Mechanism of Corrosion Fatigue Cracking of Automotive Coil Spring Steel

남태흠,권민석,김정구 대한금속·재료학회 2015 METALS AND MATERIALS International Vol.21 No.6

The AISI 300M ultra-high strength steel was applied for the automotive suspension coil spring. Recently, some premature failures were reported, which caused by synergistic effect of cyclic mechanical stress and corrosion, namely corrosion fatigue cracking. In this study, the accurate mechanism of corrosion fatigue cracking for coil spring steel was studied for the proper prevention method against the catastrophic failure. Fatigue life was evaluated in 5 wt% NaCl solution under the anodic dissolution and hydrogen embrittlement conditions, which is simulated by applying constant potentials. Scanning electron microscopy and energy dispersive X-ray spectroscopy analysis indicated that the corrosion fatigue cracking was initiated at the MnS inclusion of the pit initiation site. The calculation of hydrogen production corresponding to each corrosion fatigue test condition revealed the two operating mechanisms of the cracking process. The corrosion fatigue cracking failure of coil spring steel was mainly caused by the anodic dissolution combined with hydrogen embrittlement.

첨가제에 따른 케이블 그라우트의 부식 특성 평가

남태흠 ( Tae Heum Nam ),전우석 ( Woo Seok Jeon ),김정구 ( Jung Gu Kim ) 대한금속ᆞ재료학회 2006 대한금속·재료학회지 Vol.44 No.11

원전 매설배관 및 탱크 규제현황

김경조,남태흠,김종민,김진겸,신호상 한국비파괴검사학회 2018 한국비파괴검사학회지 Vol.38 No.1

Leakage caused by the corrosion of buried and underground pipes has recently resulted in groundwater contamination incidents. Some of these groundwater contamination incidents attatched much interest USNRC and the public. The industry issued a guidance document Nuclear Energy Institute (NEI) 09-14, “Guideline for the Management of Buried Piping Integrity” to describe a licensee’s goals and required actions resulting from this underground piping and tank initiative. The NRC conducted inspections using TI 2515/173, “Review of the Implementation of the Industry Groundwater Protection Voluntary Initiative” to assess licensee response to these incidents and determine the extent of the industry’s voluntary groundwater protection initiative. According to NEI 09-14, utility-provided procedures, risk ranking, inspection plans and asset management plans, were evaluated by USNRC in accordance with TI 2515/173, which are the same evaluations and inspections required for aging degradation of Korea nuclear power plants (NPP). The purpose of this research is to develop regulatory techniques and guideline for aging management of buried and underground pipes and tanks in Korean NPP. For this purpose, aging management, direct and indirect inspection techniques and regulatory techniques for buried and underground pipes and tank will be evaluated and a database for the damage of buried and underground pipes and tanks will be developed. From these techniques and the database information, in-service inspection guidelines and review guidelines for aging management will be developed. 매설배관의 손상은 최근 원전 산업이 직면하고 있는 중요한 현안사항 중의 하나로 대두되고 있으며, 지상의 배관과는 달리 배관 내부의 유체로 인한 부식, 배관 외부의 토양으로 인한 기계적, 화학적 손상 그리고 중 하중에 의한 피로 등을 동시에 경험하고 있다. 매설배관에서 누설이 발생할 경우에는 누설의 원인을 찾기가 어려울 뿐만 아니라 접근도 용이하지 않아 적절한 시기에 정비하기란 매우 어렵다. 현재의 매설배관 건전성 관리는 누설 시 위치를 파악하고 임시보수 또는 경상정비를 통하여 사후처리를 진행하므로, 토양 또는 콘크리트에 매립된 매설배관의 잠재적인 손상징후 파악과 그에 대한 건전성 평가에 상당한 제한을 받고 있다. 이에 따라 국내 원전에 적용 가능한 매설배관 경년열화관리 프로그램의 구축 필요성이 대두되었으며, 이를 위해 국내 원전의 관리대상 매설배관 계통을 도출하고 그에 대한 체계적인 위험도 분석, 데이터베이스 구축, 상세 평가, 외부 및 내부 비파괴검사 기술개발 및 규제지침 개발 등이 필요하다. 본 연구에서는 원전 매설배관 및 탱크에 대한 규제지침을 개발하기 위해 국외에서 연구개발 또는 적용되는 규제요건, 사업자 문서와 국내 적용현황 등을 검토하여 매설배관 규제현황을 파악하였다. 규제현황을 파악하기 위하여 매설배관의 경년열화 관련 경험을 요약한 규제요건인 NUREG GALL 보고서, 미국 규제기관의 규제지침서(ISG), 규제기관에서 발행한 규제문서(TI), 개발 중인 ASME Code Case, 매설배관 미국 산업계 관리지침인 NEI 09-14 및 EPRI TR 1021175 등을 정리하였고 국내에 적용되고 있는 매설배관 경년열화 관리현황을 검토하였다. 이를 통해, 향후 국내 원전의 매설배관 규제에 적용될 수 있는 규제지침을 개발하여 원전의 가동중검사, 계속운전 심사 등 인허가를 위한 기술적 지침으로 활용할 예정이다.

