• Title, Summary, Keyword: EPR test

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Miscibility and Properties of Ethyl-Branched Polyethylene/Ethylene-Propylene Rubber Blends( I ) (에틸 가지화된 폴리에틸렌과 에틸렌-프로필렌 고무 블렌드의 혼화성와 물성( I ))

  • Cho, Ur-Ryong
    • Elastomers and Composites
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    • v.36 no.3
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    • pp.169-176
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    • 2001
  • Ethyl-branched polyethylene[PE(2)] containing 2mole% ethyl branch and three ethylene-propylene rubbers(EPR's) haying the same ethylene(E)-propylene(P) molar ratio(E/P=50/50) with different stereoregularity, that is, random EPR(r-EPR), alternating-EPR(alt-FPR) and isotactic-alternating-EPR(iso-alt-EPR) were mixed for the investigation of their properties depending on the stereoregurarity. The three blends were immiscible at room temperature, and showed the simple additivity effect in density behavior. The melting point depression with blend composition increased in order of PE(2)/r-EPR>PE(2)/alt-EPR>PE(2)/iso-alt-EPR. In the tensile test, this blend systems have the lowest value or the breaking strength at FE(2) fraction of 0.5. This phenomenon results from the greastest separated phase morphology at this blend composition.

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A Study on the Mechanical Properties of Butt Welding Zone of Clad Steel According to the Process Design (공정 디자인에 따른 클래드강 맞대기 용접부의 기계적 특성에 관한 연구)

  • Lee, Jung-Hyun;Park, Jae-Won
    • Journal of The Korean Society of Manufacturing Technology Engineers
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    • v.21 no.4
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    • pp.532-540
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    • 2012
  • In this study, some considerations have been suggested in developing on-site techniques to evaluate the sensitization of stainless steels. Electrochemical potentiokinetic reactivation (EPR) technique is known to be a candidate tool for field applications since it enables quantitative assessment in reasonable test time, compared to oxalic etching (ditch) technique. The on-site application of the test method imposes additional restrictions on the selection of the test method (for example, minimum surface preparation requirement, insensitivity to testing temperature, etc.). The EPR and etching techniques have been compared in order to sensitization of stainless steel structures. It has been widely reported that the maximum sensitivity in the welded structure of stainless steel is shown at heat-affected zone (HAZ) than weldments with cast structure. In this work, sectioned weldments and external surfaces were investigated to reveal the degree of sensitization by the etching and the results were compared with those of EPR test. The EPR test showed little sensitivity to surface roughness and test temperature.

질소강화 type 304L stainless steel 의 예민화 저항성 평가

  • 윤지현;오용준;류우석;홍준화
    • Proceedings of the Korean Nuclear Society Conference
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    • pp.551-556
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    • 1996
  • 본 연구에서는 정량적 전기화학 시험법인 DL-EPR test 와 ASTM 에 규정된 screening test 인 oxalic acid etch test 를 통해 질소강화 type 304L stainless steel 의 예민화 저항성을 평가하고, 두 시험법의 결과 사이의 상관관계를 알아보며, 질소함량이 예민화 저항성에 미치는 영향을 고찰하고자 하였다. 실험결과 일정수준에서 질소함량이 증가할수록 예민화가 지연되는 경향을 볼 수 있었고, 이런 현상은 두 시험법의 결과에서 공히 나타났다. 또한 DL-EPR test 와 oxalic acid etch test 간의 상관관계가 비례적으로 나타났으며, 각 oxalic acid etch 조직에 해당하는 DL-EPR test 결과값 (Ir/Ia) 을 얻을 수 있었다.

