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초고강도 자동차용 강의 환원정전류인가에 따른 산화 거동 변화 연구
하헌영 ( Heon-young Ha ),김혜진 ( Hye-jin Kim ),문준오 ( Joonoh Moon ),이태호 ( Tae-ho Lee ),조효행 ( Hyo-haeng Jo ),이창근 ( Chang-geun Lee ),유병길 ( Byung-kil Yoo ),양원석 ( Won-seog Yang ) 한국부식방식학회 2017 Corrosion Science and Technology Vol.16 No.6
The change in the oxidation behavior of three types of B-added ultrahigh strength martensitic steels containing Ti and Nb induced by applying constant cathodic current was investigated. In a 3% NaCl+0.3% NH<sub>4</sub>SCN solution, the overall polarization behavior of the three alloys was similar, and degradation of the oxide film was observed in the three alloys after applying constant cathodic current. A significant increase in the anodic current density was observed in the Nb-added alloy, while it was diminished in the Ti-added alloy. Both Ti and Nb alloying decreased the hydrogen overpotential by forming NbC and TiC particles. In addition, the thickest oxide film was formed on the Ti-added alloy, but the addition of Nb decreased the film thickness. Therefore, it was concluded that the remarkable increase in the anodic current density of Nb-added alloy induced by applying constant cathodic current density was attributed to the formation of the thinnest oxide film less protective to hydrogen absorption, and the addition of Ti effectively blocked the hydrogen absorption by forming TiC particles and a relatively thick oxide film.
FeCrMnN 계 스테인리스강의 일반부식 및 공식부식 거동에 미치는 고용 탄소의 영향
하헌영 ( Heon Young Ha ),이태호 ( Tae Ho Lee ),김성준 ( Sung Joon Kim ) 대한금속재료학회(구 대한금속학회) 2011 대한금속·재료학회지 Vol.49 No.10
The effects of alloyed carbon on the pitting corrosion, the general corrosion, and the passivity behavior of Fe18Cr10Mn0.4NxC (x=0~0.38 wt%) alloys were investigated by various electrochemical methods and XPS analysis. The alloyed carbon increased the general corrosion resistance of the FeCrMnN matrix. Carbon enhanced the corrosion potential, reduced the metal dissolution rate, and accelerated the hydrogen evolution reaction rate in various acidic solutions. In addition, carbon promoted the pitting corrosion resistance of the matrix in a chloride solution. The alloyed carbon in the matrix increased the chromium content in the passive film, and thus the passive film became more protective.
침입형 원소 첨가 스테인리스강 용접부 미세조직 변화 및 부식특성에 관한 연구
문준오(Joonoh Moon),하헌영(Heon-Young Ha),이태호(Tae-Ho Lee) 대한용접·접합학회 2017 대한용접·접합학회지 Vol.35 No.4
Microstructure evolution and corrosion behavior in the simulated HAZ and real welds of high interstitial alloyed austenitic stainless steels were investigated. Three Fe-18Cr-10Mn-N-C alloys with different N and C contents were fabricated using a commercial pressurized vacuum-induction melting furnace. First, the HAZ samples with three different peak temperatures were experimentally simulated using Gleeble simulator under welding condition of 30kJ/cm heat input. In the HAZs, δ-ferrite was formed and its fraction increased with increase in the peak temperature. The electrochemical tests indicated that pitting corrosion resistance significantly decreased by the formation of δ-ferrite, however did not changed with increasing δ-ferrite fraction. Next, the samples for real welds evaluation were prepared by autogeneous welding. The corrosion behavior in real welds was good agreement with that in Gleeble-simulated HAZ. Cross sectional microstructure of real welds indicated that δ-ferrite was formed in the HAZ and thus pitting corrosion selectively occurred at δ-ferrite/austenite phase boundaries in the HAZ.
김성경 ( Seong Gyeong Kim ),강전연 ( Jun Yun Kang ),하헌영 ( Heon Young Ha ),박노진 ( Jin Park ),임창동 ( Chang Dong Yim ),강남현 ( Nam Hyun Kang ) 대한금속재료학회(구 대한금속학회) 2014 대한금속·재료학회지 Vol.52 No.6
The process of secondary recrystallization in the Mg-6Sn binary alloy that initially had bimodal grain size distribution was observed. The prevalence of the {0001}//sheet plane orientation in the initial texture was destroyed and the texture was transformed to a very strong {2□□0}-type during solution heat treatment at 480 ℃. The grain boundary character was analyzed using EBSD, in which no preference of the CSL boundary among the grain boundaries of {2□□0}- oriented grains was evident. It was observed that some fine grains were isolated within coarse {2□□0} oriented grains due to limited boundary migration and these boundaries belonged to CSL boundaries. These analyses confirmed that the secondary recrystallization was driven by the general high-angle grain boundaries surrounding {2□□0}-oriented grains. (Received July 31, 2013)
김성준 ( Sung Joon Kim ),이태호 ( Tae Ho Lee ),김성태 ( Sung Tae Kim ),박용호 ( Yong Ho Park ),배종인 ( Jong In Bae ),하헌영 ( Heon Young Ha ) 대한금속재료학회(구 대한금속학회) 2011 대한금속·재료학회지 Vol.49 No.2
Precipitation behavior of high-nitrogen duplex Fe-24Cr-7Mn-4Ni-4Mo-0.43N stainless steel aged at 850℃ was investigated using scanning transmission electron microscopy. Based on the analyses of selected area diffraction patterns, four kinds of precipitates (intermetallic sigma (σ) and chi (χ), Cr2N and secondary austenite) were identified. At the ferrite/austenite phase boundary, the σ phase and secondary austenite were formed via α→γ + σ eutectoid reaction. The precipitation of Cr2N occurred at the austenite grain boundary as well as the interior of the ferrite. The intermetallic χ phase also formed within the ferrite and showed a cube-cube orientation relationship with the ferrite. Further aging produced a lamellar structure composed of Cr2N and austenite along the ferrite/austenite boundary and enhanced the precipitation of the χ phase. The crystallographic features of the precipitates were also examined in terms of the orientation relationship with the austenite or ferrite matrix.
신영전,유원섭,하헌영,정설희 한양대학교 의과대학 2000 한양의대 학술지 Vol.20 No.1
The purpose of this study was to estimate the proportion of user charges out of total treatment costs and to investigate the occuring status of the charge of non-benefit service. The data were collected from 6 hospitals in 3 cities (Seoul 2, Incheon 3, Shihung 1), which containing 1,752 discharge-bills of discharged patients insured by health insurance. The data were analyzed after standardization of the items of non-benefit services. The result are as follows; 1. the average percent of the cost-sharing of discharged patients was 38.1%(benefit : 15.5%, non-benefit : 22.6%) and the proportion of the cost-sharing due to non-benefit services was greater than that due to benefit services. 2. The occurrence rate and the occurred number of non-benefit services were different among hospitals and showed characteristic occurrence rate in individual hospitals. 3. In acute appendicitis, the characteristics of the occurrence rate and the occurred number of non-benefit services by individual hospitals was similar to those of hospitals. It suggest that the hospitals intentionally applied non-benefit item to patients in order to increase their profit. These findings suggest that the burden of cost-sharing is still high especially due to non-benefit services, so it is necessary to extend the coverage of insurance benefits and to develop management system for the appliance of non-benefit services. Regarding the discharge-bill, all service charges should be included in the bill.