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저온에서 축수강의 (軸受鋼) 강도에 미치는 미용해탄화물의 거동에 관한 연구
천병선(Byong Sun Chun),류제광(Je Kwang Ryoo) 대한공업교육학회 1984 대한공업교육학회지 Vol.9 No.1
The results of study on the behave of Carbide affecting the strength of bearing steel (high Carbon-Chromium) in low temperature are follows. 1) Though hardness is determined by the Carbon concentration in the matrix martensite, it increases slightly by the undisolved carbide. 2) There was almost no difference between bending-strength in room temperature and in low temperature (-196℃). The both of fractographs showed partially brittle cleavage fracture. 3) The results of wear test in liquid nitrogen showed that improvement of wear resistance by the spheroidized carbide. The wear loss in liquid nitrogen was about one-fifth compared with the results of room temperature. This can be explained by the effect of cooling and lubricating of liquid nitrogen.
기계적 합금화 공정에 의한 Fe가 코팅된 Mg 탈황 분말 제조 연구
송준우,천병선,홍순직,Song, Joon-Woo,Guillermo, Otaduy,Chun, Byong-Sun,Hong, Soon-Jik 한국분말야금학회 2012 한국분말재료학회지 (KPMI) Vol.19 No.3
In this research, the coating behavior of Mg and Fe desulfurization powder fabricated by low energy and conventional planetary mill equipment was investigated as a function of milling time, which produces uniform Fe coated powders due to milling energy. Since high energy ball milling results in breaking the Fe coated Mg powders into coarse particles, low energy ball milling was considered appropriate for this study, and can be implemented in desulfurization industry widely. XRD and FE-SEM analyses were carried out to investigate the microstructure and distribution of the coating material. The thickness of the Fe coating layer reaches a maximum of 14 ${\mu}m$ at 20 milling hours. The BCC structures of Fe particles are deformed due to the slip system of Fe coated Mg particles.
윤승채,팜쾅,천병선,이홍로,김형섭,Yoon, Seung-Chae,Quang, Pham,Chun, Byong-Sun,Lee, Hong-Ro,Kim, Hyoung-Seop 한국분말야금학회 2006 한국분말재료학회지 (KPMI) Vol.13 No.6
Nanostructured metallic materials are synthesized by bottom-up processing which starts with powders for assembling bulk materials or top-down processing starting with a bulk solid. A representative bottom-up and top-down paths for bulk nanostructured/ultrafine grained metallic materials are powder consolidation and severe plastic deformation (SPD) methods, respectively. In this study, the bottom-up powder and top-down SPD approaches were combined in order to achieve both full density and grain refinement without grain growth, which were considered as a bottle neck of the bottom-up method using conventional powder metallurgy of compaction and sintering. For the powder consolidation, equal channel angular pressing (ECAP), one of the most promising method in SPD, was used. The ECAP processing associated with stress developments was investigated. ECAP for powder consolidation were numerically analyzed using the finite element method (FEM) in conjunction with pressure and shear stress.
분말야금법으로 제조된 FeSi<sub>2</sub> 열전특성 화합물의 열처리 시간에 따른 미세조직과 상변화
박경태,신진교,홍순직,천병선,Park, Kyoung-Tae,Shin, Jin-Gyo,Hong, Soon-Jik,Chun, Byong-Sun 한국분말야금학회 2010 한국분말재료학회지 (KPMI) Vol.17 No.6
In this study, $FeSi_2$ as high temperature performance capable thermoelectric materials was manufactured by powder metallurgy.The as-casted Fe-Si alloy was annealed for homogenization below $1200^{\circ}C$ for 3 h. Due to its high brittleness, the cast alloy transformed to fine powders by ball-milling, followed by subsequent compaction (hydraulic pressure; 2 GPa) and sintering ($1200^{\circ}C$, 12 h). In order to precipitate ${\beta}-FeSi_2$, heat treatment was performed at $850^{\circ}C$ with varying dwell time (7, 15 and 55 h). As a result of this experiment thermoelectric phase ${\beta}-FeSi_2$ was quickly transformed by powder metallurgical process. There was not much change in powder factor between 7h and 55h specimens.
