• 한국주조공학회지
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• 제43권5호
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• pp.223-229
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• 2023

In this study, STS316L produced by a double-melting process involving vacuum induction melting (VIM) and vacuum arc remelting (VAR) was subjected to extrusion and drawing to form a tube and was subsequently electrolytic polished (EP). The grain size of the obtained STS316L without EP was approximately 55 ㎛, with no difference found after EP. The thickness of the EP layer was measured by AES and TEM, showing values of approximately 10 nm and 15 nm, respectively. After EP, the Cr/Fe and CrO/FeO ratios of the passive layer increased from 1.48 to 1.62 and from 2.15 to 2.26, respectively, while the surface roughness decreased significantly from 0.255 to 0.024 ㎛. Consequently, the corrosion rate decreased in both NaCl and HCl solutions after the EP process. Additionally, the amounts of eluted Cr and Fe ions were reduced from 1.2 to 0.8 ppb and 10.3 to 0.8 ppb, respectively. Furthermore, polarization tests revealed that STS316L treated with EP required a lower current density to reach a passive state, indicating that corrosion behavior was retarded.

• 조명전기설비학회논문지
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• 제24권2호
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• pp.120-126
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• 2010

본 논문은 고압용 전류제한 퓨즈의 열화 요인으로 작용되는 반복과전류에 의한 퓨즈 엘리먼트의 용단특성을 시험을 통하여 분석 및 규명하였다. 반복과전류에 의한 열화 진행 속도를 규명하기 위하여 엘리먼트노칭 형상별 열 해석을 수행하였으며 판형, 환형의 다양한 시험용 엘리먼트의 형상을 설계, 제작하여 이를 기중상태 및 규사충전상태의 소호제 유무에서 부하율을 조정하여 반복과전류 시험을 통한 용단특성을 분석, 수명과의 관계를 예측할 수 있는 자료를 제시하였다. 본 논문의 시험을 통하여 반복과전류에 의한 소호제와의 마찰로 퓨즈 엘리먼트의 변형 및 단면의 감소와 반복응력으로 인한 균열이 발생하여 퓨즈 반복 횟수에 따른 수명을 단축시키는 문제점의 도출과 엘리먼트 노칭 형상에 따라서 용단 특성이 차이가 있음을 알 수 있었다. 본 논문의 결과물은 재료의 마찰과 반복 전류의 부하율에 따른 반복 수명과의 상관관계에 관한 내용으로 고압용 전류제한 퓨즈의 성능 향상 개선을 위한 설계 시 중요한 기초 자료로 활용되리라 기대된다.

• 센서학회지
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• 제26권3호
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• pp.214-222
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• 2017

In this study, the effects of internal heat treatment associated sintering temperatures were simulated by the Finite Element Method (FEM). The sintering mechanism of pulsed current activated sintering process (PCAS) is still unclear because of some unexplainable heat transfer phenomena in coupled multi-physical fields, as well as the difficulty in measuring the interior temperatures of metal powder. We have carried out simulation study to find out thermal distributions between graphite mold and Ruthenium powder prior to PCAS process. For PCAS process, heating rate was maintained at $100^{\circ}C/min$ the simulation indicates that the sintering temperature range was between $1000^{\circ}C$ to $1300^{\circ}C$ under 60 MPa. The heat transfer inside the Ruthenium sintered-body sample was modelled through the whole process in order to predict the minimum interior temperature. Thermal simulation shows that the interior temperature gradient decreased by graphite punch length and calculation results well agreed with the PCAS field test results.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.746-751
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• 2002

In order to make clear the physical relation among the arc plasma, the anode heat transfer and the weld penetration, the results of experimental measurements of temperatures of arc plasma, the distributions of heat input and current on the anode and the weld penetration were presented The experimental results showed that the electron temperature above the anode and current and heat input density on the anode was dominated by the position of the cathode. Furthermore, it was showed that electron temperature of arc plasma was dominated by the cathode shape. These results were related with the results of the welded penetration measurements. As a result, it was showed that the electron temperature above the anode and current density distribution on the anode decided the heat input density distribution on the anode and that the heat input density on the anode remarkably dominated the size of the weld penetration in argon GTA welding process. Furthermore, it was suggested that the cathode played the important role in the determination of the weld penetration in argon GTA welding process.

