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티타늄 합금판재(Ti-6Al-4V)의 고온 성형성 평가
배문기(M. K. Bae),박진기(J. G. Park),김정한(J. H. Kim),박노광(N. K. Park),김영석(Y. S. Kim) 한국소성가공학회 2009 한국소성가공학회 학술대회 논문집 Vol.2009 No.5
Titanium alloy sheets have excellent specific strength and corrosion resistance as well as good performance at high temperature. Recently, titanium alloys are widely employed not only aerospace parts but also bio prothesis and motorcycle. But the database is insufficient of the titanium alloy for press forming process. In this study, the effect of temperature on the forming limit diagram was investigated forming limit diagram was investigated for Ti-6Al-4V titanium alloy sheet through the Hecker’s punch stretching test at elevated temperature. Experimental results obtained in this study can provide a database for development of press forming process at elevated temperature of Ti-6Al-4V titanium alloy sheet. From the experimental studies it can be concluded that the formability of Ti-6Al-4V titanium alloy sheet is governed by the ductile failure for the testing temperature below and vice versa neck-induced failure above the recrystalization temperature 0.5 Tm. The formability of Ti-6Al-4V titanium alloy sheet at 750℃ increases about 7 times compared with that at room temperature.
Pattern 형상이 적용된 베어링 강(STB2)의 트라이볼러지 특성
송석웅 ( S. O. Song ),장태환 ( T. H. Jang ),배문기 ( M. K. Bae ),김태규 ( T. G. Kim ) 한국열처리공학회 2021 熱處理工學會誌 Vol.34 No.3
With the development of the industry, bearings that require higher durability and efficiency are required, and various methods to reduce friction and wear of bearings are being studied. In this study, a wear test was conducted for STB2, a bearing steel material, by machining a micro-line pattern on the race surface of the bearing by machining. The pattern pitch of the specimens was processed to 40μm, 80μm, and 150μm, and the coefficient of friction characteristics were investigated for the unpatterned specimen and the specimen with a DLC thin film deposited on the surface. As a result of the wear test, the pattern pitch showed the smallest coefficient of friction at 40μm, and it was confirmed that the smaller the pattern pitch, the better the tribology characteristics. (Received May 6, 2021; Revised May 17, 2021; Accepted May 21, 2021)
HFCVD 증착 온도 변화에 따른 단결정 다이아몬드 표면 형상 및 성장률 변화
권진욱,김민수,장태환,배문기,김성우,김태규,Gwon, J.U.,Kim, M.S.,Jang, T.H.,Bae, M.K.,Kim, S.W.,Kim, T.G. 한국열처리공학회 2021 熱處理工學會誌 Vol.34 No.5
Following Silicon Carbide, single crystal diamond continues to attract attention as a next-generation semiconductor substrate material. In addition to excellent physical properties, large area and productivity are very important for semiconductor substrate materials. Research on the increase in area and productivity of single crystal diamonds has been carried out using various devices such as HPHT (High Pressure High Temperature) and MPECVD (Microwave Plasma Enhanced Chemical Vapor Deposition). We hit the limits of growth rate and internal defects. However, HFCVD (Hot Filament Chemical Vapor Deposition) can be replaced due to the previous problem. In this study, HFCVD confirmed the distance between the substrate and the filament, the accompanying growth rate, the surface shape, and the Raman shift of the substrate after vapor deposition according to the vapor deposition temperature change. As a result, it was confirmed that the difference in the growth rate of the single crystal substrate due to the change in the vapor deposition temperature was gained up to 5 times, and that as the vapor deposition temperature increased, a large amount of polycrystalline diamond tended to be generated on the surface.
고온 저주기 피로에 의한 STS 304 압연강재의 특성연구
김치환 ( C. H. Kim ),박영민 ( Y. M. Park ),배문기 ( M. K. Bae ),신동철 ( D. C. Shin ),김대원 ( D. W. Kim ),김태규 ( T. G. Kim ) 한국열처리공학회 2019 熱處理工學會誌 Vol.32 No.1
In this study, strain-controlled low cycle fatigue test for hot rolled STS304 steel was carried out at 400oC and 600oC, respectively. High temperature fatigue test was done using an electric furnace attached on the hydraulic fatigue test machine. The results of this study show that STS304 hot rolled steel has excellent static strength and fatigue characteristics. The hysteresis loop at half life was obtained in order to calculate the elastic and plastic strain. Also, Relationship between strain amplitude and fatigue life was examined in order to predict the low cycle fatigue life of STS304 steel by Coffin-Manson equation. (Received January 7, 2019; Revised January 14, 2019; Accepted January 24, 2019)