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Page : 191 - 195
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- 염소이온 함유된 용액에서 Ti합금의 부식특성에 미치는 Hafnium함량의 영향
- The aim of this study was to investigate effects of hafnium content on the corrosion behavior of Ti alloys in electrolyte containing chloride ion. For this study, Ti-Hf binary alloys contained 10 wt%, 20 wt% and 30 wt% Hf were manufactured in a vacuum arc-melting furnace and subjected to heat treatment for 12h at 1000°C in
an argon atmosphere. The pitting corrosion behavior of the specimens was examined through potentiodynamic and potentiostatic tests in 0.9 wt% NaCl electrolyte at 36.5 ± 1°C. The corrosion morphology of Ti-xHf alloys was investigated using optical microscopy (OM) and X-ray diffractometer (XRD). From the optical microstructures and XRD results, needle-like martensite (α\\\') phases of the Ti-xHf alloys increased with an increase of Hf addition. Corrosion current density (Icorr) and current density (I300mV) in passive region decreased, whereas, corrosion potential increased with Hf content. At the constant potential (300 mVSCE), current density decreased as time increased. - KEYWORDs : Ti-xHf alloy, corrosion behavior, potentiostatic, potentiodynamic test, dental implant
- AUTHORs : 김성환? 최한철†
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Page : 196 - 204
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- UNS N08810 합금의 입계부식손상과 원인 분석
- Corrosion failure of petrochemical facilities is one of the difficulties in maintenance, since operating conditions of crude oil production, storage, and refinement are very aggressive. UNS N08810, which has been used for crude oil transportation pipes and storage tanks in petrochemical industries, shows good resistance to general
corrosion and localized corrosion in several environments. Among its environments, UNS N08810 showed better corrosion resistance in fuel gas containing sulfuric acid and phosphoric acid and sulfur. However, ductility and toughness at high temperature over about 500 ℃ were greatly reduced due to microstructural change. In general, welding process is the representative method to join the parts in industrial components. Because the alloy by welding can be sensitized and corroded, the manufacturing process should be controlled. In this work, UNS N08810
was used and heat treatment conditions including solution and stabilization treatments were controlled. Oxalic acid etch test by ASTM A262 Practice A was done to evaluate the qualitative sensitization in room temperature. Huey test by ASTM A262 Practice C was done to evaluate the intergranular corrosion rate in boiling 65% HNO3 solution. Also, the microstructure by thermal history was analyzed. Experimental alloy showed high intergranular corrosion rate and its corrosion mechanism was elucidated. - KEYWORDs : UNS N08810, intergranular corrosion, stabilization heat treatment, Titanium sulfide, Titanium
- AUTHORs : 김영식†? 황보 덕
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Page : 205 - 212
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- 5083-O 알루미늄 합금의 진폭에 따른 캐비테이션 침식 특성 평가
- With recent advances in engineering and technology, a damage on industrial machineries performing high-speed and high-power requirements has become a problem. There is an increasing possibility of cavitation damage, especially in pumps, propellers and high-speed vessels in a flowing liquid accordingly. There are several factors affecting cavitation damage on materials, including viscosity, pressure, temperature, amplitude applied. In this study, effects of cavity pressure in seawater on the damage for 5083-O aluminium alloy were evaluated by modulating
