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Mn-Mo-Ni 계 저합금강과 열재현 HAZ 의 파괴특성
김상호(Sang Ho Kim),이성학(Sung Hak Lee),임영록(Young Roc Im),이후철(Hu Chul Lee),김성준(Sung Joon Kim),홍준화(Jun Hwa Hong) 대한금속재료학회 ( 구 대한금속학회 ) 2002 대한금속·재료학회지 Vol.40 No.9
This study is concerned with the effect of alloying elements on mechanical and fracture properties of Mn-Mo-Ni low alloy steels and their heat affected zones (HAZ`s). Three kinds of steels whose composition were varied from the composition specification of SA 508 steel (Grade 3) were fabricated by vacuum-induction melting and heat-treatment, and their mechanical and fracture properties were examined. ASTM E1921 standard test method was employed to measure fracture toughness in the transition temperature region of the steels. As C content decreased and Mo and Ni contents increased, the amount of fine M2C carbides was greatly increased, while that of coarse cementites was decreased, thereby leading to the improvement of tensile and fracture properties. Brittle martensite-austenite constituents were also formed in these steels during cooling, but did not deteriorate fracture toughness because they were decomposed to ferrite and fine carbides after tempering. Their simulated heat affected zones also had sufficient impact toughness after post-weld heat-treatment. These findings suggested that the low-alloy steels with high strength and toughness could be designed by decreasing C and Mn contents and by increasing Mo and Ni contents.
어성초 ethanol 추출물의 마우스 살모넬라 감염증에 대한 항균 및 치료효과 규명
김동혁 ( Dong Hyeok Kim ),임정주 ( Jung Ju Lim ),이진주 ( Jin Ju Lee ),정원철 ( Won Chul Jung ),신현진 ( Hyeon Jin Shin ),이후장 ( Hu Jang Lee ),김곤섭 ( Gon Sup Kim ),김석 ( Suk Kim ) 한국환경농학회 2008 한국환경농학회지 Vol.27 No.2
Salmonellosis is a major bacterial zoonosis that causes a variety of disease syndromes, self-limited enteritis to fatal infection in animals and food-borne infection and typhoid fever in humans. Recently, the emergence of multidrug resistant strains of Salmonella spp. causes more serious problems in environment and public health. The present study was investigated the antibacterial effect of Houttuynia cordata ethanol extract (HCEE) for murine salmonellosis. In the cytotoxic effect of HCEE on RAW 264.7 cells, there was no detectable effect with any concentrations between 25 and 100 μg/ml after 8 h incubation. The bacteriocidal effect of HCEE was not showed on a Salmonella enterica serovar Typhimurium (S. typhimurium). HCEE makes morphological change of the RAW 264.7 cells, and there was significant decreased bacterial uptake and intracellular replication within Salmonella infected cells. And further nitric oxide (NO) production of Salmonella infected RAW 264.7 cells with HCEE was decreased comparing to RAW 264.7 cells without HCEE until 8 h post infection. Oral administration of HCEE showed a therapeutic effect for S. typhimurium infected BALB/c mice. The mortality of HCEE treated mouse was 80% until 12 days, while that of HCEE untreated mouse was 100 % until 8 days after lethal dose of S. typhimurium infection. These data suggested that HCEE has a potency treatment for intracellular replicative pathogen including salmonellosis, brucellosis, tuberculosis, listeriosis etc., and the application of HCEE makes new strategies for safety medicine development without antibiotic resistance bacterial appearance and residue problem in food and solves the public health problem from antibiotic mis- and over use.
초내열합금 Mar-M247LC 의 저주기 피로수명 평가
이후철,최병학 대한금속재료학회(대한금속학회) 1996 대한금속·재료학회지 Vol.34 No.9
The low cycle fatigue (LCF) life prediction model for directionally solidified(DS) Mar-M247LC superalloy has been stuided as the variables of plastic strain and stress range. The plastic strain range is the general criterion for LCF life prediction model like Coffin-Manson equation. On the other hand the stress range is also important to the criterion for LCF life evaluation. The complex effect of plastic strain and stress range on LCF life could be considered as the calculation of hysteresis loop area in fatigue testing. The LCF life as a function of plastic strain and stress range has been measured at the variables of strain rate and DS direction.
구리 함유 극저탄소강의 집합조직발달에 미치는 코일링 온도의 영향
이후철,서동우,양영철 대한금속재료학회(대한금속학회) 1995 대한금속·재료학회지 Vol.33 No.11
The effects of coiling temperature on the texture development and mechanical properties of a 1wt% copper containing extra low carbon steel were investigated. An experimental alloy was vacuum induction melted, forged and then hot rolled. Coiling process was simulated by annealing at 500℃ or 700℃ for 1 hour and was followed by furnace cooling. After the coiling simulation, specimens were cold rolled with reduction ratio of 80% or 90%. ε-Cu precipitates in ferrite matrix are rarely observed in specimens coiled at 500℃ and coiling does not affect the development of {111} recrystallization texture. However fine ε-Cu particles are precipitated in α-Fe matrix when coiled at 700℃ and the precipitates remarkably increase the intensities of α-fiber texture components during cold rolling, retard the recrystallization during annealing and suppress the development of {111} recrystallization texture. Coiling temperature does not affect the tensile properties of 1wt% copper containing steel but, in specimens coiled at 700℃, suppression of {111} recrystallization texture results in lower mean plastic strain ratio.
이명현,이후철 대한금속재료학회(대한금속학회) 1988 대한금속·재료학회지 Vol.26 No.6
The characteristics of mart ensitic transformation and martensite substructures in Ni(Cu)Al alloys containing up to 10 atomic percent Cu were studied. The crystallographic structure of a1l the Ni(Cu)Al martensites was identified to AuCu(I) type and their c/a ratios were decreased with increasing Cu content. Other effects of Cu substitution were as follows : The invariant shear strain was increased up to 0.163 from the near ideal value of 0.129 in NiAl alloy. Hardness of Ni(Cu)Al martensite decreased to 300㎏/㎟from 720㎏/㎟, the hardness of NiAl martensite. Martensite morphologies of Ni(Cu) Al alloys are quite similar to that of NiAl alloys but crossed morphologies are quite often observed in Ni(Cu)Al martensites. Tweed structure was also observed in Ni(Cu)Al alloys.