Al 5052 함금 후판재의 전자빔 용접부 단면 형상과 강도에 관한 연구
김인호,이길영,주정민,박경태,천병선,Kim, In-Ho,Lee, Gil-Young,Ju, Jeong-Min,Park, Kyoung-Tae,Chun, Byong-Sun 대한용접접합학회 2009 대한용접·접합학회지 Vol.27 No.3
This present paper investigated the mechanical properties and the microstructures of each penetration shapes classifying the conduction shape area and the keyhole shape area about electron beam welded 120(T)mm thick plated aluminum 5052 112H. As a result the penetration depth is increased linearly according to the output power, but the aspect ratio is decreased after the regular output power. In the conduction shape area, the Heat affected zone is observed relatively wider than the keyhole shape area. In the material front surface of the welded specimen, the width is decreased but the width in the material rear surface is increased. After the measuring the Micro Vikers Hardness, it showed almost similar hardness range in all parts, and after testing the tensile strength, the ultimate tensile strength is similar to the ultimate tensile strength of the base material in all the specimens, also the fracture point was generated in the base materials of all the samples. In the result of the impact test, impact absorbed energy of the Keyhole shape area is turned up very high, and also shown up the effect about four times of fracture toughness comparing the base material. In the last result of observing the fractographs, typical ductile fraction is shown in each weld metal, and in the basic material, the dimple fraction is shown. The weld metals are shown that there are no other developments of any new chemical compound during the fastness melting and solidification.
이종현,강용,원창환,천병선,Lee, Jong-Hyeon,Kang, Yong,Won, Chang-Whan,Chun, Byong-Sun 한국세라믹학회 1995 한국세라믹학회지 Vol.32 No.5
Li-ferrite powders were prepared from mixture of Fe and Li salts using a hydrothermal method. Their crystal structure, microstructure and magnetic property were investigated with X-ray diffraction analysis, chemical analysis, SEM, and VSM. In the case of using FeCl3 as a precursor, Li-ferrite powders were synthesized. However, Fe3O4 was formed when the precursor was a divalented Fe2SO4 or FeCl2. The precipitation rate of Li-ferrite was increased as the reaction temperature increased. The optimum conditions of synthesis were the mole ratio of Fe+++/Li+=2, pH 13, the reaction temperature of 25$0^{\circ}C$ and the reaction time of 120min. With this condition, the spherical particles with good dispersion were obtained with average particle size of 0.4${\mu}{\textrm}{m}$ and saturation magnetization of 65 emu/g.
가스분무공정을 이용한 (AgSbTe<sub>2</sub>)<sub>15</sub>(GeTe)<sub>85</sub> 열전분말의 제조 및 특성평가
김효섭,이진규,구자명,천병선,홍순직,Kim, Hyo-Seob,Lee, Jin-Kyu,Koo, Jar-Myung,Chun, Byong-Sun,Hong, Soon-Jik 한국분말야금학회 2011 한국분말재료학회지 (KPMI) Vol.18 No.5
In this study, p-type $(AgSbTe_2)_{15}(GeTe)_{85}$: TAGS-85 compound powders were prepared by gas atomization process, and then their microstructures and mechanical properties were investigated. The fabricated powders were of spherical shape, had clean surface, and illustrated fine microstructure and homogeneous $AgSbTe_2$ + GeTe solid solution. Powder X-ray diffraction results revealed that the crystal structure of the TAGS-85 sample was single rhombohedral GeTe phase, which with a space group $R_{3m}$. The grain size of the powder particles increased while the micro Vickers hardness decreased with increasing annealing temperature within the range of 573 K and 723 K due to grain growth and loss of Te. In addition, the crystal structure of the powder went through a phase transformation from rhombohedral ($R_{3m}$) at low-temperature to cubic ($F_{m-3m}$) at high-temperature with increasing annealing temperature. The micro Vickers hardness of the as-atomized powder was around 165 Hv, while it decreased gradually to 130 Hv after annealing at 673K, which is still higher than most other fabrication processes.
임계상대밀도 모델을 이용한 분말 등통로각압축 공정시 분말 치밀화 거동
복천희,유지훈,윤승채,김택수,천병선,김형섭,Bok, Cheon-Hee,Yoo, Ji-Hoon,Yoon, Seung-Chae,Kim, Taek-Soo,Chun, Byong-Sun,Kim, Hyoung-Seop 한국분말야금학회 2008 한국분말재료학회지 (KPMI) Vol.15 No.5
In this study, bottom-up powder processing and top-down severe plastic deformation processing approaches were combined in order to achieve both full density and grain refinement with least grain growth. The numerical modeling of the powder process requires the appropriate constitutive model for densification of the powder materials. The present research investigates the effect of representative powder yield function of the Shima-Oyane model and the critical relative density model. It was found that the critical relative density model is better than the Shima-Oyane model for powder densification behavior, especially for initial stage.