기술강좌(技術講座) : 과공정 Al-Si 합금에 있어서 초정 Si의 미세화에 미치는 Ce의 영향

이승회 ( Seung Heui Lee ),김정균 ( Jeong Kyun Kim ),남태운 ( Tae Woon Nam ),김봉완 ( Bong Wan Kim ),이원식 ( Won Sik Lee ) 한국주조공학회 2009 한국주조공학회지 Vol.29 No.4

7050Al 합금의 열처리공정 개발에 관한 연구

이효수,남태운,이병권 ( H . S . Lee,T . W . Nam,B . K . Lee ) 한국열처리공학회 1996 熱處理工學會誌 Vol.9 No.2

It has been investigated that the ion nitriding effects of a STD61 steel in various time conditions of 3 to 9 hours, and the microstructure of compound and diffusion layers of the ion nitrided specimen for 6 hours and subsequently reheated for 1 hour at various temperatures of 400∼800℃. As the nitriding time increased, the thickness of compound and diffusion layers was increased, but the hardness of surface was not considerably increased (Max Hv=1045 at 9hrs). Some of the nitrogen was denitrided out of the surfac and diffused into the core, and also the oxides (Fe₃O₄, Fe₂O₃) were formed on the surface of the specimen during repeating. The compound layer was partially decomposed at about 600℃ but the diffusion layer was increased up to 800℃. With increasing repeated temperture, the hardness of the surface was decreased, whereas the hardness depth of diffusion layer (0.25㎜) was increased up to 600℃ more than that of ion nitrided (0.18㎜). The blend-heat treated STD61 steel by ion nitriding is therefore expected to hold on the characteristics of ion nitriding up to 600℃.

용융염 침적법에 의한 VC coating 금형강의 굽힘 피로강도에 관한 연구

이병권,남태운 ( B . K . Lee,T . W . Nam ) 한국열처리공학회 1993 熱處理工學會誌 Vol.6 No.3

Bending fatigue strength tests were made for VC coated die steels which were coated by immersing in a molten borax bath and for hardened die steels which were quenched and tempered, in order to clarify the effect of VC coating at 1000℃ and 1025℃. The material used in this investigation was a representative cold and hot die steels STD11, STD61. The results obtained are as follows. 1) The endurance limit of VC coated die steels was a little lower than that of hardened die steels. It is considered to be mainly due to the decrease of hardness in the substrates. Accordingly, the endurance limit recovered almost to the level of hardened die steels by an additional diffusion treatment. 2) The initiation point of fatigue fracture of VC coated die steels in reversed bening was on the substrate just under the VC layer. Hence, the endurance limit is corrected to the hardness of this part. 3) But, there is a considerable scatter in this relationship and the endurance limit of VC coated die steels was a titi,le lower than that of hardened die steels with equal hardness. These results suggest that the fatigue strength of VC coated die steels is determined not only by the hardness but also by other factors. For example, the residual stress in the substrate just under VC coating layer is one of the factors besides hardness which is mainly related to the retained austenite(γ_R)

응융염 침적법에 의한 VC Coating 금형강의 인성에 관한 연구

이병권,남태운 ( B . K . Lee,T . W . Nam ) 한국열처리공학회 1993 熱處理工學會誌 Vol.6 No.2

Bending fracture strength test and impact strength test were made for VC coated die steels treated by immersing in molten borax bath and for hardened steels which were quenched and tempered, in order to clarify the effect of VC coating at 1000℃. The material used in this investigation was representative cold and hot work die steels STD11, STD61. The results obtained are as follows. 1) The bending fracture strength of VC coated die steel(STD11, STD61) was lessened with increasing the thickness of the VC coated layer. 2) With increasing the immersing time (imcreasing the thickness of the VC coated layer) the maximum hardness was obtained at 480 minutes holding, after that holding time hardness was decreased. 3) The impact strength of the VC coated die steel was not decreased. In the casse of STD11, it was higher than that of the quenched condition especially at low tempering temperature, and vice versa at high tempering temperature. However in the case of STD61 shows the result to the contrary.