Effects of Trioctyl Phosphate and Cresyl Diphenyl Phosphate as Flame-Retarding Additives for Li-Ion Battery Electrolytes

심은기,남태흠,김정구,김현수,문성인 대한금속·재료학회 2009 METALS AND MATERIALS International Vol.15 No.4

Safety concerns related to lithium-ion batteries have been the key obstacle to their application in hybrid electric vehicles. Trioctyl Phosphate (TOP) and Cresyl Diphenyl Phosphate (CDP) were studied as potential flame-retarding additives for lithium-ion batteries. The electrochemical performance and thermal stability of the additive-containing electrolytes, in combination with a cell comprising a LiCoO2 cathode and Mesocarbon Microbeads (MCMB) anode, were tested in coin cells. Cyclic Voltammetry (CV), Differential Scanning Calorimetry (DSC), Electrochemical Impedance Spectroscopy (EIS), and Scanning Electron Microscopy (SEM) were used for the experimental analysis. The study results revealed that CDP addition at 5 wt.% improved the cell stability due to the lower rate of the charge-transfer resistance increase over 30-50 cycles. CDP was demonstrated to be a better flameretarding additive than TOP. Safety concerns related to lithium-ion batteries have been the key obstacle to their application in hybrid electric vehicles. Trioctyl Phosphate (TOP) and Cresyl Diphenyl Phosphate (CDP) were studied as potential flame-retarding additives for lithium-ion batteries. The electrochemical performance and thermal stability of the additive-containing electrolytes, in combination with a cell comprising a LiCoO2 cathode and Mesocarbon Microbeads (MCMB) anode, were tested in coin cells. Cyclic Voltammetry (CV), Differential Scanning Calorimetry (DSC), Electrochemical Impedance Spectroscopy (EIS), and Scanning Electron Microscopy (SEM) were used for the experimental analysis. The study results revealed that CDP addition at 5 wt.% improved the cell stability due to the lower rate of the charge-transfer resistance increase over 30-50 cycles. CDP was demonstrated to be a better flameretarding additive than TOP.

Electrochemical Performance and Thermal Stability of Lithium-Ion batteries Containing Electrolyte Additives

심은기,남태흠,김정구,김현수,문성인 한국공업화학회 2007 한국공업화학회 연구논문 초록집 Vol.2007 No.1

Electrochemical Performance of Tris(2-Chloroethyl) Phosphate as a Flame-Retarding Additive for Lithium-Ion Batteries

심은기,박인준,남태흠,김정구,김현수,문성인 대한금속·재료학회 2010 METALS AND MATERIALS International Vol.16 No.4

We studied tris(2-chloroethyl) phosphate (TCEP) as a potential flame-retarding additive and its effect on the electrochemical cell performance of lithium-ion battery electrolytes. The electrochemical cell performance of additive-containing electrolytes in combination with a cell comprised of a LiCoO2 cathode and a mesocarbon microbeads anode was tested in coin cells. The cyclic voltammetry results show that the oxidation potential of TCEP-containing electrolyte is about 5.1 V (vs. Li/Li+). A cell with TCEP has a better electrochemical cell performance than a cell without TCEP in an initial charge and discharge test. In a cycling test, a cell containing a TCEP-containing electrolyte has a greater discharge capacity and better capacity retention than a TCEP-free electrolyte after cycling. The results confirm the promising potential of TCEP as a flame-retarding additive and as a means of improving the electrochemical cell performance of lithium-ion batteries.

A Galvanic Sensor System for Detecting the Corrosion Damage of the Steel Embedded in Concrete Structures : Laboratory Tests to Determine the Cathodic Protection and Stray-Current

Yun-Ha Yoo,남태흠,Yoon-Seok Choi,김정구,정란 대한금속·재료학회 2011 METALS AND MATERIALS International Vol.17 No.4

In order to evaluate the possible application of a galvanic sensor for cathodic protection (CP) and straycurrent monitoring of steel embedded in concrete structures, the correlation of sensor current to protection abilities (protection potential/current) and stray-current was investigated by galvanostatic tests that simulated the CP and stray-current. The results revealed a good correlation between the sensor current and the protection abilities or stray-current in terms of the sign as well as magnitude. Thus, the galvanic sensor is proposed as an effective tool for the quantitative determination of the effectiveness of CP or of the interference effect of stray-current.

Alloy 600의 양극분극거동과 기계적 성질에 미치는 수소충전 및전기전송처리의 영향에 관한 연구

박진석 ( Jin Seok Park ),김용상 ( Yong Sang Kim ),남태흠 ( Tae Heum Nam ),김정구 ( Jung Gu Kim ) 대한금속재료학회(구 대한금속학회) 2015 대한금속·재료학회지 Vol.53 No.11

Electrotransport treatment is a new method to remove the hydrogen from inside metals. Potentiodynamic polarization tests, electrochemical impedance spectroscopy (EIS), and tensile tests were used to investigate the effect of electrotransport treatment on the anodic behavior and hydrogen embrittlement characteristics of Alloy 600. The hydrogen-charged specimen exhibited a higher anodic current than that of the uncharged specimen. In particular, the anodic current was reduced so that the electrotransport treatment had features similar to that of the uncharged specimen. The EIS results showed that the capacitance loop of the hydrogen-charged specimen was smaller than that of the electrotransport treatment specimen. Results regarding tensile behavior revealed that electrotransport treatment enhanced the mechanical property of hydrogen-charged specimens.