass ratio and the pressure and temperature during the Pidgeon process. The results indicate that the CaO/MgO molar ratio was 1.4~1.5 to increase the degree of the reduction of Mg vapor in a non- equilibrium state. The thermodynamic calculations were designed to examine the effect the ferrosilicon had on specific ferrosilicon/dolime ratios. A good effect was observed between 25 and 30%. Moreover, it was determined that the optimum operating conditions which offer a high purity level of magnesium and reduce the degree of vapor was the case 5 (1200 ℃, 0.1 ~ 0.01 torr). In addition, the distribution of solid impurities in the Mg crown was calculated by a multi-stage calculation method while decreasing the temperature. Solid impurities existed as compounds in the Mg crown depending on the condensation temperature range in retort. The compound was composed of Mg2Si under 700 ℃ and CaAl2 under 500 ℃, also FeAl3, MnB under 400 ℃. A comparison of the thermodynamic calculations and experimental results regarding the types of impurities were in good agreement.(Received July 2, 2015)
Ag첨가 마그네슘 합금의 이중열처리에 따른 미세조직 및 기계적 특성변화
이병덕 ( Byeong Deok Lee ),백의현 ( Ui Hyun Baek ),장경수 ( Kyoung Soo Jang ),한정환 ( Jeong Whan Han ),손현택 ( Hyeon Taek Son ) 대한금속재료학회(구 대한금속학회) 2011 대한금속·재료학회지 Vol.49 No.6
To improving the mechanical properties of Mg alloys at high temperature, we investigated the mechanical properties at high temperature and the change of microstructure of Mg-6 wt%Zn-0.4 wt%Mn and Mg-6 wt%Zn-0.4 wt%Mn-1 wt%Ag alloys on age treatment that have a stable MgZn phase at high temperature and AgMg4 improving yield stress. In order to predict thermodynamic data of Mg alloys, a phase diagram and precipitation phase were calculated using a thermodynamic program, and it was confirmed that the MgZn and AgMg4 phase existed as main precipitation in this alloys. The experimental data examined using DSC and XRD were comparable with the calculated data for reliability. In order to analysis the microstructure and precipitate phase during aging treatment, it was measured by SEM/EDS and TEM. Lastly, mechanical properties of the MgZn and AgMg4 phase were measured by a tensile test at high temperature.
저온분사 코팅공정에서 초음속 슬릿노즐 사용시 유동장 해석
박혜영 ( Hye Young Park ),박종인 ( Jong In Park ),정훈제 ( Hun Je Jung ),장경수 ( Kyoung Soo Jang ),백의현 ( Ui Hyun Baek ),한정환 ( Jeong Whan Han ),김형준 ( Hyung Jun Kim ) 대한금속재료학회(구 대한금속학회) 2011 대한금속·재료학회지 Vol.49 No.3
The cold spray process is an emerging technology that utilizes high velocity metallic particles for surface coating. Metallic powder particles are injected into a converging-diverging de Laval nozzle and accelerated to a high velocity by a supersonic gas flow. The cold spray process normally uses a circular nozzle that has a rather narrow spraying range. To overcome this fault, a slit nozzle was considered in this study. The slit nozzle is anticipated to reduce the coating process time because it has a wider coating width than the circular nozzle. However, the slit nozzle can reduce the coating efficiency because it does not allow as much gas and particle velocity as the circular nozzle. To improve the coating efficiency of a slit nozzle, the shape of the slit nozzle was modified. And the results of gas flow and particle behaviour according to the nozzlers shape were compared by the a numerical analysis. As a results, as Expansion Ratio(ER) of 7.5 was found to be the most optimal condition for enhancing the spraying efficiency when the ER was changed by the variation of nozzle neck and exit size.