(A) study on the intercritical annealing treatment on the mechanical properties of SA106 Gr.C piping steel = 이상역 열처리가 SA106 Gr.C 배관재의 기계적 성질에 미치는 영향에 관한 연구

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From the point of view on material properties in Leak-Before-Break (LBB) analysis, the premise of LBB is that the materials used are sufficiently tough (ductile) that small through-wall crack would remain stable. It is reported, however, that the toughness and LBB safety margins of SA106 Gr.C piping steel is reduced due to dynamic strain aging (DSA) at the reactor operating temperature. In this study, intercritical annealing in two-phase ($\alpha+\gamma$) region was performed to investigate the possibility of improving the toughness and reducing DSA susceptibility for giving allowable LBB safety margins. Tensile tests were carried out under various temperatures and strain rates for assessing the material properties with the heat treatments. Also, Charpy impact tests were conducted to measure impact toughness at room temperature. After intercritical annealing, the manifestations of DSA were observed in the tensile properties. However, the ductility loss caused by DSA was smaller than the as-received material. Furthermore, the intercritical annealing was able to increase the impact toughness by 1.5 times compared to as-received material. With the heat treatment, we could obtain some kinds of microstructural changes such as the cleaner retained ferrite, increased ferrite content and somewhat finer grain size. It is considered that the reduced DSA sensitivity was induced by cleaner retained ferrite and it resulted in higher impact toughness in addition to the general toughening due to finer grain sizes and increased ferrite content.
Advisors
Kim, In-Sup김인섭
Description
한국과학기술원 : 원자력공학과,
Publisher
한국과학기술원
Issue Date
1999
Identifier
150483/325007 / 000973538
Language
eng
Description

학위논문(석사) - 한국과학기술원 : 원자력공학과, 1999.2, [ vi, 55 p. ]

Keywords

Intercritical annealing; Dynamic strain aging; Leak-before-break; SA106 Gr.C; SA106 Gr.C; 이상역열처리; 동적변형시효; 파단전누설

URI
http://hdl.handle.net/10203/49402
Link
http://library.kaist.ac.kr/search/detail/view.do?bibCtrlNo=150483&flag=dissertation
Appears in Collection
NE-Theses_Master(석사논문)
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