amplitude. Trend of the damage with respect to time and amplitude was analyzed comparatively, and surface degradation of specimens was investigated by using Scanning Electron Microscope(SEM) and 3D microscope. The result reveals that the amount of the damage increased consistently with the increase in time and amplitude while the plastic deformation zone where no appreciable damage occurred was in less than 30 minutes. - KEYWORDs : cavitation, Al alloy, amplitude, 3D analysis, seawater environment
- AUTHORs : 이승준†? 김성종
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Page : 213 - 217
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- 선진 핵연료주기 시설(AFC)의 부식건전성 조사, 분석
- The amount of spent fuel from nuclear power plants has been increasing. An effective management plan of the spent fuel becomes a critical issue, because the storage capacity of each plant will reach its storage limit in a few years. The volume of high toxic spent fuel can be reduced through a fuel processing. Advanced Fuel
Cycle (AFC) system is considered to be one of the options to reduce the toxicity and volume of the spent fuel. It is necessary to set up a test facility to demonstrate the feasibility of the process at the engineering scale. The objective of the work is a development of the safety evaluation technology for the AFC system. The evaluation
technology of the AFC structural integrity and processes were surveyed and reviewed. Key evaluation parameters for the main processes such as electrolytic reduction, electrorefining, and electrowinning were obtained. The survey results may be used for the establishment of the AFC regulatory licensing procedure. The establishment of the licensing criteria minimizes the trials and errors of the AFC facility design. Issues taken from the survey on the regulatory procedure and design safety features for the AFC facility provide a chance to resolve potential issues in advance. - KEYWORDs : AFC system, structural integrity, electrolytic reduction, electrorefining, electrowinning
- AUTHORs : 황성식
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Page : 218 - 224
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- 원전 탄소강 배관의 액적충돌침식 손상에 대한 B-Scan 검사 및 수치해석적 분석
- Liquid droplet impingement erosion (LDIE) known to be generated in aircraft and turbine blades is recently appeared in nuclear piping. UT thickness measurements with both A-scan and B-scan UT inspection equipments were performed for a component estimated as susceptible to LDIE in feedwater heater vent system. The thickness data measured with B-Scan equipment were compared with those of A-Scan. Thermal hydraulic analysis based on ANSYS FLUENT code was performed to analyze the behavior of liquid droplets inside piping. The wall thinning rate and residual lifetime based on both existing Sanchez-Caldera equation and measuring data were also calculated to identify the applicability of the existing equation to the LDIE management of nuclear piping. Because Sanchez-Caldera equation do not consider the feature of magnetite formed inside piping, droplet size, colliding frequency, the development of new evaluation method urgently needs to manage the pipe wall thinning caused by LDIE.
- KEYWORDs : liquid droplet impingement erosion, flow accelerated corrosion, UT inspection, thermal hydraulic
- AUTHORs : 황경모†? 이대영
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Page : 225 - 231
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- ASME Code Case N-806을 활용한 매설배관 사용적합성 평가 고찰
- Fitness-for-Service is a useful technology to determine replacement timing, next inspection timing or in-service when nuclear power plant\\\'s buried pipes are damaged. If is possible for buried pipes to be aged by material loss, cracks and occlusion as operating time goes by. Therefore Fitness-for-Service technology for buried pipe is useful for plant industry to perform replacement and repair. Fitness-for-Service for buried pipe is studied in terms of existing code and standard for Fitness-for-Service and a current developing code case. Fitness-for-Service for buried pipe was performed according to Code Case N-806 developed by ASME (American Society of Mechanical Engineers).
