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극한 상태에서 A490 고장력 볼트 세트의 체결 품질 연구
석한길(Han-Gil Suk),조인습(In-Seup Cho),홍현선(Hyeon-Sun Hong) 한국표면공학회 2011 한국표면공학회지 Vol.44 No.1
This test focuses on the correlation between the lubrication, ductility and strength through the change of nut lubricant which decides joining angle for A490 bolt sets required in the AASHTO (American Association of State Highway & Transportation Officials). Because the lubrication of high tension bolt, nut, washer sets becomes an important factor to ductility and joining load, the quality improvement is required for improving reliability and securing enough lubrication of maker and user. This study examines the quality characteristics required in the specification through tests because only this standard specifies joining quality in the extreme conditions (as much about two times of the joining angle on site as normal condition). Moreover, this study is limited to the test on joining axial force required in the AASHTO for the three nut lubrication conditions of A490 bolt set. It is concluded that the nuts should be coated or waxed enough for the improvement of the joining axial force and ductility of bolts required in the standards. It is shown that in the case of plain high tension bolt sets, a rust preventing lubricative oil shall be applied and the torque coefficient value for A490 bolt sets should be maintained below 0.175.
김재명,김찬욱,석한길,Kim, Jae Myung,Kim, Chan Wook,Suk, Han Gil 한국자원리싸이클링학회 2014 資源 리싸이클링 Vol.23 No.4
본 연구에서는 자원고갈에 따른 철광석의 자원화 가능성에 대한 연구를 수행하였다. 이를 위하여 Fe함량이 각각 64%(A광석)와 57%(B광석)인 Fe품위를 갖는 2종의 철광석 시료를 대상으로, 광석의 파쇄거동 특성 및 조직학적 측면에서 비교분석을 통하여 광종별 품위향상 가능성을 알아보고자 하였다. SEM 분석결과, 철광석 A의 경우 철산화물과 맥석이 분리된 형태로 분포되어 있으며, B광석의 경우는 철산화물과 맥석이 혼재되어 분포되어 있었다. 이는 B광석에 비해 A광석이 분쇄에 의한 단체분리가 보다 용이함을 의미한다. 따라서 A광석은 적절한 입도로 분쇄 후 자력선별 등에 의한 품위 향상이 가능할 것으로 판단된다. 반면 B광석은 단체분리를 위하여 A광석보다 미립으로 분쇄하여야 할 것으로 판단되나, 열처리 전 62 ~ 68% Fe조성이 열처리 후 약 81%로 증가하는 경향을 보여, 열처리를 적용한 품위 향상이 가능할 것으로 사료된다. The objective of this study is to investigate the possibility of beneficiation of low grade iron ore. Iron ore A might be upgraded by the mineral liberation effect, while iron ore B was expected to be difficult to upgrade. However, the Fe contents of iron ore B were increased from 68% to 81% by the heat treatment process. Iron ore A was found to possibly enrich the Fe components through the physical separation process, such as magnetic separation, floatation and gravity concentration. In the case of iron ore B, it was possible to concentrate the Fe components through the heat treatment process.
홍현선,정항철,김건홍,강이승,석한길,Hong, Hyun-Seon,Jung, Hang-Chul,Kim, Geon-Hong,Kang, Lee-Seung,Suk, Han-Gil 한국분말야금학회 2013 한국분말재료학회지 (KPMI) Vol.20 No.3
Nano-sized cobalt powder was fabricated by wet chemical reduction method at room temperature. The effects of various experimental variables on the overall properties of fabricated nano-sized cobalt powders have been investigated in detail, and amount of NaOH and reducing agent and dropping speed of reducing agent have been properly selected as experimental variables in the present research. Minitab program which could find optimized conditions was adopted as a statistic analysis. 3D Scatter-Plot and DOE (Design of Experiments) conditions for synthesis of nano-sized cobalt powder were well developed using Box-Behnken DOE method. Based on the results of the DOE process, reproducibility test were performed for nano-sized cobalt powder. Spherical nano-sized cobalt powders with an average size of 70-100 nm were successfully developed and crystalline peaks for the HCP and FCC structure were observed without second phase such as $Co(OH)_2$.
표면처리별 S10T, 10.9HRC 고장력 볼트 세트의 체결 품질 연구
최윤오(Youn-O Choi),석한길(Han-Gil Suk),홍현선(Hyeon-Sun Hong) 한국표면공학회 2015 한국표면공학회지 Vol.48 No.3
This test focuses on the correlations between joining axial force at non-room temperature and at room temperature according to the surface treatment (Geomet, Dacro, Green Kote, Armore Galv.). The quality characteristics of the fastening axial force required by the KSB 2819 and EN14399-10 standards were discussed. Surface treatment was implemented to S10T and 10.9HRC sets of bolts under the same environmental factors. Development for the stabilization of the fastening axial force required by each standard should continually be enforced, and the fastening and storage in the field should be maintained at room temperature. Managing stabilization of torque enumerated data is required after application of surface treatment. It is concluded that, by conducting the test of applying surface treatment to effectively manage, each lot-specific rate of axial force at room temperature conditions should be maintained below the maximum 4.47%. The decline rate of axial force should be maintained under 2.15% maximum, and the standard deviation of the room temperature condition should be maintained below 0.5.