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초음파법을 이용한 1Cr-lMo-0.25V강의 열화도 평가에 관한 연구
김정표,석창성,Kim, Jeong-Pyo,Seok, Chang-Seong 대한기계학회 2001 大韓機械學會論文集A Vol.25 No.12
It's required mechanical properties of in-service facilities to maintain safety operation in power plants as well as chemical plants. In this studdy the four classes of the thermally aged 1Cr-lMo-0.25V specimens were prepared using an artificially accelerated aging method at 630$\^{C}$. Ultrasonic tests, tensile tests, K$\_$IC/ tests and hardness tests were performed in order to evaluate the degree of degradation of the material. The mechanical properties were decreased as degraded, but the attenuation coefficient and the harmonic generation level of a ultrasonic signal were increased. Expecially the nonlinear parameter derived from the harmonic generation level is sensitive and will be a good parameter to evaluate the material degradation.
김정표(Jeong-Pyo Kim),석창성(Chang-Sung Seok) 대한기계학회 2001 대한기계학회 춘추학술대회 Vol.2001 No.8
As huge energy transfer systems like a nuclear power plant, steam power plant and petrochemical plant are operated for a long time, mechanical properties are changed by degradation. The life time of the systems can be affected by the mechanical properties. BI(Ball Indentation) test has a potential to replace conventional fracture tests like a uniaxial tensile test, fracture toughness test, hardness test and so on. In this paper, we would like to present the aging evaluation technique by the BI method. The four classes of the thermally aged lCr-lMo-O.25V specimens were prepared using an artificially accelerated aging method. Tensile tests, fracture toughness tests, hardness tests and BI tests were performed. The results of the BI tests were in good agreement with fracture characteristics by a standard fracture test method. And the material degradation was evaluated with the relationship between the results of BI test and LMP(Larson-Miller Parameter) values.
오스테나이트계 Fe-Ni based 합금강의 열화 시간에 의한 탄화물 거동과 기계적 물성 변화에 대한 연구
김기근(Keekeun Kim),박수(Soo Park),석창성(Chang-Sung Seok),최재구(Jae Gu Choi),김가연(Gayeon Kim) 대한기계학회 2018 大韓機械學會論文集A Vol.42 No.11
Fe-Ni-Cr 오스테나이트계 합금강 중 NCF3015 소재는 Ni 원소의 함량을 증가시켜 고온 기계적 물성을 우수하게 만든 소재이다. 고온 기계적 물성은 미세조직의 형상과 밀접한 관계가 있으며 미세조직의 형상은 고온노출 온도와 시간에 따라 변할 수 있기 때문에, 재료의 고온 미세조직 변화와 기계적 물성변화에 대한 연구가 필요하다. 본 연구에서는 950℃에서 NCF3015 소재의 열화 시간에 따른 미세조직 및 탄화물 변화와 기계적 물성과의 관계를 분석하기 위해 Thermo-calc 프로그램을 통한 평형 상태도 해석으로 NCF3015 소재의 고온 미세조직 변화를 예측하였으며, 실험적으로 열화된 시편의 미세조직 분석을 통해 해석결과와 비교하였다. 또한 인장시험과 비커스 경도를 측정함으로써 열화 시간에 따른 기계적 물성변화를 분석하였으며 이를 탄화물 거동변화와 관련 지어 두 변화의 상관관계를 도출하였다. NCF3015 is a Fe-Ni-Cr austenitic alloy steel that increases the content of Ni elements and which results in excellent high-temperature mechanical properties. High-temperature mechanical properties are closely related to the microstructure, and the shape of the microstructure can be changed by the exposure temperature and time. Therefore, it is necessary to study the changes in the high-temperature microstructure and mechanical properties of materials. In this research, to analyze the relationship between microstructural and carbide changes, as well as the mechanical properties of NCF3015 at 950℃, an equilibrium-state analysis is performed using the Thermo-calc program to determine the microstructural changes. The results are compared with the experimental results obtained. In addition, the tensile test and the Vicker"s hardness test are conducted to determine the variation in the mechanical properties with degradation time, which was correlated with the changes of microstructural and carbide behavior.
석창성,김정표,송성진,김훈모,김재원,김수용,Seok, Chang-Seong,Kim, Jeong-Pyo,Song, Seong-Jin,Kim, Hun-Mo,Kim, Jae-Won,Kim, Su-Yong 대한기계학회 2001 大韓機械學會論文集A Vol.25 No.12
The BI(Ball Indentation) method has a potential to assess the mechanical properties and to replace conventional fracture tests. In this study, the BI test system has been developed to evaluate material properties. Tensile tests, fracture toughness tests, hardness tests and BI tests were performed by the system using four classes of thermally aged specimens. The results of the BI tests were in good agreement with fracture characteristics from a standard fracture test method.
김정표(Jeong-Pyo Kim),석창성(Chang-Sung Seok) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5
In this study the four classes of the thermally aged ICr-IMo-0.25V specimens were prepared using an artificially accelerated aging method. Ultrasonic tests were performed to get the correlation with fracture toughness. And the modified theoretical Vary's equation, considering nonlinear response due to material degradation, was proposed for the correlations between ultrasonic parameters and fracture toughness. Experimental results indicate that ultrasonic parameters produce the correlations with fracture toughness and yield strength.