차량 내 탑승자 상태 인식용 적외선 센서의 제조 및 특성

이성현,남태운,Lee, Sung-Hyun,Nam, Tae-Woon 한국전기전자재료학회 2009 전기전자재료학회논문지 Vol.22 No.3

A noble infrared sensor was studied for passenger conditional detection in vehicle, This research relates to uncooled infrared sensors for detecting the presence, type and temperature of occupants in vehicle. It sense that the occupants purpose to control the smart airbag for safety in the case of adult or child and to control the automatic air conditioning for convenience. This paper described the design and the fabrication of microbolometers which were composed of 2 by 8 elements using the surface micromachining technology. The characteristics of the array were investigated in the spectral region of $8{\sim}12{\mu}m$. The fabricated detectors exhibited the thermal mass of $7.05{\times}10^{-9}\;J/K$, the thermal conductance of $1.03{\times}10^{-6}\;W/K$, the thermal time constant of 6.8 ms, the responsivity of $2.96{\times}10^4\;V/W$ and the detectivity of $1.01{\times}10^9\;cmHz^{1/2}/W$, at the chopper frequency of 10 Hz and the bias current of $4.4{\mu}A$. We could successfully detect the human body condition in the divided zone. As a results, we concluded that microbolometer optimized in this research could be useful for the application of passenger conditional detection in vehicle.

고 Mole 비 규산소다를 사용한 CO2 주형의 (鑄型) 잔류강도와 (殘留强度) 반응생성물의 성상에 (性狀) 관한 연구

김봉완,남태운,이계완 ( Bong Wan Kim,Tae Woon Nam,Kye Wan Lee ) 한국주조공학회 1988 한국주조공학회지 Vol.8 No.2

N/A The study was carried out to investigate the changes of retained strength and reaction products in the CO₂ sands obtained are as follows. 1) Higher mole-ratio sodium silicates have the lower retained compression strength. 2) Organic liquid additives make a notable decrease in the retained strength and, in case of when use the 2.7 mole-ratio sodium sillicate, the effect is remarkable at the range of temperature to 600℃. 3) Sodium silicate binder forms silica gel with very high bonding force, accompaning an exothemic reaction at the temperatures of around 200℃, and dehydrated brittle silica gel and hydrated sodium silicate glass with sands transformed at the temperature of ahout 600℃. 4) It forms dehydrated glass with sintering of the sand gain surfaces, at the temperatures of around 800℃ and has a value of high retatined strength. 5) The decreases in the retaired strength of CO₂sands are accelerated with the lots of defects resulted from the porosity and cracks in sodium silicate bond films which are caused by the evaporation or combustion of the organic additives.

λ/4 흡수층 구조를 갖는 NDIR 이산화탄소 가스센서용 적외선 센서의 제조 및 특성

이성현,남태운,Lee, Sung-Hyun,Nam, Tae-Woon 한국전기전자재료학회 2008 전기전자재료학회논문지 Vol.21 No.11

A noble infrared $\lambda/4$ absorbing structure using metal reflector was studied for uncooled infrared sensors. This paper described the design and the fabrication of IR uncooled detectors which were composed of 21 by 21 elements using the surface micromachining technology. The characteristics of the array were investigated in the spectral region of 4.26 ${\mu}m$. The fabricated detectors exhibited the thermal mass of $9.75\times10^{-9}$ J/K, the thermal conductance of $1.31\times10^{-6}$ W/K, the thermal time constant of 7.4 ms, the responsivity of $1.07\times10^5$ V/W and the detectivity of $1.04\times10^9$ $cmHz^{1/2}/W$, at the chopper frequency of 10 Hz and the bias current of 9.22${\mu}A$. Finally the absorptance efficiency of $\lambda/4$ absorbing structure was about 23.2 % higher than that of absence absorbing structure.