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An Evaluation of Aging Degradation Damage for Cr-Mo-V Steel by Electrochemical Potentiokinetic Reactivation Test (재활성화 분극시험에 의한 Cr-Mo-V강의 시효열화 손상 평가)

  • Kwon, Il-Hyun;Na, Sung-Hun;Song, Gee-Wook;Yu, Hyo-Sun
    • Proceedings of the KSME Conference
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    • pp.49-54
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    • 2000
  • Cr-Mo-V steel is widely used as a material for the turbine structural component in fossil power plants. It is well known that this material shows the various material degradation phenomenons such as temper embrittlement, carbide coarsening. and softening etc. or ins to the severe operation conditions as high temperature and high pressure. These deteriorative factors cause tile change of mechanical properties as reduction of fracture toughness. Therefor it is necessary to evaluate tile extent of degradation damage for Cr-Mo-V steel in life assessment of turbine structural components. In this paper. the electrochemical potentiokinetic reactivation(EPR) test in $50wt%-Ca(NO_3)_2$ solution is performed to develop the newly technique for degradation damage evaluation of Cr-Mo-V steel. The results obtained from the EPR test are compared with those in small punch(SP) tests recommended by semi-nondestructive testing method using miniaturized specimen. The evaluation parameters used in EPR test are tile reactivation current density$(I_R)$ and charge$(Q_{RC})$ reactivation rate$(I_R/I_{Crit},\;Q_R/Q_{Crit})$. The results suggest that $I_R/I_{Crit}$ in these parameters shows a good correlation with SP test results.

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Effect of Precipitate on the Electrochemical Potentiokinetic Reactivation Behaviors of Stainless Steels and Nickel Base Alloys

  • Wu, Tsung-Feng;Chen, Tzu-Sheng;Tsai, Wen-Ta
    • Corrosion Science and Technology
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    • v.2 no.2
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    • pp.59-67
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    • 2003
  • Electrochemical potentiokinetic reactivation (EPR) tests are used to evaluate the degree of sensitization (DOS) of stainless steels and nickel base alloys. The validity of EPR test to detect DOS of these alloys, however, depends all the electrolyte composition employed. The existence of precipitates such as NbC, and TiC, etc. in the alloys also affects the reactivation behaviors of these alloys. In this investigation, the reactions involved during EPR processes are analyzed. In 0.5 M $H_2SO_4$+ 0.01 M KSCN electrolyte, a reactivation peak associated with the localized attack around NbC, different from that of intergranular corrosion, is observed for the solution annealed 347 SS. For solution annealed Alloy 600, matrix corrosion and localized attack around TiC with distinct anodic peaks appeared in the EPR curves are seen in the $H_2SO_4$+ KSCN electrolyte. With proper adjustment of elect rolyte composition, the contribution from intergranular corrosion, as a result of chromium carbide precipitation along the grain boundaries, can be distingui shed from the matrix and localized corrosion for the sensitized Alloy 600.

A Study of Corrosion Resistance Improvement for Cr-Mo Steel in Long Term Service (장기간 사용한 Cr-Mo강의 내식성 향상 방법에 관한 연구)

  • Jin, Yeung-Jun
    • Journal of the Korean Society of Safety
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    • v.21 no.3
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    • pp.8-15
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    • 2006
  • It is no wonder that mechanical structures are accompanied by problems related to corrosion after being exposed to long hours of work. Corrosion of mechanical structures has been the most serious problem in the field of industry. The present study employed a laser beam irradiation test to improve the corrosion resistance of degraded Cr-Mo steel, which was used for more than 60,000 hours. To find the optimum irradiation test condition for the corrosion resistance of degraded Cr-Mo steel, hardness and residual stress measurements, micro-structural observation, and the electrochemical potentiokinetic reactivation (EPR) tests were performed with changes in laser beam test conditions including laser beam output, diameter, and velocity. Thus, the present study indicates that the optimum test condition and absorption energy for a laser beam test need to be determined to enhance corrosion resistance of degraded Cr-Mo steel.

Effects of Heat Inputs on Phase Transformation and Resistance to Intergranular Corrosion of F316 Austenitic Stainless Steel (F316 오스테나이트 스테인리스강의 상변태 및 입계부식저항성에 미치는 입열의 영향)

  • Jeong, Gyue-Seog;Lee, In-Sung;Kim, Soon-Tae
    • Corrosion Science and Technology
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    • v.19 no.3
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    • pp.146-155
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    • 2020
  • To elucidate the effect of heat inputs on phase transformation and resistance to intergranular corrosion of F316 austenitic stainless steel (ASS), thermodynamic calculations of each phase and time-temperature-transformation diagram were conducted using JMaPro simulation software, oxalic acid etch test, double-loop electrochemical potentiokinetic reactivation test (DL-EPR), field emission scanning electron microscopy with energy dispersive spectroscopy, and transmission electron microscopy analyses of Cr carbide (Cr23C6), austenite phase and ferrite phase. F316 ASS containing a relatively low C content of 0.043 wt% showed a slightly sensitized microstructure (acceptably dual structure) due to a small amount of Cr carbide precipitated at heat affected zone irrespective of heat inputs. Based on results of DL-EPR test, although heat input was increased, the ratio of Ir to Ia was only increased very slightly due to a slight sensitization. Therefore, heat inputs have little influences on resistance to intergranular corrosion of F316 austenitic stainless steel containing 0.043 wt% C.

