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자동차용 소결 밸브시트의 미세조직과 기계적 성질에 미치는 Co 함량의 영향
具原奭,朴鍾寬,崔昌守,정인상 대한금속재료학회 2002 대한금속·재료학회지 Vol.40 No.1
Valve seat inserts should have a good wear resistance because they are used in the valve train area of internal combustion engines. Currently, the most of the valve seats are being manufactured by P/M method having the three steps of sintering, Cu-infiltrating and heat treatment. In this study, the effect of Co contents on microstructures and mechanical properties have been investigated at each steps. On sintering specimens, increase of Co content results in decrease of the hardness because of decrease of the ratio of martensite by decrease of diffusion of Cr-hard particles. On Cu-infiltrating specimens, the decrease of radial crushing strength with the increase of Co is resulted from the residual pores by Kirkendall's effect. And after heat treatment, the increase of Co results in decrease the ratio of the residual austenite of the matrix because of over-diffusion of the Cr. According to the result of the engine simulation test, matrix can not be hardened without the addition of Co-hard particles, the excess addition of Co-hard particles reduce the wear resistance by the increase of residual pores. Therefore, the appropriate amount of Co-hard particles is 6 wt%(Co 3.6 wt%).
Cr첨가에 따른 자동차용 소결 밸브시트의 미세조직과 기계적 성질
具原奭,朴種寬,崔昌守,정인상 대한금속재료학회 2002 대한금속·재료학회지 Vol.40 No.8
Valve seat inserts are used in the valve train area of internal combustion engines. Good wear resistance is needed since repeated stress is applied by the valves under combustion gas atmosphere of high temperatures. Currently, most of the valve seat inserts are being manufactured by P/M route. In this study, the characteristics of materials especially the wear resistance with the addition of Cr-hard particles were investigated. The results of this study are as follows: increase in the Cr-hard particles resulted in a decrease of the density of specimens. Pores formed by Cr diffusion from Cr-hard particles was attributed to the reduction in density. As a result, radial crushing strength was decreased with increase of the Cr-hard particals. Engine simulation test indicated that matrix can be hardened with the addition of Cr-hard particles. The excess addition of Cr-hard particles, however, degrades the wear resistance by the increase of residual pores. Therefore, the appropriate amount of Fe-Cr-C hard particles is 1∼5 wt%.
구원석 ( Koo Won Suk ),윤춘경 ( Yoon Chun Gyeong ),함종화 ( Ham Jong Hwa ) 한국농공학회 2003 한국농공학회 학술대회초록집 Vol.2003 No.-
Wetland systems are widely accepted natural water purification systems around the world in nonpoint sources pollution control. In this study, the field experiment to reduce nonpoint source pollution loadings from agricultural drainage and polluted stream waters using wetland and pond system was performed. The removal rate of BOD<sub>5</sub>, TSS, T-N and T-P during growing season was 7.2%, 64.3%, 57.0%, and 60.3%, respectively. And removal rate of BOD<sub>5</sub>, TSS, T-N and T-P during winter was -49.5%, -56.1 %, 30.5%, and 47.1%, respectively. In this study, pond-wetland system is more effective than wetland-pond system to remove nutrient.
비점오염원 제어용 인공습지의 수질정화 효과 및 상관관계 분석
구원석 ( Koo Won Seok ),윤춘경 ( Yoon Chun Gyeong ),함종화 ( Ham Jong Hwa ),김형철 ( Kim Hyung Chill ) 한국농공학회 2004 한국농공학회 학술대회초록집 Vol.2004 No.-
1. 습지 식생은 자연도래를 유도하여 세 번의 생장기를 거친 2004년도에 80~90%의 식생피도를 나타내었으며, 타 지역에서도 인공습지를 조성할 경우 주변에 습지식물에 자생하면, 수위조절에 의한 적정 물관리를 통해서 습지식생이 자연도래에 의해 가능할 것으로 판단된다. 2. 생장기(3월~11월)와, 동절기(12월~2월)로 나누어 수질정화 효과를 분석한 결과 BOD<sub>5</sub>, TSS, T-N, T-P의 처리효율은 생장기의 경우 24.6%, 64.1%, 55.4%, 49.0%를 나타내었고, 동절기에는 -21%, 22.7%, 32.5%, 53.7%를 나타내었다. 3. 수온과 식생피도를 고려하여 각 항목별로 상관관계를 분석한 결과 BOD<sub>5</sub>, T-N유출수 농도가 TSS, T-P유출수 농도에 비해 더 높은 상관성을 나타내어, 기온 및 식생피도에 따른 계절적인 영향을 더 많이 받는 것으로 나타났으며, T-N유출수 농도는 수온이외에 식생피도와도 높은 상관성을 나타내었다. 4. 각 습지별로 단위면적당 수리부하율은 적용한 유입유량의 변동폭이 크지 않아, 수질항목에 큰 영향을 미치지 않았으며, 습지수위조절을 통한 체류시간상승 및 겨울철 식생을 제거하지 않는 것이 동절기 습지의 처리효율을 높이는데 더 유리하다고 판단된다. 5. 본 연구에서는 동절기를 포함하여 인공습지의 영양물질 제거율이 짧은 2~5일 정도의 체류기간만으로도 40~50% 정도로 나타내었으며, 향후 하구담수호 수질개선을 위하여 호유입부에 인공습지에 의한 오염된 유입하천수 수질정화에 대한 장기적인 처리효율 검토를 위하여 지속적인 관심과 연구가 필요하다고 생각된다. In this study, the field experiment to reduce nonpoint source pollution loadings from polluted stream waters using wetland system was performed from June 2002 to September 2004, including winter performance using four constructed wetlands. Inflow and hydraulic residence time of the system was 500m<sup>3</sup> ~ 1500m<sup>3</sup>/ day and 2~5days respectively. After 3 years operation plant-coverage was about 80 ~ 90 % from zero at initial stage even with no plantation.. Because of low influent concentration of BOD<sub>5</sub>, organic matter in sediment, and algae the removal rate of BOD<sub>5</sub> was lower than other parameter. The average removal rate of BOD<sub>5</sub>, TSS, T-N and T-P during growing season was 25%, 64%, 55%, 49%, and during winter was -21%, 23%, 33%, 54% respectively. The reason of higher BOD<sub>5</sub> effluent concentration in winter season might be that low temperature restrained microorganism activity and a organic body from the withered plant and algae was flown out. And this study water quality parameters are analyzed corelation analysis. As the results, BOD<sub>5</sub>, T-N effluent concentration were more effected by water temperature, plant coverage than T-P, TSS effluent concentration. Except the result of BOD<sub>5</sub>, the effectiveness of water quality improvement in winter season was satisfactory for treating polluted stream waters.