- KEYWORDs : buried pipe, fitness for service, soil load, ASME code case N-806, inspection
- AUTHORs : 박상규†? 이요섭? 소일수? 임부택
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Page : 232 - 241
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- 탄소강 볼트 체결된 GECM(Graphite Epoxy Composite Material)/Al 판재의 구성 부재의 부식 거동
- This work focused on corrosion of carbon steel bolted GECM/Al parts in tap water and NaCl solutions. In tap water and NaCl solutions, open circuit potential of GECM and its potentials in a series of carbon steel bolt>Ti>Al became active. Regardless of test materials, open circuit potentials in tap water were noble, and increasing NaCl
concentration, its potentials became active. Immersion test of single specimen showed that no corrosion occur in Ti and GECM. In tap water, carbon steel bolt didn\\\'t show red corrosion product and in chloride solutions, corrosion rate in 1% NaCl solution was greater than its rate in 3.5% NaCl solution and red corrosion product in 1% NaCl solution was earlier observed than that in 3.5% NaCl solution. It seems that this behavior would be related to zinc-coatings on the surface of carbon stee l bolt. On the other hand, aluminium was corroded in tap water and chloride solutions. Corrosion of aluminium in tap water was due to the presence of chloride
ion in tap water by sterilizing process. - KEYWORDs : galvanic corrosion, carbon steel bolted GECM, Al, tap water, NaCl
- AUTHORs : 김영식†? 박수진? 유영란
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Page : 242 - 246
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- 희생양극식 음극방식이 적용된 해안 교량 구조물의 방식거동
- This measurement represents the effectiveness of sacrificial anode cathodic protection (SACP) system in a coastal bridge structure. To verify the cathodic protection (CP) effect, the monitoring sensor (DMS-100) that could measure
potential, corrosion rate, current, concrete resistivity, and temperature was embedded. The measurement conducted for three years after CP system was installed. Specifically, due to the fact that fresh water and sea water was
repeated in the bridge structure, this bridge structure presented special CP behavior. Measurement factors were CP potential, CP current, concrete resistivity, and depolarization potential. In addition, visual inspection was also carried out. As a result of current and depolarization measurement, CP system was well activated in most piers. - KEYWORDs : cahtodic protection, potential, concrete resistivity, SACP, depolarization
- AUTHORs : 하지명? 진충국? 정진아†
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Page : 247 - 256
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- 조화 전류 측정에 의한 분극 저항 평가
- Harmonic current was measured for a dummy cell with various values of resistance, and the procedure developed through the measurements was applied to the investigation of effects of the amplitude of applied frequency and applied potential on the harmonic current of a stainless steel and a carbon steel in chloride containing solutions. From the measurements of harmonic current in the dummy cell, the optimum values of applied frequency and applied potential in harmonic current measurements were found to be 1 mHz and 20 mV (or lower), respectively.
Increase in harmonic current with applied frequency was observed in the case where the level of harmonic current is low as in a stainless steel. Decrease in polarization resistance was also noted in this corrosion system with either increasing applied frequency or decreasing applied potential. However, no obvious effects of applied frequency was observed on harmonic current and polarization resistance in a carbon steel in which the level of harmonic current is high. - KEYWORDs : harmonic current, applied frequency, applied potential, polarization resistance
- AUTHORs : 김종집†? 유미영
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Page : 257 - 262
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- Rotating cylinder를 이용한 탄소강의 유동가속부식 평가
- Flow accelerated corrosion (FAC) of the carbon steel piping in nuclear power plants (NPPs) has been major issue in nuclear industry. Rotating cylinder FAC test facility was designed and fabricated and then performance of the facility was evaluated. The facility is very simple in design and economic in fabrication and can be used
in material and chemistry screening test. The facility is equipped with on line monitoring of pH, conductivity, dissolved oxygen(DO), and temperature. Fluid velocity is controlled with rotating speed of the cylinder with a test specimen. FAC test of SA106 Gr. B carbon steel under 4 m/s flow velocity was performed with the rotating
cylinder at DO concentration of less than 1 ppb and of 1.3 ppm. Also a corrosion test of the carbon steel at static condition, that is at zero fluid velocity, of test specimen and solution was performed at pH from 8 to 10 for comparison with the FAC data. For corrosion test in static condition, the amount of non adherent corrosion product was almost constant at pH ranging from 8 to 10. But adherent corrosion product decreased with increasing pH. This trend is consistent with decrease of Fe solubility with an increase in pH. For FAC test with rotating cylinder FAC test facility, the amount of non adherent corrosion product was also almost same for both DO
concentrations. The rotating cylinder FAC test facility will be further improved by redesigning rotating cylinder and FAC specimen geometry for future work. - KEYWORDs : flow accelerated corrosion, rotating cylinder, carbon steel, nuclear power plant, dissolved oxygen
- AUTHORs : 박태준? 이은희? 김경모? 김홍표†
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