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Vol.47, No.9, 533 ~ 542, 2009
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| Title |
| Effects of Ni and Cr Contents on the Fracture Toughness of Ni-Mo-Cr Low Alloy Steels in the Transition Temperature Region |
| 이기형 Ki Hyoung Lee , 박상규 Sang Gyu Park , 김민철 Min Chul Kim , 이봉상 Bong Sang Lee , 위당문 Dang Moon Wee |
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| Abstract |
| Materials used for a reactor pressure vessel(RPV) are required high strength and toughness, which determine the safety margin and life of a reactor. Ni-Mo-Cr low alloy steel shows better mechanical properties than existing RPV steels due to higher Ni and Cr contents compared to the existing RPV steels. The present study focuses on effects of Ni, Cr contents on the cleavage fracture toughness of Ni-Mo-Cr low alloy steels in the transition temperature region. The fracture toughness was characterized by a 3-point bend test of precracked Charpy V-notch(PCVN) specimens based on ASTM E1921-08. The test results indicated that the fracture toughness was considerably improved with an increase of Ni and Cr contents. Especially, control of Cr content was more effective in improving fracture toughness than manipulating Ni content, though Charpy impact toughness was changed more extensively by adjusting Ni content. These differences between changes in the fracture toughness and that in the impact toughness were derived from microstructural features, such as martensite lath size and carbide precipitation behavior. |
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| Key Words |
| reactor pressure vessel, Ni-Mo-Cr Low alloy steel, cleavage fracture toughness, master curve, charpy impact toughness |
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