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플라즈마 질화처리된 중탄소합금강의 내마모특성에 관한 연구
조효석,노용식,신호강,이상윤 ( H . S . Cho,Y . S . Roh,H . K . Shin,S . Y . Lee ) 한국열처리공학회 1992 熱處理工學會誌 Vol.5 No.4
This study has been performed to investigate into some effects of temperature, gas mixing ratio and time on the optical microstructure, hardness and wear characteristics of medium carbon alloy steel treated by plasma nitriding. The results obtained from the experiment are summarized as follows : (1) Optical micrographs of AISI 4140 steel plasma-nitrided by the double stage technique have revealed that the nitrided layer is composed of the compound layer and the diffusion layer. The variation in temperature at the first stage gives effects, on the formation of compound layer and the growth rate is shown to be relatively fast at 460℃. (2) The thickness of compound layer has been found to increase with increasing nitrogen percentage in the gas mixture and the holding time. It is therefore recommended that a shorter holding time and a lower nitrogen percentage are more effective to produce a tougher compound layer and a diffusion layer only. (3) X-ray diffraction analysis for AISI 4140 steel has shown that the compound layer consist of γ`-Fe₄N and α-Fe and that tough compound layer diffustion layer only can be obtained by the double stage plasmanitriding process. (4) There is also a tendency that the total hardened layer depth increases with increasing temperature, time and nitrogen percentage in the first stage during the double stage plasma nitriding. (5) The wear resistance of plasma nitrided specimens has been found thobe considerably increased compared to the untreated specimens and the amount of increment has appeared to increase further with increasing nitriding temperature, holding time and notrogen percentage of gas mixture in the first stage treatment.
Sursulf처리후 고주파 표면경화된 저탄소강의 경도 및 마모특성에 미치는 Sursulf처리시간 및 고주파 경화 이송속도의 영향
노용식,김영희,이평호,신호강,이상윤 ( Y . S . No,Y . H . Kim,P . H . Lee,H . K . Shin,S . Y. Lee ) 한국열처리공학회 1989 熱處理工學會誌 Vol.2 No.2
This study has been performed to investigate into some effects of the Sursulf treatment time and the traveling speed of surface hardening treatment on the hardness and the wear characteristics by applying the combined heat treating techniques of Sursulf process followed by induction hardening treatment to mild steel. It has been shown that increasing the Sursulf treatment time increases the case depth, but both hardness and wear resistance are not considerably improved. When the combined heat treating technique of high frequency induction heating after Sursulf treatment is applied, an improvement in case depth as well as wear resistance is obtained. In particular, the hardness in diffusion zone is greatly increased due mainly to the formation of martensite and possibly lower bainite. Iron oxides formed during induction heating and subsequent water spray cooling in the outermost part of compound layer may be considered to cause some increases in hardness and wear resistance.
이신호,성삼경,김수민,김대곤,김순희 ( S . H . Lee,S . K . Seong,S . M . Kim,D . K . Kim,S . H . Kim ) 한국축산학회 1997 한국축산학회지 Vol.39 No.3
The Bacteriological qualities of retailed Hanwoo beef and retail stores were studied to investigate hygienic status in marketing system of Hanwoo beef. Total bacterial counts of retailed Hanwoo beefs showed average 10³∼10⁴/㎠. Bacteriolgical quality of the retailed Hanwoo beefs was affected significantly by the sanitationary conditons of the individual retail store, not by the kind of retail stores. Total bacteria( counts of knives used in the retail stores showed from 10²/㎠ to 10^5/㎠ (average 10³∼10⁴/㎠). The level of contamination was increased as they were used frequently. Total bacterial counts of balance, cutting boards, slicing machine and chopper used in the retail Hanwoo beef stores were 10¹∼10⁴/㎠z, 10⁴∼10^5/㎠, 10³∼10^5/㎠ and 10³∼10^6/㎠, respectively. Chopper showed the highest contamiantion level among various materials used in the retail Hanwoo beef stores such as knife, cutting board, slicing machine and choppor.
이신호,김순희,최우정 ( S . H . Lee,S . H . Kim,W . J . Choi ) 한국축산학회 1998 한국축산학회지 Vol.40 No.3
Bacteriological quality of working surface and decontamination method of cutting board were investigated to improve the hygienic quality of Hanwoo beef during distribution. Total bacterial wont on plastic working surface was decreased 1 log_(10) unit by wipe with disposable paper towels and cotton clothes but decreased 2 log_(10) unit by wipe with cotton cloth soaked in 1% lactic acid. Effect of lactic acid applied with cotton clothes on the decontamination was better on stainless steel surface than on plastic and wood. Viable cell counts of Listeria monocytogenes and Escherichia coli on artificially contaminated cutting board decreased below 10 after dipping the board in commercial anionic detergent(0.15%) and disinfectant(0.35%) for 5 min, respectively. Viable cells of cutting boards contaminated experimentally with L. monocytogenes and E. coli was decreased about 2∼4 log_(10) unit by the dipping in various organic acids for 30 seconds such as acetic, lactic, fumaric and propionic. Decontamination effect of the organic acids on wood was lower than that of plastic or stainless steel cutting board.
이신호,성삼경,김수민,김대곤,조옥기,정영숙 ( S . H . Lee,S . K . Seung,S . M . Kim,D . K . Kim,O . K . Jo,Y . S . Jeong ) 한국축산학회 1998 한국축산학회지 Vol.40 No.3
Effects of organic acids and vacuum packaging on storage of Hanwoo beef were investigated to improve the hygienic quality and storage life of Hanwoo beef. Viable cell count of Hanwoo beef contaminated artificially with Listeria monocytogenes was reduced L5 to 2.2 logo cycle after dippping in fumaric, propionic, acetic acid for 60 seconds. The color of Hanwoo beef was changed significantly by dipping in various organic acids such as fumaric, propionic, lactic, acetic, and gluconic acid. The Volatile Basic Nitrogen(VBN) value of vacuum packaged hanwoo beef treated with propionic, fumaric acids was lower than that of the control during storage. Thio Barbituric Acid (TBA) value of organic acid treated Hanwoo beef was lower than that of control during storage. Microbial count in vacuum packaged Hanwoo beef treated with propionic acid was inhibited apparantly during storage, and fumaric and lactic acid showed inhibitory effect during storage. Fumaric and propionic acids showed inhibitory effect of spoilage in vacuum packaged Hanwoo beef for 50 days at 4℃.
진공포장돈육에 있어서 진공정도에 따른 미생물 생태계의 변화
이신호,이무하,송인상 ( S . H . Lee,M . H . Lee,I . S . Song ) 한국축산학회 1986 한국축산학회지 Vol.28 No.1
Boneless pork chops were vacuum-packaged at the various degrees of vacuum to have 4 different levels (17.6%, 9.8%, 3.1% and 0.4%) of initial residual oxygen in the packages. During the storage period of 21 days at 4℃, changes of reisdual oxygen content, total bacteria count, psychrotrophs count, anaerobes count, lactic acid bacteria count and fluorescent pseudomonads count were investigated. At the end of storage period, all treatments showed no difference in both psychrotrophs and lactic acid bacteria count. However, control gave the highest numbers in total bacteria, anaerobes and fluorescent pseudamauads count. According to results obtained from this study, it appeared that high vacuum-packaging would be more practical method than the other three in terms of microbiological shelf-life.