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전자빔 용접된 Cu / STS 304강의 미세조직에 관한 연구
박경태,김인호,백준호,천병선,Park, Kyoung-Tae,Kim, In-Ho,Baek, Jun-Ho,Chun, Byung-Sun 대한용접접합학회 2010 대한용접·접합학회지 Vol.28 No.2
According to the research report for the recent a few years, the dissimilar welding of Cu and STS 304 alloy have been presented that a weldability is very poor. This article present a study on Lap joint by Electron beam welding dissimilar materials. The weld metals was constituted between pure copper and STS 304 steel. The experiment was performed with 125mA welding current, 520mA focusing current. The Vacuum condition of chamber is 5${\times}$10-5torr and welding speed is 300mm/min. Showing the bead shape of weld metal, the thickness of the stainless 304 using as the protect materials is 3mm and the thickness of a copper is 15mm. The analysis about the microstructure were carried out in which it was observed with SEM. The results showed that complex heterogeneous fusion zone microstructure characterized both by rapid cooling and mixing of the molten metal, however the liquation crack was formated in the fusion line.
CVD 에 의한 다이아몬드박막 성장시 바이어스가 W-필라멘트의 임계 CH4 농도 및 박막성장 특성에 미치는 영향
천병선,이철로,김관식,임재영,정광화 대한금속재료학회(대한금속학회) 1993 대한금속·재료학회지 Vol.31 No.7
In the hot W-filament CVD(HFCVD) diamond thin film growing, the filament becomes carburized and changes its resistance when the vol. % of CH₄gas is higher than the critical value. The effects of tmeperature and the negative bias of W-filament on the critical CH₄concentration were studied. The critical CHa concentration increased as temperature dropped and was almost proportional to the negative bias applied to W-filament. The diamond thin films grown with the assistance of electron bombardment (EACVD) were compared with those grown by usual HFCVD. The EACVD method gave higher film growth rate and smaller grain size than HFCVD method, and as the voltage difference between the filament and the Si substrate increased the higher growth rate and the smaller grain size were resulted. In the diamond films grwon by HFCVD the triangular microstructures were frequently seen on {111} plane, while none was found on the films grown by EACVD, suggesting that EACVD produces better quality diamond thin film than HFCVD. The XRD and RHEED diffraction patterns of all these films grown by EACVD showed the same patterns as those of natural diamond, confirming that the diamond films grown in this study were of good quality.
천병선,원창환,장대규,심건주 대한금속재료학회(대한금속학회) 1991 대한금속·재료학회지 Vol.29 No.6
The combustion synthesis of titanium carbide from elemental powders has been experimentally studied as following. 1) All the products synthesized by SHS method were nearly pure TiC powders. The lattice constant was increased with increasing C/Ti atomic ratio, however, at about 0.8 C/Ti atomic ratio the lattice constant reached a plateau of 4.325Å. 2) The combustion of titanium and carbon powders was accompanied by the evolution of gases having steady state combustion mode with propagation rate of 10㎜/sec. at 2600℃. 3) The size distribution of the product was relatively wide in the range of 2㎛ and 40㎛.
TiNI 형상기억합금의 열처리에 의한 경도 및 내마멸특성
천병선,남태현 대한금속재료학회(대한금속학회) 1986 대한금속·재료학회지 Vol.24 No.6
The hardness of TiNi alloys containing Ni from 50 at.% to 53 at.% was measured. Wear test was performed by rubbing these alloys against SUS316 or S45C. The results obtained are as follows; 1) Microvickers hardness in low load from 10gf to 100gf was very high. This is thought to be caused by the rubber elastic effect, the martensitic characteristic of these alloys. 2) The quenched Ni-Ti alloy contained Ni above 51 at.%. The hardness of these alloys in the liquid nitrogen temperature were less than in room temperature. This is thought to be due to the two reasons; one is that Ms point is below the room temperature and martensitic transformation is induced by indenter during the hardness testing, the other is the intrinsic rubber elasticity of martensite. 3) SUS316 was adhered to Ni-Ti alloy and the weight of Ni-Ti alloy was increased by 3㎎. It is thought that this is due to the high work hardenability of TiNi alloy in -196℃.
천병선,원창환,이갑호 대한금속재료학회(대한금속학회) 1991 대한금속·재료학회지 Vol.29 No.1
To obtain fundamental informations for ultrafine molybdenum powders, the preparatio of molybdenum powders by vapour phase reaction procedures of MoCl_5 with H₂ has been carried out in the temperature range of 500-900℃. The effects of reaction conditions on the reaction rate, specific surface area, particle size and morphology of ultrafine molybdenum powders were investigated by utilizing conductivity meter, BET method, X-ray diffraction, SEM and TEM techniques, respectively. It is apparent that the reaction rate and specific surface area were increased with increasing reaction temperature, H₂ and MoCl_5 gas partial pressure. The size and shape of the reaction products were nearly about 20-30㎚ and spherical, respectively. Especially, the first generated particles were agglomerated each other in chain type.
천병선,원창환,고석권 대한금속재료학회(대한금속학회) 1989 대한금속·재료학회지 Vol.27 No.7
Submicron iron powders were produced by reducing ferric chloride(FeCl₃) with hydrogen gas. The dependence of reduction rate on the various parameters were inves-tigated by measuring the conductivity of water through which the reaction gas was passed out. The reduction rate increased with increasing the temperature up to 900℃ and increas-ing both the FeCl₃ partial pressure and H₂: Ar gas ratio up to 3 : 1 The particle size and distribution were affected by all of the above three parameters.