This study is concerned with the improvement of Charpy impact properties in heat affected zones (HAZs) of API X80 linepipe steels containing complex oxides. The steels 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 as the excess amount of Mg and O2 was included in the steels. After the HAZ simulation test, the steel having many oxides contained a considerable amount of acicular ferrite in the simulated HAZ, together with bainitic ferrite and granular bainite, whereas the HAZ microstructures of the conventional steels consisted of bainitic ferrite and granular bainite with a small amount of acicular ferrite. The volume fraction of acicular ferrite increased as the amount of complex oxides increased and the heat input decreased, and thus Charpy impact properties of the oxide-containing steel HAZs were greatly improved over those of the conventional steel HAZs. These findings suggested that the active nucleation of acicular ferrite in the oxide-containing steel HAZs was associated with the great improvement of Charpy impact properties of the HAZs.
Improvement of Charpy impact properties in heat affected zones of API X80 linepipe steels containing complex oxides
2010
8 Seiten, 9 Quellen
Conference paper
English
Bainit , bainitischer Stahl , Charpy-Spitzkerbschlagversuch , dispersionsgehärteter Stahl , Ferrit (Alpha-Mischkristall) , funktionelle Elektrostimulation , Magnesiumoxid , Mikrostruktur , Nadelgefüge , Oxideinschluss , Pipeline , Rohrstahl , Schlagfestigkeit , Stahlrohr , Wärmeeinflusszone , Wärmezufuhr
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