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Vol.48, No.10, 875 ~ 884, 2010
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| Title |
| Charpy Impact Properties of Heat Affected Zones of API X80 Linepipe Steels Containing Complex Oxides |
| 성효경 Hyo Kyung Sung , 신상용 Sang Yong Shin , 차우열 Woo Yeol Cha , 오경식 Kyung Shik Oh , 이성학 Sung Hak Lee , 김낙준 Nack J. Kim |
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| Abstract |
| This study assessed the Charpy impact properties of the heat-affected zones (HAZs) of API X80 linepipe steels containing complex oxides. Three types of steel were fabricated by adding Mg and O2 to form complex oxides and their microstructures and Charpy impact properties were investigated. The number of complex oxides increased with the amount of excess Mg and O2 that was included in the steels. Simulated HAZs containing a number of oxides showed a high volume fraction of acicular ferrite (AF) because the oxides acted as nucleation sites for AF, thereby leading to an improvement in the Charpy impact properties. According to a correlation study between the heat input, the volume fraction of the AF, and the Charpy impact properties, ductile fractures occurred predominantly when the fraction of the AF was 20% or higher; moreover, the Charpy absorbed energy was excellent at more than 100 J. These findings suggest that the improvement of the Charpy impact properties of the HAZs was associated with the active nucleation of AF in the oxide-containing steel HAZs. |
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| Key Words |
| Metals, welding, toughness, impact test, heat affected zone |
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