AISI E 52100 강의 기계적 성질에 미치는 탄화물 크기의 영향

최기윤,김봉완,남태운,이병권 ( K . R . Cho,B . W . Kim,T . W . Nam,B . K . Lee ) 한국열처리공학회 1990 熱處理工學會誌 Vol.3 No.4

A study has been investigated on the effect of mechanical properties (tension strength, rotary bending fatigue strength, wear resistance, hardness) according to the carbide particle size variation by the treatment of 1) quenching tempering, and 2) quenching, subzero treatement and tempering. The material used in this investigation was a typical bearing steel, high C high Cr, AISI E 52100. The result obtained in this study were as follows : (1) Finer the carbide particle size increasing the hardness and retained austenite in same quenching condition. (2) Finer the carbide particle size reduced the tension and rotary bending fatigue which were resulted from austenite grain growth and carbide precipitation on grain boundry that induced by carbide refine heat treatment. (3) Finer the carbide particel size increasing the wear resistance which were resulted by uniform distribution of carbide and increased hardness induced by microstructural uniform hardenability of matrix. (4) When the carbide particles were refinded, subzero treatment is effective only wear resistance and hardness.

수치해석에 의한 고압다이캐스팅용 금형설계 및 주조공정해석

이창호(Chang Ho Lee),최재권(Jae Kwon Choi),남태운(Tae Woon Nam) 한국주조공학회 2000 한국주조공학회지 Vol.20 No.6

N/A Computer simulation for the predictions of casting defects is very important to produce high quality castings with less cost. Complicate shaped Al solenoid housing part was selected to be cold chamber die cast and a numerical simulation technique was applied for the optimization of the chill vent position and gating. A first design led to insufficient central flow. This flow left the last filled areas falling into the inner portion of the part. And last filled area did not fit the chill vent position. So these resulted in a high possibility of air entrapment in the casting and the design was not proper for the part. The design was improved by using a proper gating system, a more chill vent and proper overflow positions. New design provided a homogenous mold filling pattern and the last filled areas that being located at the overflow and chill vent. Casting plan which produce good quality solenoid housing part was established by using the computer simulation.

스퀴즈캐스팅용 Salt Core 의 제조 및 용탕침투성에 관한 연구

김기배,노상우,이호인,남태운 ( Ki Bae Kim,Sang Woo Noh,Ho In Lee,Tae Woon Nam ) 한국주조공학회 1997 한국주조공학회지 Vol.17 No.4

N/A Developing a salt core for squeeze casting process, two different salt cores(pure salt core and mixed salt core) were fabricated and investigated. Pure salt core was composed of 100% NaCl and mixed salt core was made by mixtures of NaCl with MgO(1%), Na₂B₄O_7(2%), and talc(1%) as a binder or a strengthening agent. Salt cores were compacted to various theoretical density, heat treated, and then squeeze-cast with molten Al alloy(AC8A). The compression strength of salt cores were measured and the squeeze-cast products were examined for shape retention, infiltration of molten metal into the cores, and microstructures. The shape of salt core compacted at above 75% of the theoretical density was maintained stably. The higher theoretical density of salt cores gave higher compression strength, and the compression strength of mixed salt core was higher than that of pure salt core. Namely at 90% theoretical density, the compression strength of mixed salt core was 6.3㎏/㎟, compared to 4.6㎏/㎟` for pure salt core. At a squeeze casting pressure of 1000㎏/㎠, molten Al alloy was infiltrated into pure salt core of under 85% of the theoretical density. At squeeze casting pressure of 1000㎏/㎠, only mixed salt core above 90% of the theoretical density were valid, but the shape of the core was altered in the case of pure salt core at 90% of theoretical density. A key factor for developing a salt core for squeeze casting process was estimated as the ultimate compressive strength of salt core.