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Vol.44, No.1, 1 ~ 10, 2006
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| Title |
| Effects of Microstructure on Charpy Impact Properties of API X70 and X80 Line-pipe Steels |
| 신상용 Sang Yong Shin , 황병철 Byoung Chul Hwang , 이성학 Sung Hak Lee , 김낙준 Nack J. Kim , 안성수 Seong Soo Ahn |
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| Abstract |
| This study is concerned with the effects of microstructure on Charpy V-notch impact properties of high-toughness API X70 and X80 line-pipe steels. Three kinds of steels were fabricated by varying alloying elements and hot-rolling conditions, and their microstructures and Charpy impact properties were investigated. In addition, their effective grain sizes were characterized by the electron back-scatter diffraction (EBSD) analysis. The Charpy impact test results indicated that the steels rolled in the single phase region had the higher upper shelf energy (USE) than the steel rolled in the two phase region because their microstructures were composed of acicular ferrites. In the X80 steel rolled in the single phase region, the decreased energy transition temperature (ETT) could be explained by the decrease in the overall effective grain size due to the presence of acicular ferrite having smaller effective grain size. Thus, it had excellent mechanical properties including high yield and tensile strengths, high USE, and low ETT, although its elongation was low. |
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| Key Words |
| API X70 and X80 Line-pipe steel, Charpy impact properties, Energy transition temperature, Effective grain size |
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