• 한국결정성장학회지
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• 제29권1호
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• pp.24-31
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• 2019

사파이어 단결정을 성장시키는 기존 합성방법들의 원료충진율을 높이기 위한 방법으로 스컬용융법을 사용하여 $Al_2O_3$ 파우더를 용융시켰다. 냉각도가니 크기는 내경 24 cm, 내부 높이 30 cm로서 2.75 MHz 발진주파수에서 15 kg의 $Al_2O_3$ 파우더를 1시간 내에 모두 용융시켰으며, 3시간 동안 융액상태로 유지 후 자연냉각 시켰다. 냉각된 잉곳의 부분별 면밀도 및 성분은 SEM-EDS를 통해 분석하였다. 잉곳의 면밀도 및 $Al_2O_3$ 함량은 고주파유도가열 시 냉각도가니 내부에 형성되는 온도 분포와 관련이 있으며, 온도가 높게 형성되었던 부분이 면밀도 및 순도가 높게 나타나는 경향을 보였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1311_1312
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• 2009

In this article, current state of development of energy storage system using superconductor was summarized. As a result of continuous efforts, high critical current density exceeding $10^4\;A/cm^3$ at 77K and strong levitation capacity have been achieved in Y-Ba-Cu-O superconductor which is fabricated by melting technique. Various applications using the levitation properties of high-Tc superconductor is expected to come true in near future.

• Journal of Welding and Joining
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• 제34권1호
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• pp.68-74
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• 2016

Adoption of narrow gap welding shall be increased for the butt joint of thick plate, because the deformation and welding cost is reduced by decrease of cross-sectional area. However, sometimes narrow gap causes defects such as lack of fusion since it has small groove angle and narrow groove width. Therefore, GMAW, GTAW and SAW process shall be adopted to narrow gap welding with small bead hight and low deposition rate. In this study, Super-TIG welding using C-type strip was applied to semi-narrow gap butt joint in order to increase the welding productivity. High deposition rate 10kg/hr was obtained by high current 600A without undercut, humping bead and other welding defects. Measuring the mean and standard deviation of the melting depth to evaluate the developed processes, the fusion line type was determined by measuring the difference between maximum and minium melting depth. Furthermore, a model on arch fusion line and linear fusion line was suggested in order to prevent LF on groove wall in narrow gap butt welding.

• 한국진공학회지
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• 제12권1호
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• pp.1-6
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• 2003

50 kW급 출력의 전자빔을 발생시킬 수 있는 축선 방식 전자총 (axial electron beam gun)과 전원장치를 제작하였다. 전자총은 전자빔 발생장치와 전자빔 궤적제어장치로 이루어졌다. 전자빔 발생장치는 필라멘트와 음극(cathode), 양극(anode)으로 구성되었고 전자빔의 최대전류는 2A, 가속전압은 평균 25kV이다. 전자빔 궤적제어장치는 전자빔의 크기를 조절하는 초점 (focusing) 코일과 전자빔의 방향을 조절하는 편향(deflection) 코일 및 주사 (scanning) 코일로 구성되었다. 전자총과 별개로 진공용기 내부에 Helmholtz 코일을 설치하여 시료의 표면에 입사되는 전자빔의 입사각도를 최적화시켰다. 각 부분의 동작 특성을 측정한 결과와 제작된 전자총으로 고융점 원소인 지르코늄 (zirconium, Zr)과 가돌리늄(gadolinium, Gd) 금속을 증발시킨 결과를 정리하였다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2009년 추계학술발표대회
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• pp.226-234
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• 2009

The purpose of this study was to investigate the melting phenomenon of filler wire in detail and to obtain the precise temperature distribution of filler wire during GTA welding under the ultra-high welding speed condition in order to develop the ultra-high-speed GTA welding process with the pulse-heated hot-wire system by using three kinds of materials. The melting phenomenon of filler wire was observed using a high-speed camera and the temperature distribution of filler wire was measured using a radiation thermometer. From the above result, the adequate welding conditions of each material to make the GTA welding process with the ultra-high welding speed could be obtained. The ultra-high-speed GTA welding process needed the adequate wire current in order to obtain the adequate temperature distribution and the adequate melting position of filler wire. Moreover, the temperature distributions of three kinds of filler wire could be estimated by using the proposed simple estimation method.

• 한국안전학회지
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• 제39권2호
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• pp.22-27
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• 2024

The purpose of this study is to explore the trend in insulation resistance values according to temperature and overcurrent by conducting an investigation on the actual condition and experiments on the electrical wiring during the melting furnace process. In addition, the Arrhenius equation is used to determine whether temperatures in the furnace operating process can be applied to the actual field. In the investigation of the actual condition, the insulation resistance started to decrease seven years after replacement, even though cables in oil pump A were replaced in 2010. Both the experimental and theoretical values of the insulation resistance obtained using the Arrhenius equation decreased with an increase in temperature. Errors in insulation resistance (MΩ) values between tests and the Arrhenius equation ranged from ±2 to ±10, demonstrating a high similarity. Results revealed that when the insulation resistance cannot be measured in a manufacturing workplace (quarterly analysis), it can be estimated by partially applying the Arrhenius equation.