A study on the interararanular corrosion behavir of stainless steel in molten carbonate salt EPR test (EPR 방법에 의한 용융탄산염 내에서의 스텐인레스강의 입계부식에 관한 연구)

  • 황응림;서병환;강성군
    • Journal of the Korean institute of surface engineering
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    • v.31 no.4
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    • pp.223-230
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    • 1998
  • The separator for a molten carbonate fuel cell(MCFC) is mode of stainless steel and known to the suscepibility to corrosion due to environments of high temperature molten carbonte electrolyte. Considering the sensitization of stainless steel in the temperature range of 425~$815^{\circ}C$, the separator is expected to be sensitized so that the interganular corrosion (IGC) occurs during the cell operation at about $650^{\circ}C$. In this study, EPR(electrochemical potentiokinetic reactivation) technique was examined by relating some elements(mainly C and Cr) to the degree of sensitization of austenitic stainless steels in the molten carbonate salt at $650^{\circ}C$and the possible mechanism of intergranular corrosion was analyzed.

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Effect of Thermal Cycle and Stress on the Intergranular Corrosion in 316 Stainless Steel (316 스테인리스강의 입계부식에 미치는 열사이클과 응력의 영향)

  • Jung, Byong-Ho;Kim, Moo-Gil
    • Journal of the Korean Society of Marine Engineering
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    • v.30 no.6
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    • pp.709-715
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    • 2006
  • The effects of thermal cycle condition and applied stress on the intergranular corrosion in austenitic 316 type stainless steels were investigated. Specimens were solution-treated at 1100$^{\circ}C$ for one hour and then sensitized in the temperature range of $500{\sim}800^{\circ}C$ by holding $2{\sim}300s$ with a various applied stresses of $0{\sim}8kg/mm^2$. Degree of sensitization. DOS %, was measured through polarization curve by electrochemical DL-EPR test. Microstructural observations were also conducted DOS % increased with an increase of sensitization temperature and/or holding time. Increase of applied stress resulted in increase of DOS % and more corroded surface because of acceleration of intergranular corrosion and fine grain size due to the stress. Cr depleted zone near grain boundary was observed. The amount of depletion was profounded with an increase of sensitization temperature, holding time and applied stress. $M_{23}C_6$ carbides were precipitated discontinuously at grain boundary. However, its amount was relatively small in the thermal cycle condition of 800$^{\circ}C$, 300sec and 4kg/mm$^2$.

Corrosion and Corrosion Fatigue Characteristics of Artificially Sensitized STS 304 (STS304 열화재의 부식및 부 식피로특성)

  • Han, Ji-Won;Bae, Dong-Ho
    • Journal of the Korean Society of Safety
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    • v.25 no.6
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    • pp.28-33
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    • 2010
  • Stainless steel is useful material for various industrial facilities such as the nuclear and steam power plant and the heavy chemical industry due to its good corrosion resistance and mechanical properties. However, it has also a large problem that is sensitized in the welding process and its corrosion resistance and mechanical properties decreases by sensitization. Thus, corrosion and corrosion fatigue characteristics of artificially sensitized austenitic STS304 were investigated through the EPR test and corrosion fatigue test. Obtained results are as follows: 1) According to the sensitizing period increase, Cr deficiency layer is linearly expanded. 2) Degree of sensitization(Ia/Ir) proportionally increased with sensitizing period. However, after 4hrs, it showed constant value. 3) Cr-carbide($Cr_{23}C_6$) in the grain boundary increased as sensitizing period increases until six hours. 4) corrosion fatigue strength of sensitized STS304 were remarkably reduced compare to non-sensitized ones.